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Geodetic constraints on afterslip characteristics following the March 9, 2011, Sanriku‐oki earthquake, Japan

2012; American Geophysical Union; Volume: 39; Issue: 16 Linguagem: Inglês

10.1029/2012gl052430

1944-8007

Yusaku Ohta, Ryota Hino, Daisuke Inazu, Mako Ohzono, Yoshihiro Ito, Masaaki Mishina, Takeshi Iinuma, Junichi Nakajima, Yukihito Osada, Kensuke Suzuki, Hiromi Fujimoto, Kenji Tachibana, Tomotsugu Demachi, Satoshi Miura,

Earthquake Detection and Analysis

A magnitude 7.3 foreshock occurred at the subducting Pacific plate interface on March 9, 2011, 51 h before the magnitude 9.0 Tohoku earthquake off the Pacific coast of Japan. We propose a coseismic and postseismic afterslip model of the magnitude 7.3 event based on a global positioning system network and ocean bottom pressure gauge sites. The estimated coseismic slip and afterslip areas show complementary spatial distributions; the afterslip distribution is located up‐dip of the coseismic slip for the foreshock and northward of hypocenter of the Tohoku earthquake. The slip amount for the afterslip is roughly consistent with that determined by repeating earthquake analysis carried out in a previous study. The estimated moment release for the afterslip reached magnitude 6.8, even within a short time period of 51h. A volumetric strainmeter time series also suggests that this event advanced with a rapid decay time constant compared with other typical large earthquakes.