Teleseismic Relocation and Assessment of Seismicity (1918–2005) in the Region of the 2004 Mw 9.0 Sumatra–Andaman and 2005 Mw 8.6 Nias Island Great Earthquakes

The M w 9.0 2004 Sumatra–Andaman Islands and M w 8.6 Nias Island great earthquake sequences have generated over 5000 catalog-reported earthquakes along ∼1700 km of the Sumatra–Andaman and western Sunda regions. Studies of prior regional seismicity have been limited to global catalog locations that often have poorly constrained epicenters and depths. Approximately 3650 teleseismically well- recorded earthquakes occurring in this region during the period 1918–2005 are relocated with special attention to focal depth. Reduced uncertainties of epicenters and depths in the region (on the order of 15 and 10 km, respectively) foster interpretation of focal mechanism data and provide additional details about the subducting Indian and Australian plates. The revised earthquake dataset reveals a sharp delineation between aftershocks of the 2004 and 2005 earthquakes near Simeulue Island and a steepening in slab dip from south to north. The downdip width of the aftershock zone of the 2004 M w 9.0 earthquake varies from ∼200 km at its northern end to ∼275 km at its southern end, and events located between 35 and 70 km focal depth occur more frequently in the southernmost section of this aftershock zone. Outer- rise and near-trench normal and strike-slip faulting earthquakes also increase in frequency following the 2004 and 2005 earthquakes. Earthquake swarms triggered along the Andaman backarc spreading center both north of Sumatra and near Siberut Island, 100 km south of the Nias Island aftershock sequence, illustrate the complex and variable nature of seismicity following these great earthquakes.

[1]  A. Dziewoński,et al.  Multiple CMT source analysis of the 2004 Sumatra earthquake , 2005 .

[2]  E. Engdahl.  Application of an improved algorithm to high precision relocation of ISC test events , 2006 .

[3]  T. Lay,et al.  Tsunami earthquakes possibly widespread manifestations of frictional conditional stability , 2002 .

[4]  John H. Woodhouse,et al.  Determination of earthquake source parameters from waveform data for studies of global and regional seismicity , 1981 .

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

[6]  H. Kanamori.  Mechanism of tsunami earthquakes , 1972 .

[7]  J. Dewey,et al.  Rupture process of an extended earthquake sequence: Teleseismic analysis of the Chilean Earthquake of March 3, 1985 , 1988 .

[8]  E. R. Engdahl,et al.  Constraints on seismic velocities in the Earth from traveltimes , 1995 .

[9]  R. Bilham,et al.  Source area and rupture parameters of the 31 December 1881 Mw = 7.9 Car Nicobar earthquake estimated from tsunamis recorded in the Bay of Bengal , 2003 .

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

[11]  L. Sykes,et al.  Loci and maximum size of thrust earthquakes and the mechanics of the shallow region of subduction zones , 1988 .

[12]  H. Kanamori,et al.  The Great Sumatra-Andaman Earthquake of 26 December 2004 , 2005, Science.

[13]  C. Thurber,et al.  Advances in seismic event location , 2000 .

[14]  N. Chamot-Rooke,et al.  The building of pericratonic mountain ranges : structural and kinematic constraints applied to GIS-based reconstructions of SE Asia , 2003 .

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

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

[17]  Kenneth W. Hudnut,et al.  Uplift and subsidence associated with the great Aceh‐Andaman earthquake of 2004 , 2006 .

[18]  H. Kanamori,et al.  Temporal variation of large intraplate earthquakes in coupled subduction zones , 1989 .

[19]  W. Mccann,et al.  Seismic history and seismotectonics of the Sunda Arc , 1987 .

[20]  Martin J. Siegert,et al.  EOS Trans. AGU , 2003 .

[21]  John H. Woodhouse,et al.  CENTROID-MOMENT TENSOR SOLUTIONS FOR 201 MODERATE AND LARGE EARTHQUAKES OF 1981 , 1983 .

