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The Tectonic Geomorphology and the Archeoseismicity of the Dead Sea Transform in Jordan Valley
Abstract
The Dead Sea transform (DST) extends 1000 km from the Sinai triple junction in the south to the Tauros- Zagros collision zone in Turkey in the north. In Jordan, the DST consists of three morphotectonic elements; the Wadi Araba in the south, the Dead Sea basin in the middle and the Jordan Valley in the north. The Dead Sea is a pull- apart basin that formed due to the overlap of the Wadi Araba fault (WAF) and the Jordan Valley fault (JVF). The movement along the transform is active as indicated from both the geomorphological features and from the seismic activity. The DST is a major left lateral strike slip fault that accommodates the relative motion of the Arabian plate to the east and the Sinai plate to the west, where 107 km of cumulative left lateral offset has occurred over the last 18 million years. Based on this offset, the accumulated slip rate is estimated to be 5-10 mm/yr. Based on aerial photographic analysis of the DST and earthquake catalogue information, it is suggested that the present day slip rate has been slower (1.5-3.5 mm/yr) when compared with the Pleistocene rates. Recent work on offset alluvial fan surfaces and drainage along the northern Wadi Araba fault indicates a slip rate of 4.7 mm/yr (Niemi et al., 2000) and 4 mm/yr (Klinger, 2000). In the Jordan Valley fault a slip rate of 7 mm/yr in the last 13000 years was estimated based on aerial photograph and satellite image interpretation (Al-Taj, 2000). Active strike slip faults display distinct morphological features along its trace. The DST in Jordan Valley has a series of morphotectonic features, such as pressure ridges and sag ponds. These features are formed in the place of fault steps or bends (Keller and Pinter, 1996). Fault scarps are formed along most of the trace indicating a dip slip component of displacement. Historical, archeological and paleoseismic data are combined from two trench sites to build a unique composite catalogue of large past earthquakes. On that basis, evidence for surface rupture during the AD 749 and AD 1033 earthquakes was shown. Overall, 8 surface-rupturing events for the last 14 kyr were identified. A temporal analysis displays clusters of seismicity as well as quiescence periods as well as a 600- to 1000-yr-long recurrence interval for large earthquakes in the last 14 kyr.
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We present a simplified three-dimensional thermomechanical model of a pull-apart basin formed at an overstepping of an active continental transform fault. The modeling shows that for a given strike-slip displacement and friction on the faults, the major parameter that controls basin length, thickness of sediments, and deformation pattern beneath the basin is the thickness of the brittle layer. The unusually large length and sediment thickness of the Dead Sea basin, the classical pull-apart basin associated with the Dead Sea Transform, can be explained by 100 km of strike-slip motion and a thick (20 22 km, up to 27 km locally) brittle part of the cold lithosphere beneath the basin. The thinner sedimentary cover in the Gulf of Aqaba basin, located at the southernmost part of the Dead Sea Transform, close to the Red Sea Rift, is probably due to a thinner brittle part (
The Crusader castle of Vadum Jacob, an outpost overlooking the Jordan River, was deformed during a destructive earthquake triggered by motion along the Dead Sea Transform. The M >7 earthquake occurred at dawn, 20 May 1202, and offset the castle walls by 1.6 m. This exceptional precision in dating and estimating displacement was achieved by combining accounts from primary historical sources, by excavating the Dead Sea Transform where it bisects the castle, and by dating faulted archaeological strata. The earthquakes of October 1759 and/or January 1837 may account for the remaining 0.5 m out of a total 2.1 m of offset. Our study exploits the potential embodied in interdisciplinary historical-archaeological-geological research and illustrates how detailed histories of seismogenic faults can be reconstructed.
Analyses and modeling of gravity data in the Dead Sea pull-apart basin reveal the geometry of the basin and constrain models for its evolution. The basin is located within a valley which defines the Dead Sea transform plate boundary between Africa and Arabia. We present a model in which the geometry of the Dead Sea basin (i.e., full graben with relative along-axis symmetry) may be controlled by stretching of the entire (brittle and ductile) crust along its long axis. There is no evidence for the participation of the upper mantle in the deformation of the basin, and the Moho is not significantly elevated. The basin is probably close to being isostatically uncompensated, and thermal effects related to stretching are expected to be minimal. The amount of crustal stretching calculated from this model is 21 km and the stretching factor is 1.19. If the rate of crustal stretching is similar to the rate of relative plate motion (6 mm/yr), the basin should be approximately 3.5 m.y. old, in accord with geological evidence.
The uppermost Pleistocene in the Jordan Valley is represented by two closed lakes: the Lisan Lake (and hence the Lisan Formation 63 to 16–15ka) and the Damya Lake (Damya Formation 16–15 to 12ka). The Lisan Formation in the central Jordan Valley consists mainly of varved sediments, is capped by a conspicuous white cliff containing abundant gypsum lamina and is overlain by evaporite-free Damya Formation. The white cliff sediments, thus, represent the driest period of the Lidan–Damya times (63–12ka). This cold, dry period extended from 23–22 to 16–15ka BP, which corresponds to the Last Glacial Maximum (LGM) world-wide and ended by the demise of Lake Lisan. We believe that the cold, dry climate of the Jordan Valley during the LGM, supported by other workers, records a rather similar paleoclimatic trend with the monsoon-affected North African Sahara, Arabia and SE Asia where cold climatic times are associated with drier, low precipitation, and expansion of desert conditions. Consequently, this might indicate a good possibility of the monsoon rains reaching the interior southern Levant during the warm, wet periods.
