TILTING MOVEMENT OF THE GROUND RELATED TO THE MATSUSHIRO EARTHQUAKES

Abstract

In order to investigate the relations between ground deformations and seismic activities in Matsushiro and neighbouring regions, continuous observations on the ground tilt and strain were carried out at Suzaka City, Nagano Prefecture. Two tiltmeters of water-tube type, two tiltmeters of horizontal pendulum type and three extensometers of Benioff type were installed in the underground gallery bored halfway up Kamatayama hill, the eastern suburb of Suzaka City. From the tiltmetric observations it proved that the direction of the ground tilt changed markedly every time an earthquake of a magnitude larger than 5.0 occurred, and an anomalous ground tilt appeared before the occurrence of the earthquakes of Sep. 27, 1966, and Feb. 8, 1967.