Extreme runup from the 17 July 2006 Java tsunami
Hermann M. Fritz,1Widjo Kongko,2Andrew Moore,3Brian McAdoo,4James Goff,5
Carl Harbitz,6Burak Uslu,7Nikos Kalligeris,8Debora Suteja,9Kenia Kalsum,9
Vasily Titov,10Aditya Gusman,9Hamzah Latief,9Eko Santoso,11Sungsang Sujoko,2
Dodi Djulkarnaen,9Haris Sunendar,9and Costas Synolakis7,8
Received 19 January 2007; revised 5 April 2007; accepted 8 May 2007; published 16 June 2007.
south coast of western Java, Indonesia, generated a tsunami
that effected over 300 km of coastline and killed more than
600 people, with locally focused runup heights exceeding
waves breaking masked any preceding withdrawal of the
water from the shoreline, making this tsunami difficult to
detect before impact. An International Tsunami Survey Team
was deployed within one week and the investigation covered
more than 600 km of coastline. Measured tsunami heights
and run-up distributions were uniform at 5 to 7 m along
200 km of coast; however there was a pronounced peak on
the south coast of Nusa Kambangan, where the tsunami
impact carved a sharp trimline in a forest at elevations up to
21 m and 1 km inland. Local flow depth exceeded 8 m along
the elevated coastal plain between the beach and the hill
the island suggest a possible local submarine slump or mass
movement. Citation: Fritz, H. M., et al. (2007), Extreme runup
from the 17 July 2006 Java tsunami, Geophys. Res. Lett., 34,
The 17 July 2006 magnitude Mw7.8 earthquake offthe
 On Monday July 17, 2006 at 08:19:28 UTC
(15:19:28 local time), a magnitude Mw 7.8 earthquake
occurred 200 km off the south coast of western Java in
Indonesia and ruptured ?200 km along the trench [Ammon
et al., 2006]. According to Reymond and Okal , this
earthquake involved very slow rupture through the energy
to moment ratio Q = log10(EE/M0) = ?6.1 compared to the
usual Q = ?4.9 [Newman and Okal, 1998]. Similarly, its T
waves recorded at Diego-Garcia feature a parameter g [Okal
et al., 2003] deficient by two orders of magnitude compared
to those of typical events from the Sumatra series [Reymond
and Okal, 2006]. This slow earthquake generated a tsunami
that severely damaged coastal communities along the south-
west and south-central Java provinces. The estimated tsu-
nami death toll exceeds 600 along a 200 km stretch of
coastline, with 413 fatalities in and around the tourist resort
of Pangandaran. Flow depths of up to 5 m caused the
destruction of 3000 houses in Pangandaran. A lifeguard
reported that, mercifully, the tsunami hit on Monday after-
noon, when there were few tourists on the beaches com-
pared to the preceding Sunday. In Pangandaran, the majority
of the dead were women (205) and children (78). This
tsunami was difficult to escape because the affected area
was too close to the epicenter for an early warning system to
have been effective, and there was little or no felt ground
shaking. Lifeguards sitting on elevated concrete towers had
difficulties in recognizing the initial ocean withdrawal,
because large wind waves breaking at the coast masked
most of the recession of the water at the shoreline that
preceded the tsunami.
 Transoceanic propagation of the tsunami was com-
puted with the MOST-model [Titov et al., 2005] and
resultant maximum tsunami wave heights are shown in
 In the far field, 2000 km SSE of the earthquake
epicenter, the tsunami struck the Steep Point region of
Western Australia close to high tide. At Steep Point, the
tsunami runup was on the order of 2 m with inundation
distances exceeding 100 m after adjusting for the tide level
upon arrival of the 3 tsunami waves between 11:30 and
12:00 UTC. At a sand spit within Shelter Bay a runup of 7 m
was reported on a steep limestone cliff within 10 m of the
shoreline [Prendergast and Brown, 2006]. The runup at
Steep Point in Australia is comparable to the 2004 Indian
Ocean tsunami runup in northern Oman at 5000 km from
the epicenter of the Sumatra-Andaman earthquake [Okal et
al., 2006]. The 7 m runup at a cliff is not comparable to
similar runup heights several hundred meters from the
shoreline in Somalia [Fritz and Borrero, 2006].
2.Post-Tsunami Field Survey
 An International Tsunami Survey Team of scientists
from Indonesia, the US, New Zealand, Norway and Greece
GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L12602, doi:10.1029/2007GL029404, 2007
1School of Civil and Environmental Engineering, Georgia Institute of
Technology, Savannah, Georgia, USA.
2Coastal Dynamic Research Center, Agency for the Assessment and
Application of Technology, Yogyakarta, Indonesia.
3Department of Geology, Kent State University, Kent, Ohio, USA.
4Department of Geology and Geography, Vassar College, Poughkeep-
sie, New York, USA.
5National Institute of Water and Atmospheric Research, Christchurch,
6Norwegian Geotechnical Institute, Oslo, Norway.
7Tsunami Research Center, Viterbi School of Engineering, University of
Southern California, Los Angeles, California, USA.