A network of 11 continuous GPS stations was constructed in Israel between 1996 and 2001 to monitor current crustal movements across the Dead Sea Fault (DSF). Analysis of the GPS measurements with respect to the ITRF2000 Reference Frame yields time series of daily site positions containing both secular and seasonal variations. Horizontal secular variations (station velocities) are evaluated with respect to the main tectonic element in the region, the DSF. We use six velocity vectors west of the DSF to define the ITRF2000 pole of the Sinai sub-plate, and rotate the velocity field for all stations into the Sinai reference frame (SRF). The velocity vectors reveal that (1) relative station movements are less than 4 mm/yr; (2) the nine stations located west of the DSF show no statistically significant motion with respect to the SRF; and (3) the two stations located in the Golan Heights (KATZ and ELRO) and a station in Damascus, Syria (UDMC) show 1.7–2.8 mm/yr northward motion with respect to Sinai, indicating a left-lateral motion along the DSF. Using locked-fault models, we estimate the current slip rate across the DSF as 3.3 ± 0.4 mm/yr. If we exclude the northern sites (ELRO and UDMC), which are located adjacent to the compressional jog of Mount Hermon, our estimate increases to 3.7 ± 0.4 mm/yr. The calculated ITRF2000 Sinai, Eurasia, and Nubia poles and a published pole for Arabia allow us to calculate the current relative plate motion of Sinai-Arabia and Sinai-Nubia.
The Dead Sea pull-apart basin is dominated by two tectonic domains, each recording a different subsidence history. The margins are controlled by large N-S-trending zigzags of normal faults and the inner basin by north-south strike-slip faults. This tectonic scenario was accentuated during the tectonically active late Pleistocene. By analyzing the differential subsidence across the basin we illuminate its fine structure. Representing the marginal tectonic domain, the Massada Plain features two fault systems, one at the western edge of the basin and one at the central part of the plain. The integrated subsidence rate for these fault systems amounts to 0.3-0.6 m/ky at the basin margin and 1 m/ ky in the basin center. This rate is in accordance with the long-term calculations from boreholes. The Lisan Peninsula reflects a very different tectonic regime controlled by the eastern segment of the strike-slip fault and the rising salt diapir. The ascent rate of this salt structure during the Holocene was 9 m/ky, as calculated from the 6000-year-old ravinement surface. The volume of this uplift combined with the volume of Mount Sedom accounts for a maximum of 5% of the subsidence in the southern Dead Sea basin, with the remainder attributed to tectonic activity. The subsidence history of the basin is useful not only for the analysis of the basin fill over time but also for correction of datum elevation of the lake level curve. Here we apply this correction to the reference curve for consistency with the global sea level datum and for analysis of the factors controlling lake levels such as bathymetry and climate changes.
The Dead Sea Transform is a major strike-slip fault bounding the Arabia plate and the Sinai subplate. On the basis of two GPS campaign measurements, 6 years apart, at 17 sites distributed in Israel and Jordan, complemented by Israeli permanent stations, we compute the present-day deformation across the southern segment of the Dead Sea Transform, the Wadi Araba fault. Elastic locked-fault modeling of fault-parallel velocities provides a slip rate of 4.9 ± 1.4 mm/a and a best fit locking depth of $12 km. This slip rate is slightly higher than previous results based only on Israeli permanent GPS stations data, which are located west of the fault. It is in good agreement with results based on offset geomorphologic and geologic features that average longer periods of time (10 ka to 1 Ma). Projection in ITRF2000 reference frame allows using our data, combined with results published earlier, to further study the kinematics between Arabia, Nubia, and Sinai. Systematic combination of Euler poles available in the literature, in addition to our new set of data, shows that a wide range of Arabia-Sinai pole positions and angular velocities predict reasonable slip rate on the Dead Sea fault. We highlight uncertainties of calculating such poles due to the small size of the blocks and their slow relative motion along a short and almost straight strand of the transform fault, which lead to a large trade-off between pole location and angular velocity.
The archaeological site of Qasr Tilah, in the Wadi Araba, Jordan is located on the northern Wadi Araba fault segment of the Dead Sea Transform. The site contains a Roman-period fort, a late Byzantine–Early Umayyad birkeh (water reservoir) and aqueduct, and agricultural fields. The birkeh and aqueduct are left-laterally offset by coseismic slip across the northern Wadi Araba fault. Using paleoseismic and archaeological evidence collected from a trench excavated across the fault zone, we identified evidence for four ground-rupturing earthquakes. Radiocarbon dating from key stratigraphic horizons and relative dating using potsherds constrains the dates of the four earthquakes from the sixth to the nineteenth centuries. Individual earthquakes were dated to the seventh, ninth and eleventh centuries. The fault strand that slipped during the most recent event (MRE) extends to just below the modern ground surface and juxtaposes alluvial-fan sediments that lack in datable material with the modern ground surface, thus preventing us from dating the MRE except to constrain the event to post-eleventh century. These data suggest that the historical earthquakes of 634 or 659/660, 873, 1068, and 1546 probably ruptured this fault segment.
The 1927 earthquake was the strongestseismic event (M = 6.2) of the 20th centuryin the Holy Land and the first significantone in the region to be recorded worldwideby seismometers. By quoting theseismological station in Ksara, the ISSlocated the epicenter 40 km north of theDead Sea. This location, which wassupported by secondary and tertiarymacroseismic `evidence' and became one ofthe most accepted `facts', was neverquestioned nor reevaluated.We show how an initial mistaken earthquakelocation, supported by questionableevidence, struck roots and eventually becamean accepted fact. This typical `chain oferrors' may serve as a warning regardingtreatment of historical macroseismicsources, as well as historical microseismicdocuments. The conclusions drawn from thisstudy, while focusing on historicaldocumentation, fit well the new epicenterof the 1927 earthquake, recalculated in ourformer study.
