Ocean Bottom Seismographic Observation at the Fukutoku-okanoba Submarine Volcano
An ocean bottom seismographic (OBS) investigation was carried out to obtain seismic characteristics around the Fukutoku-okanoba, one of the active submarine volcanoes on the southern end of the volcanic front of the Izu-Ogasawara (Bonin) arc. Crustal structure was estimated by seismic refraction survey using an airgun and OBS system. First arrivals were hardly detected within an offset of 10 km in several record sections, although an airgun with large capacity of 4000 inch3 was used. This suggests that there are low wavespeed materials and/or seismic wave attenuated zone beneath the topographically depressed region around the Fukutoku-okanoba submarine volcano. The seismicity in and around the Fukutoku-okanoba region was low during the observation period from Jun. 28 to Aug. 1, 1999. Most of the hypocenters were located outside of the OBS array and they were distributed in the connected region between the Ogasawara Ridge and Mariana Ridge. Many microearthquakes with monotonic frequency of 7-14 Hz, so-called long period event (LPE) popular in volcanic regions, were recorded at several OBSs but independently.
| Main Authors: | , , , , |
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| Format: | Journal Contribution biblioteca |
| Language: | Japanese |
| Published: |
2002
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| Online Access: | http://hdl.handle.net/1834/15728 |
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| Summary: | An ocean bottom seismographic (OBS) investigation was carried out to obtain seismic characteristics around the Fukutoku-okanoba, one of the active submarine volcanoes on the southern end of the volcanic front of the Izu-Ogasawara (Bonin) arc. Crustal structure was estimated by seismic refraction survey using an airgun and OBS system. First arrivals were hardly detected within an offset of 10 km in several record sections, although an airgun with large capacity of 4000 inch3 was used. This suggests that there are low wavespeed materials and/or seismic wave attenuated zone beneath the topographically depressed region around the Fukutoku-okanoba submarine volcano. The seismicity in and around the Fukutoku-okanoba region was low during the observation period from Jun. 28 to Aug. 1, 1999. Most of the hypocenters were located outside of the OBS array and they were distributed in the connected region between the Ogasawara Ridge and Mariana Ridge. Many microearthquakes with monotonic frequency of 7-14 Hz, so-called long period event (LPE) popular in volcanic regions, were recorded at several OBSs but independently. |
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