Ocean Bottom Seismographic Observation at Myojin Sho
The Myojin Sho is one of the active submarine volcanoes on the volcanic front of the Izu -Ogasawara (Bonin) arc. In 1998, we carried out geological and geophysical survey to elucidate the present volcanic activity of the Myojin Sho. The survey includes multi-beam swath bathym- etry, single-channel seismic reflection, seismic refraction, microseismicity, magnetic and gravity measurements. In this paper, we report mamly seismic results. Crustal stmcture was estimated by seismic refraction survey by using an anrgun and ocean bottom seismograph (OBS) system. We deployed nine OBSs on and around the volcanic edifice of the Myojin Sho region. P wavespeed structure models beneath the volcanic edifice, basement region with water depth of about 1, 500 m and transition zones between them were obtained. Seismic activities were observed by the OBSs for 18 clays during September 2and 19, 1998. Microearthquake activity was concentrated to the south of the Myojin Sho. The north south vertical section indicates that the seismicity becomes shallower towards north, that is, towards the Myojin Sho. However, there is no seismicity just beneath the Myojin Sho.
| Main Authors: | , , , |
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| Format: | Journal Contribution biblioteca |
| Language: | Japanese |
| Published: |
2000
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| Online Access: | http://hdl.handle.net/1834/15750 |
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