Earthquake related tsunami hazard along the western coast of Thailand

Abstract. The primary background for the present study was a project to assist the authorities in Thailand with development of plans for how to deal with the future tsunami risk in both short and long term perspectives, in the wake of the devastating 26 December 2004 Sumatra-Andaman earthquake and tsunami. The study is focussed on defining and analyzing a number of possible future earthquake scenarios (magnitudes 8.5, 8.0 and 7.5) with associated return periods, each one accompanied by specific tsunami modelling. Along the most affected part of the western coast of Thailand, the 2004 tsunami wave caused a maximum water level ranging from 5 to 15 m above mean sea level. These levels and their spatial distributions have been confirmed by detailed numerical simulations. The applied earthquake source is developed based on available seismological and geodetic inversions, and the simulation using the source as initial condition agree well with sea level records and run-up observations. A conclusion from the study is that another megathrust earthquake generating a tsunami affecting the coastline of western Thailand is not likely to occur again for several hundred years. This is in part based on the assumption that the Southern Andaman Microplate Boundary near the Simeulue Islands constitutes a geologic barrier that will prohibit significant rupture across it, and in part on the decreasing subduction rates north of the Banda Ache region. It is also concluded that the largest credible earthquake to be prepared for along the part of the Sunda-Andaman arc that could affect Thailand, is within the next 50–100 years an earthquake of magnitude 8.5, which is expected to occur with more spatial and temporal irregularity than the megathrust events. Numerical simulations have shown such earthquakes to cause tsunamis with maximum water levels up to 1.5–2.0 m along the western coast of Thailand, possibly 2.5–3.0 m on a high tide. However, in a longer time perspective (say more than 50–100 years) the potentials for earthquakes of similar magnitude and consequences as the 2004 event will become gradually larger and eventually posing an unacceptable societal risk. These conclusions apply only to Thailand, since the effects of an M 8.5 earthquake in the same region could be worse for north-western Sumatra, the Andaman and Nicobar Islands, maybe even for Sri Lanka and parts of the Indian coastline. Moreover, further south along the Sunda arc the potentials for large ruptures are now much higher than for the region that ruptured on 26 December 2004.

[1]  Yuki Sawai,et al.  Predecessors of the giant 1960 Chile earthquake , 2005, Nature.

[2]  Chalermchon Satirapod,et al.  Insight into the 2004 Sumatra–Andaman earthquake from GPS measurements in southeast Asia , 2005, Nature.

[3]  Kenji Satake,et al.  Report on Post Tsunami Survey along the Myanmar Coast for the December 2004 Sumatra-Andaman Earthquake , 2005 .

[4]  J. Tromp,et al.  The Great Sumatra-Andaman Earthquake , 2005 .

[5]  Remko Scharroo,et al.  Satellite Altimeters Measure Tsunami , 2005 .

[6]  Hermann Fritz,et al.  Observations by the International Tsunami Survey Team in Sri Lanka , 2005, Science.

[7]  A. Berman.  The Great Sumatra-Andaman Earthquake of December 26, 2004: New Insights That Will Change the Next 40 Years and the Plate Tectonic Paradigm , 2005 .

[8]  Peter M. Shearer,et al.  Extent, duration and speed of the 2004 Sumatra–Andaman earthquake imaged by the Hi-Net array , 2005, Nature.

[9]  Emile A. Okal,et al.  Seismology: Speed and size of the Sumatra earthquake , 2005, Nature.

[10]  Yehuda Bock,et al.  Plate-boundary deformation associated with the great Sumatra–Andaman earthquake , 2006, Nature.

[11]  E. Engdahl,et al.  Constraining the boundary between the Sunda and Andaman subduction systems: Evidence from the 2002 Mw 7.3 Northern Sumatra earthquake and aftershock relocations of the 2004 and 2005 great earthquakes , 2005 .

[12]  A. Frankel,et al.  Probabilistic seismic hazard analysis for Sumatra, Indonesia and across the Southern Malaysian Peninsula , 2004 .

[13]  Kinjiro Kajiura.  Tsunami Energy in Relation to Parameters of the Earthquake Fault Model , 1982 .

[14]  F. Pollitz,et al.  The Size and Duration of the Sumatra-Andaman Earthquake from Far-Field Static Offsets , 2005, Science.

[15]  Chen Ji,et al.  Rupture Process of the 2004 Sumatra-Andaman Earthquake , 2005, Science.

[16]  R. Bilham,et al.  A Flying Start, Then a Slow Slip , 2005, Science.

[17]  Chen Ji,et al.  Coseismic Slip and Afterslip of the Great Mw 9.15 Sumatra–Andaman Earthquake of 2004 , 2007 .

[18]  D. Wells,et al.  New empirical relationships among magnitude, rupture length, rupture width, rupture area, and surface displacement , 1994, Bulletin of the Seismological Society of America.

[19]  Y. Okada.  Internal deformation due to shear and tensile faults in a half-space , 1992, Bulletin of the Seismological Society of America.

[20]  John McCloskey,et al.  Indonesian earthquake: Earthquake risk from co-seismic stress , 2005, Nature.

