We have examined the Soviet regional earthquake catalog for Central Asia for the period 1962 to 1983 to characterize the spatial and temporal structure of the earthquake process in this highly active continental collision zone. Three areas of apparently homogeneous earthquake distribution were identified as characteristic of distinct seismic regimes: (1) a segment of the range-bounding Gissar-Kokshal fault zone, (2) the interior of the crystalline massif of the Tien Shan mountain range, and (3) the Tadjik Depression fold-thrust belt. The pair analysis technique applied in our study compares the spatial and temporal distribution of pairs of earthquakes with those determined by uniformly distributed events in the same area and time interval. We have found the earthquake distribution in this region to be dominated by significant nonrandomness in both space and time. The spatial nonrandomness is manifested in two major ways. Spatial clustering appears to characterize the overall structure of the earthquake process in the region, as it is observed regardless of the scale considered and even upon removal of foreshocks, aftershocks, and swarms from the catalog. Anomalies at larger distances could also be distinguished, suggesting the existence of a regular spatial alternation of subareas of higher and lower levels of seismic activity. The nonrandomness in temporal distribution of earthquakes is also characterized by clustering at short time intervals. In contrast with the spatial patterns, earthquakes appear to be randomly distributed in time after removal of foreshocks, aftershocks, and swarms.

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