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High-resolution seismic velocity structure beneath the Hokkaido corner, northern Japan: Arc-arc collision and origins of the 1970 M 6.7 Hidaka and 1982 M 7.1 Urakawa-oki earthquakes

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Title: High-resolution seismic velocity structure beneath the Hokkaido corner, northern Japan: Arc-arc collision and origins of the 1970 M 6.7 Hidaka and 1982 M 7.1 Urakawa-oki earthquakes
Authors: Kita, Saeko Browse this author
Hasegawa, Akira Browse this author
Nakajima, Junichi Browse this author
Okada, Tomomi Browse this author
Matsuzawa, Toru Browse this author
Katsumata, Kei Browse this author →KAKEN DB
Keywords: detailed seismic velocity structures
1970 M 6.7 Hidaka and 1982 M 7.1 Urakawa-oki earthquakes
Hokkaido corner, northern Japan
Horoman peridotite
arc-arc type collision
collisional orogen
Issue Date: Dec-2012
Publisher: American Geophysical Union
Journal Title: Journal of Geophysical Research: Solid Earth
Volume: 117
Issue: B12
Start Page: B12301
Publisher DOI: 10.1029/2012JB009356
Abstract: Using travel time data from both a nationwide dense seismic network and a dense temporary seismic network, we obtain a high-resolution three-dimensional seismic velocity structure beneath the Hokkaido corner. Considerable inhomogeneity in the seismic velocity structure is clearly imaged above the subducting Pacific slab. Our results indicate that a broad low-velocity zone of P and S waves, with velocities consistent for crustal rocks, is observed west of the Hidaka main thrust at depths of 35-90 km. The images also indicate that several smaller-scale high-velocity zones are located at depths of 0-35 km, striking approximately north-south and inclined to the east-northeastward at 40°-60°. All of these anomalous high-velocity zones are located at the deeper extension of Neogene thrust faults. The clearest high-velocity zone is located beneath the Hidaka metamorphic belt and is in contact with the eastern edge of the broad low-velocity zone. Moreover, the boundary between the clearest high-velocity and the broad low-velocity zones corresponds to the fault plane of the 1970 Mj (magnitude determined by the Japan Meteorological Agency) 6.7 Hidaka earthquake. The western boundary of another small high-velocity zone, at depths of 20 to 30 km within the broad low-velocity zone, corresponds to the fault plane of the 1982 Mj 7.1 Urakawa-oki earthquake. These observations suggest that these two large and anomalously deep inland earthquakes occurred at sharp material boundaries under a northeast-southwest compressional stress field caused by ongoing arc-arc collision process.
Rights: ©2012 American Geophysical Union
Type: article
URI: http://hdl.handle.net/2115/52799
Appears in Collections:理学院・理学研究院 (Graduate School of Science / Faculty of Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 勝俣 啓

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