[SCG61-P02] Multichannel seismic reflection imaging off western Hokkaido, Japan Sea, using the R/V Kaimei
Keywords:Japan Sea, off western Hokkaido, seismic reflection imaging, 1940 Shakotan-oki earthquake, R/V Kaimei
We conducted our seismic survey using the 2-D multichannel seismic (MCS) system of the R/V Kaimei. The seismic system of this ship has two important features. First, its receiver interval is narrower than that of general multichannel seismic reflection systems. As a result, seismic data which is obtained by this system is able to operate effectively for processing waveform data of spatial direction, such as the suppression of spatial aliasing, migration, and velocity filter. Second, it is possible to change the cable length at sea during the cruise, because the vessel has four streamer cable winches. Thus, although we set the standard cable length at about 6 km, we changed the length to 3 km or 300 m when surveying in coastal areas. The main data acquisition specifications for our survey, other than the cable length, are as follows: The shot spacing was 50 m or 25 m. The tuned air gun array in this survey used a maximum capacity of 5,300 cu in (approximately 86 L) and comprised 22 air guns. The standard air pressure was approximately 2,000 psi (approximately 14 MPa). The air gun array was kept 10 m below the sea surface throughout the experiment. The towing depth of the streamer cable was maintained at 12 m below the sea surface using depth controllers.
We present the results obtained by MCS imaging off western Hokkaido, and report the relation of these results to the presumed active faults and crustal structures of other researches in the survey area.