SEISMIC ZONING VIA DETERMINISTIC UNIFORM HAZARD RESPONSE SPECTRAL AMPLITUDES

Abstract

The region of Delhi is sensitive to earthquake hazard and lies in seismic zone IV (IS 1983, Part I: 2002). The city has experienced earthquakes in the past and is vulnerable for earthquake related damages in the future. Proximity of Himalayan region makes Delhi susceptible to the earthquakes from Himalayan seismic sources also. Many fractures and faults are noticed in the Himalayas. Therefore, to consider seismic activities around Delhi, the India Gate in Delhi as the center(28.6129°N,77.295°E), a circular region of 300 km radius has been assumed as the catchment area for Delhi city. All the potential faults of the study area mentioned in Seism tectonic Atlas of India have been digitized in Arc GIS [10.3] and 32 faults recognizable as affecting Delhi. By dividing the region into different seismic zones, we can identify the areas which are at increased risk. A seismic zone is a region in which the rate of seismic activity remains consistent. Then codal provisions are developed and improvise to design a building based on the level of risk. In this dissertation work, Deterministic seismic hazard analysis (DSHA) method is used to find the maximum possible ground motion at the site of interest by developing uniform hazard spectra curve. In Uniform Hazard Spectrum, every ordinate has an equal rate of being exceeded. So far, the PSHA methodology is being used to develop uniform hazard spectra and it also covers the effects of all combinations. In this study, the aim is to develop a uniform hazard spectra curve using DSHA methodology by considering the effect of all combinations instead of considering only one combination (having maximum PGA). The Uniform Hazard Spectrum in DSHA is developed by finding “Joint probability of non-exceedance” for spectral acceleration for a range from 0.01(g) to 2.96(g) for different time periods. Then a target rate of exceedance is chosen and the spectral acceleration amplitude for each period corresponding to that rate is identified. Then the curve is drawn in which the values of spectral accelerations is the values where target rate of exceedance cuts the UHS curve at different time periods. After that seismic zoning is carried out at different grid points (0.1° x 0.1°) in Delhi region by using the uniform hazard spectrum curve and accordingly contour of peak ground acceleration is drawn using the software Surferrs,2013.