Tectonic evolution of the Marmara Sea and its surroundings

Article (PDF Available)inMarine Geology 190(1-2):493-530 · October 2002with 609 Reads
DOI: 10.1016/S0025-3227(02)00360-2
Abstract
The basins in the Marmara Sea are the products of a superimposed evolutionary history defined by two different-aged fault systems: the early Miocene–early Pliocene Thrace–Eskişehir Fault Zone and its branches, and the late Pliocene–Recent North Anatolian Fault and its branches. The Thrace–Eskişehir fault and its westward branching secondary fault systems define the early neotectonic signature in the region. The late neotectonic period started at the end of the early Pliocene when the North Anatolian Fault divided the Thrace–Eskişehir fault into four parts. During the late neotectonic period, the North Anatolian Fault extended westward as a number of splays by joining with the Ganos, Bandırma–Behramkale and Manyas–Edremit Fault Zones. The branches of the North Anatolian Fault Zone (NAFZ) caused the evolution of a number of basins, which differ in character depending on the trend and past characteristics of the older branches that became connected. Since the northern branch of the North Anatolian Fault is connected to the N80°E-trending Ganos Fault Zone (GFZ) in the west, a single buried fault has developed in the Marmara Sea, causing the well-known troughs and ridges, superimposed onto the negative flower structure formed by the GFZ in the early neotectonic period. The middle strand, which extends from Iznik Lake to Bandırma, is oriented east–west up to the N60°E-trending Bandırma–Behramkale Fault Zone, then turns southward in the vicinity of Bandırma, forming a region dominated by compressional tectonics. This bending caused N30°E-trending tension in addition to the strike-slip motion between the eastern part of Gemlik Bay and Bandırma Bay. The southern branch of the NAFZ, on the other hand, produced three pull-apart basins with different characteristics along the Yenişehir, Bursa and Manyas segments. The southern branch of the NAFZ connected to the Manyas–Edremit Fault Zone, which is oriented N45°E to the south of Manyas, and the associated bending and rotation caused a N15°E-trending extension in addition to the strike-slip regime between Manyas and Uluabat. The branches of North Anatolian Fault cut through the Thrace–Eskişehir fault at three places: the East Marmara Sea region, in Gemlik Bay, and to the east of Bursa, giving lateral offsets of 58–59, 7–8 and 10–11 km, respectively. The cumulative motion is 75–78 km, corresponding to the total lateral offset of the North Anatolian Fault in the region. The correlation of these offsets with Global Positioning System slip vectors and with stratigraphic results implies that the North Anatolian Fault reached into the Marmara Sea region about 3.5 million yr ago. Tectonic processes forming the Marmara Sea and its environs were initiated by the Thrace–Eskişehir fault and its splays have been most recently controlled by the North Anatolian Fault and its splays during the last 3.5 million yr.
Figures - uploaded by Cenk YALTIRAK
Author content
All content in this area was uploaded by Cenk YALTIRAK
Tectonic evolution of the Marmara Sea and its surroundings
Cenk Yalt|rak a;b;
aIstanbul Technical University, Faculty of Mines, 80626 Maslak, Istanbul, Turkey
bIstanbul Technical University, Institute of Eurasian Earth Sciences, 80626 Maslak, Istanbul, Turkey
Received 1 May 2001; accepted 19 February 2002
Abstract
The basins in the Marmara Sea are the products of a superimposed evolutionary history defined by two different-
aged fault systems: the early Miocene^early Pliocene Thrace^Eskisehir Fault Zone and its branches, and the late
Pliocene^Recent North Anatolian Fault and its branches. The Thrace^Eskisehir fault and its westward branching
secondary fault systems define the early neotectonic signature in the region. The late neotectonic period started at the
end of the early Pliocene when the North Anatolian Fault divided the Thrace^Eskisehir fault into four parts. During
the late neotectonic period, the North Anatolian Fault extended westward as a number of splays by joining with the
Ganos, Band|rma^Behramkale and Manyas^Edremit Fault Zones. The branches of the North Anatolian Fault Zone
(NAFZ) caused the evolution of a number of basins, which differ in character depending on the trend and past
characteristics of the older branches that became connected. Since the northern branch of the North Anatolian Fault
is connected to the N80‡E-trending Ganos Fault Zone (GFZ) in the west, a single buried fault has developed in the
Marmara Sea, causing the well-known troughs and ridges, superimposed onto the negative flower structure formed by
the GFZ in the early neotectonic period. The middle strand, which extends from Iznik Lake to Band|rma, is oriented
east^west up to the N60‡E-trending Band|rma^Behramkale Fault Zone, then turns southward in the vicinity of
Band|rma, forming a region dominated by compressional tectonics. This bending caused N30‡E-trending tension in
addition to the strike-slip motion between the eastern part of Gemlik Bay and Band|rma Bay. The southern branch of
the NAFZ, on the other hand, produced three pull-apart basins with different characteristics along the Yenisehir,
Bursa and Manyas segments. The southern branch of the NAFZ connected to the Manyas^Edremit Fault Zone,
which is oriented N45‡E to the south of Manyas, and the associated bending and rotation caused a N15‡E-trending
extension in addition to the strike-slip regime between Manyas and Uluabat. The branches of North Anatolian Fault
cut through the Thrace^Eskisehir fault at three places: the East Marmara Sea region, in Gemlik Bay, and to the east
of Bursa, giving lateral offsets of 58^59, 7^8 and 10^11 km, respectively. The cumulative motion is 75^78 km,
corresponding to the total lateral offset of the North Anatolian Fault in the region. The correlation of these offsets
with Global Positioning System slip vectors and with stratigraphic results implies that the North Anatolian Fault
reached into the Marmara Sea region about 3.5 million yr ago. Tectonic processes forming the Marmara Sea and its
environs were initiated by the Thrace^Eskisehir fault and its splays have been most recently controlled by the North
Anatolian Fault and its splays during the last 3.5 million yr.
 2002 Elsevier Science B.V. All rights reserved.
Keywords: Marmara Sea ; North Anatolian Fault; Thrace^Eskisehir fault; superimposed tectonics; sub-basin ; neotectonics
0025-3227 / 02 / $ ^ see front matter 2002 Elsevier Science B.V. All rights reserved.
PII: S0025-3227(02)00360-2
* Fax : +90-0-212-2856210.
E-mail address: yaltirak@itu.edu.tr (C. Yalt|rak).
MARGO 3175 3-10-02
Marine Geology 190 (2002) 493^529
www.elsevier.com/locate/margeo
1. Introduction
The 1500-km-long North Anatolian Fault Zone
(NAFZ) bifurcates into three branches to the east
of the Marmara Sea (Fig. 1A). These branches
terminate where the westward escape of the Ana-
tolian Block turns into anticlockwise rotational
opening in the northern Aegean Sea and Edremit
Bay (Fig. 1B). These three branches demonstrate
di¡erent kinematic and seismic appearances in the
Marmara region. First, the NAFZ bifurcates west
of V30.5‡E latitude into two branches (Fig. 1).
The northern strand of the North Anatolian Fault
(NAFNS) extends from Bolu to Izmit (Sengo
«r,
1979; Bozkurt, 2001), while the second branch
extends southward from Bolu and bifurcates
once more in the Pamukova Plain at V30‡E lat-
itude (Kocyig
it, 1988)(Fig. 1B). The northern of
these latter branches is the middle strand of the
North Anatolian Fault (NAFMS), which extends
almost east^west along Iznik Lake, Gemlik Bay
and Band|rma Bay. It changes direction around
the western part of Band|rma Bay and turns
southwestward into a fault zone formed of
many faults (Fig. 1B). The southern branch of
the North Anatolian Fault (NAFSS) is a north-
east^southwest-trending fault extending from Pa-
mukova. The NAFSS creates the Yenisehir pull-
apart basin together with another fault to the
north (Fig. 1B). It extends from Bursa to Manyas,
bending southwest from the southern part of the
Uluabat Lake, then extends in a WNW^ESE di-
rection until the southern part of Manyas Lake
(Fig. 1B). To the southwest of Manyas Lake, the
fault changes its direction to S45‡W, then extends
from Manyas to Edremit, turning into a set of
discontinuous short fault segments.
There are di¡erent views concerning the posi-
tion and character of the NAFZ both on land and
at sea. The most important debates revolve
around the Marmara Sea problem (Crampin
and Evans, 1986; Barka and Kadinky-Cade,
1988; Ergu
«n and O
ºzel, 1995; Wong et al., 1995 ;
Okay et al., 1999, 2000; Parke et al., 1999 ; Le
Pichon et al., 1999; Aksu et al., 2000; Siyako et
al., 2000; Imren et al., 2001). These recent studies
can be classi¢ed into three groups: (1) pull-apart
and combined models (Barka and Kadinky-Cade,
1988; Wong et al., 1995 ; Ergu
«n and O
ºzel, 1995;
Barka, 1992); (2) models incorporating en echelon
fault segments (Parke et al., 1999; Siyako et al.,
2000; Okay et al., 2000); and (3) models with a
single master fault beneath the Marmara Sea
(Fig. 2;Le Pichon et al., 1999 ; Aksu et al.,
2000; Imren et al., 2001). The most distinctive
structure in the Marmara Sea is a series of east^
west-trending troughs separated by NNE^SSW-
trending ridges. Here, these are called the West
Marmara Trough (WMT; the Tekirdag
Trough
of Okay et al., 1999), Middle Marmara Trough
(MMT), and East Marmara Trough (EMT ;
C|narc|k Trough of Okay et al., 2000)(Fig. 3).
Although the initial models for the evolution of
the Marmara Sea date from the 1930s, the ¢rst
modern study concerning sea£oor topography
and seismic sections is the pull-apart model of
Barka and Kadinky-Cade (1988). Subsequently,
on the basis of 1670 line-km of shallow seismic
re£ection data collected in 1987, this pull-apart
model was modi¢ed to include compressional
and tensional rhombohedral blocks to explain
the three deep basins (‘troughs’) in the Marmara
Sea (Ergu
«n and O
ºzel, 1995; Wong et al., 1995).
During the same period, based on shallow and
conventional seismic data gathered on the south-
ern shelf, Smith et al. (1995) identi¢ed east^west-
trending normal faults and proposed that the
southern part of the Marmara Basin was a half-
graben. About 1500 line-km of conventional seis-
mic data were collected by R/V Sismik-1 of the
Mineral Research and Exploration Institute of
Turkey (MTA)in 1997. Three di¡erent working
groups interpreted these data, reaching di¡erent
conclusions. Okay et al. (1999) proposed that a
so-called master fault, which borders the southern
part of the western Marmara Sea and then arrives
on land, is a northeast^southwest thrust fault to
the east of the WMT. They also proposed a nor-
mal fault in the middle of the trough and a north-
thrusting dextral fault to the west of the trough
nearest land. Okay et al. (1999) proposed that
Ganos Mountain, 10 km wide, 30 km long, and
900 m high in 28-km-thick crust (Aygu
«l and Genc,
1999), formed because of elastic bending associ-
ated with this thrust fault geometry. Parke et al.
(1999), who interpreted all of the data collected
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529494
Fig. 1. (A) Simpli¢ed tectonic map of eastern Mediterranean region (adapted from Yalt|rak et al., 1998). (B) Seismotectonic map of the Marmara Sea region (com-
piled from Sak|nc et al., 1999 ; Yalt|rak, 2000b ; Yalt|rak et al., 1998). Abbreviations: GFZ, Ganos Fault Zone ; TEFZ, Thrace^Eskisehir Fault Zone; BFFZ, Bur-
dur^Fethiye Fault Zone; NAFZ, North Anatolian Fault Zone ; EFZ, East Anatolian Fault Zone ; NEAFZ, Northeast Anatolian Fault Zone ; AFZ, Almus Fault
Zone; YEFZ, Yag
murlu^Ezinepazar| Fault Zone. (Compiled from Barka, 1992; Yalt|rak et al., 1998 ;Bozkurt, 2001.)
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529 495
during MTA’s 1997 cruise, suggested that the
NAFZ system diminishes in importance in the
Marmara region and east^west-trending normal
faults caused the evolution of the Marmara Sea.
Finally, Le Pichon et al. (1999), who interpreted
the same data after the 1999 eastern Marmara
earthquakes, claimed that there is a buried master
fault extending through the Marmara Sea. These
authors named this master fault the Great Mar-
mara Fault and proposed that this main structure
passes through the southern boundary of the
EMT, along the central axis of the MMT, and
along the southern boundary of the WMT
(Fig. 3), causing the evolution of the troughs
and ridges due to dextral shearing forces. After
the 1999 eastern Marmara earthquake, Okay et
al. (2000) combined the data sets collected by
the MTA on the East Marmara Ridge (EMR)
and its western part (314 line-km), with the pre-
vious 1997 data set (429 line-km). They proposed
that the single master fault model might not be
valid, since the fault bifurcates. The master fault
functions as a normal fault by bounding the
northern edge of the EMT in the Eastern Mar-
mara Sea (Okay et al., 2000), then crosses through
the northern part of the eastern ridge and contin-
ues N80‡W as a strike-slip fault (Okay et al.,
2000, ¢gure 2, p. 191). In another article, pub-
lished after the 1999 earthquakes, Aksu et al.
(2000) studied the Marmara fault systems based
on 3390 line-km of single-channel shallow seismic
re£ection data collected by R/V Piri Reis in 1995.
Aksu et al. (2000) suggested that the Marmara
Sea evolved as a negative £ower structure,
bounded by two west-trending sidewall faults
that are linked to a single near-vertical master
fault. Siyako et al. (2000) used 5500 line-km of
conventional multichannel seismic data collected
by the Turkish Petroleum Cooperation to propose
that three en echelon strike-slip fault segments
cross the Marmara troughs forming a negative
£ower structure, and that the Marmara troughs
are bounded by shallowly dipping normal faults.
Recently, on the basis of seismic data collected
during the MTA 1997 and 2000 cruises (2200
line-km), Imren et al. (2001) modi¢ed the model
proposed by Le Pichon et al. (1999).
Recent publications employ 8500 line-km of
deep seismic data and 5000 line-km of shallow
seismic data covering an area 200 km by 80 km
in the Marmara Sea (Barka and Kadinky-Cade,
1988; Ergu
«n and O
ºzel, 1995; Wong et al., 1995 ;
Okay et al., 1999, 2000; Parke et al., 1999 ; Le
Pichon et al., 1999; Aksu et al., 2000 ; Siyako et
al., 2000; Imren et al., 2001). Although these
studies propose internally consistent interpreta-
Fig. 2. Tectonic models of the Marmara Sea. (A) Pull-apart models. (B) ‘En echelon’ models. (C) Master fault models. Bold lines
represent the main faults which played active roles in forming the Marmara Sea. The thinner lines show secondary faults.
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529496
tions, none of them forms a synthesis combining
studies on land geology, land tectonics, gravity,
magnetics, topography and bathymetry, Global
Positioning System (GPS), stratigraphy, basin
characteristics, and seismotectonics. In this paper,
the full set of available data will be considered,
not only for the Marmara Sea but also its envi-
rons; all of the geological and geophysical data
used in previous works will be reviewed and in-
terpreted in the light of detailed land observa-
tions. Using all these of data, the evolution of
the faults and basins will be discussed.
2. Data and methods
Two data sets are utilised in this study. The ¢rst
includes structural and geological maps which
were produced from detailed geologic surveys on
land. Geological mapping was initiated in 1995 in
Eastern Thrace and the Gelibolu Peninsula.
Faults were observed from satellite images (Yal-
t|rak, 1996), de¢ned by land seismicity (Perincek,
1991), and mapped precisely based on ¢eld obser-
vations (Sak|nc et al., 1999). In the southern Mar-
mara region, the disposition of the Thrace^Es-
kisehir fault (Sak|nc et al., 1999) was determined
using satellite images and digital topographic
maps prepared from SAR interferometry, and
was then plotted on the geological maps based
on the control of ¢eld observations (Yalt|rak,
2000a). The gravity and magnetic maps of (Akdo-
g
an, 2000) and digital topography maps were con-
sulted to corroborate fault placement. The depo-
sitional units de¢ned during the ¢eld observations
Fig. 3. Sea£oor morphology and superimposed multibeam
image of the Marmara Sea. (Compiled from Ardel and Kurt-
er, 1973; Y|lmaz, 1996; Gu
«neysu, 1998; Gu
«neysu, 1999;
Aksu et al., 1999; Multibeam image from Turkish Navy, De-
partment of Navigation, Hydrography and Oceanography.)
Arrows show landslides and turbidity^current £ow directions.
Dashed lines (black/white) show landslide boundaries. Abbre-
viations: WMT, Western Marmara Trough; WMR, Western
Marmara Ridge; MMT, Middle Marmara Trough ; MMR,
Middle Marmara Ridge; KT, Kumburgaz Trough; EMR,
Eastern Marmara Ridge; EMT, Eastern Marmara Trough ;
IF, Imarl| Flat; EHT, Eastern Hersek Trough; GT, Gemlik
Trough; BT, Band|rma Trough.
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529 497
at di¡erent localities were compared in a strati-
graphic manner. The formations were dated and
the depositional environments compared (Yal-
t|rak et al., 1998; Sak|nc et al., 1999; Yalt|rak
et al., 2000a).
