3:00 PM - 4:00 PM
[J08-P-16] Inhomogeneous rifting structure in the northern Okinawa Trough, an active backarc basin southwest of the Japan Islands
We have conducted multi-channel seismic (MCS) reflection surveys to acquire detailed images of deformation in shallow structures reflecting variable tectonic backgrounds of the Okinawa Trough since 2008. We fired a trigun cluster with a total volume of 1,050 cubic inches at a 50 m shot interval and used 240-channel (3,000 m long) seismic streamer. The MCS data were processed by a standard procedure including band-pass filter, deconvolution, normal move out correction and CMP stacking.
The MCS results reveal a number of normal faults and intrusions beneath all the seismic lines inside the northern trough. In the western part of the trough with a flat seafloor, there are thick sedimentary layers with over 3,000 m thick at most. However we detected several intrusions below the seafloor and some of them penetrate into the uppermost sediments. On the contrary, the eastern part shows the rough seafloor and the existence of many volcanic features. The MCS profiles reveal many igneous intrusions reaching above the seafloor, which corresponds to the volcanic front in this region.