Inhomogeneous spherical-earth finite element model of coseismic offset due to the 2012 Indian Ocean Earthquake

On April 11, 2012, a Mw 8.6 earthquake struck off the west coast of northern Sumatra approximately 300 km west of the Sunda trench following by Mw 8.2 two hours afterward. The 2012 Indian Ocean Earthquake sequence, which was the largest intraplate earthquake in recorded history, yielded seismic moment of 1.2-1.3 × 1022 N m and 0.2-0.3 × 1022 N m for the main shock (Mw 8.6) and the after shock (Mw 8.2), respectively. Aceh GPS Network for Sumatran Fault System (AGNeSS) observed a predominantly ENE coseismic offset up to 10 cm while the sites on the Andaman Island observed southward and southern part Sumatra GPS Array (SuGar) network observed northward. Limited far-field and inland GPS observation network might lead the homogeneous and half-space model insufficient to explain the coseismic offset. In that of sense, in order to estimate more realistic surface displacement due to complex subduction and far-field GPS station, we consider developing inhomogeneous three-dimensional finite element model incorporate subducting slab, three-dimensional velocity earth structure, realistic topography and bathymetry as well as sphericity of the earth. We calculate coseismic offset by forward modeling using slip distribution as reported from Wei et al. [7]. This study investigates the effect of inhomogeneous structure and spherical geometry model in reproducing actual coseimic offset due to 2012 Indian Ocean Earthquake.