8Department of Environmental Engineering, Technical University of
Crete, Chanea, Greece.
9Department of Oceanography, Center for Coastal and Marine
Development, Institute of Technology Bandung, Bandung, Indonesia.
10NOAA Pacific Marine and Environmental Laboratory, Seattle,
11Center of Technology for Land Resources and Disaster Mitigation,
Agency for the Assessment and Application of Technology, Jakarta,
Copyright 2007 by the American Geophysical Union.
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surveyed more than 600 km of coastline within 3 weeks of
the event. The survey team was granted access to the high
security prison island of Nusa Kambangan. The team
measured local flow depths, tsunami heights, maximum
runup, inundation distances, collected sediment samples
and interviewed eyewitnesses in accordance with estab-
lished methods [Synolakis and Okal, 2005]. The survey
team measured 168 tsunami flow depths and runup heights.1
Figure 2 shows the measured maximum tsunami and runup
heights. Tsunami heights and runup distributions show a
the prison town Permisan. Measured data were corrected for
tide level at the time of tsunami arrival on the basis of tide
predictions for the ports of Cilacap, Tjilauteurem, and
Segoro. The tsunami arrived as the sea approached low tide
rendering the tide level correction less sensitive to the exact
 The tsunami deposited sand sheets ?5–15 cm thick
at several locations along the coast, primarily in rice paddy
fields that dominate behind the beach ridge. The sand sheet
thinned inland although deposition continued to within
meters of the inundation limit. The sands are commonly
plane laminated, and often have a layer of magnetite at the
base. In places, some of the underlying soil was ripped-up
and incorporated into the overlying deposit. At Pasir Putih,
Pangandaran Peninsula National Park, a layer of fresh coral
rubble was deposited on what had been a white sand beach.
 Numerous video interviews of eyewitnesses were
carried out to record estimates of the number of waves,
their height, period and tsunami arrival time. Eyewitnesses
described two to three main waves with an initial recession
of 100 m corresponding to a leading depression N-wave
[Tadepalli and Synolakis, 1994]. The second wave was
reported as the highest with a white upper part suggestive
of bore formation and a black sediment-rich lower section.
The wave was described as preceded by a rumbling noise.
The tsunami arrived between 16:00 and 16:30 pm local time
depending on location, with sea conditions returning to
normal after about 30 min.
 Even with little ground shaking as warning, in some
locales many people noticed the incoming tsunami and
correctly identified it as such about tens of seconds prior
to impact. A common problem seems to have been a lack of
understanding where the nearest tsunami safe location was,
how high of an elevation would provide safety, and how
long to stay there. Evacuation drills are thus seen particu-
larly important when the tsunami is recognized only shortly
before impact, when self-evacuation occurs spontaneously.
3.Nusa Kambangan Trimline in Coastal Forest
 Nusa Kambangan, literally ‘‘floating island’’, is off
the southern coast of Central Java province. It is separated
from Java’s mainland by a narrow strait, Segara Anakan.
The island is approximately 30 km long and 4 km wide with
a central ridge up to 202 m high (Figure 3). The island,
often referred to as the ‘‘Alcatraz’’ of Indonesia, is off-limits
to most casual visitors because of the three high-security
prisons located on the island; however, the team was
granted limited, ‘‘escorted’’ access.
 Nusa Kambangan has a vast nature reserve with
large stretches of virgin forest. The tsunami impact carved
Figure 1. Maximum estimated tsunami heights across the entire Indian Ocean computed using the MOST-model.
1Auxiliary materials are available at ftp://ftp.agu.org/apend/gl/
FRITZ ET AL.: 2006 JAVA TSUNAMI
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a sharp trimline in the forest at elevations between 10 and
21 m along the hill slope behind a 1.5 km long and 50 m
wide beach, significantly exceeding runup measurements
elsewhere along the coast. Pandanus, Hibiscus and large
Cocos trees up to 500 m inland were damaged and/or
uprooted by the tsunami and their debris piled several
meters high along the coastal plain separating the beach
and the hill slope (Figure 4). The severely damaged forest –
several hundred meters inland – along with the several
meters high piles of debris from uprooted trees suggests that
protective coastal vegetation can be overwhelmed by large
enough tsunamis [Latief and Hadi, 2006], whereas in some
cases during 2004 the Indian Ocean tsunami a protective
role was attributed to coastal vegetation [e.g., Danielsen et
al., 2005; Synolakis and Kong, 2006]. Beach erosion with
removal of more than 1 vertical meter of sand was observed,
with substantial sediment deposits found in the floodplain
behind the beach ridge. Local flow depths exceeded 8 m
above terrain along the elevated coastal plain 200 m inland
from the beach – for reference, flow depths during the 2004
Indian Ocean tsunami reached 5 m in Sri Lanka [Liu et al.,
2005], 16 m in Banda Aceh [Borrero, 2005] and 20 m on
Pulau Breuh off the north tip of Sumatra [Jaffe et al., 2006].
