Is the Bay of Bengal becoming a potential source zone for future large or moderate-to-strong intraplate earthquakes?
摘要
An earthquake of magnitude mb 5.3 occurred on 25 February 2025 in the Bay of Bengal (BoB), with tremors felt across Bhubaneswar, Kolkata, Kharagpur, and nearby regions of the East coast of India. This study investigates whether the BoB is evolving into a potential source zone for future large or moderate-to-strong intraplate earthquakes by integrating updated earthquake data, seismicity patterns, and focal mechanism solutions with the identification of weak zones (or fractures) based on gravity and magnetic anomalies from previous works. Since 1917, the region has recorded approximately 120 earthquakes, including several of magnitude ≥6.0. The average b-value across the BoB is 1.06 ± 0.15, with spatial variations from 0.72 in offshore regions to 0.99 near the coastline. Also, stress has been released due to the occurrence of 21 May 2014 and 25 February 2025 earthquakes in the near-offshore areas. Higher b-values near the coast indicate lower crustal stress, while lower offshore b-values suggest elevated stress and the presence of active fracture zones. Evidence of differential stress accumulation and changes in b-value distribution indicating heightened future seismic potential. This study also suggests that evolving stress conditions, sediment loading, and reactivation of deep-seated fracture zones are progressively increasing the seismic hazard potential in this offshore region.
Research highlightsIntegrated seismicity, b-value, stress inversion, and geophysical data reveal evolving intraplate seismic hazard in the Bay of Bengal (BoB). Low offshore b-values and fracture-zone alignment indicate elevated stress and potential for moderate-to-strong intraplate earthquakes. Reactivation of basement fractures, sediment loading, and velocity transition zones indicate evolving seismic hazard in the deep offshore BoB.