Evaluating and comparing seismic hazard parameters for Northeast India: a comprehensive study

This comprehensive study focuses on the evaluation and comparison of seismic hazard parameters in the Northeast Indian region, covering longitude 87°–98°E and latitude 20°–30°N, which is characterized by high seismicity and complex tectonic structures. The study aims to estimate seismicity parameters such as the magnitude-frequency distribution and Gutenberg-Richter a and b-values using maximum likelihood method (MLM) through the Zmap and the statistical approach proposed by Kijko. The study area is divided into six seismogenic source zones, and zone-wise seismicity parameters are estimated using the declustered catalog considering whole earthquake data and data within the completeness period. The study estimated seismicity parameters using completed catalogs. The results showed that the a value ranged from 2.85 to 5.06, and the b value ranged from 0.76 to 0.92 when using Zmap. Meanwhile, when using the Kijko approach, the estimated a value ranged from 2.70 to 4.65, and the b value ranged from 0.64 to 0.85. The estimated seismicity parameters are used to estimate the return periods and probabilities of earthquakes with different magnitudes for each zones. From the probability curve, it is observed that the probability of earthquake occurrences decreases exponentially with magnitude. For all zones, a high probability of occurrence is observed for earthquake magnitude 6 both in 50 and 100 years. The return periods for different magnitudes estimated from the Zmap and Kijko methods are consistent with some variations among the six source zones. Zmap estimates were lower for smaller magnitudes and higher for larger magnitudes than the Kijko method. The difference factor varied depending on the source zone and magnitude. In general, Zmap estimates were lower by a factor of 1.0 to 1.34 for lower magnitudes and higher by a factor of 1.01 to 1.35 for higher magnitudes.