Viscoelastic relaxation in a heterogeneous Earth following the 2004 Sumatra–Andaman earthquake

Abstract Consideration of the three-dimensional heterogeneity of mantle rheology allows models of viscoelastic relaxation following the 2004 Sumatra–Andaman earthquake to simultaneously fit both the observed far-field and near-field postseismic deformation. We use horizontal and vertical campaign and continuous GPS observations from the Andaman, Nicobar, and Sumatran forearc islands, mainland Sumatra, Thailand, the Malay Peninsula, the Indian Ocean, and southern India, spanning the first five years of postseismic deformation. The postseismic relaxation models consider contributions from the 2004 Mw 9.2 Sumatra–Andaman, the 2005 Mw 8.7 Nias, and 2007 Mw 8.4 Bengkulu earthquakes. Far-field motions to the east of the ruptures are equally well fit by homogeneous or laterally variable earth models. However, only models with contrasting rheology across the subducting slab, a ten-times higher mantle viscosity under the Indian Ocean lithosphere than the backarc mantle, can also produce the observed enduring postseismic uplift along the forearc and lack of far-field transient displacements in southern India. While postseismic uplift of forearc stations can also be produced by rapid and enduring down-dip afterslip, the inferred rheology structure is consistent with the distribution of mantle temperature inferred from seismic tomography.

[1]  Timothy Ian Melbourne,et al.  Rapid postseismic transients in subduction zones from continuous GPS , 2002 .

[2]  R. Dietmar Müller,et al.  Digital isochrons of the world's ocean floor , 1997 .

[3]  Modelling post-seismic displacements in Thai geodetic network due to the Sumatra-Andaman and Nias earthquakes using GPS observations , 2012 .

[4]  A. R. Bansal,et al.  GPS measurements of postseismic deformation in the Andaman-Nicobar region following the giant 2004 Sumatra-Andaman earthquake , 2008 .

[5]  Kelin Wang,et al.  Three-dimensional viscoelastic finite element model for postseismic deformation of the great 1960 Chile earthquake , 2004 .

[6]  Walter D. Mooney,et al.  Poroelastic stress-triggering of the 2005 M8.7 Nias earthquake by the 2004 M9.2 Sumatra–Andaman earthquake , 2010 .

[7]  K. Heki,et al.  Slow postseismic recovery of geoid depression formed by the 2004 Sumatra‐Andaman Earthquake by mantle water diffusion , 2007 .

[8]  Kelin Wang,et al.  Deformation cycles of subduction earthquakes in a viscoelastic Earth , 2012, Nature.

[9]  Archie Paulson,et al.  Modelling post-glacial rebound with lateral viscosity variations , 2005 .

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

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

[12]  E. Engdahl,et al.  Structural context of the great Sumatra‐Andaman Islands earthquake , 2008 .

[13]  Slow Slip Acceleration beneath Andaman Islands Triggered by the 11 April 2012 Indian Ocean Earthquakes , 2014 .

[14]  F. Pollitz,et al.  Effect of 3-D viscoelastic structure on post-seismic relaxation from the 2004 M= 9.2 Sumatra earthquake , 2008 .

[15]  R. Bilham,et al.  Postseismic deformation of the Andaman Islands following the 26 December, 2004 Great Sumatra–Andaman earthquake , 2007 .

[16]  Kelin Wang,et al.  Spherical‐Earth finite element model of short‐term postseismic deformation following the 2004 Sumatra earthquake , 2012 .

[17]  Hiroshi Takiguchi,et al.  Crustal deformations associated with the great Sumatra-Andaman earthquake deduced from continuous GPS observation , 2005 .

[18]  Peter M. Shearer,et al.  Lessons Learned from the 2004 Sumatra-Andaman Megathrust Rupture , 2010 .

[19]  T. Dixon,et al.  17. Elastic and Viscoelastic Models of Crustal Deformation in Subduction Earthquake Cycles , 2007 .

[20]  Rongjiang Wang,et al.  Investigation on afterslip and steady state and transient rheology based on postseismic deformation and geoid change caused by the Sumatra 2004 earthquake , 2011 .

[21]  Michael H. Ritzwoller,et al.  Thermodynamic constraints on seismic inversions , 2004 .

[22]  Roland Bürgmann,et al.  Evidence of power-law flow in the Mojave desert mantle , 2004, Nature.

[23]  A. Lowry,et al.  Andaman Postseismic Deformation Observations: Still Slipping after All These Years? , 2012 .

[24]  J. Avouac,et al.  From Geodetic Imaging of Seismic and Aseismic Fault Slip to Dynamic Modeling of the Seismic Cycle , 2015 .

[25]  Georg Dresen,et al.  Rheology of the Lower Crust and Upper Mantle: Evidence from Rock Mechanics, Geodesy, and Field Observations , 2008 .

[26]  E. Apel Shells on a Sphere: Tectonic Plate Motion and Plate Boundary Deformation , 2011 .

[27]  Fred F. Pollitz,et al.  Upper mantle rheology from GRACE and GPS postseismic deformation after the 2004 Sumatra‐Andaman earthquake , 2010 .

[28]  Yehuda Bock,et al.  Frictional Afterslip Following the 2005 Nias-Simeulue Earthquake, Sumatra , 2006, Science.

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

[30]  David J. Wald,et al.  Slab1.0: A three‐dimensional model of global subduction zone geometries , 2012 .

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

[32]  Riccardo E. M. Riva,et al.  Postseismic GRACE and GPS observations indicate a rheology contrast above and below the Sumatra slab , 2015 .

[33]  F. Pollitz,et al.  Post-seismic relaxation following the great 2004 Sumatra-Andaman earthquake on a compressible self-gravitating Earth , 2006 .

[34]  Eric J. Fielding,et al.  Coseismic and Postseismic Slip of the 2004 Parkfield Earthquake from Space-Geodetic Data , 2006 .

[35]  Chen Ji,et al.  Partial rupture of a locked patch of the Sumatra megathrust during the 2007 earthquake sequence , 2008, Nature.

[36]  K. Sieh,et al.  Rupture Kinematics of the 2005 Mw 8.6 Nias-Simeulue Earthquake from the Joint Inversion of Seismic and Geodetic Data , 2007 .

[37]  Fred F. Pollitz,et al.  Coseismic Slip Distributions of the 26 December 2004 Sumatra–Andaman and 28 March 2005 Nias Earthquakes from gps Static Offsets , 2007 .