Space distribution of preshocks

The space distribution of decelerating and accelerating preshocks is examined for six samples of forty-three mainshocks which have occurred recently in the western Mediterranean, the Aegean Sea, Anatolia, California, Japan and central Asia. It is observed that the frequency of shocks of a decelerating or accelerating preshock seismic sequence decays rapidly with distance from an easily located distinct geographical point according to a power-law. This point is defined as the physical center of the decelerating Pf, and the accelerating Pq, preshocks, respectively. On the basis of the mean distance and the corresponding uncertainty of the forty-three mainshock epicenters taken from the corresponding physical centers of the decelerating and accelerating preshocks, respectively, a simple procedure is proposed for a possible contribution of the locations of the two physical centers of preshocks to the location of an ensuing mainshock.