We Present a GPS-derived velocity field 1988-2005 for the zone of
interaction of the Arabian African Nubian and Somalian and Eurasian
plates The Velocity field indicates counterclockwise motion of a broad
area of the Earth s surface that includes the Arabian plate adjacent
parts of the Zagros and Central Iran Turkey and the Aegean at rates in
the range of 20 -- 30 mm yr This relatively rapid motion occurs within
the framework of the slow-moving 5 mm yr relative motions Eurasian
Nubian and Somalian plates The circulatory pattern of motion increases
in rate towards the Hellenic trench system suggesting that subduction in
the eastern Mediterranean is the dominant process responsible for
regional deformation Using seismic and other geophysical and geological
information we develop an elastic block model and use the GPS velocity
field to estimate relative block motions This model provides a
reasonable fit to the observed motions with the principal block
boundaries corresponding to known seismically active faults e g Sinai
and Marmara regions The GPS observations for Sinai imply that the Sinai
Peninsula and Levant region comprise a separate sub-plate sandwiched
between the Arabian and Nubian plates
We analyzed the aftershock sequence of the Gulf of Aqaba earthquake recorded by short period and broad band stations between November 1995 and December 1996. The seismicity pattern reveals significant activity often confined to known surface traces of active faults or within local grabens. Most of the aftershock activity is concentrated north of the main shock in the Aragonese and Eilat basins, while the activity is diffused south of the main shock in the Dakar and Tiran basins. Most of the moderate to strong aftershocks of the whole aftershock sequence occurred in the Aragonese basin, mainly in the first 100 days following the main shock. The Eilat basin is characterized by a larger number of aftershocks composed mainly of small-magnitude implying a slower decay rate. Assuming a detection level of ML=3.2 we obtain b-values of 1.01, 1.15, and 0.89 for the whole Gulf of Aqaba, and Eilat and Aragonese basins, respectively, in good agreement with recent studies of the Dead Sea fault. Following Omori's law, we obtained a decay parameter of 0.94, 0.88, and 0.96 for the aftershock sequences in the whole Gulf of Aqaba, and the Eilat and Aragonese basins, respectively, correlative with regions of low heat flow.For 1630 events in the local magnitude range of 0.6≤ML≤6.2 we found seismic moment estimates, M0, of 5×1018≤M0≤7.7×1026 dyn cm, and Brune stress drop estimates, Δσ, between 1 and 200 bars, with a characteristic value of 90 bars in the Eilat and Aragonese basins for M0>5×1021 dyn cm. These characteristics are comparable to those for events occurring on the main Dead Sea–Jordan fault. Most of the moment release in the basins occurred shortly after the occurrence of the main shock. The total moment release in the Eilat and Aragonese basins is only a fraction of the moment release of the main shock suggesting an almost complete stress release.
We investigate the late Quaternary active deformation along the Jordan Valley segment of the left-lateral Dead Sea Fault and provide new insights on the behaviour of major continental faults. The 110-km-long fault segment shows systematic offsets of drainage systems surveyed at three sites along its southern section. The isotopic dating of six paleoclimatic events yields a precise chronology for the onset of six generations of gully incisions at 47.5 ka BP, 37.5 ka BP, 13 ka BP, 9 ka BP, 7 ka BP, and 5 ka BP. Additionally, detailed mapping and reconstructions provide cumulative displacements for 20 dated incisions along the fault trace. The individual amounts of cumulative slip consistently fall into six distinct classes. This yields: i) an average constant slip rate of 4.7 to 5.1 mm/yr for the last 47.5 kyr and ii) a variable slip rate ranging from 3.5 mm/yr to 11 mm/yr over 2-kyr- to 24-kyr-long intervals. Taking into account that the last large earthquake occurred in AD 1033, we infer 3.5 to 5 m of present-day slip deficit which corresponds to a Mw ∼ 7.4 earthquake along the Jordan Valley fault segment. The timing of cumulative offsets reveals slip rate variations critical to our understanding of the slip deficit and seismic cycle along major continental faults.
The northern part of the Dead Sea Fault Zone is one of the major active neotectonic structures of Turkey. The main trace of the fault zone (called Hacıpaşa fault) is mapped in detail in Turkey on the basis of morphological and geological evidence such as offset creeks, fault surfaces, shutter ridges and linear escarpments. Three trenches were opened on the investigated part of the fault zone. Trench studies provided evidence for 3 historical earthquakes and comparing trench data with historical earthquake records showed that these earthquakes occurred in 859 AD, 1408 and 1872. Field evidence, palaeoseismological studies and historical earthquake records indicate that the Hacıpaşa fault takes the significant amount of slip in the northern part of the Dead Sea Fault Zone in Turkey. On the basis of palaeoseismological evidence, it is suggested that the recurrence interval for surface faulting event is 506 ± 42 years on the Hacıpaşa fault.
Lake Lisan, the late Pleistocene precursor of the Dead Sea, existed from ∼70,000 to 15,000 yr B.P. It evolved through frequent water-level fluctuations, which reflected the regional hydrological and climatic conditions. We determined the water level of the lake for the time interval ∼55,000–15,000 cal yr B.P. by mapping offshore, nearshore, and fan-delta sediments; by application of sequence stratigraphy methods; and by dating with radiocarbon and U-series methods. During the studied time interval the lake-level fluctuated between ∼340 and 160 m below mean sea level (msl). Between 55,000 and 30,000 cal yr B.P. the lake evolved through short-term fluctuations around 280–290 m below msl, punctuated (at 48,000–43,000 cal yr B.P.) by a drop event to at least 340 m below msl. At ∼27,000 cal yr B.P. the lake began to rise sharply, reaching its maximum elevation of about 164 m below msl between 26,000 and 23,000 cal yr B.P., then it began dropping and reached 300 m below msl at ∼15,000 cal yr B.P. During the Holocene the lake, corresponding to the present Dead Sea, stabilized at ca. 400 m below msl with minor fluctuations. The hypsometric curve of the basin indicates that large changes in lake area are expected at above 403 and 385 m below msl. At these elevations the lake level is buffered. Lake Lisan was always higher than 380 m below msl, indicating a significantly large water contribution to the basin. The long and repetitious periods of stabilization at 280–290 m below msl during Lake Lisan time indicate hydrological control combined with the existence of a physical sill at this elevation. Crossing this sill could not have been achieved without a dramatic increase in the total water input to the lake, as occurred during the fast and intense lake rise from ∼280 to 160 m below msl at ∼27,000 cal yr B.P.
