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| | Abstract | | A new ocean bottom gravimeter has been developed to better understand the subsurface structure of the transition zone of the Japanese coastal areas. The gravimeter consists of a Scintrex CG-5 gravimeter as a gravity sensor with free gimbals suspensions and a data logger within a pressure-resistant spherical container made from titanium. Observation data can be recorded to the data logger at a frequency of 6 Hz. A field experiment for the gravimeter was conducted in February 2010 in the Kaneda Bay of the Miura Peninsula. Gravity measurements were carried out at three gravity stations on the sea floor at depths from 20 to 40m below sea level. Tilt and temperature corrections were made for them after a conversion from raw data to relative gravity values from the base station at the port. The absolute observed gravity values were finally determined by tying to absolute gravity stations. Bouguer, terrain and other corrections were made by the gravity data processing procedure, SPECG1988. The density for both Bouguer and terrain corrections is taken to be 2.3 g/cm3. Bouguer anomalies at the gravity stations on the sea floor seem to conform in amplitude with regional gravity anomalies compiled mainly by shipborne gravity surveys. |
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