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Two subevents across the Japan Trench during the 7 December 2012 off Tohoku earthquake ( M w 7.3) inferred from offshore tsunami records
Author(s) -
Inazu Daisuke,
Saito Tatsuhiko
Publication year - 2014
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2013jb010892
Subject(s) - seismology , trench , geology , tsunami earthquake , seismometer , epicenter , submarine pipeline , seafloor spreading , magnitude (astronomy) , moment magnitude scale , aftershock , geophysics , oceanography , chemistry , physics , geometry , mathematics , organic chemistry , layer (electronics) , astronomy , scaling
A tsunamigenic earthquake with a moment magnitude of 7.3 occurred near the Japan Trench, off Tohoku, northeast Japan, on 7 December 2012. Operational seismic monitoring inferred that the earthquake was composed of doublet sources of comparable magnitudes: the first event was reverse faulting and the second event, which occurred 10–20 s later, was normal faulting. An associated tsunami was observed at offshore stations, having an amplitude of 10 −1 to 10 1 cm. Inverse modeling using the observed tsunami records reveals possible vertical seafloor deformations. We can then constrain, in terms of the source location, that the tsunamigenic earthquake involves two subfaults across the Japan Trench: one is the outer trench reverse faulting as the first event and the second is the inner trench normal faulting. The present study shows that tsunami analysis with seismograph analyses effectively constrains the epicenter locations, even in the case of complex earthquakes like doublets.