The 11 March 2011 Tohoku-Oki (Japan) Megathrust Event: FEM models of Coseismic and Postseismic deformation captured by DInSAR and GPS Data

The Mw 9.0 Tohoku-Oki earthquake on March 11 2011 occurred near the northeast coast of Honshu, Japan. No historical records exist of an equal or greater magnitude earthquake along the Japan Trench. The Jogan earthquake of AD 869 may be the only possible exception. The Tohoku-Oki earthquake resulted from a thrust faulting on the subduction zone boundary between the Pacific and North America plates. Previous modeling of the megathrust earthquake indicate that the fault ruptured over an area approximately 400km long (strike direction) by 150 km wide (down-dip direction). In order to investigate the surface displacement field we have applied Differential SAR Interferometry (DInSAR) to Envisat and ALOS PALSAR data. We have processed three strips composed of 13 (track 347, descending orbit), 8 (track 074) and 6 (track 189) Envisat frames over Honshu island. We have also processed ALOS data along ascending path. The interferometric strips cover the whole Honshu Island and the epicentral region and a large coastal area. The strips have been unwrapped to measure the Line Of Sight surface movement. The maximum displacement reaches about 2.5 m relative to a reference point within the entire frames located nearby the southern boundary. They provided a map overview of the interferogram, as well as detailed views of Fukushima, Chiba and Sendai. The Preliminary GPS time series are provided by the ARIA team at JPL and Caltech. All original GEONET RINEX data provided to Caltech by the Geospatial Information Authority (GSI) of Japan. Here we present 3D Finite Element Model (FEMs) for the 11 March earthquake constrained from the available DInSAR and GPS data. The model presented is designed to simulate coseismic and postseismic (poroelastic) deformation for the megathrust fault, while simultaneously accounting for the known geologic structure and geophysical context of Japanese subduction zone. We estimate the slip distribution pattern by combining space deformation data and FEMs generated kernels into a linear inversion scheme. Furthermore the coseismic estimated slip is used in a forward problem to predict the transient postseismic poroelastic deformation.