Processed 3D multichannel seismic data in the Nankai Trough accretionary prism, acquired by the R/V Maurice Ewing in 1999 (EW9907 and EW9908)

The western Nankai 3-D experiment was conducted in 1999 on the R/V Maurice Ewing Legs 7 (EW9907) and 8 (EW9908). This is a collaborative project between UTIG, University of Hawaii, University of California, Santa Cruz, University of Tokyo, Japanese Geological Survey and STA JAMSTEC. The project consists of 81 dip lines ( Line numbers 92 through 172) each 80 km long with a shot spacing of 50 m. The streamer was 240 channels, 6 km long. There are also a few lines outside of the region, lines Nan-1 (the first line shot and has no navigation), 19, 20, 40, 42, and 50. Two 3-D data volumes are available, one a pre-stack time migration and the other a pre-stack depth migration. The goal of the study is to examine changes in physical properties along the thrust as it changes from aseismic to seismic expression. Understanding this transition from compaction and aseismic slip to brittle failure is a major unknown in understanding lithospheric consumption and earthquake dynamics. Funded by NSF grants OCE 9730637, OCE 9802264, and OCE 9802295.