PROBLEM TO BE SOLVED: To keep a development of an active fault causing an earthquake on the basis of a seismic wave received at an observation point under surveillance, and to observe a sign of the earthquake.SOLUTION: The earthquake sign observation device is configured to comprise: data acquisition means that acquires earthquake data actually measured at a plurality of observation points; pulse calculation means that acquires information on a propagation environment in which the seismic wave is propagated from an epicenter of the earthquake to each observation point, performs a time reversal process to the seismic wave received at the plurality of observation points in consideration of the propagation environment and calculates a time reversal pulse at each observation point; line calculation means that calculates a parametric line in a lengthwise direction of a fault from an orientation distribution of a frequency spectrum of the time reversal pulse calculated by the pulse calculation means; head search means that analyzes a seismic wave received in the vicinity of the parametric line calculated by the line calculation means and searches for a parametric head; and surveillance means that keeps a development of a crack of the fault under surveillance by observing the parametric head searched by the head search means.
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