In light of the accumulated evidence now published, the oft-denigrated suggestion that major earthquakes took place in the Aegean and Eastern Mediterranean areas during the late 13th and early 12th centuries bc must be reconsidered. A new study of earthquakes occurring in the Aegean and Eastern Mediterranean region during the 20th century, utilizing data recorded since the invention of seismic tracking devices, shows that this area is criss-crossed with major fault lines and that numerous temblors of magnitude 6·5 (enough to destroy modern buildings, let alone those of antiquity) occur frequently. It can be demonstrated that such major earthquakes often occur in groups, known as “sequences” or “storms”, in which one large quake is followed days, months, or even years later by others elsewhere on the now-weakened fault line. When a map of the areas in the Aegean and Eastern Mediterranean region affected (i.e. shaken) by 20th centuryad earthquakes of magnitude 6·5 and greater and with an intensity of VII or greater is overlaid on Robert Drews' map of sites destroyed in these same regions during the so-called “Catastrophe” near the end of the Late Bronze Age, it is readily apparent that virtually all of these LBA sites lie within the affected (“high-shaking”) areas. While the evidence is not conclusive, based on these new data we would suggest that an “earthquake storm” may have occurred in the Late Bronze Age Aegean and Eastern Mediterranean during the years 1225–1175bc . This “storm” may have interacted with the other forces at work in these areas c. 1200bc and merits consideration by archaeologists and prehistorians.
This survey of well-documented repeated fault rupture confirms that some faults have exhibited a "characteristic" behavior during repeated large earthquakes---that is, the magnitude, distribution, and style of slip on the fault has repeated during two or more consecutive events. In two cases faults exhibit slip functions that vary little from earthquake to earthquake. In one other well-documented case, however, fault lengths contrast markedly for two consecutive ruptures, but the amount of offset at individual sites was similar. Adjacent individual patches, 10 km or more in length, failed singly during one event and in tandem during the other. More complex cases of repetition may also represent the failure of several distinct patches. The faults of the 1992 Landers earthquake provide an instructive example of such complexity. Together, these examples suggest that large earthquakes commonly result from the failure of one or more patches, each characterized by a slip function that is roughly invariant through consecutive earthquake cycles. The persistence of these slip-patches through two or more large earthquakes indicates that some quasi-invariant physical property controls the pattern and magnitude of slip. These data seem incompatible with theoretical models that produce slip distributions that are highly variable in consecutive large events.
The Dead Sea earthquake of 23 April 1979 (mb = 5.1) was felt throughout Israel and in parts of the neighboring countries. The epicentral distribution of this earthquake, its aftershocks, two of the largest Dead Sea earthquakes during the last 50 yr and recent microearthquake data suggest that an active segment of the Dead Sea rift fault system lies along the eastern part of the Dead Sea. A detailed intensity study shows a pronounced dependence of seismic intensities on ground characteristics. Strong motion seismograph measurements were obtained for the first time in the Levant countries and they suggest that peak ground accelerations are not significantly different from worldwide data.
A catalog of historical seismicity from the VIIth to the XVIIIth century A.D. was compiled from Arabic documents (many of which are unpublished manuscripts) for the near and Middle East, and in a lesser measure, for North Africa and Spain.
In most cases, detailed descriptions have allowed us to assign Modified Mercalli intensities to the shocks for the localities where they were reported.
The detailed chronology of a protracted episode of seismicity in northern Syria between 1156 and 1159 is given shock by shock from the relation of a Damascus chronicler.
A seismic refraction experiment involving the use of 9 OBS and 11 portable seismic land stations was conducted along a profile in the north basin of the Dead Sea. The seismometers were deployed along a north-south profile in the lake and the adjacent land area. The interpretation of the recorded seismograms indicates the presence of two large Pliocene salt diapirs in the young basin fill. The basement lies at a relatively shallow depth (6–8 km) under the north basin. Further south along the profile a major fault affecting the basement was detected. The apparent sense of the faulting is down to the southeast, representing the boundary of the south basin. This major faulting with a downthrow of some 4–5 km has depressed the crystalline basement and the overlying Cretaceous and pre-Cretaceous sediments. The faulting was followed by the deposition of over 8 km of Recent and Tertiary sediments resulting in a 14 km thick sedimentary sequence in the south basin of the Dead Sea.
Recent neotectonic, palaeoseismic and GPS results along the central Dead Sea fault system elucidate the spatial distribution of crustal deformation within a large (c.180-km-long) restraining bend along this major continental transform. Within the 'Lebanese' restraining bend, the Dead Sea fault system splays into several key branches, and we suggest herein that active deformation is partitioned between NNE-SSW strike-slip faults and WNW-ESE crustal shortening. When plate motion is resolved into strike-slip parallel to the two prominent NNE-SSW strike-slip faults (the Yammouneh and Serghaya faults) and orthogonal motion, their slip rates are sufficient to account for all expected strike-slip motion. Shortening of the Mount Lebanon Range is inferred from the geometry and kinematics of the Roum Fault, as well as preliminary quantification of coastal uplift. The results do not account for all expected crustal shortening, suggesting that some contraction is probably accommodated in the Anti-Lebanon Range. It also seems unlikely that the present kinematic configuration characterizes the entire Cenozoic history of the restraining bend. Present-day strain partitioning contrasts with published observations on finite deformation in Lebanon, demonstrating distributed shear and vertical-axis block rotations. Furthermore, the present-day proportions of strike-slip displacement and crustal shortening are inconsistent with the total strike-slip offset and the lack of a significantly thickened crust. This suggests that the present rate of crustal shortening has not persisted for the longer life of the transform. Hence, we suggest that the Lebanese restraining bend evolved in a polyphase manner, involving an earlier episode of wrench-faulting and block rotation, followed by a later period of strain partitioning.
