Open Access

Aftershock observation of the Noto Hanto earthquake in 2007 using ocean bottom seismometers

  • Tomoaki Yamada13Email author,
  • Kimihiro Mochizuki13,
  • Masanao Shinohara13,
  • Toshihiko Kanazawa13,
  • Asako Kuwano13,
  • Kazuo Nakahigashi13,
  • Ryota Hino23,
  • Kenji Uehira33,
  • Takeo Yagi13,
  • Naoto Takeda13 and
  • Shinichi Hashimoto13
Earth, Planets and Space200860:BF03352860

Received: 30 June 2007

Accepted: 25 February 2008

Published: 7 November 2008


The Noto Hanto earthquake in 2007 (Mj 6.9) occurred on March 25, 2007 near the west coast of the Noto peninsula, Honshu, Japan. To study the aftershock activity under the sea, we deployed pop-up type ocean bottom seismometers (OBSs) from April 5 to May 8, 2007. We combined data from ten ocean bottom and four onshore seismic stations located around the rupture area of the earthquake and determined the preliminary distribution of the aftershocks. Most of the offshore aftershocks are located in a depth range between 2 and 10 km, and no earthquakes are observed in the lower crust. Hypocenters of deep events occurring at depths greater than 5 km are confined to an area northeastward from the largest aftershock in offshore region. Most of the aftershocks aligned along a high angle and southeast dipping plane, which is consistent with the geometry of the active faults revealed by previous seismic reflection surveys.

Key words

The 2007 Noto Hanto earthquakeOBSaftershock distribution