| Accession number;05A0159481 |
| Title;Interpretation of the Miyakejima 2000 eruption and dike emplacement using time animations of earthquakes |
| Author;WRIGHT T L(Univ. Tokyo Earthquake Res. Inst., Tokyo, Jpn) SAKAI S(Univ. Tokyo Earthquake Res. Inst., Tokyo, Jpn) |
Journal Title;Bulletin of the Earthquake Research Institute, University of Tokyo
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Journal Code:S0002A
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ISSN:0040-8972
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VOL.79;NO.1/2;PAGE.1-16(2005)
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| Figure&Table&Reference;FIG.6, TBL.5, REF.24 |
| Pub. Country;Japan |
| Language;English |
| Abstract;The seismic sequence of over 12,000 earthquakes accompanying the 2000 eruption of Miyakejima volcano has been studied by viewing time animations of the earthquakes beneath transparent topography. Seismic activity began on the evening of June 26 extending southwest from Miyakejima's summit. A few hours later the seismicity abruptly shifted to the WNW and a submarine eruption occurred off the West Coast of Miyakejima on the morning of June 27. Phreatic eruptions at Miyakejima's summit in July were accompanied by the formation of a new caldera. Following caldera formation explosive eruptions occurred in August. The eruption ended with minor explosions in September. The seismic activity that began with a low-magnitude swarm beneath Miyakejima grew to a major swarm with hundreds of events of M>4 extending more than 40km WNW from Miyakejima. Lesser numbers of earthquakes occurred on two N-S trending lines extending south and north of the main seismic trend. The seismicity has been interpreted as evidence for emplacement of a massive dike on the main trend that triggered additional earthquakes on the two cross trends. Our interpretation involves more restricted dike emplacement west of Miyakejima, including the possibility of additional submarine eruption, following cracking of the Philippine Sea plate. The seismic activity associated with explosive eruptions in August helps to define Miyakejima's magma plumbing. A shallow reservoir beneath the southwest slope is defined by concetrations of earthquakes at 4-6km depth, and a deeper source is suggested by a smaller number of earthquakes extending to 10km vertically beneath the shallow source. Seismic activity preceding and accompanying eruptions at Miyakejima's summit are defined by seismic swarms extending from 4km depth to the surface along a path connecting the summit with the shallow reservoir.... (author abst.) |
