DIAGNOSIS OF TIMES OF INCREASED PROBABILITY (TIPs) FOR STRONG EARTHQUAKES IN NORTHERN APPALACHIANS

V. I. Keilis-Borok, and I. M. Rotwain

Abstract

The similarity of premonitory seismicity patterns in the interplate and intraplate regions is investigated. The CN algorithm, which was first designed for intermediate-term earthquake prediction in such interplate region as California-Nevada is applied for this purpose without readaptation to the Appalachian mountain belt between latitudes $46.2^{\circ}$~N and $36.6^{\circ}$~N, 1964--July 1993. This territory was divided into northern and southern regions by the latitude $42.4^{\circ}$~N. Two earthquakes with magnitude above 5.0, both in the northern region, did occur in the time period considered: June 15, 1973, $M=5.2$; and October 7, 1983, $M=5.3$. The Time of Increased Probability (TIP) of a strong earthquake was diagnosed by the CN algorithm before the second earthquake only, while the total duration of all 4 TIPs diagnosed is 6,5 years, i.e., 23\% of the whole time interval. No TIPs are diagnosed in the southern region, where strong earthquakes did not occur. Though the statistical significance of prediction cannot yet be estimated, the results obtained support a previous conclusion on the premonitory seismicity patterns in the normalized robust definition; their worldwide similarity, extending to intraplate seismicity; and the large size of the fault system, where these patterns are formed. This gives an additional insight into the origin of intraplate earthquakes; further reduction of TIPs' duration is necessary to make such predictions practically useful, in view of the fact that the earthquakes considered affect densely populated megalopolis.

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Computational Seismology, Vol. 1.