Multi-rupture Fault-based Seismic Hazard Assessment for the Dauki Fault System, Northeastern India

The east-west-trending, north-dipping Dauki Fault System (DFS) is among the well-identified active fault systems in the North-Eastern part of India, and it marks the southern geological boundary of the Shillong Plateau, separating it from the Bengal alluvium basin and Sylhet trough. With a length of about 350 km stretching from about 89.9° E to 93° E, DFS is reverse in nature and can be divided into 4 segments, namely, Western, Central, Eastern and Easternmost with variable dip and strike values. Mitra et al. (2018) has indicated that this fault can produce an Mw ∼8 earthquake.
Fault segmentation, fault connectivity, and multi-segment rupture scenarios have been explicitly incorporated into a fault-system-based probabilistic seismic hazard framework for the Dauki Fault System. The SHERIFS (Seismic Hazard and Earthquake Rates In Fault Systems) methodology has been employed to enforce a global magnitude–frequency distribution while converting geological and geodetic slip rates into earthquake rates at the system scale. To account for geometric complexities such as bends and step-overs, a range of rupture hypotheses has been explored, including single-segment ruptures, partial multi-segment ruptures, and through-going system-wide ruptures. Epistemic uncertainties associated with maximum magnitude, rupture connectivity, slip-rate variability, and off-fault seismicity have been quantified using a logic-tree approach.
The resulting earthquake rupture forecasts are tested against available seismicity data of the region. The findings underscore the critical role of fault interactions in determining the seismic hazard along the DFS and indicate the need for system-level modelling to provide a reliable assessment of seismic hazard.
This study is the first to offer a seismic hazard framework based on the multi-rupture scenario for the Dauki Fault System and it also contributes to the improvement of seismic risk assessment for northeastern India and the Indo–Burman–Shillong tectonic domain.