Large intraslab earthquake (2011 April 7, M 7.1) after the 2011 off the Pacific coast of Tohoku Earthquake (M 9.0): Coseismic fault model based on the dense GPS network data

Yusaku Ohta, Satoshi Miura, Mako Ohzono, Saeko Kita, Takeshi Linuma, Tomotsugu Demachi, Kenji Tachibana, Takashi Nakayama, Satoshi Hirahara, Syuichi Suzuki, Toshiya Sato, Naoki Uchida, Akira Hasegawa, Norihito Umino

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)

Abstract

We propose a source fault model for the 2011, April 7, earthquake (M 7.1 ) deduced from a dense GPS network. The coseismic displacements obtained by GPS data analysis clearly show the spatial pattern specific to intraslab earthquakes, not only in the horizontal components but also the vertical ones. A rectangular fault with uniform slip was estimated by a non-linear inversion approach. The results indicate that the simple rectangular fault model can explain the overall features of the observations. The amount of moment released is equivalent to Mw7.17. The hypocenter depth of the main shock estimated by the Japan Meteorological Agency is slightly deeper than the neutral plane between down-dip compression (DC) and down-dip extension (DE) stress zones of the double-planed seismic zone. This suggests that the depth of the neutral plane was deepened by the huge slip of the 2011, M 9.0, Tohoku Earthquake, and the rupture of the thrust M 7.1 earthquake was initiated at that depth, although more investigations are required to confirm this idea. The estimated fault plane has an angle of ∼60 degrees from the surface of the subducting Pacific plate. It is consistent with the hypothesis that intraslab earthquakes are thought to be a reactivation of the pre-existing hydrated weak zones produced in the bending process of oceanic plates around outer-rise regions.

Original languageEnglish
Pages (from-to)1207-1211
Number of pages5
Journalearth, planets and space
Volume63
Issue number12
DOIs
Publication statusPublished - 2011

Keywords

  • 2011 off the pacific coast of tohoku earthquake
  • GPS
  • Intraslab earthquake

ASJC Scopus subject areas

  • Geology
  • Space and Planetary Science

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