Imaging the source regions of normal faulting sequences induced by the 2011 M9.0 Tohoku-Oki earthquake

Aitaro Kato, Toshihiro Igarashi, Kazushige Obara, Shinichi Sakai, Tetsuya Takeda, Atsushi Saiga, Takashi Iidaka, Takaya Iwasaki, Naoshi Hirata, Kazuhiko Goto, Hiroki Miyamachi, Takeshi Matsushima, Atsuki Kubo, Hiroshi Katao, Yoshiko Yamanaka, Toshiko Terakawa, Haruhisa Nakamichi, Takashi Okuda, Shinichiro Horikawa, Noriko TsumuraNorihito Umino, Tomomi Okada, Masahiro Kosuga, Hiroaki Takahashi, Takuji Yamada

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)

Abstract

Intense swarm-like seismicity associated with shallow normal faulting was induced in Ibaraki and Fukushima prefectures, Japan, following the 2011 Tohoku-Oki earthquake. This seismicity shows a systematic spatiotemporal evolution, but little is known of the heterogeneity in crustal structure in this region, or its influence on the evolution of the seismicity. Here, we elucidate a high-resolution model of crustal structure in this region and determine precise hypocenter locations. Hypocenters in Ibaraki Prefecture reveal a planar earthquake alignment dipping SW at ∼45°, whereas those in Fukushima Prefecture show a more complex distribution, consisting of conjugate sets of aligned small earthquakes. On the north of the hypocenter of the largest earthquake in the sequence (the M7.0 Iwaki earthquake), we imaged a high-velocity body at shallow depths that lacks aftershock seismicity. Based on fault source models, the large-slip region of the Iwaki earthquake is situated along a zone that roughly coincides with this high-velocity body. We delineated a separate low-velocity anomaly directly beneath the hypocenter of the Iwaki earthquake, indicating crustal fluids in this region. We hypothesize that strong crust underwent structural failure due to the infiltration of crustal fluids into the seismogenic zone from deeper levels, causing the Iwaki earthquake.

Original languageEnglish
Pages (from-to)273-278
Number of pages6
JournalGeophysical Research Letters
Volume40
Issue number2
DOIs
Publication statusPublished - 2013 Jan 28

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

Fingerprint Dive into the research topics of 'Imaging the source regions of normal faulting sequences induced by the 2011 M9.0 Tohoku-Oki earthquake'. Together they form a unique fingerprint.

Cite this