Assessing seismic hazard from a potential magnitude 8.0 earthquake along the Indo-Burmese wedge and its impact on Northeast India

The 2016 Mw 6.7 Manipur earthquake in Northeast India caused significant structural damage across the region. This study simulates a plausible Mw 8.0 earthquake to assess its potential impact, employing the Empirical Green's Function Method (EGFM) to estimate probable ground motions while incorporating path and site effects. Fault parameters for the simulated event were validated using recorded data from the Manipur earthquake, revealing a similar rupture directivity pattern in the Peak Ground Acceleration (PGA) distribution between the element earthquake (a smaller recorded event used for modeling) and the simulated earthquake. PGA values across Northeast India ranged from 3 gals to 103 gals for the Mw 6.7 event and from 11 gals to 342 gals for the simulated Mw 8.0 earthquake, with Shillong recording the highest PGA due to seismic wave interference, rupture directivity, and site amplification, despite being situated 214 km from the intermediate-depth source zone (typically between 55 km and 160 km depth). The source depth likely enabled direct wave propagation over long distances, emphasizing the need to analyze simulated earthquake waveforms across varying geological formations. A comprehensive understanding of ground response parameters, simulation methodologies, and the effects of geological and geomorphological features is crucial for refining earthquake preparedness strategies in Northeast India. This study investigates ground motion characteristics and tectonic features across the Indo-Burma subduction zone, focusing on a significant Mw 6.7 earthquake. The lower panel presents a lithospheric cross-section from the Shillong Plateau to the Burma Plate, illustrating the under thrusting of the Indian Plate beneath the Burma Plate. Key geological structures—including the Deformation Front, Central and Outer Indo-Burma Fronts (IBF), and active fault systems such as CCF, KLF, and CMF—are marked, revealing the complex tectonic architecture. The subducting slab experienced the earthquake hypocenter nearly at ∼60 km depth. The observed and simulated peak ground acceleration (PGA) for various seismic stations (such as TADON, SHL, LPSFF, KOHIM), with the highest PGA (342 cm/s²) at SHL, indicating localized amplification effects likely influenced by tectonic and geological conditions in addition to the seismic interference of the direct wave with that of the Shillong plateau. This graphical summary underscores the seismic hazard implications due to active subduction and associated crustal deformation in this region. • Varied ground motions from waveforms reflect how subsurface material heterogeneities affect seismic behavior. • High surface wave amplitudes from wave interference, rupture directivity & site effects caused peak PGA at Shillong. • Rupture directivity and site effects at various formations are key for estimating regional seismic hazard. • Geomorphological factors shape response spectra, aiding risk mitigation and hazard assessment in NE India.