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Test of Poisson process for earthquakes in Mexico City

1967; American Geophysical Union; Volume: 72; Issue: 14 Linguagem: Inglês

10.1029/jz072i014p03741

2156-2202

Sergio G. Ferráes,

Geochemistry and Geologic Mapping

The data for the annual number of earthquakes in Mexico City during the period 1925-1966, with epicenters inside a localized area, are presented. It is found that the data do not fit a Poisson distribution. I believe that the earthquakes in Mexico City are not events occurring randomly and independently of each other in time, since they are not generated from a simple Poisson process. Knopoff [1964] has found that a sequence of earthquake events in southern California does not fit a Poisson distribution. Aki [1956] has independently reached the conclusion that major earthquakes are not completely random and independent events. The report of the Panel on Earthquake Prediction follows Knopoff, Aki, and others in concluding that the observed deviations from the Poisson distribution arise from departure from randomness in time; therefore, there is a general tendency toward generalizing that earthquakes are not distributed by a Poisson law. Lomnitz [1966] has pointed out, however, that ‘little attention seems to have been given to the possibility that these deviations may be due to lack of randomness in space rather than in time’ In addition, there is no physical basis for assuming that earthquake occurrence should be random in time in all the active seismic regions of the world.