Rapidness and Robustness of Finite-Source Inversion of the 2011 Mw 9.0 Tohoku Earthquake by an Elliptical-Patches Method Using Continuous GPS and Acceleration Data
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The kinematic rupture process of the 2011 Mw 9.0 Tohoku earthquake is inverted with an elliptical-patches method, using a genetic algorithm, for the purpose of rapid and robust estimation of the source parameters of a mega-earthquake. We use the ground-displacement field provided by a continuous GPS network and the ground-velocity field recorded by acceleration networks. In addition to the typical inversion procedure in which a data duration long enough to cover the whole rupture process is used, inversions based on shorter signals, giving an incomplete view over the ground shaking sequence, are also carried out. How fast can a robust estimation of the source parameters be obtained? Using the elliptical approximation, we find that robust solutions of Mw ~ 9.0-earthquakes are rather quickly obtained regardless of the frequency band and the elliptical patch description. It is also confirmed that, because of the absence of off-shore recording stations on the east side of the fault, some uncertainties in the rupture process cannot be completely removed. In fact, at the very low frequencies considered, the western part of the fault (deeper portion) contributes more significantly to the recorded signals than does the other end close to the trench. This problem also prevents refinement of the description of the rupture process, in particular when using more than one ellipse.
KeywordsKinematic inversion Tohoku Elliptical patch method
We thank Prof. Takuya Nishimura for providing us GPS data in the framework of the French-Japanese ANR-JST joint program DYNTOHOKU (2011–2013). We used the data from the National Institute for Earth Science and Disaster Prevention, Japan and Geospatial Information Authority of Japan. Discussions with Prof Raul Madariaga and Dr. Sergio Ruiz were very fruitful. This is a contribution to the French national project S4 (Subduction: Slow & Standard Seismology, 2012-2014, ANR-2011-BS56-017) supported by the Agence National de la Recherche. We also benefit from funding from the European Seventh Framework Programme project MARsite for the methodology development. Some calculations were carried out at the French national supercomputing centre GENCI-CINES (Grant c2013-046700). Finally, we thank two anonymous reviewers for their careful comments on an earlier version of this article and John Douglas for proofreading.
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