Precise aftershock distribution of the 2011 off the Pacific coast of Tohoku Earthquake revealed by an ocean-bottom seismometer network

Masanao Shinohara, Yuya Machida, Tomoaki Yamada, Kazuo Nakahigashi, Takashi Shinbo, Kimihiro Mochizuki, Yoshio Murai, Ryota Hino, Yoshihiro Ito, Toshinori Sato, Hajime Shiobara, Kenji Uehira, Hiroshi Yakiwara, Koichiro Obana, Narumi Takahashi, Shuichi Kodaira, Kenji Hirata, Hiroaki Tsushima, Takaya Iwasaki

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)

Abstract

The 2011 off the Pacific coast of Tohoku Earthquake occurred at the plate boundary between the Pacific plate and the landward plate on March 11, 2011, and had a magnitude of 9. Many aftershocks occurred following the mainshock. Obtaining a precise aftershock distribution is important for understanding the mechanism of earthquake generation. In order to study the aftershock activity of this event, we carried out extensive seafloor aftershock observations using more than 100 ocean-bottom seismometers just after the mainshock. A precise aftershock distribution for approximately three months over the whole source area was obtained from the observations. The aftershocks form a plane dipping landward over the whole area, nevertheless the epicenter distribution is not uniform. Comparing seismic velocity structures, there is no aftershock along the plate boundary where a large slip during the mainshock is estimated. Activity of aftershocks in the landward plate in the source region was high and normal fault-type, and strike-slip-type, mechanisms are dominant. Within the subducting oceanic plate, most earthquakes have also a normal fault-type, or strike-slip-type, mechanism. The stress fields in and around the source region change as a result of the mainshock.

Original languageEnglish
Pages (from-to)1137-1148
Number of pages12
Journalearth, planets and space
Volume64
Issue number12
DOIs
Publication statusPublished - 2012

Keywords

  • Aftershock
  • Focal mechanism
  • Ocean-bottom seismometer (OBS)
  • Seismicity
  • The 2011 off the pacific coast of tohoku earthquake

ASJC Scopus subject areas

  • Geology
  • Space and Planetary Science

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