The second data set consists of marine seismic
pro¢les. Multichannel conventional seismic sec-
tions of Okay et al. (1999),Okay et al. (2000),
Siyako et al. (2000), and Imren et al. (2001),
and shallow seismic sections of Ergu
«n and O
ºzel
(1995),Wong et al. (1995), Smith et al. (1995),
and Aksu et al. (2000) were combined and re-in-
terpreted. This re-interpretation has resulted in a
new structural map. A bathymetric map was also
drawn for this study. The navigation charts of the
Turkish Navy and the Department of Navigation,
Hydrography and Oceanography were used with
5-m accuracy for shelf areas (Ardel and Kurter,
1973; Y|lmaz, 1996; Gu
«neysu, 1998, 1999). For
deeper areas below 100-m water depth, bathymet-
ric contours with 50-m depth contours of Aksu et
al. (1999) were utilised. These data were combined
with the multibeam swath data (20-m grid size)
collected by the Department of Navigation, Hy-
drography and Oceanography along the troughs
of the Marmara Sea (Fig. 3). On this bathymetric
map, the deep Marmara troughs, which are
known since Andrussov (1890), are clearly de-
¢ned.
The faults traced on the seismic sections were
plotted and a simpli¢ed structural map was com-
posed for the main faults at sea. From the combi-
nation of marine and land data, the fault-
bounded structural blocks in the Marmara Sea
were de¢ned. The characteristics of these bound-
ary faults are known from fault plane solutions.
Finally, palinspastic tectonical evolution maps
were drawn for every 500 000 yr using the strati-
graphic age determinations in the marine and land
areas, GPS slip vectors, and kinematic features of
the fault planes.
3. Sea£oor morphology of the Marmara Sea
3.1. Shelf areas
The shelf areas can be classi¢ed into four re-
gions: Tekirdag
, Silivri, Cekmece, and Adalar.
Many canyons cut the shelf edge and continental
slopes (Fig. 3). The shelf in the Tekirdag
region
narrows between Kumbag
and Marmara Ereg
lisi.
The arc-shaped Silivri region between Marmara
Ereg
lisi and Bu
«yu
«kCekmece has the widest shelf
area on the northern side of the Marmara Sea.
The shelf of the Ku
«cu
«kCekmece region becomes
narrower toward the Strait of Istanbul, where the
shelf edge approaches the coast. The Adalar re-
gion is separated from the western shelf area by
the Marmara canyon of the Strait of Istanbul
(Fig. 3).
On the southern shelf, there are two di¡erent
areas. To the north of the Armutlu Peninsula, the
shelf is narrow ( 61 km). Between Armutlu Is-
land and Marmara Island, the widest underwater
plain of the Marmara Sea is found (Fig. 3). This
plain is between the Kap|dag
Peninsula, Imral|
Island and Marmara Island, and extends into
Gemlik and Band|rma bays. Its slope is 1^2‡.
The most interesting features are the islands and
small troughs on the sea£oor (Fig. 3). The second
shelf area occurs to the east of the Strait of
Canakkale, where an underwater valley extends
from the strait into the WMT. This valley is con-
nected with two others running southwest of the
Kap|dag
Peninsula and Marmara Island (Fig. 3).
3.1.1. Shelf troughs
Gemlik Trough: the deepest point of Gemlik
Bay is 110 m deep, 50 m below the elevation of
the southern shelf (Fig. 3). Band|rma Trough
(BT): this is a triangular-shaped trough separated
from the 60^70-m-deep shelf area in Band|rma
Bay by a 30 m-deep sill. The trough becomes
deeper towards the city of Band|rma. To the
east of this trough, on the narrow area between
the Kap|dag
Peninsula and Band|rma, a rocky
shoal extends between the western part of the
shelf and the BT (Fig. 3). East Hersek Trough
(EHT): this trough is situated in Izmit Bay. It is
a rather narrow trough and its deepest part ex-
ceeds 200 m. It is separated from the Marmara
Sea by a ridge formed by the sediments of Hersek
Delta. The slope of its southern margin is 15‡,
while gradients are 8^10‡ along the northern slope
(Fig. 3).
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529498
3.1.2. Underwater valleys
Canakkale underwater valley : this is the east-
ward elongation of the strait. It is more than
50 km in length and terminates at the WMT.
Another valley, coming from the western part of
the Biga Peninsula, is connected to this valley
(Fig. 3). These valleys are shallow, open,
‘V-shaped’ features connected with other minor
valleys. They link to master valley branches on
land.
Istanbul underwater canyon: this feature is the
north^south-trending extension of the combined
system of the Strait of Istanbul and Golden
Horn into the EMT. It is a 7-km-long valley deep-
ening towards the trough. There is a dextral
strike-slip o¡set of V1^2 km between the land-
ward end of this canyon and its southern end
(Fig. 3).
3.2. Troughs, slopes and ridges
3.2.1. West Marmara Trough
The WMT is a rhombohedral feature with its
long axis trending northeast^southwest (Fig. 3).
Its maximum depth is 1190 m, with an average
of 1100 m. To the north, along an arc-shaped
area, there are canyons and gullies perpendicular
to the shore that cut across the continental slope
from the 100-m contour down to 1100 m depth as
slopes change from 18 to 30‡ (Fig. 3). To the
northwest of the WMT, a wide underwater debris
fan progrades to the south. This feature is 10 km
long and 8 km wide (Fig. 3). To the south of the
WMT, the gradient of the continental slope is 14^
24‡. Two canyons o¡ Marmara Island extend to
the southwest of this trough. There are two more
prominent canyons: one is the eastward extension
of the Strait of Canakkale and the other one co-
incides with the Ganos Fault Zone (GFZ) (Fig. 3).
Between these, southeast of the town of Ganos,
there is another underwater landslide fan
(12U8 km size) that extends from 100 m water
depth down to the bottom of the trough (Fig. 3).
The surface of this fan, with a slope of about 10‡,
has a step-like morphology. Bathymetric and
swath data suggest that this fan was caused by
underwater failures.
3.2.2. West Marmara Ridge
The WMR is located to the east of the WMT.
It is 440 m deep and bounded by 840-m-deep
valleys at its two sides (Fig. 3). The valley to
the north is the boundary between the WMR
and the 100-m-deep shelf (Fig. 3). To the south,
a fault step in front of Marmara Island, which
belongs to the NAFZ, forms the southern bound-
ary of the WMR. There is a valley here between
the shelf and the WMR that almost coincides with
the NAFNS and extends to the MMT.
3.2.3. Middle Marmara Trough
The MMT contains the deepest point (V1250 m)
in the Marmara Sea (Fig. 3). Many canyons per-
pendicular to the shelf edge enter the MMT from
the northern continental shelf. These canyons
terminate near the edge of the basin £oor at
V1200 m depth. To the south, canyons starting
near the shelf edge extend in a NNW^SSE direc-
tion towards the western side of the MMT (Fig. 3).
In the south^central part of the MMT, an under-
water fan with a gentle slope covers a large area.
3.2.4. Middle Marmara Ridge
The Middle Marmara Ridge (MMR) is situated
to the east of the MMT (Fig. 3). The MMR is
uplifted above the troughs to the east and west.
An east^west-trending valley cuts through its cen-
tral part, so that the centre of the ridge is its
deepest part (V650 m). Convex bulges in the
slopes north and south of the central basinal
area form the ends of the MMR (Fig. 3).
3.2.5. Kumburgaz Trough
The Kumburgaz Trough (KT) is an 820-m-deep
trough located to the east of the convex central
valley traversing the MMR (Fig. 3). It has the
shape of an ellipse extending ENE^WSW and ap-
pears to have formed by partial ¢lling of a valley
during uplift of the MMR (Fig. 3).
3.2.6. East Marmara Ridge
The EMR is situated to the west of the KT
(Fig. 3). It is a 640-m-deep rise trending in an
east^west direction for about 24 km, located be-
tween the KT and the EMT. There is a 400-m
elevation di¡erence between the western and east-
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529 499
ern edges of the EMR, the west side being shal-
lower. Relative to its height, this is a rather wide
ridge (Fig. 3).
3.2.7. East Marmara Trough
The easternmost depression in the Marmara
Sea is the triangular-shaped EMT (Fig. 3). The
widest part (10 km) of this 1200-m-deep trough
is located to the west. The EMT becomes nar-
rower eastward as it approaches the western
part of Izmit Bay (Fig. 3). In the Adalar region
(Prince Islands), many canyons extend down to
the bottom in a north^south direction. In its west-
ern part, to the south of the Strait of Istanbul,
large underwater fans supplied by slope failures
are evident in front of these canyons (Alpar and
Yalt|rak, 2000). O¡shore Tuzla, ridges between
the canyons are eroded in the shape of concave-
northwards arcs (Fig. 3). To the south of the
EMT, there are also many canyons extending
downslope from the Armutlu Peninsula (Fig. 3).
The convex anomaly, 20 km long and 1 km wide,
extending into the trough at V29‡E latitude is an
underwater landslide (Alpar and Yalt|rak, 2000).
Along the southwestern part of the EMT, the
slopes are rather smooth. To the west of this
smooth slope, two canyons extend from the vicin-
ity of Imral| Island toward the trough (Fig. 3).
3.2.8. Imral| Flat
The Imral| Flat (IF), which is situated in the
area between Imral| Island and the southwest
edge of the EMT, has a di¡erent morphology
than either the shelves and the troughs. The deep-
est point on this plain is at V3420 m. It becomes
shallower (to V300 m) towards the northeast.
The IF has a rhombohedral shape (20U16 km).
There are no deep or apparent canyons along the
southern slopes (Fig. 3).
4. Regional geology and basins
There are two main sedimentary successions in
the Marmara region, with di¡erent stratigraphic
features. These formed during the early Miocene^
early Pliocene and late Pliocene^Recent. These
sequences developed during the activation of
two di¡erent fault systems : the Thrace^Eskisehir
Fault Zone (TEFZ), and extensions of the NAFZ
(Fig. 1). The Thrace Neogene Basin developed
under the control of the GFZ, the Band|rma^Beh-
ramkale Fault Zone (BBFZ) and the Manyas^
Edremit Fault Zone (MEFZ), the TEFZ itself
and its splays. The basins of the Marmara Sea,
Saros, Manyas^Ulubat, Bursa, Yenisehir, Iznik
and Go
«nen developed under the control of the
Marmara strands of the NAFZ (Fig. 4).
4.1. Thrace Neogene Basin (early Miocene^
early Pliocene)
The Thrace Neogene Basin can be divided into
three early Miocene^early Pliocene sub-basins,
mutually related laterally and covering the mod-
ern basins of Southern Marmara, the Marmara
Sea and Eastern Thrace (Fig. 4). The northern-
most one is the Ergene Sub-basin (ES-B) devel-
oped under the control of the TEFZ (Fig. 4). To
the south, the Gelibolu^Marmara Sub-basin is lo-
cated on the GFZ where it was inverted from the
TEFZ (see Fig. 4; GMS-B). The other basin is the
Southern Marmara Sub-basin, which covers the
southern shelf of the Marmara Sea and adjacent
land area. It is situated above the BBFZ and the
MEFZ that were inverted from the TEFZ (Figs. 4
and 5).
4.1.1. Ergene Sub-basin
The central part of the East Thrace Peninsula is
underlain by sediments deposited in the early
Miocene^early Pliocene ES-B (Figs. 4 and 5).
The ES-B rests unconformably on upper Oligo-
cene lacustrine units at its base and conglomerates
toward the basin edges. The fossils found at the
base of the basin ¢ll indicate an age of early^mid-
dle Miocene (Sak|nc et al., 1999). The sequence
passes upward into braided river deposits. Ande-
sitic and shoshonitic volcanic rocks are interca-
lated with these sediments, and intrusive equiva-
lents cut these units locally along the TEFZ.
These volcanics give radiometric ages of 21^15
Ma and basic volcanic rocks give 15^5 Ma
(Y|lmaz and Polat, 1998). In the ES-B, the young-
est units are lacustrine limestones and intercalated
sandstones deposited in a zone of normal faults
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529500
that were formed by the southward migration of
the TEFZ. Alluvial fans composed of upper Plio-
cene^Quaternary reddish conglomerates uncon-
formably overlie all these units and also the
TEFZ (Fig. 5)(Sak|nc et al., 1999).
4.1.2. Gelibolu^Marmara Sub-basin
This sub-basin covers the area of the central
and western part of the Marmara Sea, Gulf of
Saros and Gelibolu Peninsula (Figs. 4 and 5).
Speckled mudstones overlie the basement uncon-
formably, passing upward into braided £uvial de-
posits and contemporaneous shoreline facies
(Sak|nc et al., 1999). Fossils indicate an early to
early^late Miocene age (Yalt|rak et al., 1998 ;
Sak|nc et al., 1999). The thickness of the basin
¢ll varies, and becomes thinner towards the
fault-controlled basin edges. In the Alc|tepe bore-
hole on the Gelibolu Peninsula, the succession is
1000 m thick (Yalt|rak et al., 1998 ; Yalt|rak and
Alpar, 2002a). Uppermost, lagoonal, fossiliferous
limestone layers (late Miocene^early Pliocene) are
intercalated with siliciclastics deposits (Yalt|rak et
al., 1998; Sak|nc et al., 1999). Toward the basin
edges, the £uvial series observed at the base pass
laterally into more distal central basin deposits.
On the Gelibolu Peninsula, upper Pliocene^upper
Pleistocene alluvial fan units rest unconformably
above this concordant sequence ; they accumu-
lated under the in£uence of the Anafartalar
Thrust Fault (Fig. 5)(Yalt|rak et al., 2000a). Dur-
ing early Miocene^early Pliocene, the GMS-B was
developed over a fault system in which negative
and positive £ower structures operated together,
under the control of the dextral GFZ. The gently
dipping normal faults, which bound the shelf
edges of the modern western and central Mar-
mara Sea, and ENE^WSW-trending master fault
Fig. 4. Early and late neotectonic features superimposed on the basins of the Marmara region. Abbreviations of main fault
zones: TEFZ, Thrace^Eskisehir Fault Zone; GFZ, Ganos Fault Zone; BBFZ, Band|rma^Behramkale Fault Zone ; MEFZ,
Manyas^Edremit Fault Zone. (Compiled from Siyako et al., 1989; Yalt|rak et al., 1998, 2000b; Sak|nc et al., 1999.) Abbrevia-
tions: (1) sub-basins in Thrace Neogene Basin: ES-B, Ergene Sub-basin; GMS-B, Gelibolu^Marmara Sub-basin; SMS-B, South
Marmara Sub-basin; (2) Marmara region basins, (a) Marmara Sea basins : WMS-B, West Marmara Sub-basin ; MMS-B, Middle
Marmara Sub-basin; KS-B, Kumburgaz Sub-basin; EMS-B, East Marmara Sub-basin; BS-B, Band|rma Sub-basin; GS-B, Gem-
lik Sub-basin; EHS-B, Izmit Sub-basin; (b) Marmara land basins: ILB, Iznik Lake Basin; YB, Yenis ehir Basin; INB, Inego
«l Ba-
sin; BB, Bursa Basin; M-UB, Manyas^Uluabat Basin; GB, Go
«nen Basin.
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529 501
Fig. 5. Geological map of the Marmara region. (Compiled from Ergu
«l et al., 1986; Siyako et al., 1989 ; Yalt|rak et al., 1998 ; Sak|nc et al., 1999 ; Yalt|rak and Al-
par, 2002b; Alpar and Yalt|rak, 2002 and ¢eld study.)
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529502
controlled the GMS-B. In the area placed between
these faults, the sediments, which become as thick
as 1000 m towards Gelibolu, were deposited on
the basinal axis.
4.1.3. South Marmara Sub-basin
The Neogene series penetrated by boreholes on
the southern Marmara shelf are made up of lacus-
trine units intercalated with volcanic rocks at the
base (Marathon Petroleum, 1976). Upward, these
units gradually pass into strata equivalent to the
multicoloured terrestrial series observed at the
base of the GMS-B (Marathon Petroleum,
1976). These units seem to be the lateral continu-
ation of the area between Gelibolu and Gaziko
«y
on the southern Marmara shelf (Figs. 4 and 5).
The South Marmara Sub-basin (SMS-B), which is
situated between Gemlik and Band|rma and split
into two by the Mudanya^Band|rma uplift under
the e¡ect of the NAFZ at present, contains a ¢ll
of conglomerates and sandstones around Bursa,
Manyas, Uluabat and northward. To the south,
the dominant units are sandstones intercalated
with volcanic ash and occasional coal layers.
The thickness of these units is rather variable (Er-
gu
«l et al., 1986). The sandstone units are locally
folded and overturned, showing local internal un-
conformities. Their ages cover a period between
the middle Miocene and early Pliocene (Ergu
«let
al., 1986; Emre et al., 1998 ; Yalt|rak, 2000a). The
faults controlling the SMS-B are those extending
westward from the TEFZ, with similar character-
istics to those of the GFZ (Figs. 4 and 5). These
are the BBFZ to the north and the MEFZ to the
south (Figs. 4 and 5).
