P-wave velocity structure in the southernmost source region of the 2011 Tohoku earthquakes, off the Boso Peninsula, deduced by an ocean bottom seismographic survey

Kazuo Nakahigashi, Masanao Shinohara, Kimihiro Mochizuki, Tomoaki Yamada, Ryota Hino, Toshinori Sato, Kenji Uehira, Yoshihiro Ito, Yoshio Murai, Toshihiko Kanazawa

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

We present the result of a seismic experiment conducted using ocean bottom seismometers and controlled sources in the region off Ibaraki and the Boso Peninsula. This region is the southern edge of the rupture zone of the 2011 off the Pacific coast of Tohoku Earthquake. We estimated the f-wave seismic velocity structure beneath the profile using a 2-D ray-tracing method. The crustal structure in the southern area is more heterogeneous than that of the northern area. This heterogeneity is thought to be related with subducting the Philippine Sea plate (PHS). The plate boundary between the landward plate and the Pacific plate (PAC) is positioned at depths of 20 km at a distance of 170 km from the southern end of the profile. The subducting PHS is imaged on the southern part of the profile. However, we could not obtain a distinct image of the contact zone of PHS and PAC. The contact zone of PHS and PAC is estimated to have a large heterogeneity resulting from strong deformation due to the collision of the two plates. We infer that the termination of the rupture, and the large afterslip in the collision region, are caused by this strong heterogeneity.

Original languageEnglish
Pages (from-to)1149-1156
Number of pages8
Journalearth, planets and space
Volume64
Issue number12
DOIs
Publication statusPublished - 2012

Keywords

  • Crustal structure
  • Ocean bottom seismometer (OBS)
  • Pacific plate
  • Philippine sea plate
  • Plate boundary
  • The 2011 off the pacific coast of tohoku earthquake

ASJC Scopus subject areas

  • Geology
  • Space and Planetary Science

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