Estimation of maximum magnitude (Mmax): Impending large earthquakes in northeast region, India

In the present study, the cumulative seismic energy released by earthquakes (Mw ≥ 5) for a period of 1897 to 2009 is analyzed for northeast (NE) India. For this purpose, a homogenized earthquake catalogue in moment magnitude (Mw) has been prepared. Based on the geology, tectonics and seismicity, the study region is divided into three source zones namely, 1: Arakan-Yoma Zone (AYZ), 2: Himalayan Zone (HZ) and 3: Shillong Plateau Zone (SPZ). The maximum magnitude (Mmax) for each source zone is estimated using Tsuboi’s energy blocked model. As per the energy blocked model, the supply of energy for potential earthquakes in an area is remarkably uniform with respect to time and the difference between the supply energy and cumulative energy released for a span of time, is a good indicator of energy blocked and can be utilized for the estimation of maximum magnitude (Mmax) earthquakes. The proposed process provides a more consistent model of gradual accumulation of strain and non-uniform release through large earthquakes can be applied in the assessment of seismic hazard. Energy blocked for source zone 1, zone 2 and zone 3 regions is 1.35×1017 Joules, 4.25×1017 Joules and 7.25×1017 Joules respectively and will act as a supply for potential earthquakes in due course of time. The estimated Mmax for each source zone AYZ, HZ, and SPZ are 8.2, 8.6, and 8.7 respectively. Mmax obtained from this model is well comparable with the results of previous workers from NE region.