Probable Evidence for Periodicities in Seismicity in Gujarat and Adjoining Region, India: Implications on Future Earthquake Hazard

Abstract eng:
The observations of temporal variation of seismic activity in Gujarat and adjoining region indicate evidence that a periodic seismicity probably exists. A complete data set from 1819 to 2006 of shallow earthquakes distributed over Gujarat and adjoining regions have been used for the first time to test the possible existence of periodicities and its implications on the future earthquake occurrences on the basis of stationary model of seismicity rates and seismic energy released in 11-years time window. The results exhibits a network of periodicities with predominant period at 1819-1848, 1898-1956 in low seismicity rate intervals followed by the 1856-1891 and 1962-2006 in high seismicity rate intervals with a period of 105 years in a harmonic variation of seismic energy release. The time interval of low seismicity rates is slightly larger than high seismicity rates. The low seismicity rate varies from 0.2 to 0.3events/year whereas the high seismicity rate varies from 0.4 to 1.0 events/year. The frequency distribution of earthquakes show that the earthquakes of small magnitude (M 4.0-5.9) follow the Poisson distribution and hence such earthquakes can not be predicted. However, the frequency distribution of large earthquakes (M 6.0-7.8) follows the nonrandom distribution (exponential distribution). The characteristics of non-randomness of earthquakes indicate that the prediction of magnitude and time of occurrences of forthcoming large earthquakes may be possible. The temporal variation of earthquake magnitude for three different magnitude ranges (4.0-4.9, 5.0-5.9 and 6.0-7.8) reflects that large earthquakes are preceded by high seismic activity in lower magnitude ranges. The seismic energy released in 11 year time windows shows a harmonic variation with a period of 105 years. The maxima of the harmonic curve coincide with the occurrence of large earthquakes. The detection of such kind of periodicities is important in earthquake study, because these patterns may lead to the prediction of large earthquakes.

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