JPS56125680A - Decision method for terrestrial vibration - Google Patents

Abstract

PURPOSE:To make earthquake decision having high accuracy by detecting only the electric signals of the prescribed frequency band out of the electric signals which an earthquake receiver detects, converting these to absolute values then obtaining average values momentarily and outputting an earthquake decision signal. CONSTITUTION:An earthquake receiver 1 detects the vibrations at the point where it is installed. Said electric signals are passed through a band-pass filter of a narrow band, thence they are inputted to an absolute value circuit 3. These signals are taken of average values momentarily in every extremely short fixed time for a fixed time region (1-10sec) in a average value circuit 4. When these average value signals arrive more than a fixed value, they are inputted to a time decision circuit 8. When they continue for more than a fixed time, the signal indicating the beginning of terrestrial vibrations is outputted. When the average value signals continue of the state below the prescribed after this, the signal for the end of the terrestrial vibration is outputted. With vibrations other than earthquakes, the signals of high levels will not continue in the predetermined frequency band, and therefore the earthquake decision is made highly accurately by said manner.