Open AccessEffect of 3‐D viscoelastic structure on post‐seismic relaxation from the 2004 M = 9.2 Sumatra earthquake
Author(s) -
Pollitz Fred,
Banerjee Paramesh,
Grijalva Kelly,
Nagarajan B.,
Bürgmann R.
Publication year - 2008
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.2007.03666.x
Subject(s) - viscoelasticity , geology , standard linear solid model , rheology , deformation (meteorology) , stress field , geophysics , seismology , mechanics , physics , thermodynamics , oceanography , finite element method
SUMMARY The 2004 M = 9.2 Sumatra–Andaman earthquake profoundly altered the state of stress in a large volume surrounding the ∼1400 km long rupture. Induced mantle flow fields and coupled surface deformation are sensitive to the 3‐D rheology structure. To predict the post‐seismic motions from this earthquake, relaxation of a 3‐D spherical viscoelastic earth model is simulated using the theory of coupled normal modes. The quasi‐static deformation basis set and solution on the 3‐D model is constructed using: a spherically stratified viscoelastic earth model with a linear stress–strain relation; an aspherical perturbation in viscoelastic structure; a ‘static’ mode basis set consisting of Earth's spheroidal and toroidal free oscillations; a “viscoelastic” mode basis set; and interaction kernels that describe the coupling among viscoelastic and static modes. Application to the 2004 Sumatra–Andaman earthquake illustrates the profound modification of the post‐seismic flow field at depth by a slab structure and similarly large effects on the near‐field post‐seismic deformation field at Earth's surface. Comparison with post‐seismic GPS observations illustrates the extent to which viscoelastic relaxation contributes to the regional post‐seismic deformation.