Publication Date:
2017-04-04
Description:
The aim of this work is to quantitatively set up a simple hypothesis for occurrence of
earthquakes conditioned by prior events, on the basis of a previously existing model and the use
of recent instrumental observations. A simple procedure is presented in order to determine the conditional
probability of pairs of events (foreshock-mainshock, mainshock-aftershock) with short time
and space separation. The first event of a pair should not be an aftershock, i.e., itmust not be related to
a stronger previous event. The Italian earthquake catalog of the Istituto Nazionale di Geofisica (ING)
(1975–1995, M 〉 3:4), the earthquake catalog of the Japan Meteorological Agency (JMA) (1983–
1994, M 〉 3:0) and that of the National Observatory of Athens (NOA) (1982–1994, M 〉 3:8) were
analyzed. The number of observed pairs depends on several parameters: the size of the space-time
quiescence volume defining nonaftershocks, the inter event time, the minimum magnitude of the two
events, and the spatial dimension of the alarm volume after the first event. The Akaike information
criterion has been adopted to assess the optimum set of space-time parameters used in the definition
of the pairs, assuming that the occurrence rate of subsequent events may be modeled by two Poisson
processes with different rates: the higher rate refers to the space-time volume defined by the alarms
and the lower one simulates earthquakes that occur in the nonalarm space-time volume. On the basis
of the tests carried out on the seismic catalog of Italy, the occurrence rate of M 〉 3:8 earthquakes
followed by a M 〉 3:8 mainshock within 10 km and 10 days (validity) is 0.459. We have observed,
for all three catalogs, that the occurrence rate density for the second event of a couple (mainshock
or aftershock) of magnitude M2 subsequent to a non aftershock of magnitude M1 in the time range
T can be modeled by the following relationship: .T , M2/ D 10a
0Cb.M1M2/ with b varying from
0.74 (Japan) to 1.09 (Greece). The decrease of the occurrence rate in time for a mainshock after a
foreshock or for large aftershocks after a mainshock, for all three databases, obeys the Omori’s law
with p changing from 0.94 (Italy) to 2.0 (Greece).
Description:
Published
Description:
107-121
Description:
JCR Journal
Description:
reserved
Keywords:
foreshock, aftershock, validity, probability gain, Akaike information criterion
;
04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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