4.2. Marmara region basins (late Pliocene^
Recent)
The Marmara basins are superimposed, under
the control of the NAFZ, on the component sub-
basins of the Thrace Neogene Basin (Fig. 4). The
sediments were deposited in the late Pliocene and
later, unconformably above the Thrace Basin
(Figs. 4 and 5)(Sak|nc et al., 1999). Middle Mio-
cene^lower Pliocene units on the Istanbul, Kocae-
li and Armutlu Peninsulas represent low-energy
depositional environments (Sak|nc et al., 1999;
Alpar and Yalt|rak, 2002). These units are over-
lain by small-scale basins re£ecting the e¡ects of
the NAFZ (Figs. 4 and 5).
4.2.1. Marmara Sea Basin
Sediments in the Marmara Sea Basin (i.e. the
modern Marmara Sea) unconformably overlie a
variety of older rocks. This depression started its
evolution in the late Pliocene, superimposed on
units of early Miocene^early Pliocene age belong-
ing to the basins of Marmara^Gelibolu and South
Marmara (Fig. 4)(Yalt|rak, 1996 ; Yalt|rak et al.,
2000a). On the northern shelf, the Neogene units
have been completely eroded except in the area
around and to the south of Istanbul. The thick-
ness of the Neogene series is about 1000 m in the
Doluca and Is|klar boreholes drilled on the south
and west Marmara shelves (Marathon Petroleum,
1976; Yalt|rak et al., 1998 ; Yalt|rak and Alpar,
2002a). The Marmara Sea Basin can be divided
into eight sub-basins that can be de¢ned by
troughs and ridges of di¡erent depths and sizes
(Figs. 4 and 5). Five of them are on the northern
strand of the NAFZ. Three of them are di¡erent
from the rest in terms of their depths and sizes.
Twenty-six published multichannel seismic pro-
¢les (Okay et al., 1999; Okay et al., 2000 ; Siyako
et al., 2000; Imren et al., 2001), cutting across
these sub-basins, were reinterpreted and sixteen
of these, together with 3390 line-km of high res-
olution seismic data (49 lines) have been used in
this study (Fig. 6).
The Marmara Sea Basin, which is de¢ned by
the present coastline, is made up of deep troughs
and bounding shelf areas. These deep troughs
each have di¡erent basinal characteristics and
we denote them as sub-basins in this study, in-
stead of using the term ‘trough’, which is a mor-
phological term. For example, the Imral| Trough
(Okay et al., 2000) has no characteristics of a
morphological trough. On the contrary, the area
northeast of Imral| Island is a step-shaped plat-
form (Fig. 3), 400 m below present sea level. It is
located below a shelf in the shape of a isosceles
triangle, with two sides of 25 km and a base line
of 30 km, to the west of the Armutlu Peninsula.
This implies that this platform is not a trough,
and should be termed the Imral| Sub-basin due
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529 503
to its depositional characteristics and bounding
faults. Similarly, the troughs in the central Mar-
mara Sea must be considered neighbouring sub-
basins separated by saddles. Underwater failures,
turbidite fans, abyssal plain deposits, deformed
ridges and basin-controlling faults serve to de¢ne
these sub-basins. In conclusion, we prefer using
the term ‘sub-basin’, rather than ‘trough’, in order
to emphasise both the sedimentary units and
faults.
4.2.1.1. West Marmara Sub-basin
The maximum depth of this sub-basin is 1190
m. Except along its eastern side (640 m), it is
bounded by shelf areas (100 m). This rhomboidal
sub-basin covers the area of the WMT and its
environs (Figs. 3 and 4). The deposits in the
West Marmara Sub-basin (WMS-B) are thicker
than 2000 m (Okay et al., 1999). The WMS-B is
interpreted as a negative £ower structure which
formed under the control of the northern strand
of the North Anatolian Fault, which passes to the
south. The block to the south of this fault con-
tains folded sediments (Fig. 7, Seismic Lines 05
and 06). In this part of the WMS-B, deposits
north of the fault are horizontal (Fig. 7, Seismic
Lines 05 and 06). Due to the releasing bend na-
ture of the main fault, normal faults can be seen
in the seismic pro¢les. The folding to the south, in
contrast, is caused by dextral shearing of the
southern block. To the southwest of the sub-ba-
sin, imbricated landslides have prograded north-
ward by overlapping horizontal deposits of the
basin £oor (Figs. 3 and 8, Seismic Line 03). The
imbricated geometry of these landslide packages
(Fig. 8) has been interpreted as a thrust fault by
Okay et al. (1999), who believed that the complex
deposits overlying the horizontally bedded sedi-
ments were in the hanging wall of the thrust.
However, this complex structure corresponds to
a typical landslide complex; its lineated surface
is evident on the multibeam bathymetry map
(Fig. 3).
To the northwest, a low-angle normal fault
bounds this sub-basin (Fig. 7, Seismic Line 05).
Young deposits overlap this fault. In this area,
there are no landslides similar to those observed
south. Instead, wide submarine fans spread basin-
ward in front of many small canyons (Fig. 3). To
the east of the WMS-B, the WMR has been up-
lifted under the control of a northeast^southwest-
trending thrust fault leading to folding of the east-
ern part of the ¢ll of the sub-basin (Fig. 7, Seismic
Lines 01 and D8). The WMR is completely com-
Fig. 6. Seismic Line location map. This study includes two di¡erent types of seismic sections. Thin dashed lines are one-second-
penetration high-resolution seismic pro¢les (data from Ali Aksu and Richard Hiscott, Memorial University of Newfoundland; to-
tal 3390 km). Multichannel deep-penetration seismic pro¢les are from Okay et al. (1999, 2000),Siyako et al. (2000), and Imren
et al. (2001).
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529504
Fig. 7. Re-interpreted and not interpreted time-migrated seismic re£ection pro¢les (from Okay et al., 1999, 2000; Siyako et al.,
2000; Imren et al., 2001). Seismic Lines 03 and D8 were re-interpreted in this study. Seismic line T4 was interpreted by Siyako et
al. (2000).
MARGO 3175 11-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529 505^508
posed of folded sediments and its northern
boundary has a thrust character (Fig. 7, Seismic
Line D8).
4.2.1.2. Middle Marmara Sub-basin
The Middle Marmara Sub-basin (MMS-B),
located in the middle of the Marmara Sea
(Fig. 4), resembles a parallelogram. It includes
the 1250-m-deep MMT (Fig. 3) and also the
gentle surrounding slope areas. northwest^south-
east-trending, step-wise normal faults mark the
east and west margins of the basin. The other
two margins of the basin are the southern and
northern shelves landward of gently dipping
normal faults (Figs. 6 and 7,SeismicLineD2).
The northern strand of the NAFZ crosses the
centre of the basin in a direction of N80‡E
(Figs.3,4,6and7, Seismic Line D2). The basin
is under the control of the normal faults which
developed due to dextral shearing forces. The
sediment thickness is more than 2.5 km (Imren
et al., 2001), supplied through the canyons ex-
tending from the southern and northern shelves
(Fig. 3).
Fig. 8. Not interpreted (from Okay et al., 1999)(A) and re-interpreted (this study) (B) time-migrated seismic re£ection pro¢les
along Seismic Line 02. This seismic line shows a landslide complex and the North Anatolian Fault North Segment (Ganos
Fault). (C) Location of the seismic line and position of the northern segment of the North Anatolian Fault.
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529 509
4.2.1.3. Kumburgaz Sub-basin
To the northeast of the MMR, the northeast^
southwest-elongated Kumburgaz Sub-basin (KS-
B) is 800 m deep (Figs. 6 and 7, Seismic Line
14). Along its northern side, the KS-B is con-
trolled by a strike-slip fault, almost vertical but
dipping southward and with a normal component
of motion. There is also a thrust fault bounding
the northwest edge of the EMR (Figs. 3, 4, 6 and
7, Seismic Line 15). Younger sediments are £at
lying but older layers become progressively more
folded.
4.2.1.4. East Marmara Sub-basin
The East Marmara Sub-basin (EMS-B) has the
shape of an acute triangle between the Kocaeli
and Armutlu Peninsulas. It includes the eastern
£anks of the EMT and EMR (Figs. 3 and 4).
The northern edge of this sub-basin is outlined
by normal faults, which are almost vertical to
the east, while dipping southward to the west
(Figs. 6 and 7, Seismic Lines T4, 33, 29, 30).
The southern edge of this sub-basin, on the other
hand, is outlined by the eastern segment of the
northern strand of the NAFZ, which is dextral
strike-slip fault trending east^west and dipping
northward (Figs. 6 and 7, Seismic Lines 29, 30,
37, 33). To the west of the sub-basin, the mean
sea bottom slope is about 8‡ between a 12-km-
wide area forming the deepest part of the basin
(1200 m) and the top of the EMR (500 m).
Young deposits in the western part of the basin
are folded and even imbricated due to dextral
shearing ; this shearing has also caused the east-
ern £ank of the EMR to be folded and uplifted
(Figs. 6, 7 and 9A,B, Seismic Lines 15, M13). The
EMR is an anticline formed by compression, but
the near-surface faults record shallow gravity-
driven extension along the anticline axis and
give a wavy appearance to the surface of this
ridge (Fig. 9B,C). These structures were inter-
preted as mega-ripples by Imren et al. (2001)
and as folds by Okay et al. (2000). Similar struc-
tures elsewhere in the Eastern Mediterranean re-
gion were considered as mega-ripples by Ediger et
al. (2000). However, these other structures are
also clearly shallow normal faults (A.E. Aksu,
pers. commun., 2001) like those on the EMR
(Fig. 9C).
4.2.1.5. East Hersek Sub-basin
The East Hersek Sub-basin (EHS-B) covers a
portion of Izmit Bay east of the Hersek Delta. Its
deepest point is 204 m in the EHT (Fig. 3). This
sub-basin is developing on the releasing bend of
the northern strand of the NAFZ, caused by
small jumps between related fault segments where
the NAFZ enters the Marmara Sea. In the eastern
parts of this rather young sub-basin, the Holocene
deposits unconformably overlie acoustic basement
(Alpar and Yalt|rak, 2002).
4.2.1.6. Imral| Sub-basin
This sub-basin lies below the 300^400 m-deep
IF (Fig. 3), located between the EMT and the
southern Marmara shelf o¡ the Armutlu Peninsu-
la. The IF becomes shallower northwestward and
forms the centre of this sub-basin (Fig. 3). Con-
sistent with the dextral movement of the Imral|
Fault Zone (IFZ) and the NAFNS, but also re-
£ecting the normal component of motion on the
IFZ, this sub-basin has developed due to tilting of
the hanging-wall block (Figs. 3, 4, 6, 7, Seismic
Lines 15, 33). Dextral faults extending along the
northwest coast of the Armutlu Peninsula accom-
modate the subsidence of the basin £oor (Fig. 7,
Seismic Line, and Fig. 10).
4.2.1.7. Band|rma and Gemlik Sub-Basins
The Band|rma Sub-Basin (BS-B) and the Gem-
lik Sub-basin (GS-B) are situated on the middle
strand of the NAFZ near the south coast of the
Marmara Sea (Figs. 1 and 10). They are located
in Band|rma and Gemlik Bays. The GS-B is situ-
ated at a water depth of 110 m and has the shape
of an ellipse with a northwest^southeast major
axis. It is a pull-apart basin caused by the inter-
section of the middle strand of the NAFZ with an
older northwest^southeast-oriented fault system
(Yalt|rak and Alpar, 2002b). The BS-B covers
an area which is separated from the rest of the
Marmara Sea by a 60^70 m-deep sill east of the
triangular BT (Fig. 3). It has developed above a
small-scale releasing bend where the west-trending
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529510
middle strand of the NAFZ bends southwest at
Band|rma Bay.
4.2.2. Iznik Lake Basin
Iznik Lake Basin (ILB) is located beneath Iznik
Lake. It has subsided under the control of the
middle strand of the NAFZ, located near its
southern shoreline (Fig. 5), and step-wise normal
faults to the north, which are oblique to the
strike-slip fault (Figs. 3, 4 and 10). It is separated
from Gemlik Bay by a narrow valley. Quaternary
alluvial fans occur in front of the faults along the
southern shores of the lake (Figs. 5 and 10). In
this area there are many step-wise and small-scale
normal faults, which are parallel to the master
fault.
Fig. 9. Not interpreted (from Okay et al., 2000) (A) and re-interpreted (this study) (B) time-migrated seismic re£ection pro¢le
along Seismic Line M13. (C) This seismic line shows the EMR. The anticlinorium is controlled by two major thrust faults. While
folding processes are dominant in the core of the anticlinorium, upward some domino-type shallow normal faults developed on a
detachment surface due to the extension occurring on that surface.
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529 511
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529512
4.2.3. Yenisehir Basin
The Yenisehir Basin (YB) is located on land
atop the southern branch of the NAFZ (Figs. 5
and 10). It is a pull-apart basin developed due to
jumping of the southern branch of the NAFZ to
another nearby dextral segment. The basin started
to develop in the late Pliocene. The rhombohedral
Yenisehir Plain forms the centre of this basin
(Figs. 5 and 10). Strike-slip faults bound the basin
edges and largely encompass the Pliocene basin
¢ll (Yalt|rak, 2000a). For example, the thickness
of young alluvial deposits is 1^2 m beyond the
southwestern edge of the basin, thickening to
80 m just northeast of the basin-bounding fault
(Yalt|rak, 2000a).
4.2.4. Inego
«l basin
The Inego
«l Basin (IB) initially developed on the
Thrace^Eskisehir Fault. It was uplifted and par-
tially eroded during the Miocene under the con-
trol of strike-slip tectonics (Kaymakc|, 1991)
(Figs. 5 and 10). More recently, these strike-slip
faults were reactivated as normal faults by move-
ment on the southern strand of the NAFZ, caus-
ing subsidence of the Inego
«l Plain and IB to re-
commence.
4.2.5. Bursa Basin
The Bursa Basin (BB) overlies the Neogene
Southern Marmara Basin (Figs. 4, 5 and 10).
The dextral strike-slip fault outlining the northern
boundary of the Yenisehir Basin crosses the
southern part of the Bursa Plain (Figs. 5 and
10;Yalt|rak, 2000a). The town of Bursa, Mount
Uludag
and its slopes are situated on the alluvial
fans developed in front of the normal faults
parallel to this fault. Some normal faults, re-
activated by the intersection of the southern
strand of the NAFZ with the northwest^south-
east-trending TEFZ, outline the eastern border
of the triangular-shaped Bursa Plain (Figs. 5
and 10).
4.2.6. Manyas^Uluabat Basin
The Manyas^Uluabat Basin (M-UB) is super-
imposed on the Southern Marmara Basin and has
developed under the control of the NAFZ (Fig. 4).
The southern strands of the NAFZ to the south
of the basin control modern sedimentation. This
fault is made up of three segments. Its western
and eastern segments exhibit strike-slip while the
central part is a normal-oblique fault on which
the Manyas and Uluabat Lakes have developed
(Figs. 4, 5 and 10). Holocene alluvial deposits
overlie Pliocene conglomerates at the margins of
this wide plain with angular unconformity. To the
north of the basin, between Karacabey and
Band|rma, the boundary between the alluvial
and Neogene deposits forms a distinct morpho-
logical step. Rivers that extend southward across
this step have carved deep trenches. The M-UB
has opened along normal faults with a dextral
oblique component. These faults are located to
the north and south of the basin.
4.2.7. Go
«nen Basin
The Go
«nen Basin (GB) developed where the
middle and southern strands of the NAFZ be-
came closest to each other (Figs. 4 and 10). Qua-
ternary alluvium ¢lls this fault-bounded basin, un-
conformably overlying folded Neogene rocks of
the Southern Marmara Sub-basin. The basin de-
veloped here because of opening between the ‘el-
bows’ of the various fault strands, caused by
southwestward bending of the southern strand
of the NAFZ.
Fig. 10. Tectonic map of Marmara region (land area compiled from Ergu
«l et al., 1986; Siyako et al., 1989 ; Yalt|rak et al., 1998 ;
Sak|nc et al., 1999 ; Yalt|rak and Alpar, 2002b ; Alpar and Yalt|rak, 2002 and ¢eld study). Faults on the map were identi¢ed on
LANDSAT 5TM images and through ¢eld observations. Marine faults were mainly mapped using the shallow-penetration seismic
lines of the Memorial University of Newfoundland. Not interpreted deep lines are from Okay et al. (1999, 2000); Siyako et al.
(2000); Imren et al. (2001). Fault plane solutions are from Taymaz, (1990, 1999, 2000);Kalafat (1995), and Gu
«rbu
«z et al. (2000).
GPS vectors are plotted with respect to a ¢xed station at Istanbul (black star) (from Straub et al., 1997). Abbreviations: TEFZ,
Thrace^Eskis ehir Fault Zone; WMS-B, West Marmara Sub-basin; MMS-B, Middle Marmara Sub-basin; KS-B, Kumburgaz
Sub-basin; EMS-B, Eastern Marmara Sub-basin; BS-B, Band|rma Sub-basin; GS-B, Gemlik Sub-basin; EHS-B, Eastern Hersek
Sub-basin; ILB, Iznik Lake Basin; YB, Yenisehir Basin; INB, Inego
«l Basin; BB, Bursa Basin; M-UB, Manyas^Uluabat Basin;
GB, Go
«nen Basin.
