Publication Date:
1981-01-01
Description:
The present system to observe the bottom pressure by use of a quartz pressure sensor was laid at a depth of 2, 200 m on the sea bed 100 km off the south coast of the Tokai district, Japan, in August, 1978. The on-line real-time bottom pressure signal is transmitted to the shore through a submarine cable. The system is designed so as to have high reliability, which assures us of fruitful observation for more than ten years. Characteristic instrumental noises are occasionally recognized on the records. It is inferred that the noises are caused by the short period bottom temperature changes. The utility of the data, however, is not significantly impaired by them. A linear trend of the record due to the aging of quartz is +9.6 cmH2O/year in 1979. This may make it impossible to discriminate the secular vertical crustal movement, but the record has an advantage over the coastal tide records for the detection of the large precursory vertical movement just prior to a great earthquake, because the meteorological and oceanographic disturbances on the ocean bottom are far less than those on the coastal sea surface. It is shown that the pressure sensor also acts as a long-period accelerometer of the frequency band 0 to 1/6 Hz and a resolution of 0.01 Gal. © 1981, The Seismological Society of Japan, The Volcanological Society of Japan, The Geodetic Society of Japan. All rights reserved.
Print ISSN:
0022-3743
Electronic ISSN:
1884-2305
Topics:
Geosciences
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