Abstract
Seismotectonic processes of the Shillong Plateau (SP) have been influenced by the Himalayan orogeny, the India-Burmese subduction, and the Bengal Basin evolution leading to high seismic activity in the region. With a goal of assessing seismic hazards in the SP and providing a scientific information to engineering and disaster risk management communities, a probabilistic seismic hazard analysis is employed to determine hazard in highly-populated districts of SP and particularly in Shillong, Nongpoh, and Tura cities, located within the districts. This analysis is based on the use of historical and instrumentally recorded regional earthquakes since 1411 and deals with uncertainties related to earthquake magnitudes, rupture locations, and the frequency of ground motion exceedance. Individual hazard curves indicate that the Barapani fault possesses the highest frequency of seismic hazard for Shillong city and Nongpoh, and the Eocene hinge zone and Dauki faults are responsible for the highest frequency of seismic hazard at Tura. The results of the hazard assessment together with those obtained earlier using a scenario-based approach demonstrate that although the Oldham fault located near Tura can produce a great, but rare earthquake, few other nearby faults are capable of producing smaller magnitude events with a higher probability of occurrence.
Highlights
The northeastern (NE) India is tectonically active region intertwined with numerous faults, which have been the source of several strong to great damaging earthquakes
All hazard curves show that the stronger a ground motion (PHA) is, the lower is the frequency of occurrence of the that motion in a specified time period
The probabilistic seismic hazard (PSH) analysis has been performed for the districts of the East Khasi hills, Ri-Bhoi, and the West Garo hills, located within the Shillong Plateau (SP)
Summary
The northeastern (NE) India is tectonically active region intertwined with numerous faults, which have been the source of several strong to great damaging earthquakes. Baro et al (2018) performed deterministic (scenario-based) seismic hazard (DSH) assessment for the Shillong Plateau (SP) located in the southwestern part of NE-India and encompassing the state of Meghalaya (Figure 1(a)) They found that the Barapani, the Oldham, and the Dauki faults were the most-seismic hazard causing sources with estimated peak horizontal acceleration (PHA) of up to 0.47 g within the SP, which was higher than that recommended by the Indian code of seismic design of structure (IS 1893 2016). This DSH analysis considered the worst scenarios for each seismic source based on its maximum possible earthquake magnitude, and did not account for the likelihood of the scenarios to occur, e.g., during the design life of constructed building and other infrastructure in the region
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