Simple and reliable finite fault solutions for large earthquakes using the W‐phase: The Maule (<i>M</i>_<i>w</i> = 8.8) and Tohoku (<i>M</i>_<i>w</i> = 9.0) earthquakes

Abstract

We explore the ability of W‐phase waveform inversions to recover a first‐order coseismic slip distribution for large earthquakes. To date, W‐phase inversions for point sources provide fast and accurate moment tensor solutions for moderate to large events. We have applied W‐phase finite fault inversion to seismic waveforms recorded following the 2010 Maule earthquake ( M w =8.8) and the 2011 Tohoku earthquake ( M w =9.0). Firstly, a W‐phase point source inversion was performed to assist us in selecting the data for the finite fault solution. Then, we use a simple linear multiple‐time‐window method accounting for changes in the rupture velocity with smoothing and moment minimization constraints to infer slip and rake variations over the fault. Our results describe well the main features of the slip pattern previously found for both events. This suggests that fast slip inversions may be carried out relying purely on W‐phase records.