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

[23]  Pierre Henry,et al.  The Sumatra subduction zone: A case for a locked fault zone extending into the mantle , 2004 .

[24]  C. Frohlich,et al.  How well constrained are well‐constrained T, B, and P axes in moment tensor catalogs? , 1999 .

[25]  R. Mccaffrey.  Active tectonics of the Eastern Sunda and Banda Arcs , 1988 .

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

[27]  Walter H. F. Smith,et al.  New, improved version of generic mapping tools released , 1998 .

[28]  E. R. Engdahl,et al.  Step-wise relocation of ISC earthquake hypocenters for linearized tomographic imaging of slab structure , 1992 .

[29]  Harmen Bijwaard,et al.  Closing the gap between regional and global travel time tomography , 1998 .

[30]  William Hung Kan Lee,et al.  International handbook of earthquake and engineering seismology , 2002 .

[31]  Clifford H. Thurber,et al.  Advances in Global Seismic Event Location , 2000 .

[32]  K. Sieh,et al.  Paleogeodetic records of seismic and aseismic subduction from central Sumatran microatolls, Indonesia , 2004 .

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

[34]  C. Scholz.  Earthquakes and friction laws , 1998, Nature.

[35]  J. Curray,et al.  Tectonics and history of the Andaman Sea region , 2005 .

[36]  G. Stone,et al.  Hurricane Ivan's Impact along the northern Gulf Of Mexico , 2005 .

[37]  B. Kennett,et al.  The relationship of the seismic source and subduction zone structure for the 2004 December 26 Sumatra-Andaman earthquake , 2005 .

[38]  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.

[39]  Yehuda Bock,et al.  Crustal motion in Indonesia from Global Positioning System measurements , 2003 .

[40]  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 .

[41]  K. Sieh,et al.  The giant subduction earthquakes of 1797 and 1833, West Sumatra: Characteristic couplets, uncharacteristic slip , 2004 .

[42]  G. L. Choy,et al.  Broad-band deconvolution of GDSN data , 1982 .

[43]  Y. Bock,et al.  Strain partitioning during oblique plate convergence in northern Sumatra: Geodetic and seismologic constraints and numerical modeling , 2000 .

[44]  K. Sieh,et al.  A Comparative Study of the Sumatran Subduction-Zone Earthquakes of 1935 and 1984 , 2002 .

[45]  P. Earle,et al.  Seismicity Associated with the Sumatra–Andaman Islands Earthquake of 26 December 2004 , 2007 .

[46]  K. Sieh.  Aceh–Andaman earthquake: What happened and what's next? , 2005, Nature.

[47]  Javier F. Pacheco,et al.  Nature of seismic coupling along simple plate boundaries of the subduction type , 1993 .

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

[49]  L. Ruff,et al.  Outer-rise earthquakes and seismic coupling , 1983 .

[50]  Masanao Shinohara,et al.  Aftershock distribution of the 26 December 2004 Sumatra-Andaman earthquake from ocean bottom seismographic observation , 2006 .

[51]  G. Ekström.  A very broad band inversion method for the recovery of earthquake source parameters , 1989 .

[52]  Stephen C. Myers,et al.  Epicentre accuracy based on seismic network criteria , 2004 .

[53]  Sunaryo,et al.  Lateral variation in slab orientation beneath Toba Caldera, northern Sumatra , 1996 .

[54]  B. Kennett,et al.  Traveltimes for global earthquake location and phase identification , 1991 .

[55]  R. Bürgmann,et al.  The motion and active deformation of India , 2001 .

[56]  Danny Hilman Natawidjaja,et al.  Neotectonics of the Sumatran fault, Indonesia , 2000 .

[57]  M. Yamano,et al.  The seismogenic zone of subduction thrust faults , 1997 .

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

[59]  Göran Ekström,et al.  Global CMT analysis of moderate earthquakes, Mw ≧ 4.5, using intermediate-period surface waves , 1998, Bulletin of the Seismological Society of America.