Seismic Hazards Assessment in the Eastern Himalayas Region

Abstract

Spatial distribution of seismicity and seismic characteristics (fractal dimension, b-value, energy release, reoccurrence period) are assessed for the Himalayan Region (27° – 30°N and 85°– 97°E). The database consists of relocated earthquakes M ≥ 3.8 selected for the period 1964-2017 from the International Seismological Centre (ISC) catalogues (Engdahl, van der Hilst, and Buland (EHB) 2007). The <i>Gutenberg - Richter</i> frequency-magnitude relation (b-value) is calculated by the Maximum Likelihood Method (MLM) and by Least Square Method. The fractal dimension is estimated using the correlation integral method. The entire event set was also used for estimating radiated energy in the region. Four probabilistic models namely, <i>Weibul, Gamma, Lognormal and Exponential</i> have been used to estimate the probability of the occurrence of moderate earthquakes (M ≥ 5.5 and M ≥ 6.5) during a specified interval of time using the Maximum Likelihood Estimates (MLE) for estimating the model parameters. The highly stressed zones in the entire region are indicated by low b-values, low fractal dimension and low radiated energy. The vulnerable zones (Arunachal Himalayas, Mishami thrust zone) have been identified by these maps which are further corroborated with the probabilistic models to assess the seismic hazards in the Himalaya region. These areas are indicative of future probable earthquakes regions.