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529 513
5. Tectonic setting
As there are no detailed structural maps for the
Marmara region, the exact location of the strands
of the NAFZ on the land are not well established.
The structural architecture of the region is com-
piled using existing 1:250 000 ¢eld maps,
1 :500 000 satellite imagery, and digital topogra-
phy maps (Figs. 5 and 10). This compilation re-
vealed the presence of two di¡erent-aged systems
in the Marmara Sea region, which intersect each
other. The peculiar geometrical shapes of the
Marmara Sea and the faults extending around
its surroundings have clear di¡erences in their ori-
entation. The most important is the N45‡W-
trending TEFZ (Figs. 5 and 10). Others are the
N80‡E-oriented GFZ, the N45‡E-oriented BBFZ
and, parallel to this, the MEFZ (Figs. 5 and 10).
With the exception of the TEFZ, these faults con-
tinue their activity controlled by the activity in the
NAFZ. The splays of the TEFZ, which stay with-
in the in£uence area of the NAFZ, play an active
role in the evolution of the present geometry of
the Marmara Sea.
5.1. Northwest Anatolia early neotectonic period
(early Miocene^early Pliocene) fault systems
Early Miocene^early Pliocene faults in North-
west Anatolia include the dextral strike-slip
TEFZ, which was active prior to the NAFZ,
and its westward de£ections, the GFZ, BBFZ
and Edremit-Go
«nen Fault Zone (Figs. 5 and 10).
5.1.1. Thrace Eskisehir Fault Zone
At present, the TEFZ is dissected by the strands
of the NAFZ and divided into four segments
(Figs. 5, 9 and 11). Studies on the TEFZ in
Eskisehir^Ino
«nu
«(Go
«zler et al., 1985; Bozkurt,
2001), Inego
«l(Kaymakc|, 1991), Bursa^Mudanya
(Yalt|rak, 2000a), and Thrace (Perincek, 1991) de-
¢ne a major dextral strike-slip system which was
active during the early Miocene^early Pliocene.
5.1.1.1. Eskisehir^Inego
«l Segment
This segment of the TEFZ occurs between Bur-
sa and Tuzgo
«lu
«and is known under di¡erent
names. Kaymakc| (1991) called the Inego
«l Seg-
ment the ‘Inego
«l Fault Zone’. Altunel and Barka
(1998) de¢ned the Eskisehir Segment of the TEFZ
as a normal fault. Bozkurt (2001) proposed that
the TEFZ is a dextral normal fault developed
during the Plio^Quaternary period. The Es-
kisehir^Inego
«l segment is the longest segment
(400 km) of the TEFZ, extending between the
western part of the Tuzgo
«lu
«and Bursa through
Eskisehir (Fig. 11A,B). In many localities to the
south, this fault segment is buried beneath Plio-
cene and Quaternary units. Around Tuzgo
«lu
«, Es-
kisehir, Ino
«nu
«, and Inego
«l(Fig. 1A), Miocene
dextral strike-slip faults later reactivated as nor-
mal faults creating Quaternary basins. This is also
clearly visible on the Bouguer and magnetic maps
prepared by MTA as well as on digital SAR in-
terferometry topography maps (Fig. 11C,D).
5.1.1.2. Bursa^Mudanya Segment
This segment is V48 km long and occurs be-
tween Bursa and Mudanya (Yalt|rak and Alpar,
2002b). It exhibits characteristics of a normal
fault and plays an important role throughout
the evolution of the Bursa Plain (Figs. 5 and 10).
5.1.1.3. Imral| Segment
The Imral| segment is a V62 km long, north-
west^southeast-trending fault which occurs be-
tween Gemlik Bay and the Imral| Sub-basin. In
Gemlik Bay, and between the eastern part of the
Imral| Island and the MMS-B it displays charac-
teristics of a normal fault (Figs. 5 and 10).
5.1.1.4. Adalar^Thrace Segment
This segment starts from Tuzla and extends to
Thrace. It is the extension of the Imral| segment,
which was o¡set by the northern strand of the
NAFZ. It outlines the northern boundary of the
EMS-B, where it displays normal sense separa-
tions (Figs. 6 and 10). Farther west, it loses its
normal character and extends toward Thrace
along the northern edge of the Central Marmara
Trough, in the form of three parallel strike-slip
zones (Figs. 5 and 10). The dextral strike-slip fault
zone de¢ned by a horsetail structure has initially
been mapped by Perincek (1991). At present, this
structure, which is V220 km long in East Thrace,
and the northwest^southeast-trending zone is cov-
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529514
ered by Plio^Quaternary deposits (Figs. 5 and 10).
This fault zone continues northward into Bulga-
ria, and one strand of it bends southward con-
necting with the Xanti^Kavala Fault in Greece
(Tap|rdamaz and Yalt|rak, 1997).
5.1.2. Ganos Fault Zone
The GFZ starts from the KS-B and is com-
posed of southward bending faults of the TEFZ
(Figs. 5 and 10). It continues towards the North
Aegean Trough. The GFZ is V700 km long. To
Fig. 11. (A) Digital elevation model map of West Turkey from Gaziog
lu et al. (2002). Arrow shows TEFZ. (B) Main tectonic
lines drawn from superimposed digital elevation model map, gravity and magnetic maps. Abbreviations: TEFZ, Thrace^Eskisehir
Fault Zone; BFFZ, Burdur^Fethiye Fault Zone; NAFZ, North Anatolian Fault Zone. (C) Shaded Bouguer anomaly map of
West Turkey (T = 20 km) from Akdog
an (2000). Arrow shows TEFZ. (D) Shaded total magnetic intensity map of West Turkey
from Akdog
an (2000). Arrow shows TEFZ.
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529 515
the west, the south and north boundaries of the
GFZ are the gently sloped normal faults de¢ning
the primitive structure of the Marmara Sea
(Figs. 1, 5 and 6). Between these boundary faults,
there are the northeast^southwest-trending
WMR, the Ganos Mountain, Dolucatepe, Helva-
tepe, Anafartalar Thrust Fault, which are all lo-
cated on the GFZ, occurring oblique to, and to
the north and south of the master fault (Yalt|rak
and Alpar, 2002a). Westward, the GFZ joins the
North Aegean system (Fig. 1B). In the present-
day Gulf of Saros, the GFZ continues as a neg-
ative £ower structure controlled by the master
fault, with compression to the south, i.e. the Gel-
ibolu Peninsula (Yalt|rak et al., 1998, 2000a,b).
The most distinguishing feature of this structure
is its geometry. This V-shaped structure along the
main fault composed of compressional and exten-
sional blocks is similar to splays deviating from
the master fault (e.g. the Yag
murlu^Ezinepazar
Fault Zone and the Almus Fault Zone on the
NAFZ; Bozkurt and Kocyig
it, 1996;Bozkurt,
2001).
5.1.3. Band|rma^Behramkale Fault Zone
The Band|rma^Behramkale Fault Zone (BBFZ)
extends from the Band|rma Bay to the western
part of Edremit Bay and is composed of a number
of strike-slip faults of varying lengths (Figs. 1, 5
and 6;Siyako et al., 1989). This fault zone de¢nes
the interface between the Neogene units and the
basement rocks to the south. Most of these seg-
ments are dextral and developed early Miocene^
late Miocene depocentres dominated by local
compression (Siyako et al., 1989). A net displace-
ment of 8 km has been determined on a segment
of this fault zone (see Inova^Sar|ko
«y Fault; Siya-
ko et al., 1989). Besides, there are 1^5 km o¡sets
on other segments. It is highly possible that this
system evolved as a fault bundle controlled by the
internal deformations in the block to the south of
TEF and GFZ.
5.1.4. Manyas-Edremit Fault Zone
The Manyas-Edremit Fault Zone (MEFZ) con-
sists of en echelon faults, extending northeast^
southwest from Go
«nen to Edremit Bay, within a
10^15-km-wide zone (Figs. 1, 5 and 6). It forms
the interface between the Neogene units and the
basement to its northwest. Many small-scale ter-
restrial basins have been developed along this dex-
tral strike-slip fault. In one of these basins near
Kalk|m, the sediments intercalate with middle
Miocene volcanic rocks forming a boundary be-
tween the faults and Neogene (Fig. 5). The layers
of these deposits, which are folded and almost
upright in position, imply that the activities of
these faults even continued after the basin evolu-
tion.
5.2. Northwest Anatolia late neotectonic period
(late Pliocene^Present) fault systems
The three strands of the NAFZ in the Eastern
Marmara region came into existence in the late
neotectonic period. These faults are superimposed
on the early neotectonic fault systems.
5.2.1. Northern strand of the North Anatolian
Fault Zone
The NAFNS starts from Bolu and reaches to
the Eastern Marmara area through Izmit Bay
(Fig. 1). In the Eastern Marmara Sea region, the
NAFZ dips north and can be traced to the west-
ernmost end of the EMT (Figs. 6, 9 and 12).
Further west, the NAFNS is connected to GFZ
of the EMR within an V10-km wide region
(Figs. 7, 9 and 12). The EMR is a typical restrain-
ing band, similar to those observed in dextral
strike-slip systems (Sylvester, 1988; Ben-Avra-
ham, 1992). The oblique tension developed be-
tween the Adalar Fault Zone, the northern
boundary of the EMT. The oblique extension be-
tween the Adalar Fault Zone, extending north of
the EMT, and the North Anatolian Fault caused
the opening of the EMS-B. Because the GFZ
crosses the MMT obliquely southward the
oblique compression caused the development of
the ENE^WSW-trending MMR. Because the
GFZ changes its direction westward, WNW^
ESE-trending normal faults created the MMS-B
(Figs. 7, 8, 10 and 12). Further west, the GFZ,
trends westward, causing the development of the
northeast^southwest-trending WMR (Figs. 7, 8,
10 and 12). This typical push-up is controlled by
the thrust faults developed at an angular to the
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529516
right-lateral movement (Sylvester, 1988). To the
west of the WMR, the BMS-B opened as the re-
sult of a north^south extension created by the
bending associated with compression in the GFZ
(Figs. 7, 10 and 12). Further west, GFZ extends
to the Northern Aegean Sea crossing a land
bridge (Figs. 1 and 10). At present, in the central
and western Marmara Sea region, the sub-basins
and ridges continue their evolution in a tectonic
regime superimposed on the negative £ower struc-
ture created by the GFZ (Figs. 6, 9, 12 and 13).
Further east, due to intersection of the TEFZ and
the NAFZ, the Thrace^Eskisehir fault trending
45‡ oblique to the NAFZ (i.e. Adalar and Imrali
Fault Zones) gains activity created by the exten-
sional regime consistent with the right-lateral
strike-slip systems. These faults were converted
into normal faults (Fig. 10). Thus, the GFZ and
the northern strand of the NAFZ are connected
to each other under the CMR, which will transmit
the dextral movement further (Fig. 13). The con-
sequence of the NAFZ reaching the Marmara re-
gion in late neotectonic period and propagating
towards the GFZ, the NAFNS formed a deep
and single structure beneath the EMR, connecting
the two segments of the master fault in the west-
ern and eastern Marmara in a single structure at
depth.
5.2.2. Middle strand of the North Anatolian Fault
Zone
The North Anatolian Fault bifurcates in Bolu.
Then it again bifurcates around Pamukova or
Geyve (Figs. 1 and 10;Kocyig
it, 1998). The
middle strand, which extends to Gemlik Bay
via Pamukova and Iznik Lake, intersects with
the TEF, causing the opening of the Gemlik
pull-apart basin. The reactivated segments of
TEF caused the deepening of this basin (Yalt|rak
and Alpar, 2002b). At present, the middle strand
follows the coastal line from Gemlik Bay to
Band|rma Bay and it de£ects 20‡ southward into
Band|rma Bay. The main reason for this de£ec-
tion is its connection with the BBFZ (Figs. 5, 9
and 13). At present, the BBFZ continues its ac-
tivity as a middle strand of the NAFZ, the
NAFMS, similar to the GFZ at the western Mar-
mara Sea.
5.2.3. Southern strand of the North Anatolian
Fault Zone
The NAFSS follows the southern boundary of
the Yenisehir Basin (Fig. 10). Further west, the
movement is transferred into a fault situated to
the north of the Inego
«l Basin, and the southern
strand intersects the TEF for the third time east
of Bursa (Figs. 5 and 10). The NAFSS outlines
the southern boundary of the Bursa Plain, and
then follows the southern margins of Uluabat
and Manyas Lakes. The block that de£ects south-
ward due to compression causes an oblique ten-
sional regime between Manyas and Uluabat (Figs.
5 and 10). The southern strand extends into Edre-
mit Bay via the MEFZ, with a progressively re-
duced rate of motion.
6. Regional seismicity
Many historical earthquakes with magnitudes
s7 are known to have occurred within the study
area (Ambraseys and Jackson, 2000). Fault plane
solutions of the earthquakes considered in this
study show the e¡ective deformation responsible
for the opening and evolution of the Marmara
basins and are in good agreement with the ob-
served faults.
6.1. Earthquakes on the northern strand of the
North Anatolian Fault
These earthquakes occurred on east^west-
trending strike-slip faults dominantly dextral in
sense with 6.6^7.4 Msand V10 km focus depth.
Starting from the east, these are the 1943 Hendek,
1951 Kursunlu, 1957 Abant, 1967 Mudurnusuyu^
Adapazar|, 1999 Izmit, and 1999 Du
«zce earth-
quakes (Mc Kenzie, 1972 ; Ambraseys and Jack-
son, 1998; Taymaz et al., 1991, 2001 ; Taymaz,
1999, 2000). The earthquakes with magnitudes
66.4 occurring in the Marmara Sea have di¡er-
ent characteristics from the above. In particular,
distributions of earthquakes measured at local
stations since 1997 and the focal mechanism solu-
tions of the aftershocks of the 1999 Izmit earth-
quake (Ergin et al., 2000) give kinematic clues for
the Marmara faults (Fig. 10). The biggest of the
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529 517
Fig. 12. Structural block diagram of the Marmara Sea composed from seismic lines re-interpreted in this paper (Fig. 6).
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529518
earthquakes in the Marmara region occurred in
the Adalar Fault Zone in 1963. Its fault plane
solution indicates a northwest^southeast-trending
extension along normal faults (Taymaz, 1990,
2000). Here, the northwest^southeast-trending
normal faults form the northern boundary of
the EMT (Fig. 10). It is important to note that
the aftershocks of the 1999 earthquakes (Ergin et
al., 2000) are stacked along the margins of the
EMT, possibly caused by the splitting of the fault
into two branches. Comparison of the aftershock
distribution with the fault map of Ergin et al.
(2000),Alpar and Yalt|rak (2002) have suggested
that the trends in the aftershocks are a production
of deformation scattered at the end of the fault of
the 1999 Izmit earthquake, which terminated
around the eastern end of the EMT. The tectonic
setting proposed by Alpar and Yalt|rak (2002)
and fault plane solutions re£ect the character of
a dextral strike-slip deformation at the margins of
the EMS-B. The results of a seismographs net-
work operated before the 1999 earthquakes obvi-
ously indicate a series of earthquakes also corre-
sponding with the deep Marmara troughs (Fig. 10 ;
Gu
«rbu
«z et al., 2000). On this line, there are two
earthquakes focused to the south of the EMT.
The eastern earthquake revealed a northwest^
southeast-oriented normal right-lateral oblique
solutions, while the second earthquake, which is
located to the central west of the EMT, gave a
northeast^southwest minor compression (Fig. 10).
The fault plane solution of another earthquake on
the EMR also indicated compression with a mi-
nor right-lateral component. This fault, along
which these three earthquakes are aligned, extends
from the Izmit Bay to the EMR and dips north-
ward (Figs. 9, 12 and 13).
Fault plane solutions for earthquakes along the
fault extending between the KT and the MMT
give northeast^southwest-oriented strike-slip with
varying extension as well as northwest^southeast-
directed extension that can be correlated with nor-
Fig. 13. Structural model block diagram of the Marmara region faults. This ¢gure shows the linkages between the Thrace^Eskise-
hir Fault parts and the North Anatolian Fault segments. Abbreviations: TEFZ, Thrace^Eskis ehir Fault Zone; NAFNS, North
Anatolian Fault North Segment, i.e. ‘Great Marmara Fault’ of Le Pichon et al. (1999) ; NAFMS, North Anatolian Fault Middle
Segment; NAFSS, North Anatolian Fault South Segment.
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529 519
mal faults in the region (Gu
«rbu
«z et al., 2000). In
the central part of the MMT, the master fault
passes through the central portion of the trough
reaching the WMR. Here, the fault plane solu-
tions show strike-slip with extension (Fig. 10).
The fault plane solution for the earthquake lo-
cated on a thrust fault between the WMT and
WMR (Fig. 10;Gu
«rbu
«z et al., 2000) show north-
east^southwest compression. All these earth-
quakes have their focal depth 615 km (Gu
«rbu
«z
et al., 2000). There are few fault plane solutions
for the western part of the Marmara region on the
NAFNS. One of them gives northeast^southwest-
directed compression, possibly correlating with a
similar trending trust fault on the GFZ around
Ganos Mountain (Fig. 10;Kalafat, 1995). Dex-
tral strike-slip o¡sets of 65.5 m observed be-
tween Gaziko
«y and the Gulf of Saros developed
as the results of the 1912 Sarko
«y^Mu
«refte earth-
quake (Altunel et al., 2000; Alt|nok et al., 2001).
