Observations of Crustal Movements by Newly-Designed Horizontal Pendulum and Water-Tube Tiltmeters with Electromagnetic Transducers (1)

Abstract

In order to detect temporal variations in the amplitude and phase of earth tidal tilts, in relation to crustal deformations, horizontal pendulum and water-tube tiltmeters with electromagnetic transducers have been newly designed. The horizontal pendulum tiltmeter has a pendulum of 2.6kg weight, with a free period of about 6 sec and the mechanical amplification factor of about 45. A differential transformer is used as a transducer. The water-tube tiltmeter consists of three detectors, which are located at the vertices of a triangle and connected by vinyl chloride tubes. Each detector has a float of glass, and its displacement in accordance with the level change of the water surface is detected by a magnetic sensor. Two components of the horizontal pendulum tiltmeters and one set of the water-tube tiltmeter were installed in December 1975 and July 1976, respectively, in the observation vault of the Kamitakara Crustal Movement Observatory (36°17'N, 137°20'E, H=800m) and the observations have been continued since that time. The overall sensitivities of two kinds of tiltmeters are 4"×10^-4 and 3"×10^-4/mm on the recording chart, respectively. In this paper, the structures, principles and calibration techniques of these instruments are described, and some preliminary results from tidal analyses of the tiltmeter records are also presented.