Continuous Observation of Crustal Deformation at Abuyama Seismological Observatory (from 1972 do 1977)

概要

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Since 1972, the crustal deformation has been observed by use of silica tube exten someters, water-tube and horizontal pendulum tiltmeters at Abuyama Seismological Observatory. The principal axis of compressional strain obtained seismologically and geodesicallylies in approximately E-W direction, but the observation of secular strain in our vault indicates the extension in E-W direction. This contradiction may be explained as follows. The fold with NS axis is advanced by the compresnional force in E-W direction and the hanging wall of fracture zone (N20?KE strike; dip angle of 20?KW) at the local antiform slides down to the west side. Thus, the progress of shear fold results in the extension in E-W direction. Some of instruments are set across a fracture zone about 1 m thick. The thickness of this fracture zone with left lateral slide component is increased by precipitation and decreased by discharge of water. The discharge from observation, vault increased abruptly mid-1975 and 1976. The variations of discharge, strain and tilt are compared with the weekly count of micro-earthquakes, assuming the seismicity may represent the stress change in wider area. But the correlation between them is vague.
日本測地学会の論文