Spatial Potential Analysis of Earthquakes in the Western Himalayas Using b-value and Thrust Association

Abstract

In this study, we have analysed the spatial variation of b-values (from frequency-magnitude distribution (FMD)) in the western Himalayas as an indicator to demarcate the potential zones of earthquake occurrences. This is done under the acceptance of interpretation that decrease of b-values is correlated with a stress increase in the epicentral region of an approaching earthquake event. In addition to this, the spatial association of the earthquake epicenters with the major thrusts in the region using weights of evidence method, to identify potential zones of earthquake occurrences have also been analysed. Both analyses were carried out using a historical earthquake (Mw> 4) database of the1900-2015 period. Finally, based on the spatial variation of b-values and ‘contrasts’ derived from weights of evidence method (thrust associations), the derived map information was geospatially combined to prepare a “spatial earthquake potential” map of the western Himalayas. This map demarcates the western Himalayas into 3 zones - high, medium and low potential for future earthquake occurrences.