Estimation of Seismicity Parameters and Development of Seismotectonic and Isoseismal Maps for Bihar, India

Abstract

The present study aims to estimate seismicity parameters, to develop seismotectonic and isoseismal maps for the Bihar state, India. The earthquake catalog is prepared with historical and instrumental seismic events for the last 190 years (from 1833 to 2022). The completeness period for different classes of magnitude (Mw), such as 3.5 < Mw ≤ 4.5, 4.5 < Mw ≤ 5.5, 5.5 < Mw ≤ 6.5, and 6.5 < Mw ≤ 8.0, is 80 (1940–2001), 170 (1851–2022), 140 (1881–2022), and 180 (1831–2011) years, respectively. The study area's seismicity parameters a and b range from 5.13 to 5.79 and 0.64 to 0.76, respectively. The return period of major seismic events (3.5 ≤ Mw ≤ 8.5) in the Himalayan region are estimated using Gumbel’s statistical analysis along with time- and magnitude-predictable model. It is obtained that return period (Tr) of Mw ≥ 7.0 is 44 years. A seismotectonic map is developed for the 350 km radius of the influence zone from the centre of Bihar (latitude 25.8560° N and longitude 85.7868° E) by taking accounts of faults, shear zones and lineaments. Intensity-based isoseismal maps have been developed for five past major earthquakes to determine how significantly they affected the study area. It is found that a maximum Medvedev–Sponheuer–Karnik (MSK) scale intensity of X could be felt in Bihar if similar seismic events occur. The outcome of this study may be further used for the seismic hazard assessment and assessment of seismic scenario-based planning purposes of the study area.