The origin of the Dead Sea rift has generally been linked with that of the Red Sea, the widening of the latter involving left-lateral strike-slip on the rift. Its extension through the Lebanese fold belt has been denied by some because of the absence of linear and displacement continuity. Others, however, have been unable to see any other choice in spite of these difficulties, but a satisfying structural model has not yet been offered. The present author claims that the rift system is a transform plate boundary between the Arabian plate and the Sinai-Levant plate, but without uniformity along its length. It is here suggested that during the Lower Miocene the Arabian planation surface, which before the opening of the Red Sea was the probable extension of the African mid-Tertiary surface, was ruptured by the first phase of movement on the west Arabian transform fault system, which probably reflected a geosuture zone in the continental plate and was originally a simple arc. The Arabian plate moved northward with the opening of the Red Sea and the closing of the Bitlis ocean, leaving behind the Sinai-Levantine part of the African Plate. Oblique compression on the northern Syria unstable platform across the East Anatolian transform fault caused dextral distortion on the Lebanon-Palmyra zone to create mountain ranges of two styles and a translation in the alignment of the rift segment. This inhibited further uniform strike-slip movement on the rift and displacement on the Yammouné fault was subsequently predominantly vertical. The movements on the rifts to the south and the north thus became independent. There was Arabian plate lithosphere consumption north-east of the Houlé depression to accommodate the second phase of rift movement. On the basis of this explanation, the vexed question of transmission of left lateral strike-slip across the Lebanon segment does not arise.
Historical records of earthquakes can contribute significantly to understanding active faulting and seismic hazards. However, pre twentieth century historians were unaware of the association of earthquakes and fault ruptures. Consequently, historical texts usually report the time and damage caused by earthquakes, but not the associated faults. Conversely, observed fault ruptures are often difficult to date. In order to overcome these difficulties, we have analyzed archaeological and sedimentological observations in recent excavations in the ancient city of Tiberias and have combined them with interpretation of historical accounts. Tiberias was founded in A.D. 19 by King Herod on the western shore of the Sea of Galilee (Kinneret). Herod's stadium, exposed in these excavations for the first time, was damaged by boulder-bearing flash floods and by an earthquake. Later buildings, dated as late as the early eighth century, are all covered by alluvium and lake deposits. They are also damaged and offset by normal faults, whereas buildings from the late eighth century are intact. We therefore attribute the damage to the earthquake of 18 January 749. The paleoseismic observations are in good agreement with the distribution of damage on the basis of historical records. Both data sets indicate a 100-km-long rupture segment between the Kinneret and the Dead Sea pull-apart basins, demonstrating that it is capable of generating M > 7 earthquakes.
The two-man submersible Delta, which dove in the north end of the northern Dead Sea basin during December 1999, revealed indications of recent tectonic activity along the Jericho fault, a major strand of the Dead Sea transform in the area. The fault is expressed by steep (70°-90°) vertical cliffs that are covered by layers of salt. Marl is observed in areas where salt has been chipped away. Recent activity is inferred by the observation of an open interface between the sea floor and the vertical cliff, which is the underwater expression of the Jericho fault. Differences in salt crystal size between the vertical wall and surrounding areas (from 2-3 mm on the surface to 5 cm at the interface), along with the presence of suspected halophilic microorganisms, suggest seepage of fresher water through cracks along the fault zone-again suggesting active faulting.
Tectonic movements continuously remould the surface of Earth in response to plate motion. Yet such deformation is rarely taken into account when assessing landscape change and its impact on human land use, except perhaps as an occasional hazard to human life or a temporary disruption in the longer term patterns of human history. However, active tectonics also create and sustain landscapes that can be beneficial to human survival, forming a complex topography of potentially fertile sedimentary basins enclosed by mountain barriers that can facilitate the control and explotation of food resources, especially animal prey. We discuss the tectonic history of northwest Greece and show how the Paleolithic sites of the region are located to take advantage of tectonically created features at both a local and a regional scale. We suggest that the association of significant concentrations of early Paleolithic sites with tectonically acitve regions is not coincidental and that on the longer time spans of human biological evolution, active tectonics has been an important selective agent contributing to the development of the human species as an intelligent predator.
A study of major earthquake occurrence along the Dead Sea transform (35.5°–36.5° E; 27.2°–37.5° N) during the past four millenia has been attempted. Geological, archaeological, biblical, historical, and seismological evidence were integrated in an effort to quantify the space-time distribution of seismicity in the said province. The overall earthquake activity in the conterminous Near East indicates a stable pattern and appeared to have been stationary over the examined time window. About 110 earthquakes in the magnitude range 6.7 ≤ ML ≤ 8.3 affected the area during the past 2500 years. Of these, 42 originated along the Dead Sea fault system itself, while 68 were imported from the Helenic-Cyprian arcs and the Anatolian-Elburz-Zagros fault systems. These events were responsible for the repeated destruction of many cultural centers. In the Dead Sea region proper, the major seismic activity since 2100 B.C.E. (Before Christian Era), has been confined to the vicinity of its eastern shore with extremal seismicity at its southern tip near the prehistorical site of Bab-a-Dara'a (31° 15'N, 35° 32'E). This may constitute the first solid evidence that the Biblical “cities of the Plain” (Sodom, Gommorah, etc.) were located there. Recent studies of earthquake deformations in the Lisan deposits near Bab-a-Dara'a, agree with our findings. At the present time, a magnitude 6¾ earthquake is pending at the northern edge of the Levant rift, with its average recurrence interval (83 years) exceeded by one standard deviation (32 years).
The large Dead Sea graben is located within the Dead Sea fault, a plate boundary of the transform type. The graben is composed of two basins. The northern one is occupied by a lake, about 300 m deep and has a sedimentary fill of about 6 km. The southern Dead Sea basin however, is unusually deep, with about 14 km of sedimentary fill. The geometry of the southern Dead Sea basin is anomalous along the entire Dead Sea fault. We suggest that the southern Dead Sea basin was formed during the first stage of the formation of the Dead Sea fault when the tips of propagating faults, one from the collision front in the north and one from the Red Sea in the south met in this area. The fault tips overlapped and curved towards each other, isolating a block of crust and lithosphere that dropped into the mantle. Geophysical data indicate that the basin is probably bordered on all sides by vertical faults that cut deep into basement. The deep part of the southern Dead Sea basin is not a pull-apart but instead a “drop down” basin. The Salton Trough in California is probably another example of such a basin.
