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标题：Subsurface structure of the Myojin Knoll pumiceous volcano obtained from multichannel seismic reflection data
其他标题：Subsurface structure of the Myojin Knoll pumiceous volcano obtained from multichannel seismic reflection data
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作者：Tetsuro Tsuru ; Ayumi Okuda ; Tetsuo No 等
期刊名称：Earth, Planets and Space
电子版ISSN：1880-5981
出版年度：2008
卷号：60
期号：7
页码：721-726
DOI：10.1186/BF03352820
出版社：Springer Verlag
摘要：The Myojin Knoll is a submarine volcano that has a classically beautiful conical-shaped silicic caldera whose surface is covered by pumice. To determine the tectonic structure inside the caldera wall and beneath the caldera floor of this pumicious submarine volcano, we carried out a structural interpretation study using newly collected deep-penetrating multichannel seismic (MCS) reflection data. We also conducted a detailed velocity analysis of the MCS data, which facilitated the interpretation study. The results demonstrate that approximately 90% of the caldera wall is composed of pumiceous volcanic breccia. This finding supports those of previous researchers who, based on seafloor observations, single-channel seismic reflection, and gravity and geomagnetic data, concluded the Myojin Knoll is a knoll having a pumiceous caldera wall underlain by a pre-caldera rhyolitic stratovolcano edifice. We also determined a down-warping reflector approximately 800 m beneath the caldera floor. A seismic unit immediately above the reflector has a higher P -wave velocity than the pumice units and shows a chaotic seismic reflection pattern. We interpreted the reflector to be the bottom of a possible shallow magma chamber where the magma would undergo repeated expansion and contraction as a result of recurrent eruption activities.
关键词：Myojin Knoll ;caldera ;pumice ;seismic reflection ;magma