Journal of The School of Marine Science and Technology,Vol.6 No.3
Precise gravity measurements around the Omaezaki peninsula, Shizuoka, Japan,for finding the interseismic and coseismic gravity changes
Shigekazu KUSUMOTO, Toshiki SAKAI, Toshiyasu NAGAO, Mikio SATOMURA,
Wenke SUN and Shuhei OKUBO
Abstract
We carried out precise gravity measurements at the bench marks around the Omaezaki peninsula, Shizuoka,Japan,by2relative gravimeters of LaCoste ＆ Romberg G-581and Burris B-19gravimeters,in order to collect and accumulate fundamental data for finding the interseismic and/or coseismic gravity changes.Before data processing,we established the calibration line having gravity difference of836mGal among Mizusawa (Iwate)-Kyoto (Kyoto)-Aso (Kumamoto)and carried out the calibration of scale factor of the Burris gravimeter,B-19.As a result,it was found that we must assign the correction factor of 1.02309 to the scale factor and that the magnitude of this
correction factor is very larger than other gravimeters.We compared gravity values obtained in 1970with the gravity
data given by data processing with this corrected factor.Although it was shown that the gravity changes around the
Omaezaki peninsula can be caused basically by height variations of the Eurasian plate side due to subduction of the
Philippine Sea plate, it was suggested that gravity variation pattern differ in different observation area, despite of small area.