Detailed ¢eld observations conducted on the GFZ
closer to the Marmara Sea indicated the presence
of northeast^southwest-trending thrust faults
oblique to the master fault (Yalt|rak, 1996).
The fault plane solutions of an earthquake
which occurred in 1975 on the northern strand
of the NAFZ extending along the northern mar-
gin of the Saros Trough (Yalt|rak and Alpar,
2002a) gave right-lateral o¡set with normal com-
ponent (Fig. 10;Taymaz, 1990, 2000).
6.2. Earthquakes on the middle strand of the
North Anatolian Fault
No large earthquakes have been recorded on
the middle strand of the NAFZ and its eastern
extension during the period when seismographic
data were available. However, there is a dense
seismic activity around Gemlik and Band|rma
Bays (Fig. 1B). Gu
«rbu
«z et al. (2000), identi¢ed
seven small earthquakes between Iznik Lake and
the Southeast Marmara Sea (Fig. 10). Fault plane
solution of earthquakes located north of Iznik
lake give northwest^southeast-trending extension
along normal faults, whereas those closer to the
Armutlu Peninsula give northeast^southwest dex-
tral strike-slip.
Fault plane solutions of Gu
«rbu
«z et al. (2000)
for Gemlik Bay are consistent with the oblique
normal faults observed in the seismic re£ection
pro¢les (Fig. 10). Although there is no earthquake
west of the middle strand of the NAF, three of
fault plane solutions given by Gu
«rbu
«z et al. (2000)
on land are close to the master fault (Fig. 10), and
show dextral strike-slip character (Fig. 10). In
addition, fault plane solutions of the 1953 and
1969 Yenice earthquakes on the eastern part of
the middle strand give northeast^southwest-trend-
ing thrust faults with right-lateral component and
pure dextral strike-slip faults, respectively (Fig. 10;
Taymaz, 1990, 2000), consistent with the south-
ward bending of the middle strand and westward
escape of the Anatolian Block.
6.3. Earthquakes on the southern strand of the
North Anatolian Fault
On the southern strand of the North Anatolian
Fault the largest earthquakes throughout the pe-
riod when seismographic data were available are
the 1964 Manyas and the 1983 Yenisehir earth-
quakes (Ketin, 1966; Taymaz, 1990). Di¡erent
epicentres have been proposed for the 1983 earth-
quake (Taymaz, 1999; Gu
«rbu
«z et al., 2000). How-
ever, fault trends for either solutions are in the
same direction with the southern strand of the
North Anatolian Fault (Fig. 10).
Around Bursa, the fault plane solutions of Gu
«r-
bu
«z et al. (2000) give di¡erent fault directions
consistent to the geometry the intersection of the
NAFSS and TEFZ (Figs. 1B and 10). The 1964
Manyas earthquake is another event related to the
southern strand, giving an almost east^west-
trending normal fault plane solution (Fig. 10 ;
Taymaz, 1990). Although its epicentre is placed
to the north of the Uluabat^Manyas Basin (Tay-
maz, 1990), detailed ¢eld surveys conducted after
the earthquake along the fault rupture placed it to
the south of the basin indicated surface deforma-
tions associated with a dextral strike-slip fault
(Ketin, 1966, 1969). The NAFSS bends 45‡ south
starting at the town of Go
«nen and turns a transfer
zone compressed by ‘echelon’ faults (Fig. 10). The
fault plane solution of the 1971 earthquake at
the western extension of this fault, gives north-
east^southwest-trending compression along thrust
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529520
faults, oriented dominated by the right-lateral
strike-slip component (Fig. 10;Gu
«rbu
«z et al.,
2000).
7. O¡sets of the strands of the North Anatolian
Fault in the Eastern Marmara region
Until recently the amounts displacement on the
strands of the NAFZ could not be precisely de-
termined, thus estimates of total displacements
ranged from 20 to 85 km (e.g. Bozkurt, 2001).
Detailed measurements can now be made by com-
bining GPS vectors, digital topographic maps
compiled using SAR interferometry, and marine
seismic pro¢les.
Due to the digital topography map prepared by
Wright et al. (2001) and SAR interferometry the
relation of the strands of the NAFZ with the
TEFZ can be evaluated in the region of Bursa
(Fig. 14), as well as the Sakarya River, which
has been o¡set by the NAFZ at two sites : south
of Du
«zce Plain and Pamukova where the NAFZ
bifurcates (Fig. 14). The digital topography map
shows that the Sakarya River is o¡set by the
NAFNS V58 km from its older riverbed to the
north (Fig. 14). However, a V18-km displace-
ment is observed at Pamukova where it is cut
through by the NAFZ (Kocyig
it, 1988). The
TEF is also cut through by the southern strand
of NAFZ by V10^11 km (Fig. 14).
Alpar and Yalt|rak (2002) used seismic re£ec-
tion data to calculate the displacement of the TEF
by the middle strand of the NAFZ in Gemlik Bay
as 7^8 km (Fig. 14). The total of the Bursa and
Gemlik o¡sets are almost exactly 18 km on the
digital topographical map. In the Marmara Sea,
there is 56^63-km o¡set between the segments of
the TEF cut by the northern strand of the NAFZ
(Fig. 6), which is consistent with the 58-km o¡set
observed on the Sakarya River (Fig. 14). The oth-
er way controlling the o¡sets on the NAFZ ob-
tained by seismic data is the calculation based on
age determination of the discontinuity between
the end of the early Pliocene and late Pliocene,
as caused by the activity of the NAFZ, by using
GPS slip vectors. This discontinuity corresponds
to 3.4^3.7 Ma (Yalt|rak et al., 2000a). Using the
GPS slip vectors (Straub et al., 1997) the relative
displacements during the last 3.5 Ma between the
blocks are calculated as 59.5 km along the
NAFNS (average velocity 17 mm/yr), as 7.4 km
along the NAFMS (average velocity 2.1 mm/yr)
and as 10.5 km along the NAFSS (average veloc-
ity 3 mm/yr). Hence, the displacements of the
strands of the NAFZ around the Marmara Sea
region are 58^59, 7^8, and 10^11 km, on the
northern, middle, and southern branches, respec-
tively. These ¢gures indicate a total of 75^78-km
total displacement in the region, which is consis-
tent with the 85  5-km and 80-km displacements
calculated by Sengo
«r (1979) and Hubert-Ferrari
(1998) for the central and eastern parts of the
NAFZ, respectively. The highest westward escape
of the Anatolian Block is along the northern
strand (77%), followed by southern (14%) and
middle (9%) strands.
8. Geological evolution of the Marmara Sea region
using palinspastic modelling
Palinspastic maps were prepared using fault
plane solutions and GPS slip vectors representing
each block de¢ned by the strands of the NAFZ
(Fig. 15). On these maps, the city of Istanbul is
assumed to be a ¢xed base point, the blocks were
then simultaneously moved for every 500 000 yr.
The TEFZ and its spalys were in the Marmara
region V4Ma(Fig. 15A). Four blocks located to
the west of the TEFZ (TB, MB, GB, and BB)
were separated from each other by the dextral
GFZ, BBFZ and MEFZ. While to the east of
the TEFZ, the Thrace Armutlu Block extended
towards Anatolia (Fig. 15A). When the NAFZ
reached the eastern Marmara region V3.5 Ma,
it cut through the TEFZ at three locations, ceas-
ing the activity of the TEFZ in Thrace. However,
the GFZ, BBFZ and MEFZ were incorporated
into the NAFZ, and thus continued their activity.
During this period, the northwest^southeast-
trending segments of the TEFZ were reactivated
as normal faults (Fig. 15B). The EMS-B started to
evolve due to segmentation of the TEF resulting
from the ¢rst o¡set along the nascent NAFZ,
which activates as a boundary of TKB between
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529 521
the NAFNS and GFZ (Fig. 15B). During this
period the Ganos region and the Gaziko
«y^Geli-
bolu areas started to uplift (Fig. 15A). The GFZ
and the eastern parts of the NAFZ in the Eastern
Marmara Sea de¢ne the northern boundary of the
Marmara Block which continued its westward es-
cape 3^2.5 Ma ago (Fig. 15B^D). The step be-
tween these two faults ¢rst caused the evolution
of the EMS-B, but later, the EMR started to up-
lift by the stretching of the northeast margin and
squeezing of the western parts (Fig. 15E^G). To
the west the Gaziko
«y^Gelibolu uplift abandoned
the MMS-B and placed it to the south of WMS-B
(Fig. 15D,E,G). During this period, the Marmara
Basin started to evolve superimposed on the
GMS-B (Fig. 4). Simultaneously, some of the
right-lateral faults with thrust components devel-
oped on the negative £ower structure by the GFZ.
While the Eastern Marmara part of the NAFZ
progressed westward, EMR started to uplift and
rotate clockwise (Fig. 15E^J). While westward es-
cape of the Anatolian Block resulted compres-
sional forces on the eastern and central Marmara
ridges, causing their uplift, some thrusts oriented
45‡ oblique to the master fault were developed in
the western Marmara area. Meanwhile in the
southern Marmara region the Imral| Sub-basin,
together with the EMS-B, continued its evolution
in front of the TEF segment which was reacti-
vated as a normal fault (Fig. 15B^J).
Another important feature revealed by the pal-
inspastic maps is the degree of the north^south
extension. During the last 2.5 Ma, the southern
coast of the Marmara Sea separated from the
northern coast 2 km in north^south direction
and 42 km in west^east direction, implying that
Fig. 14. Morphotectonic map of the East Marmara region. Faults from Yalt|rak (2001a), Alpar and Yalt|rak (2002),Yalt|rak
and Alpar (2002b). Digital elevation map from Wright et al. (2001). Shaded rectangle shows total displacement on the NAFZ
segments. This study used by indicator TEFZ and Sakarya River for displacement. A^B: Sakarya River 58 km displaced by
NAFZ. C^D: Sakarya River in Pamukova, 18 km displaced by NAFZ. C^D = E^F: TEFZ in Bursa, 10 km displaced by
NAFZ). G^H: TEFZ in Gemlik, 8 km displaced by NAFZ.
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529522
the dominant movement responsible for the evo-
lution of the Marmara Sea is strike-slip.
9. Discussion
All models proposed for the evolution of the
Marmara Sea are largely based on marine seismic
pro¢les, with limited land data (Barka and Ka-
dinky-Cade, 1988; Wong et al., 1995; Ergu
«n
and O
ºzel, 1995; Barka, 1992 ; Parke et al., 1999 ;
Siyako et al., 2000; Okay et al., 2000 ; Le Pichon
et al., 1999; Aksu et al., 2000 ; Imren et al., 2001).
Thus, these studies failed to provide a comprehen-
sive tectonic model for the evolution of the Mar-
mara region. The common point of these studies
is the assumption that the NAFZ is an unique
element responsible for the development of struc-
tures in the Marmara region. Yalt|rak (2000b)
showed that faults on land that are older than
NAFZ, such as the TEFZ, GFZ, BBFZ, and
MEFZ, were active in the western Marmara
area as early as the early Miocene, and that basins
formed in relationship to these faults shaped the
area before the NAFZ, or the ‘neotectonic period’
as de¢ned by Sengo
«r (1980). This early neotecton-
ic period includes the evolution of the TEFZ and
its splays and the development of Northwest Ana-
tolia in early Miocene^early Pliocene to Recent
times. The suggestion of Perincek (1991) that
the TEFZ was the continuation of the NAFZ
requires an impossible kinematic model, requiring
the 45‡ clockwise rotation of the Anatolian Block
to trend northward. Paleomagnetic data on
Thrace giving counterclockwise rotations do not
support this interpretation (Tap|rdamaz and Yal-
t|rak, 1997). Similarly, the TTT-triple junction
model proposed by Okay et al. (2000), correlating
the evolution of the northwest^southeast-trending
inactive strike-slip faults on the Thrace with the
NAFZ, also poses a kinematic impossibility. Here
the central block in the Marmara Sea is proposed
to escape westward. The westward escape of the
Anatolian Block does not require the north and
south branches of the NAFZ, particularly in the
presence of the GFZ. If this model were true, an
northeast^southwest extension would be needed
on the Thrace^Eskisehir Fault Zone, which
should also display as much o¡set as that ob-
served on the NAFZ. However, seismic re£ection
pro¢les from Thrace does not show the presence
of a deep graben structure ¢lled with young sedi-
ments (Perincek, 1991), thus does not corroborate
with this interpretation. The gravity, magnetic
and seismic data as well as detailed ¢eld studies
clearly document that the Thrace^Eskisehir Fault
Zone in Thrace and Anatolia is a a huge structure
that was not created by the NAFZ.
The age of the North Anatolian Fault has been
discussed by many researchers (Ketin, 1948, 1969 ;
McKenzie, 1972;Sengo
«r, 1979; Barka, 1992 ;
Barka et al., 2000; Barka and Kadinky-Cade,
1988; Kocyig
it, 1988, 1989, 1991; Sarog
lu,
1988; Toprak, 1988; Barka and Gu
«len, 1989;
Bozkurt and Kocyig
it, 1996; Yalt|rak, 1996 ;
Okay et al., 1999, 2000; Tu
«ysu
«z et al., 1998; Yal-
t|rak et al., 2000a,b, 1998). Some of the recent
studies proposed that it has been active for the
last 5 Ma (Kocyig
it, 1988, 1989, 1991; Sarog
lu,
1988; Toprak, 1988; Bozkurt and Kocyig
it, 1996;
Yalt|rak, 1996; Tu
«ysu
«z et al., 1998). However
stratigraphic studies around the Marmara Sea re-
gion suggest an age of 3.5 Ma (Yalt|rak et al.,
1998; 2000a,b; Sak|nc et al., 1999; Alpar and
Yalt|rak, 2002; Yalt|rak and Alpar, 2002a,b).
This younger age is corroborated by the argu-
ments put forward in this study ; e.g. the relation
between the TEFZ and NAFZ, regional stratigra-
phy, palinspastic maps reconstructed from devel-
opment history of the sub-basins. The initiation
of the NAFZ is ultimately related to the near-
constant opening of the Red Sea and the Gulf
of Aden during the last 4 Ma (Chu and Gordon,
1998; Dauteuil et al., 2000). In addition, the stud-
ies on the Dead Sea Fault in Syria indicated that
the Ghab Basin started its evolution in Early Plio-
cene (4.5 Ma) (Brew et al., 2001). The V4-Ma
age is probably the maximum age for the NAFZ
at its easternmost termination : we expect that it is
younger in western Anatolia. For example, U
ºnay
et al. (2001) obtained an age of late Pliocene
(2 Ma) from deposits in front of a normal fault
with dextral oblique component placed between
the two strands of the North Anatolian Fault
(see also Fig. 14; the northwest^southeast-ori-
ented fault between Sapanca and Mudurnu).
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529 523
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529524
This late Pliocene age implies that the faults
oblique to the North Anatolian Fault are younger
than the main system and the basins along the
North Anatolian Fault and its surrounding are
also younger than 3.5 Ma.
During the last 3.5 Ma the NAFZ reactivated
some of the northwest^southeast-trending older
faults associated with TEFZ in Northwest Anato-
lia, by inverting them as normal faults, causing
the development of several basins. Several young
basins developed associated with the NAFZ be-
came superimposed with these older basins. The
structures observed on the marine seismic data
illustrate this superimposed geological history.
It is necessary to distinguish the structures west
and east of the EMR. The western and central
Marmara regions are characterised by a negative
£ower structure. The EMR was formed as the
northern strand of the NAFZ crossed the south-
ern boundary of the EMT to the GFZ to the
north. It is believed that faults interpreted as
two separate segments by Okay et al. (2000) and
Siyako et al. (2000) south and north of the EMR
must be connected by a master at depth. Because
the focal depths of the earthquakes along the
NAFZ occur at V10^20 km, the deep faults in-
terpreted as separate segments by Okay et al.
(2000) and Siyako et al. (2000) south and north
of the EMR probably correspond to a single
buried master fault. Although in principle the sin-
gle fault models proposed by Le Pichon et al.
(1999),Aksu et al. (2000), and Imren et al.
(2001) are correct, but incomplete because they
do not take into account the structures associated
with the early and late neotectonic periods. In the
en echelon fault models Parke et al. (1999),Okay
et al. (2000) and Siyako et al. (2000) explain the
kinematic evolution of the region by a series of
separate fault segments. But, they ignore that nar-
rowing amount between the segments would be
much higher in case the fault activates in seg-
ments.
The lateral o¡set along the North Anatolian
Fault varies between 20 and 85 km (e.g. Ketin,
1948, 1969; Sengo
«r, 1979; Sengo
«r et al., 1985;
Armijo et al., 1999; Bozkurt, 2001). In this study,
the o¡set along the North Anatolian Fault is cal-
culated as 75^78 km.
10. Conclusion
The Marmara region is a superimposed struc-
ture, which was formed by two di¡erent fault sys-
tems during two di¡erent periods. These struc-
tures are the TEFZ and its splays in the early
neotectonic period and the NAFZ and its strands
in the late neotectonic period. The total o¡set of
the NAFZ in the Marmara Sea is V75^78 km.
