Abstract

A catalog for northeast India and the adjoining region for the period 1897–2009 with 4,497 earthquakes events is compiled for homogenization to moment magnitude Mw,GCMT in the magnitude range 3–8.7. Relations for conversion of mb and Ms magnitudes to Mw,GCMT are derived using three different methods, namely, linear standard regression, inverted standard regression (ISR) and orthogonal standard regression (OSR), for different magnitude ranges based on events data for the catalog period 1976–2006. The OSR relations for Ms to Mw,GCMT conversion derived in this paper have significantly lower errors in regression parameters compared to the relations reported in other studies. Since the number of events with magnitude C7 for this region is scanty, we, therefore, considered whole India region to obtain the regression relationships between Mw,GCMT and Ms,ISC. A relationship between Mw,GCMT and Mw,NEIC is also obtained based on 17 events for the range 5.2 B magnitude B 6.6. A unified homogeneous catalog prepared using the conversion relations derived in this paper can serve as a reference catalog for seismic hazard assessment studies in northeast India and the adjoining region.