Multi-channel seismic reflection survey in the northern Izu-Ogasawara island arc –KR07-09 cruise–

Abstract

Multi-channel seismic reflection (MCS) experiments were carried out in KR07-09 cruise to investigate crustal struc- tures and deformations in the northern Izu-Ogasawara island arc, by using the R/V KAIREI of Japan Agency for Marine-Earth Science and Technology (JAMSTEC). Swath bathymetry, geomagnetic, and gravity data are also simultaneously observed dur- ing this cruise. Five MCS survey lines (Lines IBr5, IBr9, KT01, KT04, and KT05) with 2001.6km of total line length were obtained in this survey. An airgun array with a total capacity of 12,000 cubic inches (eight airguns with 1,500 cubic inches each) was shot with shot spacing of 50 m, air pressure of 2000 psi, and towing depth of 10 m. These airgun signals are record- ed by a 204-channel hydrophone streamer cable with group interval of 25 m. The record length and sampling interval were 18 sec (Lines IBr5 and IBr9) or 15sec (Lines KT01, KT04, and KT05) and 4 msec, respectively. The MCS data has sufficient quality to know the crustal deformation of the arc-backarc transition zone. The preliminary interpretations from the onboard processing result indicated unique features of the basement and sediment in the northern Izu-Ogasawara island arc.