Temporal variation of seismicity in a Himalayan tectonic block and the 1991 Uttarkashi earthquake, India

Abstract

Spatial and temporal variation of the seismicity between 1970 and August 1991 in the northwestern Himalaya and adjoining areas of Tibet, immediately to the north, were investigated using a function of the CN algorithm. The aim of the exercise was to detect a pattern which, if known earlier, could have been used to predict the Uttarkashi earthquake of 19 October 1991 in the Garhwal Himalaya. It is observed that strong earthquakes occurring in a block, defined by longitudes 75° and 83°E and latitudes 30° and 38°N approximately, yield a distinctive pattern of temporal variation in the seismicity for the purpose. We conclude from the analysis that the seismicity in the northwestern Himalayan segment of the Alpide-Himalayan seismic belt may not be independent of seismicity in southwestern Tibet.