HR: 1330h
AN: T12C-0471    [PDF]
TI: Melting features along the western Ryukyu slab edge (northeast Taiwan) and Ryukyu slab tear (southernmost Okinawa Trough): Seismic evidence
AU: Lin, J
EM: jylin@ifremer.fr
AF: Ifremer Centre de Brest, B.P. 70, Plouzane, 29280 France
AU: Hsu, S
EM: hsu@oc.gep.ncu.edu,.w
AF: Institute of Geophysics, National Central University, Chung-Li, 32054 Taiwan
AU: * Sibuet, J
EM: jcsibuet@ifremer.fr
AF: Ifremer Centre de Brest, B.P. 70, Plouzane, 29280 France
AB: Behind the sedimentary Ryukyu arc lies the Okinawa Trough whose termination is located at the tip of the Ilan plain (northern Taiwan), just above the Ryukyu slab edge. The present-day active volcanic front, located 80-100 km above the Ryukyu slab, extends from Japan to Kueishantao Island, an islet situated 10-km offshore the Ilan plain. 3370 earthquakes recorded in northern Taiwan by 65 seismic land stations between December 1990 and May 1999 were used to determine the 3-D Vp and Vs velocity structures and Vp/Vs ratios. A low Vp, low Vs and high Vp/Vs sausage like body, about 20 km in diameter, lies within the Eurasian mantle wedge, on top of the western Ryukyu slab extremity, from depths ranging between 20 km and 100 km. We suggest that the friction of the Ryukyu slab edge against the Eurasian lithosphere and/or the upwelling of the underlying Philippine Sea plate lithospheric mantle around the slab edge would cause an abnormal heating resulting in the formation of partial melt. Part of this melt feeds obliquely the Kueishantao andesitic Island. An abnormal amount of volcanism occurs within the Okinawa Trough, east of a slab tear located 140 km from the Ryukyu slab edge. The power spectrum analysis of magnetic data shows the presence of a thick crust located above the slab tear, suggesting that a similar pattern to the one identified above of the Ryukyu slab edge might exist in the slab tear region, feeding obliquely this area of abnormal volcanism.
DE: 8110 Continental tectonics--general (0905)
DE: 8123 Dynamics, seismotectonics
DE: 8159 Rheology--crust and lithosphere
DE: 8180 Tomography
DE: 8434 Magma migration
SC: Tectonophysics [T]
MN: 2003 Fall Meeting