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Hokkaido University Collection of Scholarly and Academic Papers >
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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
| 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)
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Submitter: 勝俣 啓
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