The Dead Sea is a large, active graben within the Dead Sea rift, which is bounded by two major strike-slip faults, the Jericho and the Arava faults. We investigated the young tectonic activity along the Jericho fault by excavating trenches, up to 3.5 m deep, across its trace. The trenches penetrate through Late Pleistocene and Holocene sediments. We found that a zone, up to 15 m wide, of disturbed sediments exists along the fault. These disturbed sediments provide evidence for two periods of intensive activity or more likely, for two major earthquakes, that occurred during the last 2000 years. The earthquakes are evident in small faults, vertical throw of a few layers, cracks, unconformities and wide fissures. We further documented evidence for recent sinistral shear along the Jericho fault in deformed sediments and damage to an 8th Century palace on a subsidiary fault. We suggest that the two earthquakes may be correlated with the 31 B.C. earthquake and the 748 A.D. earthquake, reported by the ancients.
The Rachaya and Serghaya faults are the easternmost fault branches of the Dead Sea Transform Fault within the Lebanese restraining bend. They lie east of the Yammouneh fault (the main strand of the Dead Sea Transform Fault within the restraining bend), extend along the western and eastern flanks of the Anti-Lebanon range, respectively, and show left-lateral strike-slip movement manifested as offset drainage. We studied both faults through combined field investigations in geomorphology and paleoseismology. Young fault scarps, mole tracks, pressure ridges and offset streams detected along the faults' traces attest to recent coseismic ruptures. Two paleoseismic investigations highlight their seismogenic potential and indicate earthquake recurrence along them: the Rachaya and Serghaya faults are active and the sources of recent historical earthquakes, the last of which might be the 30 October–25 November 1759 (Ms 6.6 and 7.4) earthquake sequence that caused severe damage in the eastern Mediterranean region. Such a possible correlation suggests that the two faults are probably structurally interconnected, as movement on one fault may stimulate movement on the other fault. In addition, both faults may define together an active seismogenic fault system that accommodates some of the regional displacement that takes place within the Lebanese restraining bend. Our results highlight that the seismogenic potential of the Rachaya and Serghaya faults must be included in any seismic hazard assessment of the region.
This work studies the effects of long human habitation on site geotechnical conditions. It is focused on the city of Zefat that is located on the borders of the Dead Sea Transform in northern Israel. The city of Zefat, suffered severe damage and loss of life in historical earthquakes, as a consequence of earthquake induced landslides (EILS). In this work we evaluate the current EILS hazard for the city of Zefat using a GIS-based regional Newmark analysis, with calibration of the calculated Newmark displacement (representing EILS hazard) using maps of field evidence and historical documents testifying to slope instability that occurred in historical earthquakes.
The Elat fault (a segment of the Dead Sea Transform) runs along the southern Arava valley (part of the Dead Sea Rift, Israel) forming a complex fault zone that displays a time-dependent seismic behaviour. Paleoseismic evidence shows that this fault zone has generated at least 15 earthquakes of magnitude larger than M 6 during the late Pleistocene and the Holocene. However, at present the Elat fault is one of the quietest segments of the Dead Sea Transform, lacking even microsesimicity. The last event detected in the southern Arava valley occurred in the Avrona playa and was strong enough to have deformed the playa and to change it from a closed basin with internal drainage into an open basin draining to the south.Paleoseismological, geophysical and archaeological evidences indicate that this event was the historical devastating earthquake, which occurred in 1068 AD in the eastern Mediterranean region. According to the present study this event was strong enough to rupture the surface, reactivate at least two fault branches of the Elat fault and vertically displace the surface and an early Islamic irrigation system by at least 1 m. In addition, the playa area was uplifted between 2.5 and 3 m along the eastern part of the Elat fault shear zone. Such values are compatible with an earthquake magnitude ranging between M 6.6 and 7. Since the average recurrence interval of strong earthquakes during the Holocene along the Elat fault is about 1.2 ± 0.3 ky and the last earthquake occurred more about 1000 years ago, the possibility of a very strong earthquake in this area in the future should be seriously considered in assessing seismic hazards.
In the mid eighth century, towards the end of the Umayyad regime, a major earthquake occurred in Palestine and the East, of which we know from Christian, Jewish and Muslim sources. Archaeologists relate to destruction by this earthquake layers in several sites, such as Jerusalem, Gerasa in Arabia, and sites mostly along the Jordan valley, among them Kh. Mefjer near Jericho, Pella, Capernaum, Sussita-Hippos, and recently, Bet Shean-Scythopolis (see below).
The exact date of this earthquake is controversial; some scholars date it to 746, others to 747 or 748, In 1960, M. Margaliot suggested that the earthquake took place in 749. In this article we present new archaeological and numismatic evidence in support of this later date (see below p. 234, and pl.II).
This paper summarizes evidence for surface faulting in historical and recent earthquakes in the Eastern Mediterranean region and in the Middle East. Such information is particularly important for studies of active tectonics and for palaeoseismology. We have found 78 cases of faulting pre-1900 and 72 post-1900, some of which show that faults that have apparently been inactive this century had already ruptured before 1900. For some cases faulting could not have been predicted from 20th century activity, and in others it could have been expected, but has not been observed during the instrumental period. The data are sufficient to allow the derivation of relationships between magnitude and rupture length.
Earthquake deformations and induced sedimentary structures preserved in Quaternary sediments include faults, folds, fissures, slumps, sand boils and other effects of liquefaction. Such deformations and structures are well preserved in the Lisan deposits of the Dead Sea. Of most importance are the fold-type deformations known as décollement structures which are present all along the eastern side of the Lisan and seem to decrease gradually westwards to disappear in the middle of the Lisan. These may indicate that palaeoearthquakes originating along the Araba fault have triggered such structures due to shaking of elastoplastic unconsolidated sediments over gentle slopes dipping to the west.