We infer that the focused tsunami and runup heights on the
island suggest a possible local submarine slump or mass
movement given the favorable bathymetry in the area with
an offshore canyon. The discriminant I2= 5.9 ? 10?2,
which relates the maximum runup to the characteristic width
is significantly larger than the limit I2 = 10?4between
tectonic and landslide sources indicating a landslide source
[Okal and Synolakis, 2004]. However, this inference
remains to be investigated by bathymetric surveys.
 Fortunately the coastal zone on Kambangan was
largely uninhabited limiting the death toll to 19 ‘‘farmers’’
although at least one of the prisons was inside the flood
plain near the maximum inundation distance. The island
Figure 3. Nusa Kambangan overview and detail with measured runup heights (dark grey) and tsunami heights (light grey).
Figure 2. Measured tsunami runup (dark grey) and tsunami heights (light grey) along Java’s south coast.
FRITZ ET AL.: 2006 JAVA TSUNAMI
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took the brunt of the impact and protected the town of
Cilacap located on the mainland behind a submerged shoal
and the island, just to the east of Permisan. Cilacap has the
only natural harbor with deep-water berthing facilities on
Java’s south coast as well as an oil terminal and is therefore
visited by large vessels. The harbor is located in the strait
naturally shielded by Nusa Kambangan. At the pilot station,
the moored pilot boat Maiden III (GRT 332t) touched the
ground corresponding to an initial 1.5 m draw down of the
water level, which was followed by a 1 m rise.
 Given that this is the second tsunami in 12 years to
strike South Java – the 1994 event was also produced by a
slow earthquake and killed about 200 people [Synolakis et
al., 1995; Tsuji et al., 1995] – community-based education
and awareness programs are particularly essential to help
save lives in locales at risk from near-source tsunamis, when
neither the shoreline recession nor the ground shaking can
be expected to be easily recognized as precursors [Sieh,
2006; Synolakis, 2006]. One encouraging sign is the con-
duct of evacuation drills in south Java, undertaken in the
immediate aftermath of this tsunami [Kerr, 2006].
 The rapid response of the survey team in visiting
Java after the 17 July 2006 event led to the recovery of
important data on the characteristics of tsunami impact in
the near field. This tsunami was difficult to escape as the
earthquake was hardly felt, no warnings were given to the
affected population prior to the impact, and the initial
drawdown was masked by the receding tide and wind
waves. The prison island of Nusa Kambangan in Central
Java was by far the area hardest hit with runup heights up to
21 m and local flow depths exceeding 8 m. We infer that the
focused tsunami and runup heights on the island suggest a
possible local submarine slump or mass movement. The
destruction of an entire forest several hundred meters inland
with debris piling several meters high demonstrates the
limits of forests as protective measures against tsunamis.
National Science Foundation through the NSF SGER-award CMS-
0646278 and by NSF PIRE award 0530151 to B.G.M. This publication
is partially funded by the Joint Institute for the Study of the Atmosphere
and Ocean (JISAO) under NOAA Cooperative Agreement NA17RJ1232,
Contribution 1399, NOAA contribution 3071.
The survey team was supported by the
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carved into the forest by the tsunami, and (b) scars on the bark of a tree indicating more than 8 m flow depth 200 m from
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D. Djulkarnaen, A. Gusman, K. Kalsum, H. Latief, H. Sunendar, and
D. Suteja, Department of Oceanography, Center for Coastal and Marine
Development, Institute of Technology Bandung, Jalan Ganesha 10,
Bandung 40132, Indonesia.
H. M. Fritz, School of Civil and Environmental Engineering, Georgia
Institute of Technology, 210 Technology Circle, Savannah, GA 31407,
J. Goff, National Institute of Water and Atmospheric Research, P.O. Box
8602, Christchurch, New Zealand. (firstname.lastname@example.org)
C. Harbitz, Norwegian Geotechnical Institute, P.O. Box 3930, Ulleval
Stadion, N-0806 Oslo, Norway. (email@example.com)
N. Kalligeris, Department of Environmental Engineering, Technical
University of Crete, Chanea GR-73100, Greece.
W. Kongko and S. Sujoko, Coastal Dynamic Research Center, Agency
for the Assessment and Application of Technology, Yogyakarta 55281,
B. McAdoo, Department of Geology and Geography, Vassar College,
Box 735-124, Poughkeepsie, NY 12604, USA. (firstname.lastname@example.org)
A. Moore, Department of Geology, Kent State University, Kent, OH
44242, USA. (email@example.com)
E. Santoso, Center of Technology for Land Resources and Disaster
Mitigation, Agency for the Assessment and Application of Technology, J1.
MH Thamrin No. 8, Jakarta 10340, Indonesia. (firstname.lastname@example.org)
C. Synolakis and B. Uslu, Tsunami Research Center, Viterbi School of
Engineering, University of Southern California, USC-2531, Los Angeles,
CA 90089-2531, USA. (email@example.com)
V. Titov, NOAA Pacific Marine and Environmental Laboratory, 7600
Sand Point Way NE, Seattle 98115, WA, USA. (firstname.lastname@example.org)
FRITZ ET AL.: 2006 JAVA TSUNAMI
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