During its westward escape at 22 mm per yr,
the Anatolian Block causes 59, 7^8, and 10^11 km
lateral o¡sets on the northern, middle, and south-
ern strands of the NAFZ, respectively. The ratios
of the westward escape of the Anatolian Block are
77, 9, and 14% along the northern strand, middle,
and southern branches, respectively. The NAFNS
is an almost east^west-trending arc-shaped fault
which is buried only under the EMR. Westward,
it reaches to the Gulf of Saros via the GFZ. The
middle strand changes its westward trend by
bending southward at Band|rma. On these areas,
it has thrust component and right-lateral charac-
ter. The M-UB developed on the extensional re-
gion caused by the southward bending of the
southern strand at Manyas. While the Yenisehir
Basin opens as a typical pull-apart basin due to
northeast^southwest extensional regime, the M-
UB opens due to the north^south extensional re-
gime, because the Bal|kesir^Bursa Block to its
south escapes southward. The fault plane solu-
Fig. 15. Palinspastic palaeogeographic reconstruction maps showing Plio^Quaternary tectonic evolution of the Marmara region.
The palinspastic maps have been prepared for every 500 000 yr on the basis of regional GPS vectors given by Straub et al.
(1997).(Fig. 10 shows GPS vector.) The city of Istanbul was held constant and each block was reconstructed backward on the
basis of the boundary faults and GPS vectors. Abbreviations: IKB, Istanbul^Kocaeli Block; TB, Thrace Block; TKB, Thrace^
Kocaeli Block; MB, Marmara Block; EMB, Edremit^Manyas Block; BBB, Bursa^Bal|kesir Block; TEFZ, Thrace^Eskisehir
Fault Zone; GFZ, Ganos Fault Zone; BBFZ, Band|rma^Behramkale Fault Zone ; MEFZ, Manyas^Edremit Fault Zone ; NAF,
North Anatolian Faults
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529 525
tions obtained in the Marmara Sea region are in
good agreement with the faults proposed in this
study.
All of the basins in the Marmara region opened
by the NAFZ have the features of the early neo-
tectonic period. Therefore, even while each of
these basins opened due to di¡erent tectonic pro-
cesses, they are consistent with each other within
the frame of the regional tectonic picture. The
pull-apart geometry of the Gemlik and Yenisehir
Basins show di¡erent features. It is not possible to
suggest that a north^south extensional regime ex-
isted in the Marmara region just looking to the
features of the Uluabat^Manyas Basin. In addi-
tion, one can not interpret NE-SW trending
strike-slip faults similarly just looking to the fea-
tures of the Yenisehir Basin or one cannot claim
compression just looking to the compressional
areas where the middle and southern strands of
the NAFZ bend southward.
The shaping of the Marmara Sea is still con-
tinuing under the compressional forces in the
Western Marmara (Gelibolu^Biga Peninsula)
caused by to northwest^southeast right-lateral
shearing mechanism and the north^south exten-
sional forces between Band|rma and Bursa. The
ridges and compressional troughs in the central
Marmara Sea developed due to the jumps be-
tween the fault segments. The normal faults
bounding the Marmara shelves, which started
their activities in the early neotectonic period
and are also known as the northern and southern
boundary faults, can be still active as normal
faults due to existing rotational extensions (1^
2 km) between the blocks.
It is impossible to relate all of the structures
in the Marmara Sea region to the NAFZ genet-
ically and to assume that the North Anatolian
Fault created everything. As a result, the pro-
posed evolution models are forced to de¢ne the
evolution of the region by the same tectonic re-
gime. The main result of this study is a new syn-
thesis based on the combination of data presented
in previous works. Therefore, this synthesis con-
¢rms all of the data presented in previous works,
but it does not con¢rm all of the previous tectonic
models proposed for the evolution of the Mar-
mara Sea.
Acknowledgements
This paper was written when the author was a
visiting scientist at the Memorial University of
Newfoundland. Research funds are acknowledged
from the Natural Sciences and Engineering Re-
search Council of Canada (Marmara Sea Gate-
way Project). Thanks are due to Aksu, Hiscott
and Calon for the shallow Seismic Lines. The au-
thor is also indebted to Mehmet Sak|nc, Fazl| Y.
Oktay and Cengiz Tap|rdamaz, who have accom-
panied his studies in the Marmara Sea region
since 1990 and contributed to the results pre-
sented here. Further thanks are due to Bedri Al-
par, who was the ¢rst researcher suggesting the
author to combine marine geological and geo-
physical data with those observed on land and
his immense data sets of shallow seismic data col-
lected mainly after the 1999 earthquake. Thanks
are due also to the Marine Geology reviewers
Jeremy Hall and Erdin Bozkurt for their helpful
suggestions and to Aral Okay who was the ¢rst to
propose the study on the GFZ, leading to this
paper, and provided conventional seismic sections
collected by the MTA. Finally, the author likes to
thank his wife Kezban Saki-Yalt|rak, who is re-
sponsible for the C.E.P. Foundation, which spon-
sored all his investigations.
References
Akdog
an, N., 2000. Tu
«rkiye magnetik-gravimetrik
cizgisellikleriyle neotetis paleotektonik u
«niteleri
cizgiselliklerinin korelasyonu ve bazi sonuclar. Cumhuriyetin
75. Yildonumu Yerbilimleri ve Madencilik Kongresi MTA,
Ankara, pp. 331^345.
Aksu, A.E., Hiscott, R.N., Yasar, D., 1999. Oscillating Qua-
ternary water levels of the Marmara Sea and vigorous out-
£ow into the Aegean Sea from the Marmara Sea-Black Sea
drainage corridor. Mar. Geol. 153, 275^302.
Aksu, A.E., Calon, T.J., Hiscott, R.N., Yasar, D., 2000. Anat-
omy of the North Anatolian fault zone in the Marmara Sea.
Western Turkey: Extensional basins above a continental
transform. GSA Today 10, 1^2.
Alpar, B., Yalt|rak, C., 2000. C|narc|k C ukuru ve cevresinin
morfotektonig
i. In: Uysal, Z., Salihog
lu, I. (Eds.), 1. Ulusal
Deniz Bilimleri Konferans|, 30 May|s^2 Haziran 2000,
ODTU
º, Erdemli Deniz Bilimleri Enstitu
«su
«ve TU
ºBITAK,
Bildiri ve Poster O
ºzetleri. ODTU
º, Ankara, pp. 189^194.
Alpar, B., Yalt|rak, C., 2002. Characteristic features of the
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529526
North Anatolian Fault in the Eastern Marmara region and
its tectonic evolution. Mar. Geol. 190, S0025-3227(02)00353-
5.
Alt|nok, Y., Alpar, B. Yalt|rak, C., 2001. Tsunami of the 1912
Earthquake (Ms = 7.4), extension of the associated faulting
in the Marmara Sea. NATO Advanced Research Workshop
On ‘Underwater Ground Failures on Tsunami Generation,
Modeling, Risk and Mitigation’, May 23^25, 2001, Istanbul.
Altunel, E., Barka, A.A., 1998. Neotectonic activity of Es-
kis ehir fault zone between Ino
«nu
«and Sultandere. Geol.
Bull. Turk. 41, 41^52.
Altunel, E., Barka, A.A., Akyu
«z, H.S., 2000. Slip distribution
along the 1912 Murefte-Sarko
«y earthquake, North Anatoli-
an Fault, Western Turkey. In: Barka, A.A., Kozac|, O
º.,
Akyu
«z, S.H., Altunel, E. (Eds.), 1999 Izmit-Du
«zce Earth-
quakes: Preliminary Results. Istanbul Technical University
Publ., pp. 341^349.
Ambraseys, N.N., Jackson, J.A.., 1998. Faulting associated
with historical and recent earthquakes in the Eastern Med-
iterranean region. Geophys. J. Int. 133, 340^406.
Ambraseys, N.N., Jackson, J.A., 2000. Seismicity of the Sea of
Marmara (Turkey) since 1500. Geophys. J. Int. 141, F1^F6.
Andrussov, N., 1890. Die Schichten von Cap Tschauda. Ann.
der K.K. Naturhistor. Hofmuseums, Wien 5, 66^76.
Ardel, A., Kurter, A., 1973. Marmara Denizi. I. U
º. Cog
raf.
Derg. 18^19, 57^75.
Armijo, R., Meyer, B., Barka, A.A., Hubert, A., 1999. Prop-
agation of the North Anatolian fault into the Northern Ae-
gean: timing and kinematics. Geology 27, 267^270.
Aygu
«l, H., Genc, T., 1999. Marmara bo
«lgesi ve civar|n|n izos-
tasi durumunun gravite, topografya ve batimetri verileri kul-
lan|larak incelenmesi. In: Barka, A., Akyu
«z, S., Altunel, E.,
C ak|r, Z., (Eds.), Aktif Tektonik II, Tu
«rkiye Deprem Vakf|,
pp. 121^129.
Barka, A.A., 1992. The North Anatolian Fault Zone. Ann.
Tecton. 6, 164^195.
Barka, A.A., Kadinky-Cade, K., 1988. Strike^slip fault geom-
etry in Turkey and its in£uence on earthquake activity. Tec-
tonics 7, 663^684.
Barka, A.A., Gu
«len, L., 1989. New constraints on the age and
total o¡set of the North Anatolian Fault Zone: implications
for tectonics of the Eastern Mediterranean region. Middle
East Tech. Univ. J. Pure Appl. Sci. 21, 39^63.
Barka, A.A., Akyu
«z, S.H., Cohen, H.A., Watchorn, F., 2000.
Tectonic evolution of the Niksar and Tasova-Erbaa pull-
apart basins, North Anatolian Fault Zone: their signi¢cance
for the motion of the Anatolian block. Tectonophysics 322,
243^264.
Ben-Avraham, Z., 1992. Development asymmetric basins
along continental transform faults. Tectonophysics 215,
209^220.
Bozkurt, E., 2001. Neotectonics of Turkey ^ a synthesis. Geo-
din. Acta 14, 3^30.
Bozkurt, E., Koc yig
it, A., 1996. The Kazova basin : an active
negative £ower structure on the Almus Fault Zone, a splay
fault system of the North Anatolian Fault Zone, Turkey.
Tectonophysics 265, 239^254.
Brew, G., Lupa, J., Barazangi, M., Sawaf, T., Al-Imam, A.,
Zaza, T., 2001. Structure and tectonic development of the
Ghab basin and the Dead Sea fault system Syria. Journal of
Geological Society, London 158, 665^674.
Chu, D., Gordon, R.G., 1998. Current plate motions across
the Red Sea. Geophys. J. Int. 135, 313^328.
Crampin, S., Evans, R., 1986. Neotectonics of the Marmara
Sea region of Turkey. J. Geol. Soc. London 143, 343^
346.
Dauteuil, O., Huchon, P., Quemeneur, F., Souriot, T., 2000.
Propagation of an oblique spreading centre: the western
Gulf of Aden. Tectonophysics 332, 423^442.
Ediger, V., Velegrakis, A.F., Evans, G., 2000. U
ºst K|ta Ya-
mac| Sediman Dalgalanmalar|, Kilikya Havzas|. In: Uysal,
Z. (Ed.), Kuzeydog
u Akdeniz. 1. Deniz Bilimleri Konferans|
Bildiri O
ºzetleri Kitapc|g
|, 30 May|s^2 Haziran 2000. Ku
«ltu
«r
ve Kongre Merkezi ODTU
º, Ankara, 63 pp.
Emre, O
º., Erkal, T., Tchepalyga, A., Kazanc|, N., Kecer, M.,
U
ºnay, E., 1998. Neogene^Quaternary evolution of the East-
ern Marmara Region, Northwest Turkey. Bull. Miner. Res.
Explor. Inst. Turk. 120, 119^145.
Ergin, M., O
ºzalaybey, M.T., Aktar, M.T., Tap|rdamaz, C.,
Yo
«ru
«k, A., Bicmen, F., 2000. Aftershock analysis of the
August 17, 1999, Izmit, Turkey, earthquake. In: Barka,
A., Kozac|, O
º., Akyu
«z, S., Altunel, E. (Eds.) The 1999 Izmit
and Du
«zce Earthquakes: Preliminary Results. Istanbul
Technical University Press, Istanbul, pp. 171^178.
Ergu
«l, E., Go
«zler, Z., Akcago
«ren, F., O
ºztu
«rk, Z., 1986. Geol-
ogy map of Turkey, Bandirma E6 section, Scale 1 :10 000.
Mineral Research and Exploration of Turkey, Ankara, 10
pp.
Ergu
«n, M., O
ºzel, E., 1995. Structural relationship between the
sea of Marmara basin and the North Anatolian Fault. Terra
Nova 7, 278^288.
Gaziog
lu, C., Go
«kas an, E., Algan, O., Yu
«cel, Z.Y., Tok, B.,
Dog
an, E., 2002. Morphologic features of the Marmara Sea
from multibeam data. Mar. Geol. 190, S0025-
3227(02)00356-0.
Go
«zler, Z., Cevher, F., Ku
«cu
«kayman, A., 1985. Eskisehir civ-
ar|n|n jeolojisi ve s|cak su kaynaklar|. Bull. Miner. Res. Ex-
plor. Turk. 104, 40^54.
Gu
«neysu, A.C., 1999. Bathymetry map of the Izmit Bay. Turk.
J. Mar. Sci. 5, 167^170.
Gu
«neysu, C., 1998. Submarine and coastal geomorphology of
the Southern Marmara Sea. In : Progress in Marine Geo-
logical Studies in Turkey, Tu
«bitak University-MTA, Nation-
al Marine Geology Programme, Workshop IV, 14^15 May
1998, Istanbul, pp. 166^171.
Gu
«rbu
«z, C., Aktar, M., Eyidog
an, H., Cisternas, A., Haessler,
H., Barka, A., Ergin, M., Tu
«rkelli, N., Polat, A., U
ºc er, S.B.,
Kuleli, S., Bar|s , S., Kaypak, B., Bekler, T., Zor, E., Bicmen,
F., Yo
«ru
«k, A., 2000. The seismotectonics of the Marmara
region (Turkey): results from a microseismic experiment.
Tectonophysics 316, 1^17.
Hubert-Ferrari, A., 1998. La Faille Nord-Anatolienne (Cine
¤-
matique, Morphologie, Localisation, Vitesse et De
¤calage To-
tal) et Modelisations Utilisant la Contrainte de Coulomb sur
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529 527
Di¡e
¤rentes Echelles de Temps. Ph.D. Thesis. University of
Paris VII Denis Diderot, Paris.
Imren, C., Le Pichon, X., Rangin, C., Demirbag
, E., Ecevito-
g
lu, B., Go
«ru
«r, N., 2001. The North Anatolian fault within
the Sea of Marmara: a new interpretation based on multi-
channel seismic and multi-beam bathymetry data. Earth
Planet. Sci. Lett. 186, 143^158.
Kalafat, D., 1995. Anadolu’nun Tektonik Yap|lar|n|n deprem
Mekanizmalar| Ac |s|ndan Irdelenmesi (in Turkish with Eng-
lish abstract). Unpubl. Ph.D. Thesis. Institute of Marine
Sciences and Management, Istanbul University, 217 pp.
Kaymakc |, N., 1991. Neotectonic Evolution of the Inego
«l
(Bursa) Basin. Unpubl. M.Sc. Thesis. Middle East Technical
University, Ankara, 73 pp.
Ketin, I., 1948. U
ºber die tektonisch-mechanischen Folgerun-
gen aus den grossen Anatolischen Erdbeben des letzten De-
zenniums. Geol. Rundsch. 36, 77^83.
Ketin, I., 1966. 6 Ekim 1964 Manyas depremi esnas|nda ze-
minde meydana gelen tansiyon catlaklar|. Tu
«rk. Jeol. Kur-
umu Bu
«l. 10, 1^2.
Ketin, I., 1969. Kuzey Anadolu Fay| Hakk|nda. Bull. Miner.
Res. Explor. Inst. Turk. 76, 1^25.
Koc yig
it, A., 1988. Tectonic setting of the Geyve basin : age
and total displacement of Geyve fault zone. METU Pure
Appl. Sci. 21, 81^104.
Koc yig
it, A., 1989. Susehri basin : an active fault-wedge basin
on the North Anatolian Fault Zone, Turkey. Tectonophys-
ics 167, 13^29.
Koc yig
it, A., 1991. Neotectonic structures and related land-
forms expressing the contractional and extensional strains
along the North Anatolian Fault at the northwestern margin
of the Erzincan Basin, NE Turkey. Bull. Tech. Univ. Istan-
bul 44, 455^473.
Le Pichon, X., Taymaz, T., Sengo
«r, A.M.C., 1999. The Mar-
mara Fault and the future Istanbul Earthquake. Proc. ITU-
IAHS International Conference on the Kocaeli Earthquake,
Istanbul, pp. 41^54.
Marathon Petroleum, 1976. Marmara-1 well. Final Report, 26
pp.
McKenzie, D., 1972. Active tectonics of the Mediterranean
region. Geophys. J. R. Astron. Soc. 30, 109^185.
Okay, A., Demirbag
, E., Kurt, H., Okay, N., Kuscu, I., 1999.
