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A detailed subduction structure in the Kuril trench deduced from ocean bottom seismographic refraction studies
https://nied-repo.bosai.go.jp/records/4215
https://nied-repo.bosai.go.jp/records/42158ed109e6-c698-4621-9f2e-6c9c68d2644b
| Item type | researchmap(1) | |||||||||||||||||||||
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| 公開日 | 2023-03-30 | |||||||||||||||||||||
| タイトル | ||||||||||||||||||||||
| 言語 | en | |||||||||||||||||||||
| タイトル | A detailed subduction structure in the Kuril trench deduced from ocean bottom seismographic refraction studies | |||||||||||||||||||||
| 言語 | ||||||||||||||||||||||
| 言語 | eng | |||||||||||||||||||||
| 著者 |
Takaya Iwasaki
× Takaya Iwasaki
× Hajime Shiobara
× Azusa Nishizawa
× Toshihiko Kanazawa
× Kiyoshi Suyehiro
× Naoshi Hirata
× Taku Urabe
× Hideki Shimamura
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| 抄録 | ||||||||||||||||||||||
| 内容記述タイプ | Other | |||||||||||||||||||||
| 内容記述 | In 1983, we conducted an ocean bottom seismograph (OBS) experiment in the southernmost part of the Kuril trench, beneath which the Pacific Plate is subducting under Hokkaido Island, Japan. The aim of this experiment was to determine crust and upper mantle structure from the oceanic basin to the continental slope by dense seismic refraction profiling, using explosives and airguns. The total length of the profiles was 560 km, along which ten OBS's were deployed. The observed data were of good quality, which enabled us to obtain a detailed velocity structure of the active margin down to 20-30 km. We constructed a velocity structure model by ray-tracing and amplitude modeling. In the oceanic basin, the crust has a typical oceanic structure characterized by three layers with P-wave velocities of 1.8, 3.8-6.5 and 6.5-7.0 km/s. The velocity gradient in layer 3 increases downward from 0.075 to 0.10 s-1. The Moho discontinuity was well constrained by clearly observed Pn and PmP phases. The total thickness of the oceanic crust was determined to be 8 km and almost constant in the oceanic basin. The P-wave velocity is 7.9 km/s beneath the Moho discontinuity, which increases downward with a rather small velocity gradient, 0.015-0.03 s-1. Beneath the continental slope, we found relatively low velocity (2.5 to 5.5-5.8 km/s) material. The oceanic Moho discontinuity associated with the subducting plate was traced down to a depth of 25 km. Our seismic data strongly suggest that oceanic layer 2 is smoothly subducting and does not break up to form a wedge structure. This result is in remarkable contrast with the velocity structure in the active margin of the Ryukyu trench area (about 1000 km south of the present experimental area), where we found a 12 km-thick, prominent low-velocity wedge is situated 50-150 km landward from the trench axis. On the seaward side of the wedge, the surface of the igneous basement undulates severely. The wedge was probably formed by materials of oceanic origin. Such a difference in velocity structure suggests that the subduction mechanism in the trench area differs from region to region in the northwestern Pacific. © 1989. | |||||||||||||||||||||
| 言語 | en | |||||||||||||||||||||
| 書誌情報 |
en : Tectonophysics 巻 165, 号 1-4, p. 315-336 |
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| 収録物識別子タイプ | ISSN | |||||||||||||||||||||
| 収録物識別子 | 0040-1951 | |||||||||||||||||||||
| DOI | ||||||||||||||||||||||
| 関連識別子 | 10.1016/0040-1951(89)90056-5 | |||||||||||||||||||||
