Seismic moment deficit and hazard assessment of the Eastern Himalayan Syntaxis

Abstract The largest earthquake ever recorded on land, the Assam (moment magnitude, Mw8.6), occurred in the Eastern Himalayan Syntaxis. To assess the current seismic hazard in this region, we evaluated the seismic potential of major faults in the Eastern Himalayan Syntaxis by comparing the accumulation and release of seismic moments. First, constrained by long-term global positioning system measurements, we calculated the slip rates and locking depths of major faults using a three-dimensional elastic block model. Second, we estimated the seismic moment release of the major faults from 1800 to 2023 using an earthquake catalog. The results indicate that the Main Himalayan Thrust remains a significant seismic hazard in the Eastern Himalayan Syntaxis, capable of producing earthquakes with a magnitude of Mw greater than or equal to 7.9. Additionally, the Naga Thrust and Jiali Fault have the potential to generate earthquakes of Mw greater than 7.4. Presently, the probability of earthquakes exceeding Mw7.0 on other faults is relatively low. If seismicity along the Main Himalayan Thrust follows the Gutenberg–Richter law, the recurrence period for the Assam earthquake is approximately 2000 years. The results of this study provide a reference for future seismic hazard analyses in this region.