Earth Planets Space, Vol. 53 (No. 4), pp. 321-326, 2001
Akira Asada1 and Tetsuichiro Yabuki2
1Institute of Industrial Science, University of Tokyo, 7-22-1 Roppongi, Minato-ku, Tokyo 106-8558, Japan
2Japan Hydrographic Department, 5-3-1 Tsukiji, Chuo-ku, Tokyo 104-0445, Japan
(Received July 1, 1999; Revised June 21, 2000; Accepted June 21, 2000)
Abstract: We are developing a synthetic aperture technique using a Sea Beam 2000 multi-beam echo sounder to observe subsea crustal movements for earthquake studies. Augmented by the Kinematic GPS and a motion sensor, the synthetic aperture technique was successfully applied to the Sea Beam 2000 with a 12 kHz frequency acoustic signal. The 4.3-meter long projector produces a transmission fan beam in alongtrack beamwidth of 2 degrees, but a synthesis of the data achieved about 37 m aperture length, equivalent to a 0.3 degrees alongtrack beamwidth. Bathymetry measurements at the water depth of 900 m obtained through the synthetic aperture processing show considerable improvement of the signal-to-noise ratio and reveal detailed features of the seafloor.