[21]  Costas E. Synolakis,et al.  A Theoretical Comparison of Tsunamis from Dislocations and Landslides , 2003 .

[22]  H. Kanamori,et al.  Seismology: Energy radiation from the Sumatra earthquake , 2005, Nature.

[23]  H. Kanamori.  Seismological Aspects of the December 2004 Great Sumatra-Andaman Earthquake , 2006 .

[24]  Jeroen Tromp,et al.  Earth's Free Oscillations Excited by the 26 December 2004 Sumatra-Andaman Earthquake , 2005, Science.

[25]  E. Engdahl,et al.  Global teleseismic earthquake relocation with improved travel times and procedures for depth determination , 1998, Bulletin of the Seismological Society of America.

[26]  Kenji Satake,et al.  Time and size of a giant earthquake in Cascadia inferred from Japanese tsunami records of January 1700 , 1996, Nature.

[27]  Vasily Titov,et al.  The Global Reach of the 26 December 2004 Sumatra Tsunami , 2005, Science.

[28]  Carl B. Harbitz,et al.  The Storegga Slide tsunami—comparing field observations with numerical simulations , 2005 .

[29]  Farrokh Nadim,et al.  On Tsunami Risk Assessment for the West Coast of Thailand , 2006 .

[30]  R. Bilham,et al.  Partial and Complete Rupture of the Indo-Andaman Plate Boundary 1847-2004 , 2005 .

[31]  E. R. Engdahl,et al.  41 - Global Seismicity: 1900–1999 , 2002 .

[32]  G. Pedersen.  Grid effects on tsunamis in nearshore regions , 1995 .

[33]  Yun‐tai Chen,et al.  International Handbook of Earthquake and Engineering Seismology , 2004 .

[34]  Q. Schiermeier.  Natural disasters: The chaos to come , 2005, Nature.

[35]  Lori Dengler,et al.  Northwest Sumatra and Offshore Islands Field Survey after the December 2004 Indian Ocean Tsunami , 2006 .

[36]  W. Iwan.  Preface to the Special Issue on the Great Sumatra Earthquakes and Indian Ocean Tsunamis of 26 December 2004 and 28 March 2005 , 2006 .

[37]  A. Arakawa,et al.  Numerical methods used in atmospheric models , 1976 .

[38]  Costas E. Synolakis,et al.  Runup Measurements of the December 2004 Indian Ocean Tsunami , 2006 .

[39]  J. Wiseman,et al.  The general bathymetric chart of the oceans , 1955 .

[40]  P. Shearer,et al.  Rupture details of the 28 March 2005 Sumatra Mw 8.6 earthquake imaged with teleseismic P waves , 2005 .

[41]  Thorne Lay,et al.  Rigidity variations with depth along interplate megathrust faults in subduction zones , 1999, Nature.

[42]  Tsunami generation and propagation from the Mjølnir asteroid impact , 2007 .

[43]  A. E. Gill.  Atmosphere-Ocean Dynamics , 1982 .

[44]  Kenji Satake,et al.  Tsunami Source of the 2004 Sumatra–Andaman Earthquake Inferred from Tide Gauge and Satellite Data , 2007 .

[45]  C. Synolakis,et al.  Northern Sumatra Field Survey after the December 2004 Great Sumatra Earthquake and Indian Ocean Tsunami , 2006 .

[46]  Satish C. Singh.  Sumatra earthquake research indicates why rupture propagated northward , 2005 .

[47]  John J. Clague,et al.  Evidence for large earthquakes at the Cascadia Subduction Zone , 1997 .

[48]  John McCloskey,et al.  Seismology: Earthquake risk on the Sunda trench , 2005, Nature.

[49]  Efim Pelinovsky,et al.  Simulation of the trans-oceanic tsunami propagation due to the 1883 Krakatau volcanic eruption , 2003 .

[50]  Gerassimos A. Papadopoulos,et al.  The large tsunami of 26 December 2004: Field observations and eyewitnesses accounts from Sri Lanka, Maldives Is. and Thailand , 2006 .

[51]  P. Liu,et al.  An analysis of 2004 Sumatra earthquake fault plane mechanisms and Indian Ocean tsunami , 2006 .

[52]  G. Pedersen,et al.  Propagation of the Dec. 26, 2004, Indian Ocean Tsunami: Effects of Dispersion and Source Characteristics , 2006 .

[53]  C. Mei.  The applied dynamics of ocean surface waves , 1983 .

[54]  K. Haugen,et al.  A parametric study of tsunamis generated by submarine slides in the Ormen Lange/Storegga area off western Norway , 2005 .

[55]  G. Pedersen.  A note on tsunami generation by earthquakes , 2001 .

[56]  R. K. Chadha,et al.  Tsunami Runup Survey along the Southeast Indian Coast , 2006 .

[57]  Matthias Ohrnberger,et al.  Tracking the rupture of the Mw = 9.3 Sumatra earthquake over 1,150 km at teleseismic distance , 2005, Nature.

[58]  Christopher H. Scholz,et al.  The Mechanics of Earthquakes and Faulting 3 rd Edition , 2002 .

[59]  Thorkild Aarup,et al.  Tide gauge observations of the Indian Ocean tsunami, December 26, 2004 , 2005 .