An active, deep marine strike^slip basin along the North
Anatolian fault in Turkey. Tectonics 18, 129^147.
Okay, A., Kas l|lar-O
ºzcan, A., Imren, C., Boztepe-Gu
«ney, A.,
Demirbag
, E., Kuscu, I., 2000. Active faults and evolving
strike^slip basins in the Marmara Sea, northwest Turkey : a
multichannel seismic re£ection study. Tectonophysics 321,
189^218.
Parke, J.R., Minshull, T.A., Anderson, G., White, R.S.,
McKenzie, D., Kuscu, I., Bull, J.M., Go
«ru
«r, N., Sengo
«r,
C., 1999. Active faults in the Sea of Marmara, Western
Turkey, imaged by seismic re£ection pro¢les. Terra Nova
11, 223^227.
Perinc ek, D., 1991. Possible strand of the North Anatolian
Fault in the Thrace Basin, Turkey: an interpretation. Am.
Assoc. Pet. Geol. Bull. 75, 241^257.
Sak|nc , M., Yalt|rak, C., Oktay, F.Y., 1999. Palaeogeograph-
ical evolution of the Thrace Neogene Basin and the Tethian-
Paratethian relations at northwest Turkey (Thrace). Palaeo-
geogr. Palaeoclimatol. Palaeoecol. 153, 17^40.
Sarog
lu, F., 1988. The age and o¡set on the North Anatolian
Fault. Middle East Tech. Univ. J. Pure Appl. Sci. 21, 65^79.
Sengo
«r, A.M.C., 1979. The North Anatolian Transform Fault:
its age, o¡set and tectonic signi¢cance. J. Geol. Soc. London
136, 269^282.
Sengo
«r, A.M.C., 1980. Tu
«rkiye’nin Neotektonig
inin Esaslar|
‘Principles of the Neotectonism of Turkey’. Tu
«rkiye Jeoloji
Kurumu, Ankara, 40 pp.
Sengo
«r, A.M.C., Go
«ru
«r, N., Sarog
lu, F., 1985. Strike^slip
faulting and related basin formation in zones of tectonic
escape: Turkey as a case study. In: Biddle, K.T., Christie-
Blick, N. (Eds.), Strike^slip Faulting and Basin Formation.
Soc. Econ. Paleontol. Mineral. Spec. Publ. 37, 227^264.
Sylvester, A.G., 1988. Strike^slip faults. Geol. Soc. Am. Bull.
100, 1666^1703.
Siyako, M., Bu
«rkan, K.A., Okay, A.I., 1989. Biga ve Gelibolu
yar|madalar|n|n Tersiyer jeolojisi ve hidrokarbon olanaklar|.
Bull. Turk. Assoc. Pet. Geol. 1, 183^199.
Siyako, M., Tan|s, T., Sarog
lu, F., 2000. Marmara Denizi aktif
fay geometrisi. TU
ºBITAK Bilim Tek. Derg. 388, 66^71.
Smith, A.D., Taymaz, T., Oktay, F.Y., Yu
«ce, H., Alpar, B.,
Basaran, H., Jackson, J.A., Kara, S., Simsek, M., 1995.
High-resolution seismic pro¢ling in the Sea of Marmara
(northwest Turkey): late Quaternary sedimentation and
sea-level changes. Geol. Soc. Am. Bull. 107, 923^936.
Straub, C., Kahle, H.G., Schindler, C., 1997. GPS and geo-
logic estimates of the tectonic activity in the Marmara Sea
region, NW Anatolia. J. Geophys. Res. Solid Earth B12,
27587^27601.
Tap|rdamaz, C., Yalt|rak, C., 1997. Trakya’da Senozoyik vol-
kaniklerinin paleomanyetik o
«zellikleri ve bo
«lgenin tektonik
evrimi. Bull. Min. Res. Explor. Turk. 119, 27^42.
Taymaz, T., 1990. Earthquake Source Parameters in the East-
ern Mediterranean Region. Ph.D. Thesis. Cambridge Uni-
versity, Cambridge, 244 pp.
Taymaz, T., 1999. Seismotectonics of the Marmara region:
Source characteristics of 1999 Go
«lcu
«k-Sapanca-Du
«zce earth-
quakes. Proc. ITU-IAHS, International Conference on the
Kocaeli Earthquake 17 August 1999, Istanbul, pp. 55^78.
Taymaz, T., 2000. Seismotectonics of the Marmara region:
source characteristics of 1999 Go
«lcu
«k-Sapanca-Du
«zce earth-
quakes. In: Barka, A.A., Kozac|, O
º., Akyu
«z, S.H., Altunel,
E. (Eds), 1999 Izmit-Du
«zce Earthquakes: Preliminary Re-
sults. Istanbul Technical University Publ., Istanbul, pp.
79^97.
Taymaz, T., Jackson, J., McKenzie, D.P., 1991. Active tecton-
ics of the North and Central Aegean Sea. Geophys. J. Inter.
106, 433^490.
Taymaz, T., Kasahara, J., Hirn, A., Sato, T., 2001. Investiga-
tions of microearthquake activitiy within the Sea of Mar-
mara and surrounding regions by using ocean bottom seis-
mometers (OBS) and land seismographs: Initial results. In :
Taymaz, T. (Ed.), Symposia on Seismotectonics of the
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529528
North-Western Anatolia-Aegean and Recent Turkish Earth-
quakes. Scienti¢c Activities 2001, May 8, 2001. Faculty
of Mines, Istanbul Technical University, Istanbul, pp. 42^
51.
Toprak, V., 1988. Neotectonic characteristics of the North
Anatolian fault zone between Koyulhisar and Susehri (NE
Turkey). Middle East Tech. Univ. J. Pure Appl. Sci. 21,
155^168.
Tu
«ysu
«z, O., Barka, A.A., Yig
itbas , E., 1998. Geology of the
Saros Graben: its implications on the evolution of the North
Anatolian Fault in the Ganos-Saros region, NW Turkey.
Tectonophysics 293, 105^126.
U
ºnay, E., Emre, O
º., Erkal, T., Kecer, M., 2001. The rodent
fauna from the Adapazar| pull-apart basin (NW Anatolia):
its bearings on the age of the North Anatolian Fault. Geo-
din. Acta 14, 169^175.
Wong, H.K., Ludmann, T., Ulug
, A., Go
«ru
«r, N., 1995. The
Sea of Marmara, a plate boundary sea in escape tectonic
regime. Tectonophysics 244, 231^250.
Wright, T., Parsons, B., Fielding, E., 2001. The 1999 Turkish
earthquakes: source paramaters from InSAR and observa-
tions of triggered slip. In: Taymaz, T. (Ed.), Symposia on
Seismotectonics of the North-Western Anatolia-Aegean and
Recent Turkish Earthquakes. Scienti¢c Activities 2001, May
8, 2001. Faculty of Mines, Istanbul Technical University,
Istanbul, pp. 54^71.
Yalt|rak, C., 1996. Tectonic history of the Ganos Fault system
(in Turkish with English abstract). Bull. Turk. Assoc. Pet.
Geol. 8, 137^156.
Yalt|rak, C., 2000a. Kuzey Anadolu fay|n|n Marmara kollar|
ve bo
«lgenin tektonik yap|s| (in Turkish). Guney Marmara
Depremleri ve Jeo¢zik Toplant|s|, TMMOB Jeo¢zik Mu
«hen-
disleri Odasi, 22 September 2000, Bursa, pp. 44^48.
Yalt|rak, C., 2000b. Problem of Marmara (in Turkish with
English abstract). In: Uysal, Z., Salihog
lu, I. (Eds.), 1st Na-
tional Marine Science Conferences, May 30^June 2, 2000.
Middle East Technical University, Ankara, pp. 202^207.
Yalt|rak, C., Alpar, B., 2002a. Kinematics and evolution of the
Northern Branch of the North Anatolian Fault (Ganos
Fault) between the Sea of Marmara and the Gulf of Saros.
Mar. Geol. 190, S0025-3227(02)00354-7.
Yalt|rak, C., Alpar, B., 2002b. Evolution of the middle strand
of North Anatolian Fault and shallow seismic investigation
of the Southeastern Marmara Sea (Gemlik Bay). Mar.
Geol., this volume.
Yalt|rak, C., Alpar, B., Yu
«ce, H., 1998. Tectonic elements
controlling the evolution of the Gulf of Saros (Northeastern
Aegean Sea). Tectonophysics 300, 227^248.
Yalt|rak, C., Sak|nc, M., Oktay, F.Y., 2000a. Westward prop-
agation of the North Anatolian fault into the northern Ae-
gean: timing and kinematics, Comment. Geology 28, 187^
188.
Yalt|rak, C., Alpar, B., Sak|nc, M., Yu
«ce, H., 2000. Origin of
the Strait of Canakkale (Dardanelles) : regional tectonics
and the Mediterranean ^ Marmara incursion. Mar. Geol.
164, 139^156, with erratum 167, 189^190.
Y|lmaz, B., 1996. Marmara Denizinde Bu
«yu
«kcekmece (Istan-
bul) Marmara Ereg
lisi (Tekirdag
) k|y| kesimini jeolojisi (in
Turkish with English summary). Unpublished M.Sc. Thesis.
Istanbul Technical University, 61 pp.
Y|lmaz, Y., Polat, A., 1998. Geology and Evolution of the
Thrace volcanism, Turkey. Acta Vulcanol. 10, 293^303.
MARGO 3175 3-10-02
C. Yalt|rak / Marine Geology 190 (2002) 493^529 529
  • Article
    Full-text available
    The Nallıhan and Çayırhan regions in western Anatolia host the stratigraphically and tectonically important features of Nallıhan Wedge. The stratigraphic relationships and structural architecture of the wedge are not well understood, which are essential for better understanding of the timing and tectonic evolution of western Anatolia. Today, the Nallıhan Wedge is bounded by the North Anatolian Fault and the Thrace-Eskişehir Fault in the northwest and southwest, respectively. The existence of Dağküplü Mélange within the wedge represents the closure of the İzmir-Ankara Ocean. The occurrence of the Lower Jurassic shelf, slope, reef and deep sea successions transitioning upward into the Cretaceous shelf and slope successions represent the opening and closing cycles of the Intra-Pontide Ocean. The tight and asymmetric folds (steep in the west, gentle in the east) within this stratigraphic sequence and the development of the Eocene units reflect the closure of the Intra-Pontide and İzmir-Ankara oceans. The geometric structure and evolution of the Nallıhan Wedge is directly related to the final continental collision. W-E and SW-NE striking large-scale oblique thrusts also exhibit notable strike-slip components within the study area. The principal direction of the fold axes are W-E and WNW-ESE oriented for the Eocene and Neogene units. During the Eocene, the depositional environment of the study area was a ramp basin mainly dominated by a braided river, when a portion of the Intra-Pontide Ocean was situated on the northern side of the study area. The compressional tectonic regime continued to the end of the Oligocene, which is followed by a new tectonic regime during the Miocene, when the triangular shape region between the Thrace-Eskişehir Fault and the North Anatolian Fault developed as an intermontane basin. The evolution of this basin can be compared with the Tercan Wedge, bordered by the North Eastern Anatolian Fault and the North Anatolian Fault. In the Nallıhan and Çayırhan regions the N-S-trending compressional regime started during the Upper Cretaceous and continued until the final continental collisional during the Upper Eocene. The compressional structures in the area became reactivated during the post-collisional escape tectonic phase in western Anatolia, leading to the development of the prominent Isparta Angle during the Miocene. During this period, the Thrace-Eskişehir Fault and Burdur-Fethiye Shear Zone also formed as intracontinental transform fault zones in western Anatolia. The Nallıhan Wedge started to form in a wedge-shaped area between the Thrace-Eskişehir Fault and the zone of strike-slip faults with thrust component that later developed into the North Anatolian Fault. Thus, Eocene and pre-Eocene structures obtain strike-slip component by an inversion during the Miocene. During and post Pliocene, the Thrace-Eskişehir Fault lost its tectonic activity as the North Anatolian Fault propagated westward into the region previously controlled by the Thrace-Eskişehir Fault. During this interval the Nallıhan Wedge entered a new stage of deformation, which is also observed today.
  • Article
    Full-text available
    South-western Turkey is a tectonically active region where extensional, strike-slip and compressional tectonics co-occur. The Burdur-Fethiye Shear Zone is located in the middle of this complex area. Understanding tectonic evolution of this region is crucial, but the controversial Neogene chronostratigraphy does not allow robust synthesis because of poor age control. The middle section of the Burdur-Fethiye Shear Zone includes three basins: the Acıpayam, Çameli and Gölhisar basins. All these basins represent restricted portions of ancient larger carbonate lakes. The lacustrine sediments are locally covered or cut by lamproites with sparse intercalations of tuff levels. New 40Ar39Ar biotite and U-Pb zircon radiometric ages from volcanics and a tuff layer in this study demonstrate that previously suggested Pliocene age for these sediments are incorrect, and that these Neogene sediments are middle Miocene in age.
  • Article
    Full-text available
    We investigated microseismicity, geodetic slip and structural setting along the western North Anatolian Fault (NAF) to characterize their influence on pre-, co- and post-seismic stages of the 2014 North Aegean Earthquake (M 6.9). We identified that the NAF in North Aegean Sea (NAS) operates beneath three basins and two transpressional ridges rather than a single through-going basin. Refined hypocenters indicate that NAF is a narrow shear-zone in the east, and systematically expands towards the west. Microseismicity has a wide spread epicentral pattern at pre-seismic stage of the 2014 earthquake, but later tightens during post-seismic stage. This suggests that pre-seismic strain accumulation was completed on the main fault and transferred to surrounding secondary structures, and the slip returned back to the main fault following the mainshock. Overall microseismicity pattern shows that seismogenic zone becomes deeper to the west and shallower to the east. Three fault segments merged with two step-overs have failed during the 2014 North Aegean Earthquake rupturing a ~90 km section of the NAF. The co-seismic slips reach ~90 cm beneath western step-over and remains below ~60 cm beneath eastern step-over. Along-fault pre- and co-seismic geodetic slips show a complementary pattern verifying that the 2014 mainshock generated the highest slip at pre-seismically locked patches, located beneath transpressive ridges hosting two step-overs. The existence of high pre-shock concentrations underneath suggests fracturing at seismogenic basement overcoming frictional strength at these two fault step-overs.
  • Thesis
    In this study, time-dependent probabilistic tsunami hazard analysis (PTHA) is performed for Tuzla in the Sea of Marmara, Turkey, related to the possible rupture of Prince Island Fault within next 50, 100, 500 and 1000 years. The study associates the probabilistic seismic hazard analysis with tsunami numerical modelling. Synthetic earthquake catalogue, which includes 100 events, was generated by Monte Carlo (MC) simulation technique. This catalogue includes earthquakes having magnitudes between Mw 6.5 and 7.1 (that comes from the maximum moment magnitude range this fault system can generate), of which probability of occurrence and associated tsunami wave heights are calculated. Tsunami numerical code NAMI DANCE using Non-Linear Shallow Water Equations are used for tsunami simulations. According to results of the tsunami numerical modelling, distribution of probability of occurrence with respect to minimum and maximum water surface elevations and maximum flow depth on land are represented. Moreover, tsunami inundation maps of Tuzla region are prepared with regard to probability of exceedance of 0.3 m flow depth and probability of exceedance of 0.3 m tsunami wave heights at synthetic gauge points for different time scales. This was observed that tsunami wave heights up to 1 m have 65% probability of exceedance for 50 years return period and this value reaches up to 85% in Tuzla region for next 100 year. Inundation depth also exceeds 1m in Tuzla region with probabilities of occurrence of 60% and 80% for next 50 and 100 years, respectively. When return period increases by 500 and 1000 years, earthquake occurrences demonstrate very high probabilities. Furthermore, inundation maps show that the probability of occurrence of certain flow depths ranges between 10% and 75% when exceedance threshold of wave height considered as 0.3 m for 50 and 100-year time exposure. The maximum inundation distance calculated among entire earthquake catalogue is 60 m in this test site. Looking at the situation for the synthetic gauge points, only few of them has a probability between 75% - 85% when probability of exceedance of 0.3 m wave height is considered for next 50 years and this probability value increases up to 90% for 100-year exposure time. Probabilities are observed more than 95% for 500 and 1000-year return periods due to the short return periods of characteristic faults in Marmara Sea.
