[J07-P] Poster

[J07-P-07] Investigation of long period behaviors of seafloor pressure records based on field data and laboratory test results

^○Ryota Hino¹, Syuichi Suzuki¹, Makiko Sato¹, Yusaku Ohta¹, Yoshihiro Ito², Hiroaki Kajikawa³, Tokihiko Kobata³ (1.Tohoku University, Sendai, Japan, 2.Kyoto University, Kyoto, Japan, 3.National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan)

Seafloor pressure monitoring is an effective mean to detect vertical crustal deformation in offshore areas. A small sensor of high precision and low power consumption enables to build an ocean bottom observation system to make continuous observations for one to two years. Several studies demonstrated that the bottom pressure monitoring can detect transient signals associated with tectonic events having time constants shorter than a month. However, it is difficult to detect tectonic events of much slower deformation rates due to lack of the knowledge about exact origins of longterm variations in the pressure records obtained at the seafloor. In this paper, we discuss about longterm characteristics of ocean bottom pressure records based on the actual data obtained by repeating deployment of free-fall/pop-up type instruments in the Japan Trench area as well as by laboratory experiments. A similar pattern of the temporal variation can often be identified on the seafloor records obtained by the identical pressure sensor. Previous laboratory experiments on the response of pressure sensors of the same kind showed a transient behavior after applying high pressure has several similarities to those on the seafloor observation records. These suggest that the sensor specific characteristics can be dominant in the field data and may be removed after estimating it through laboratory tests. Motivated by this idea, we are carrying out a laboratory experiment to clarify exact behavior of the pressure sensor previously used in the field observations. Another experiments are done to know stability of a counting clock for frequency measurement.