Quantitative Assessment of Seismic Hazard in Eastern-Northeastern India Through Poisson Probability Density Function Analysis

Temporal occurrence of earthquakes of magnitude ≥ 5.5 and 6.0 was statistically analysed for the entire eastern-northeastern India which is seismically active. High seismicity in the region is related to plate margin activity in the Himalaya and Burmese arc. Non-stationary Poisson distribution provides a good fit to analyse earthquake sequence for the entire area of eastern-northeastern India and two subareas within it, viz., the Himalaya and the Burmese arc. For the entire area there is a 90% probability for the occurrence of at least one earthquake of magnitude (Mb₀)≥ 6.0 in any time window of 5 years, while the probability is 98% for an event of Mb₀ 5.5 in any two years time slot. Similarly for the Himalayan tectonic domain, the probability is 70% and for the Burmese arc it is 90% for at least one earthquake of Mb≥ 6.0 within a recurrence period of ten years. As earthquakes in the region above the threshold magnitudes of 5.5 and 6.0 follow a poisson distribution, probability density function maps for both the threshold magnitude were prepared for 1°x1° blocks with rate of occurrence(λ) for each 0.5° overlapping grid. These maps are used to calculate p~rcent probabilities with different return periods. Seismic hazard maps with percent probabilities for the occurrence of at least one earthquake with return periods of 20 and 50 years are presented for Mb₀≥6.0 and with return periods of 5 and 10 years for Mb₀≥5.5.