  • Article
    Full-text available
    Marmara Denizi ve yakın çevresinde 32 si tarihsel, 2 si güncel olmak üzere toplam 34 yıkıcı deprem olmuştur. Bunların yanı sıra, Marmara kıyılarındaki yerleşimlerde 64 tane,, hakkında herhangi bir yeri yıktığı konusunda bilgi bulunmayan ama hissedilen deprem vardır. Bu depremlerin içinde bilgi verenler M.S.484 yılından itibaren başlar. 484 yılından bu yana 1515 yıl içinde tarihi yerleşimlere göre, Marmara Denizi ve çevresinde olan depremler; Şarköy, batı, orta ve doğu Marmara, İstanbul'un güney batısı ile İzmit Körfezi civarında olmak üzere 6 ana grupta toplanabilmektedir. Bu ayrımların yapılması basit bir temel metoda dayanır. Öncelikle, tarihsel depremlerin en güvenilir sonuçları saptanmıştır. Bu saptamaların en önemlisi, bir depremin yıkım yapıp yapmadığıdır. Bundan sonra, nereyi yıkmıştır veya çevrede etkilediği alan neresidir sorusuna yanıt aranmıştır. Bunu yapabilmek için depremler etki alanlarına göre sınıflanmışlardır. Kıyılarda bulunan, tarihsel olarak sürekli yerleşim olan bölgeler sınıflanırken doğu-batı yönüne göre değerlendirilmiştir. Böylece, yıkımın merkezi ve etki alanı ile depremin Marmara'nın hangi kesiminde olduğu ortaya çıkarılmıştır. İkinci aşamada, bu depremlerin İstanbul'da yaptıkları etkiler sınıflanmıştır. Bu sınıflamada, kriter olarak, İstanbul'un anıtsal yapılarında oluşan hasarlar ele alınmıştır. Tarihsel depremlerin İstanbul'a etkisi; surlarda, tapınaklarda, Ayasofya kubbesinde, Galata'da, Bakırköy-Yeşilköy civarında ve Boğaz hisarlarında oluşan hasarlar, can kaybı, deprem sonrası salgın ve göç, tsunami dalgasının olup olmadığına göre beş seviyede değerlendirilmiştir. Bunlar, hissedilen, ağır hissedilen (panik yaratacak derecede), hafif yıkıcı, yıkıcı ve ağır yıkıcı etkilerdir. Bu yaklaşımdan sonra depremlerin alansal dağılımı ve İstanbul'a olan etkileri bir araya getirilerek, Marmara Denizi çevresinde hasar merkezlerinin doğu batı ekseninde konumu saptanmıştır. Bu metotla 484, 824, 1083, 1354,1659 ve 1912 depremlerinin Saroz Körfezi ile Marmara denizi batısı arasında bir yerde depremlerinin İstanbul'un batısı ve İstanbul sur içinde etkin olduğu saptanmıştır. İstanbul'da ağır hasar yapan ve etki alanı içinde de hasar yaratan depremler ise sadece 557, 989 ve 1509 depremleridir. Bu üç deprem de İstanbul'da ağır hasar yapmış, çok sayıda ölüme neden olmuştur. Tsunami dalgası oluşturan, sur kulelerini yıkan, Ayasofya Kubbesini yıkan veya hasar verenler de bu depremlerdir. Yalova, Bursa, Marmara Ereğlisi, Hersek Deltasında yıkıcı etkileri olan bu depremler, Doğu Marmara çevresinde etkindirler. İzmit Körfezi ve doğusunda etkin olan depremler ise 551, 740, 975, 1296, 1501, 1719 depremleridir, Yalova ile İzmit'in doğu kesimi arasında etkindirler.
  • Article
    Marmara bölgesi deprem açısından çok kırılgan bir bölgedir. Ekonomik potansiyel yüksek olduğundan önem arz etmektedir. Yoğun nüfusuyla ve sanayinin bulunduğu bölge olduğundan daha fazla risk taşımaktadır. Bu nedenle 1999 Kocaeli ve Düzce depremlerinden sonra Marmara bölgesi için deprem hasarlarını azaltma çalışmaları yapılmaktadır. Sismoloji, erken uyarı sistemleri, CBS ve afet algısı çalışmaları yanında depremde iletişim, kentsel dönüşüm, deprem haritalarının yenilenmesi, yapısal olmayan elemanlar gibi çalışmalar da yapılmıştır. Bölgedeki nüfusun hazırlıklı ve dirençli bir toplum olması onemli hale gelmiştir. Bu makalede Marmara bölgesi için son çeyrek asır yapılan çalışmalar değerlendirilmiştir. Ancak bu çalışmalarda elde edilen sonuçlara bakıldığında bölge için master bir çalışmanın hala yapılmaya ihtiyaç duyulduğu anlaşılmıştır.
  • Article
    Recent sedimentation and Plio-Quaternary stratigraphy of northern Marmara shelf has been investigated by high-resolution seismic datasets. Seismic data indicate that a thin cover of Plio-Quaternary unit (termed Unit 1) overlies the Miocene/Oligocene age older sediments (termed Unit 2). The erosional surface between Unit 1 and Unit 2 is the regional unconformity for the shelf formed during the last sea level low stand. Unit 1 is subdivided into two sub-units as Unit 1a for Holocene deposits accumulated after the last glacial maximum (LGM) and Unit 1b for fluvial sediments deposited during the last low stand of the Marmara Sea. The thickness of the Holocene sediments is maximum at SW of Bosphorus outlet, in the Büyükçekmece Bay and along the coastal area between Silivri and Büyükçekmece reaching approximately 32 m. Mean sedimentation rate of the entire northern shelf is calculated as 0.4 m/1000 yr for the last 12,000 yr based on the Holocene sediment thickness. There are four depressions in the western part of the shelf, which correspond to palaeolakes during the LGM filled by Plio-Quaternary sediments. Transition from lacustrine to marine conditions in the palaeolakes occurred when the Marmara Sea level exceeded −62 m threshold depth during the sea level rise following the LGM at approximately 12,500–13,000 yr before present (BP).
  • Conference Paper
    Full-text available
    Marmara bölgesi deprem açısından çok kırılgan bir bölgedir. Ekonomik potansiyel yüksek olduğundan önem arz etmektedir. Yoğun nüfusuyla ve sanayinin bulunduğu bölge olduğundan daha fazla risk taşımaktadır. Bu nedenle 1999 Kocaeli ve Düzce depremlerinden sonra Marmara bölgesi için deprem hasarlarını azaltma çalışmaları yapılmaktadır. Sismoloji, erken uyarı sistemleri, CBS ve afet algısı çalışmaları yanında depremde iletişim, kentsel dönüşüm, deprem haritalarının yenilenmesi, yapısal olmayan elemanlar gibi çalışmalar da yapılmıştır. Bölgedeki nüfusun hazırlıklı ve dirençli bir toplum olması önemli hale gelmiştir. Bu makalede Marmara bölgesi için son çeyrek asır yapılan çalışmalar değerlendirilmiştir. Ancak bu çalışmalarda elde edilen sonuçlara bakıldığında bölge için master bir çalışmanın hala yapılmaya ihtiyaç duyulduğu anlaşılmıştır. Anahtar kelimeler: Marmara bölgesi, kentsel dönüşüm, depremde iletişim, deprem haritaları, yapısal olmayan elemanlar
  • Article
    Based on 3D and 2D high-resolution multichannel seismic reflection data in theWestern High-Sea ofMarmara, this study reviews shallow gas occurrence and related structures and classifies gas conduit systems within the upper, few hundred meter-thick sediment layers below the seafloor. Acoustic anomalies including high amplitude-reverse polarity reflections (bright spots), low amplitude transparent zones, chaotic or discontinuous reflections, pull-down effects, and plumes in the water column are interpreted in terms of natural gas occurrence and fluid flow structures (e.g., mud volcanoes, pockmarks). The gas occurrence is thought to be mostly of thermogenic origin. Mud volcanoes are one of the primary gas conduits forming craters on the seabed due to overpressure of fluidized gassy sediment flows. Following the reach of theNorthern Branch of the North Anatolian Fault (NAFN) to theWestern High, the thermogenic fluids are believed to migrate vertically and horizontally to shallow depths mainly through the faults. Natural gas most probably originates fromthe Thrace Basin Eocene source rock or the Eocene-Oligocene reservoir rock, which extends below the Western High. Shallow gas is distributed by minor faults and gas pipes. Gas, to some extent, emanates from the seafloor via pockmarks and mud volcanoes or is trapped by the crests of the anticlines coinciding with erosional surfaces, impermeable sediments, and gas hydrate-bearing layers. Shallow traps below the tectonized BWestern High^ structure are likely located in thin layers of sands imbedded with impermeable silty clay layers. However, there is no shallow reservoir in the usual sense within the upper layers imaged by the 3Dseismic data (< 300 ms two-way travel time). The existence of gas is an indicator of hydrocarbon-rich layers at depth and of active tectonics, and it also impacts the global climate and marine life conditions.
  • Article
    At the northwestern margin of the Erzincan strike-slip basin, two major groups of neotectonic structures and related tectonic landforms are well-exposed. In the Kocyatagi-Isikpinar sector of the margin, dextral to sinistral strike-slip faults, oblique-slip faults with thrust-slip component, thrust faults, contractional duplex showing positive flower structure and fault-parallel pressure ridges are exposed. These structures reflect an active contractional strain and uplift in this sector. In contrast, in the Isikpinar-Cakirman sector of the Erzincan basin, oblique-slip faults (strike-slip and normal-slip components), syndepositional normal mesofaults, rhyolitic, rhyodacitic and dacitic-andesitic domes and aligned hot water springs occur. These neotectonic features reflect an active extensional strain and subsidence. -from Author
  • Article
    Full-text available
    Major Problems of Western Anatolian Geology Yücel Yılmaz1 1Department of Geology, Istanbul Technical University, Maslak, 34469, Istanbul, Turkey yilmazyucel@itu.edu.tr Abstract. Despite a pile of new data that has been collected during the last decades some major problems of western Anatolian geology still remain controversial. Among these cause and timing of generation of the Menderes Massif and the magmatic associations, the N-S trending grabens and time of inception of the E-W grabens are at the forefront. Almost all of these geological events appear to be genetically closely linked with the extensional tectonics, because the extension has played strong tectonic and geologic control on their development. Therefore a first order problem that needs to be address is to discuss if the extensional regime is continually active since it began possibly during the late Eocene time or it has evolved in pulses. As a consequence of the nature of the problem to establish a cross connection between the different events and to evaluate them in time-space and regional geological perspective are critical. In this paper main geological entities of western Anatolia are reviewed under separate headings, the ongoing controversies around them are discussed first and then some solutions are proposed. The data set reviewed on the major geological events as outlined above display an apparent discontinuity in their development and thus support collectively the pulse extension model. Introduction The Western Anatolian region is characterized by a number of approximately E-W trending, sub parallel, normal fault zones, which border a swarm of grabens and the intervening horst blocks (Fig.1). As a consequence of this there is an intense seismic activity, as evidenced by a number of instrumentally recorded and also historical earthquakes, roughly encircling the active faults. Motions on the faults confirm an extension approximately in N-S direction. Therefore the western Anatolian and Aegean regions have long been known to represent a broad zone of extension stretching from Bulgaria in the North to the Hellenic arc in the South (McKenzie 1972, 1978, Jackson and McKenzie 1978, McKenzie and Yılmaz 1991, Taymaz 1996). The seismic data suggest that extension is accommodated by large faults during the big earthquakes (> 6; Patton 1992 A, B, Eyidoğan and Jackson 1985,Taymaz et al. 2007, Yolsal-Çevikbilen et al. 2012, 2014). According to the fault plane solutions of the big earthquakes the seismogenic layer in western Anatolia is thin (> 12 km; Saunders et al. 1998, Karabulut et al. 2003, Taymaz et al. 2008). This is supported further by the high heat flow (Öztürk et al. 2006). In western Anatolia two groups of rocks may readily be distinguished; a) the Neogene and younger rocks and b) the older rocks (Fig. 2). The former forms a common cover of no marine origin to the latter, which comprises a tectonic mosaic developed prior to the deposition of the Neogene units (Fig. 2). Among the tectonic mosaic the following tectonic zones are differentiated from the North to the South, the Sakarya continent, the İzmir-Ankara Suture, the Menderes Massif and the Taurides (Fig. 2). They were amalgamated as a result of total demise of the İzmir-Ankara branch of the Tethyan Ocean and the consequent collision of the bordering continents during the Late Cretaceous-Eocene period (Şengör and Yılmaz 1981, Yılmaz 1981,Yılmaz et al. 1995). The following evolutionary history may be summarized as illustrated in Fig. 3. The late Cretaceous marked the beginning of convergent regime at all fronts in Turkey, and was particularly characterized by the emplacement of ophiolite nappes (Figs. 3B,C and Fig. 4). These nappes moved onto extensive carbonate platforms that began subsiding "en masse" with the onset of obduction (Fig. 4). The initial phase of metamorphism of the Menderes Massif may, in part be ascribed to this subduction and the subsequent obduction events Fig. 3B, C and Fig. 4). Following the obduction of the ophiolitic nappes onto the Tauride-Anatolide platform the platform began to be severally deformed; folded and internally imbricated (Fig. 4). Starting from the Late Cretaceous a thick (> 6km) nappe stack formed. This was the result of accreted lithospheric units, piled by thrusting from the north to the south as a consequence of the total elimination of the separating oceans (Şengör and Yılmaz 1981, Jolivet and Brun, 2010). The shortening deformation caused the continental crust and the lithosphere to have excessively thickened. As a result the crust is assumed to have reached over 50 km in thickness (Le Pichon and Angelier 1979, Jackson and McKenzie 1988, Dewey and Şengör 1979, Şengör et al. 1984, Tirel et al. 2004, Stampfli and Hochard, 2009) (the crust is measured to be about 30-32 km in thickness now (Saunders et al. 1998, Taymaz et al. 2008 Zhu et al. 2006), During the late Eocene the initial uplift of the Aegean metamorphic complexes occurred, and they were partly unroofed (Yılmaz 1997, Burchfiel et al. 2003, Lacassin et al. 2007). During the Oligocene period the whole Aegean Region including western Anatolia, the Aegean Sea area, and the Balkan Region collectively formed a high land and began to be effectively eroded (Siyako and Huvaz 2007, Yılmaz et al. 2010, Elmas et al. 2011) (Fig. 3 DF and Fig. 11). Sometime during the Late Oligocene (?)-Early Miocene (?) the entire western Anatolia together with the Menders Massif suffered a semi brittle-brittle, N-S compressional deformation. As a result of this the whole region were shortened, internally imbricated and thickened. In the Menderes Massif thick-skinned deformation occurred, and its tectonic components were structurally rearranged. The deeply buried metamorphic rocks (the core rocks) were thrust above the cover rocks (see Fig. 9 for the structural rearrangement of the Menderes Massif). This was followed by an extensional phase possibly as a result of the collapse of the orogene. During the Late Miocene period the Western Anatolian domain subsided near the sea level (Steinenger et al. 1985, Görür 1988, Görür et al. 1997, Popov et al. 2006, Yılmaz et al. 2010, Elmas et al. 2011) (Fig.3H). A regional denudation that already began during the Late Eocene -Oligocene effectively eroded the region during the Late Miocene-early Pliocene period. It was accompanied by tectonic erosion. Under the collective influences of the two forces the crust thinned and a regionally developed flat-lying erosional surface formed above the successions including the Upper Miocene-Lower Pliocene strata (Fig. 3 DG). The following major tectonic units and geological events of the western Anatolia are still debated: 1. The Menderes Massif; its origin, time and mechanism of the metamorphism, the main tectonic components, and their structural arrangements. 2. The Magmatic Associations; age of development and the mechanisms of generation 3. The Neogene Cover rocks; the tectonic regime, under which they were developed, and their tecto-stratigraphic divisions. 4. The N-S extensional regime; its time and mechanism of initiation and continuity. A number of different views have been proposed on each one of these subjects (see also Çemen et al 2014). Because models proposed by different authors were commonly incompatible with one another we, as a team undertook a major project and mapped the region extensively. The area mapped stretches from the Marmara region to the Mediterranean region. In the following years we revisited the regions repeatedly to check and test the new views and ideas that appear in the literature. In the following paragraphs the major problems are reviewed
  • Article
    Studies of Neogene-Quaternary basins within and adjacent to the North Anatolian fault zone indicate that initiation of the fault zone as a wide right-lateral shear zone began in about late Miocene time. The observed offset of late Miocene sediments, and the size of pull-apart basins along the fault zone, show that the total displacement decreases from 40±5km near Erzincan in the east, to 25±5 near Bolu in the west. Recently completed slip data for the 1939-1967 migrating large earthquake sequence along the fault zone demonstrate that the maximum slip during the 1939 Erzincan earthquake reached 7-7.5m, and that only 30% of this amount was transferred to the central part of the 1943 rupture zone. Although part of the untransferred 70% of slip of the 1939 earthquake must have been taken up by internal deformation in the Anatolian block, the balance remains to be transferred westward, revealing a potential seismic gap in the central part of the fault zone. -from Author
  • Article
    Full-text available
    ABSTRACT Although it straddles an area of extreme earthquake risk, the origin of the Marmara Sea transtensional basin has been enigmatic. Recently acquired high-resolution seismic profiles and earthquake hypocenter locations show the crustal architecture to be characterized by a negative flower structure, bounded by two west-trending sidewall faults that are linked to a single vertical to steeply south-dipping master fault that extends to depths of >30 km. The negative flower structure has a complicated architecture consisting of relatively intact detached basinal blocks, separated by southwest-trending ridges which serve as strike-slip transfer zones between the basins. The basins and ridges are rotating counter-clockwise, accommodated by the southward retreat of the southern sidewall of the flower structure as crustal material is passed from its eastern to western end along the transtensional strike-slip zone. This new interpretation provides a better context for understanding seismicity in the region and for understanding complexities of fault segmentation in large transtensional basins along ontinental transforms in zones of tectonic escape.