Assessment of maximum earthquake potential of the Kopili fault zone in northeast India and strong ground motion simulation

Abstract Maximum magnitude (MM) earthquake in the Kopili fault zone of North-East India has been assessed using different approaches, which are primarily dependent on various parameters such as fault geometry, slip rate, geodetic moment rate, and convergence rate. The analyses reveal that the source zone has accumulated strain energy, during the last 72 years since 1943, enough to produce a strong earthquake of magnitude ≥ 7. On supplementing with the historical data, we conclude M w 7.3 as the maximum potential earthquake for the Kopili source zone. Such large earthquake, on its occurrence, may cause widespread significant ground shakings and damage to infrastructures in the study region. We, therefore, also simulated strong ground motion, in the form of peak ground acceleration (PGA), for the M w 7.3 potential earthquake using Empirical Green’s Function (EGF) approach for ten different sites. In the analysis, an earthquake of magnitude M w 6.5, which has been simulated using a recorded M w 5.3 earthquake, is used as Green’s Function. The two-step approach is adopted in the simulation process, as the required criteria, i.e., moment ratio of  w 7.3) and the element event (M w 5.3) could not be met. We found that the cities like Tezpur, Masamari, Tumuki, Dhekiajuli, Nagaon, Bomdila, Udalguri, Seppa, Hajoi, Behali, Guwahati, and Itanagar that are located ∼ 60–130 km from the source zone may experience very strong to moderate ground shaking with PGA ranging between 0.36–0.14 g. However, the cities located in the distance range of ∼ 130 – 300 km from the source, namely Jorhat, Ziro, Mokokchung, Dhubri, and Kokrajhar are expected to have low ground shaking with PGA