Earthquake hazard potential of Indo-Gangetic Foredeep: its seismotectonism, hazard, and damage modeling for the cities of Patna, Lucknow, and Varanasi

摘要

The Indo-Gangetic Foredeep region lies in close proximity to the Himalayan collision tectonics and the Peninsular Shield thereby subjecting it to repeated strong ground shaking from large and great earthquakes from these active tectonic regimes. An attempt is, therefore, made to understand the seismotectonic regime of the Indo-Gangetic Foredeep region while performing probabilistic seismic hazard modeling of its important cities of Patna and Lucknow and the religious city of Varanasi based on consideration of seismogenic source characteristics, smoothened gridded seismicity zoning, and generation of next generation ground motion attenuation models appropriate for this region along with other existing region-specific ground motion prediction equations in a logic tree framework. In the hazard modeling, peak ground acceleration (PGA) and 5% damped pseudo-spectral acceleration (PSA) at different time periods for 10 and 2% probability of exceedance in 50years with a return period of 475 and 2475years have been estimated at firm rock site condition (site class B/C) with an average shear-wave velocity of about 760m/s, of which, however, the results of only 475years of return period have been presented here for urban development and earthquake engineering point of view. Surface-consistent probabilistic seismic hazard is modeled using the International Building Code-compliant short and long period site factors corresponding to topographic gradient-derived shear-wave velocity-based site classes. The estimated surface-consistent PGA is seen to vary in the range of 0.222-0.238g in Patna City, while it varies in the range 0.257-0.295g in Lucknow and 0.146-0.172g in the city of Varanasi. The cumulative damage probabilities in terms of none,' slight,' moderate,' extensive,' and complete' have been assessed using the capacity spectrum method in the Seismic Loss Estimation Approach (SELENA) using both the fragility and capacity functions for six model building types in these cities.