Multi-channel seismic reflection survey in the Izu-Ogasawara-Mariana island arc –KR06-13 cruise report–

Abstract

Multi-channel seismic (MCS) reflection experiments were carried out in KR06-13 cruise to investigate crustal struc- tures and deformations of the arc-backarc transition zone in the Izu-Ogasawara-Mariana 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 simultaneously observed during this cruise. Four MCS survey lines (Lines A02, A06, A07, and IBr12) with 1043.55km of total line length were obtained in this survey. An airgun array with a total capacity of 12,000 cubic inches (eight airguns with 1,50 0 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 recorded on a 204-channel hydrophone streamer cable with group interval of 25 m. The record length and sampling interval were 18 sec and 4 msec, respectively. The MCS data has sufficient quality to assess the crustal deformation of the arc-backarc transition zone. The preliminary interpretations on the onboard processing result indicated unique features of the basement and sediment in the transition zone.