THE FIRST AND 3RD ASYMPTOTIC DISTRIBUTIONS OF EXTREMES AS APPLIED TO THE SEISMIC SOURCE REGIONS OF INDIA AND ADJACENT AREAS

The seismic source regions are identified on the basis of spatial and temporal distributions of shocks (1900-1989), recurrence relations and the tectonic architecture of the Indian subcontinent and adjoining ar eas. The probable occurrence of the maximum magnitude earthquake is es timated using the theory of extreme values of Gumbel. The parameters o f the first and third asymptotic distributions of extremes and their u ncertainty values are computed for the seven identified seismic source regions of India and adjacent areas. The third-type distribution curv e is preferable to the first type in all the regions, as revealed by t he chi(2) test. The results of the third asymptotic distribution indic ate the upper bound to earthquake magnitude w is equal to 8.94 +/- 0.2 1 for Assam, 8.56 +/- 0.29 for Bihar-Nepal, 8.43 +/- 0.10 for Kangra, 8.97 +/- 0.27 for Hindukush, 7.61 +/- 0.24 for Pakistan-Cutch, 7.34 +/ - 0.12 for Koyna and 8.98 +/- 0.27 for Andaman Sea seismic source regi ons. The predicted most probable largest earthquake magnitude is compu ted for return periods of 10, 20, 50, 75 and 100 yr in each source reg ion.