Sumatra Project Page


Subduction Megathrust Earthquakes

The seismic and tsunami hazard posed by great subduction zone earthquakes has long been recognized, but in light of the Mw 9 2004 Sumatra-Andaman Islands and 2011 Japan earthquakes, and the resulting tsunamis, infrastructure damage and huge loss of life, it is clear that we continue to underestimate the hazard posed by such events. The studies presented here aim to better understand the processes controlling slip along subduction megatrust faults and ultimately improve seismic hazard assessment.


The December 26, 2004, Sumatra-Andaman Islands earthquake is one of the five largest in the seismic record, and it was followed three months later by the Mw 8.7 Banyak Islands earthquake along an ajacent segment of the subduction zone. Two years later, a third magnitude 8+ earthquake occurred offshore southern Sumatra. These earthquakes, however, have generated large aftershock sequences that essentially illuminate over 2000 km of subduction megathrust and allow us to conduct high resolution relocation and imaging studies that help us understand how these societally significant earthquakes work.


Methods and Major Findings

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EHB Catalog (note, this does not include auto-derived depth phases) - link to ISC

Relocations as described in Pesicek et al., JGR, 2010 - tomoDD.reloc.JGR.gz (439 Kb)

Relocations as described in Pesicek et al., JGR, 2010 extended through 2009 - tomoDD.reloc.NEW.gz (458 Kb)

Reloc format description -DD_reloc_format.pdf

Velocity Models:

P-wave velocity model as described in Pesicek et al., GJI, 2010 - PSumatraReg.pert (937 Kb)

Pert format description - pert_format.pdf



Widiyantoro S., J. Pesicek, and C. Thurber (2011), Subducting slab structure below the eastern Sunda arc inferred from non-linear seismic tomographic imaging, in R. Hall, M. Cottam, and M. Wilson (eds.), The SE Asian Gateway: History and Tectonics of Australia-Asia Collision, Geological Society of London Special Publication, 355,139-155.

Pesicek, J.D., C.H. Thurber, H. Zhang, H.R. DeShon, and E.R. Engdahl (2010b), Teleseismic Double-difference Relocation of Earthquakes along the Sumatra-Andaman Subduction Zone using a Three-Dimensional Model, J. Geophys. Res., 115, B10303, doi: 10.1029/2010JB007443. PDF

Pesicek, J.D., C.H. Thurber, S. Widiyantoro, H. Zhang, H.R. DeShon and E.R. Engdahl (2010a), Sharpening the tomographic image of the subducting slab below Sumatra, the Andaman Islands and Burma, Geophys. J. Int., 182, 433-453, doi: 10.1111/j.1365-246X.2010.04630.x. PDF

Pesicek, J., C.H. Thurber, S. Widiyantoro, E.R. Engdahl, and H.R. DeShon (2008), Complex slab subduction beneath Sumatra, Geophys. Res. Letts, 35, L20303, doi:10.1029/2008GL035262. PDF

Engdahl, E.R., A. Villasenor,  H.R. DeShon, and C. Thurber (2007), Teleseismic relocation and assessment of seismicity (1918-2005) in the region of the 2004 Mw 9 Sumatra-Andaman and 2005 M 8.7 Nias great earthquakes, Bull. Seismo. Soci. Am., 97 (1A), S43-S61, doi:10.1785/0120050614. PDF

Related Publications

Bilek, S., E.R. Engdahl, H.R. DeShon, and M. El Hariri (2011), The 25 October 2010 Sumatra tsunami earthquake: Slip in a slow patch, Geophys. Res. Letts., in press

DeShon, H.R., E.R. Engdahl, C.H. Thurber, and M. Brudzinski (2005), 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, Geophys. Res. Letts, 32, L24307, doi:10.1029/2005GL024188. PDF

Lay, T., H. Kanamori, C.J. Ammon, M. Nettles, S.N. Ward, R. Aster, S.L. Beck, S.L. Bilek, M.R. Brudzinski, R. Butler, H.R. DeShon, G. Ekstrom, K. Satake, and S. Sipkin (2005), The great Sumatra-Andaman earthquake of 26 December 2004, Science, 308, 1127-1133. PDF

General Information



Principle Investigators:

Heather DeShon - CERI at Univ. of Memphis

Cliff Thurber - Univ. of Wisconsin, Madison Jeremy Pesicek - Univ. of Wisconsin, Madison Haijiang Zhang - Univ. of Wisconsin, Madison

Bob Engdahl - Univ. of Colorado, Boulder

Sri Widiyantoro - Bandung Inst. of Technology

Mike Brudzinski - Miami Univ. Ohio


The study were supported by the National Science Foundation Earth Science directorate (EAR-0608988 to HRD, CT and HZ; EAR-0733505 to HRD; EAR-0337743 and EAR-0609613 to ERE; EAR- 0609535 to MB) and NASA (NNX06AF10G to CT). University and Institute support of the PIs, postdocs, and students was also critical to the success of these studies.

Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation, NASA, or the Universities.

Contact Us

hdeshon at, 901.678.1527

clifft at

pesicek at

Bob.Engdahl at Colorado.EDU

brudzimr at