Preliminary results from studies on décollement structures preserved in a section representing some 1733 years of continuous deposition in the uppermost? Pleistocene, in the vicinity of Wadi Araba, indicate that: (1) seismic activity has fluctuated with time. Average recurrence period is about 340 ∓ 20yr for earthquakes with magnitudes greater than or equal to 6.5. Earthquakes with magnitude greater than 7 seem to have occurred along the Araba fault. (2) Deduced earthquake magnitudes conform to the frequency-magnitude relationship: log N = 5.24 - 0.68M. (3) The deduced seismic slip rate along the Araba fault seems to be not less than 0.64 5 0.04 cm yr⁻¹.
Geothermal measurements utilizing a special probe designed for the determination of heat flow in lakes have been made in the water-covered portions of the Dead Sea rift, i.e., Lake Kinneret, the Dead Sea and the northern part of the Gulf of Elat. Corrections have been applied for variations in bottom water temperature, sedimentation and topography. The preliminary results indicate a low to normal heat flow along the Dead Sea rift: the average of values in Lake Kinneret is 1.8 H.F.U., in the Dead Sea 0.7 H.F.U., and in the northern part of the Gulf of Elat 1.6 H.F.U. The values in the Dead Sea are comparable to other nearby continental values in Israel, and to those in the eastern Mediterranean.
The 2000 edition of the "Archaeology in Jordan" newsletter again presents brief reports on recent excavations and archaeological projects in the Hashemite Kingdom of Jordan (fig. 1). General projects and surveys are presented first, followed by excavation reports organized chronologically. In both sections, reports are presented in approximate north-south order. This year's newsletter bids farewell to Virginia Egan, who provided technical editing for five years, and to Patricia Bikai, who spearheaded the efforts to create the newsletter and edited reports for technical content for the six years since the inception of the series. The new editors would like to thank them for their work in establishing the high standards for the "Archaeology in Jor-dan" newsletter, and we wish them continued suc-cess.
Empirical relations involving seismic moment M_o, magnitude M_S, energy E_S and fault dimension L (or area S) are discussed on the basis of an extensive set of earthquake data (M_S ≧ 6) and simple crack and dynamic dislocation models. The relation between log S and log M_o is remarkably linear (slope ∼ 2/3) indicating a constant stress drop Δσ; Δσ = 30, 100 and 60 bars are obtained for inter-plate, intra-plate and “average” earthquakes, respectively. Except for very large earthquakes, the relation M_S ∼ (2/3) log M_o ∼ 2 log L is established by the data. This is consistent with the dynamic dislocation model for point dislocation rise times and rupture times of most earthquakes. For very large earthquakes M_S ∼ (1/3) log M_o ∼ log L ∼ (1/3) log E_S. For very small earthquakes M_S ∼ log M_o ∼ 3 log L ∼ log E_S. Scaling rules are assumed and justified. This model predicts log E_S ∼ 1.5 M_S ∼ 3 log L which is consistent with the Gutenberg-Richter relation. Since the static energy is proportional to σ̅L^3, where σ̅ is the average stress, this relation suggests a constant apparent stress ησ̅ where η is the efficiency. The earthquake data suggest ησ̅ ~ 1/2 Δσ. These relations lead to log S ∼ M_S consistent with the empirical relation. This relation together with a simple geometrical argument explains the magnitude-frequency relation log N ∼ − M_S.
Prehistorical earthquake induced features, such as faults, folds, fissures, and slumps have been discovered during the Karameh dam construction. The dam is located close to the plate tectonics boundary formed by the active Jordan Valley Fault. Of most importance are those known as the fold-type deformations ``dcollement type of structure'' which are well preserved in the laminated Lisan formations. These features show that historical moderate to strongly sized earthquake activities are likely to have been originated in the vicinity of the dam site. Such features may well provide valuable information for identification of areas of highly strong earthquake regions.
This article is of an inter-disciplinary nature, relevant to the fields of both earth sciences and historiography, which come
together in the investigation of long-term earthquake hazard. The paper emphasises the need for systematic and consistent
analysis of historical earthquake data and sets out an example for such a task. The results from the historical study of earthquakes
will be of value to earth scientists and engineers only when historical information is converted into “numbers” representing
epicentral location and magnitude of the events, accompanied by an estimate of the reliability of their assessment. However,
as we go further back in time before our era, the historical record gradually disappears and the archaeological record takes
over. Unfortunately, the archaeological record is too coarse and ambiguous, without any precise internal archaeological indicators.
Dating is based on, or influenced by the very few historical records, such as in the Bible and inscriptions, which provide
an example of how their assumed accuracy may influence archaeologists' interpretation and dating. Quite often this develops
into a circular process in which archaeological assumptions or theories are transformed into facts and used by earth scientists
to confirm the dates and size of their proposed events. In this article we discuss the problems that arise when Biblical and
archaeological information is used at face value to assess earthquakes in the Holy Land. This combination may produce earthquakes
of hypothetical location and of grossly exaggerated magnitude with consequences for the assessment of seismic hazard.
