Synthetic Ground Motion Simulation for Varanasi City

Varanasi (latitude 25°28′ N and longitude 82°96′ E), the cultural capital of India, is presently clustered with a maze of ancient narrow lanes (Gullies) and old buildings. Being a sacred city, it is not well planned and structured, due to lack of adherence to earthquake-resistant building design philosophies and techniques. Consequently, even a smaller magnitude of an earthquake can cause a considerable loss. The city is also near to Faizabad ridge, which has been seismically sedentary for last 300 years. Due to unavailability of earthquake ground motion (G.M.) records in this region, it is necessary to simulate G.M. based on regional seismic data. In this regard, the stochastic approach has been adopted for the synthesis of G.M. at bedrock level. An EXSIM methodology has been used in this study for synthesis of strong G.M. for various identified faults (Allahabad Fault, Azamgarh Fault, Gorakhpur Fault, Deoria Fault, Lucknow Fault, Siwan Fault, Shajhanpur Fault and Great Boundary Fault) around the city. Various stress drops 70, 100, 125, 150, 175 and 200 bars have been taken for simulations to account for uncertainty in stress drop. Acceleration time histories due to various faults for Varanasi city has been simulated and plotted. The maximum PGA estimated was 0.078 g for Azamgarh Fault at 200 bar among all the faults around the city. Further Response Spectra has been plotted for stress drop (70–200 bar).