HR: 1330h
AN: T52A-0242    [PDF]
TI: Present-day Deformation Across the Southwest Japan Arc: Oblique Subduction of the Philippine Sea Plate and Lateral Slip of the Nankai Forearc
AU: * Tabei, T
EM: tabei@cc.kochi-u.ac.jp
AF: Department of Natural Environmental Science, Kochi University, Kochi, 780-8520 Japan
AU: Hashimoto, M
EM: hasimoto@rcep.dpri.kyoto-u.ac.jp
AF: Disaster Prevention Research Institute, Kyoto University, Uji, 611-0011 Japan
AU: Miyazaki, S
EM: miyagsi@pangea.stanford.edu
AF: Department of Geophysics, Stanford University, Stanford, CA 94305-2215 United States
AU: Ohta, Y
EM: oota@eps.nagoya-u.ac.jp
AF: Graduate School of Environmental Studies, Nagoya University, Nagoya, 464-8602 Japan
AB: Interseismic deformation of the forearc at an oblique subduction zone may be a mixture of short-term crustal shortening in the direction of plate convergence and long-term/permanent arc-parallel block movement. We estimate long-term/permanent crustal deformation in the Nankai forearc, southwest Japan that would remain after one earthquake deformation cycle at the subduction zone. A short-term deformation caused by oblique subduction of the Philippine Sea plate is modeled based on coseismic fault slips associated with the latest subduction earthquakes at the Nankai Trough, and subtracted from the interseismic crustal velocity field observed by GPS. The long-term/permanent deformation left in the data shows arc-parallel movement of the forearc at a rate of 5-10mm/yr, with its rear side bounded by the Median Tectonic Line (MTL), the arc-parallel strike-slip fault system that separates the forearc from the rest of the overriding plate. We interpret that the forearc movement is driven by the oblique plate convergence and accommodated by steady aseismic slip on the deep portion of fault plane of the MTL. The rate of the forearc movement estimated is consistent with the geological slip rate of the MTL in the late Quaternary, and also with that expected from a slight deflection of slip vector of the latest subduction earthquake from current plate convergence vector.
DE: 1206 Crustal movements--interplate (8155)
DE: 1243 Space geodetic surveys
DE: 8150 Plate boundary--general (3040)
SC: Tectonophysics [T]
MN: 2003 Fall Meeting