Three-dimensional excavations of buried stream channels that have been displaced by the Jordan Fault, the primary strand of the Dead Sea fault zone in northern Israel, demonstrate that late Holocene slip has been primarily strike–slip at a minimum rate of 3 mm/yr. The palaeoseismic study was carried out in the Bet-Zayda Valley, the delta of the Jordan River at the north shore of the Sea of Galilee. The site was chosen where a north-striking scarp with up to 1-m vertical expression crosses the flat valley. One group of trench excavations was located where a small stream crosses the scarp. The active stream, which is incised into the scarp, is not offset by the fault. However we found two palaeo channels about 2 m below the surface offset sinistrally 2.7±0.2 m by the fault and two younger nested channels offset 0.5±0.05 m. Based on radiocarbon dates we attribute the last 0.5 m rupture to the earthquake of October 30, 1759. The older offset of 2.2 m most probably occurred in the earthquakes of May 20, 1202. These two events correlate with the findings at Ateret, about 12 km north of Bet-Zayda, where the 1202 earthquake produced 1.6 m of lateral displacement in E–W-striking defence walls of a Crusader castle, and an Ottoman mosque was offset 0.5 m in the earthquake of 1759. In the second group of trenches some 60 m farther south we found another offset channel. Its northern margin is displaced 15 m sinistrally whereas the southern margin shows only 9 m of sinistral offset. The dip slip component is 1.2 m, west side down. The different amounts of margin offset can be explained by erosion of the southern margin during the first 6 m of displacement. Additional slip of 9 m accrued after the stream had been abandoned and buried by a 2-m-thick lacustrine clay layers. Radiocarbon dates on organic residue provide the age control which indicates that the 15 m of slip has accrued over the past 5 kyr, yielding a short-term slip rate of 3 mm/yr for the late Holocene. It is possible that our study covers only part of the fault zone, hence we regard this mean slip rate to be a minimum for the DST. Based on other palaeoseismic studies the best estimate for Quaternary slip rate is 4±1 mm/yr.
The long historical record of earthquakes, the physical effects on ancient building structures and the palaeoseismology provide a unique opportunity for an interdisciplinary tectonic analysis along a major plate boundary and a realistic evaluation of the seismic hazard assessment in the Middle East. We demonstrate with micro-topographic surveys and trenching that the Dead Sea fault (DSF) offsets left-laterally by 13.6±0.2 m a repeatedly fractured ancient Roman aqueduct (older than AD 70 and younger than AD 30). Carbon-14 dating of faulted young alluvial deposits documents the occurrence of three large earthquakes in the past 2000 years between AD 100 and 750, between AD 700 and 1030 and between AD 990 and 1210. Our study provides the timing of late Holocene earthquakes and constrains the 6.9±0.1 mm/yr slip rate of the Dead Sea transform fault in northwestern Syria along the Missyaf segment. The antepenultimate and most recent faulting events may be correlated with the AD 115 and AD 1170 large earthquakes for which we estimate Mw=7.3–7.5. The ∼830 yr of seismic quiescence along the Missyaf fault segment implies that a large earthquake is overdue and may result in a major catastrophe to the population centres of Syria and Lebanon.
We studied the local seismicity of the Dead Sea basin for the period 1984–1997. Sixty percent of well-constrained microearthquakes (ML≤3.2) nucleated at depths of 20–32 km and more than 40% occurred below the depth of peak seismicity situated at 20 km. With the Moho at 32 km, the upper mantle appeared to be aseismic during the 14-year data period. A relocation procedure involving the simultaneous use of three regional velocity models reveals that the distribution of focal depths in the Dead Sea basin is stable. Lower-crustal seismicity is not an artifact created by strong lateral velocity variations or data-related problems. An upper bound depth uncertainty of ±5 km is estimated below 20 km, but for most earthquakes depth mislocations should not exceed ±2 km. A lithospheric strength profile has been calculated. Based on a surface heat flow of 40 mW m−2 and a quartz-depleted lower crust, a narrow brittle to ductile transition might occur in the crust around 380°C at a depth of 31 km. For the upper mantle, the brittle to ductile transition occurs in the model at 490°C and at 44 km depth. The absence of micro-seismicity in the upper mantle remains difficult to explain.
A high-resolution Holocene seismic history of the Dead Sea Transform (DST) is established from laminated sedimentary cores recovered at the shores of the Dead Sea. Radiocarbon dating and annual laminae counting yield excellent agreement between disturbed sedimentary structures (identified as seismites) and the historical earthquake record: All recent and historical strong events of the area were identified, including the major earthquakes of A.D. 1927, 1837, 1212, 1033, 749, and 31 B.C. The total of 53 seismites recognized along the entire Holocene profile indicate varying recurrence intervals of seismic activity between a few and 1000 years, with a conspicuous minimum rate at 2100–31 B.C. and a noticeable maximum during the past six to eight centuries. Most of the epicenters of the correlated earthquakes are situated very close to the Dead Sea (within 150 km) or up to 400 km north of it along the DST. Between 1000 B.C. and A.D. 1063, and from A.D. 1600 to recent time the epicenters are all located on the northern segment of the DST, whereas prior to 1000 B.C. and between A.D. 1000 and 1600 they appear to scatter along several segments of the DST. We establish how the local intensity exerts a control on the formation of seismites. At historically estimated intensities greater than VII, all well documented earthquakes are correlated, whereas at intensities smaller than VI none are matching.The periods with enhanced earthquake rate along the DST correlate with those along the North Anatolian Fault as opposed to the intervening East Anatolian Fault. This may indicate some elastic coupling on plate-boundary scale that may also underlie escape and extrusion tectonics, typical of continental collision.
Geomorphic and sedimentologic field studies and analyses of LANDSAT 5 images and topographic maps indicate 15 km of left-lateral displacement of a Pliocene large stream and alluvial fans along the Dead Sea transform in southern Israel and Jordan. In the central Arava valley, a rift valley located along the transform, there is a notable discrepancy between the number and location of the feeding drainage basins within the eastern margins of the Arava valley and those of the alluvial fans and the cross-rift large stream. A few of these large alluvial fans lack any feeding drainage basin. Furthermore, east of the large stream there is no drainage basin that could have fed it. These discrepancies between the physiography, locations, sizes, and lithological compositions of the feeding drainage basins and of the alluvial fans can be explained by 15 km of left-lateral movement since the Late Pliocene or the Early Pleistocene along the Arava-Dead Sea segment of the transform. This is one of the largest displacements of a landform and surficial alluvial deposit in the world. However, the resulting average long-term rate of movement is relatively small (0.3–0.75 cm/year).