Tomographic image of low P velocity anomalies above slab in northern Cascadia subduction zone
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- Zhao Dapeng
- Department of Earth Sciences, Ehime University
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- Wang Kelin
- Pacific Geoscience Centre, Geological Survey of Canada
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- Rogers Garry C.
- Pacific Geoscience Centre, Geological Survey of Canada
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- Peacock Simon M.
- Department of Geology
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At the Cascadia margin the Juan de Fuca plate is subducting beneath the North America plate, causing active seismicity within both plates. Earthquakes occur down to a maximum depth of 80 km within the descending oceanic plate and to about 30 km in the overriding continental plate. We use a method of seismic tomography to invert 28, 230 P wave arrival times from 2666 local earthquakes that occurred in and around Vancouver Island from 1970 to 1990. The tomography model uses about 30 km horizontal and 12-19 km vertical grid spacing and assumes that the seismic velocity perturbations vary continuously between grid points. Velocity structures can be obtained to a depth of 65 km. The obtained tomographic image shows an extensive low velocity zone above the subducted slab at about 45 km depth and patches of low velocities at shallower depths just seaward of the volcanic front. The deeper extensive low velocity zone may indicate the presence of partially hydrated mantle, most likely serpentinite, as a result of slab dehydration associated with the transformation of metabasalt to eclogite. One of the shallow low velocity patches coincides with an abrupt increase in surface heat flow and may reflect the presence of partial melts or water in the crust.
収録刊行物
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- Earth, Planets and Space
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Earth, Planets and Space 53 (4), 285-293, 2001
地球電磁気・地球惑星圏学会 、公益社団法人 日本地震学会、特定非営利活動法人 日本火山学会、日本測地学会、日本惑星科学会
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詳細情報 詳細情報について
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- CRID
- 1390001206511382016
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- NII論文ID
- 10007638902
- 130003780816
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- NII書誌ID
- AA11211921
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- ISSN
- 18805981
- 13438832
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- NDL書誌ID
- 5770527
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- 本文言語コード
- en
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- データソース種別
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- JaLC
- NDL
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