TY - JOUR
T1 - Upper boundaries of the Pacific and Philippine Sea plates near the triple junction off the Boso Peninsula deduced from ocean-bottom seismic observations 4. Seismology
AU - Ito, Aki
AU - Sugioka, Hiroko
AU - Obana, Koichiro
AU - Hino, Ryota
AU - Suetsugu, Daisuke
AU - Nakahigashi, Kazuo
AU - Shinohara, Masanao
AU - Nakano, Masaru
AU - Yamamoto, Yojiro
N1 - Funding Information:
This study was partly supported by the Special Coordination Funds for the Promotion of Science and Technology (MEXT, Japan) designated as integrated research for the 2011 Tohoku Earthquake off the Pacific coast. We used data obtained from the Hi-net and F-net systems operated by NIED, and onshore observations obtained by JMA. Tsutomu Takahashi performed initial SPOBS data processing. We thank Naoki Uchida for providing a list of repeating earthquakes. The editor Junich Nakajima and an anonymous reviewer helped to greatly improve the manuscript.
Publisher Copyright:
© 2017 The Author(s).
PY - 2017/12/1
Y1 - 2017/12/1
N2 - We determined hypocenter distributions and focal mechanisms of earthquakes off the Boso Peninsula, Japan, based on seafloor observations using ocean-bottom seismometers (OBSs). From OBS data, we detected and located earthquakes that were closer to the trenches than had previously been reported. The determined focal depths of relocated hypocenters were systematically shallower than those in the Japan Meteorological Agency catalog determined from land-based data. The hypocenter distribution was separated into two groups: one associated with the Pacific plate (PAC) and the other with the North American and/or Philippine Sea plates (PHS). For the former group, both the focal depths and mechanisms of low-angle thrust-faulting earthquakes were consistent with the geometry of the PAC determined by previous studies. Among the latter group, we selected low-angle thrust-faulting earthquakes with a slip direction parallel to the direction of PHS subduction or with a dip direction parallel to the PHS to delineate the upper boundary of the PHS. The depth of the plate upper boundary off the Boso Peninsula was found to be approximately 6 km shallower than previously reported estimates.
AB - We determined hypocenter distributions and focal mechanisms of earthquakes off the Boso Peninsula, Japan, based on seafloor observations using ocean-bottom seismometers (OBSs). From OBS data, we detected and located earthquakes that were closer to the trenches than had previously been reported. The determined focal depths of relocated hypocenters were systematically shallower than those in the Japan Meteorological Agency catalog determined from land-based data. The hypocenter distribution was separated into two groups: one associated with the Pacific plate (PAC) and the other with the North American and/or Philippine Sea plates (PHS). For the former group, both the focal depths and mechanisms of low-angle thrust-faulting earthquakes were consistent with the geometry of the PAC determined by previous studies. Among the latter group, we selected low-angle thrust-faulting earthquakes with a slip direction parallel to the direction of PHS subduction or with a dip direction parallel to the PHS to delineate the upper boundary of the PHS. The depth of the plate upper boundary off the Boso Peninsula was found to be approximately 6 km shallower than previously reported estimates.
KW - Boso Peninsula
KW - Hypocenter distribution
KW - Ocean-bottom seismometer
KW - Pacific plate
KW - Philippine Sea plate
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U2 - 10.1186/s40623-017-0608-4
DO - 10.1186/s40623-017-0608-4
M3 - Article
AN - SCOPUS:85012092897
VL - 69
JO - Earth, Planets and Space
JF - Earth, Planets and Space
SN - 1343-8832
IS - 1
M1 - 30
ER -