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