Infrasonic waves caused by the earthquake on 12 July 1993 in Japan

摘要

The remarkable infrasonic wave trains have been recorded at Beijing Infrasound Observatory at 21:21 BT (Beijing Time), July 12, 1993. They are complete local waves (including primary wave, shear wave and Rayleigh waves) and epicentral infrasonic wavs caused by an earthquake in Japan. They have periods of 12 s, 12 s, 30 s, amplitudes of 0.8 Pa, 0.4 Pa, 1.3 Pa,and durations of 3.4 min, 1 min, 12 min respectively. The period of epicentral infrasonic wave is 137 s, with makimum amplitude of 6.9 Pa and duration of 28 min. They are superimposed on a much longer and more usual series of waves of period about 12 min and amplitude of 10 Pa;such waves, which are of natural origin, are characteristically received during meteorological lnvers1ons.