Seismic velocity discontinuities in the crust and uppermost mantle beneath the Kanto district, central Japan, identified from receiver function imaging and repeating earthquake activity |
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| Authors: | Toshihiro Igarashi |
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| Institution: | aEarthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-0032, Japan |
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| Abstract: | We constructed vertical cross-sections of depth-converted receiver function images to estimate the seismic velocity structure of the crust and uppermost mantle beneath the Kanto district, central Japan. Repeating earthquake data for the plate boundary were also used to estimate geometries of the subducting Philippine Sea plate and the subducting Pacific plate. As a result, we present images of some major seismic discontinuities. The upper boundary of the Pacific plate dips to the northwest in northern Kanto and to the west–southwest in southern Kanto with some undulations. On the other hand, the upper boundary of the Philippine Sea plate as a whole dips to the northwest. However, it is concave to the northeast in the southern Boso peninsula. We suggest that the low-velocity mantle wedge may be indicated on the top of both subducting plates. Plate thickness gradually decreases to the northeast. The northeastern end of the Philippine Sea plate is interpreted to be at depths of 45–90 km. The Moho discontinuity in the overriding plate is deeper than 25 km in the northern Kanto. It contacts the subducting Philippine Sea plate in the southwestern part near 35.8°N. |
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| Keywords: | Receiver function Repeating earthquake Seismic velocity discontinuity Plate configuration Kanto district |
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