Seismic Hazard at the Historical Site of Kancheepuram in Southern India

摘要

A Probabilistic Seismic Hazard Assessment (PSHA) at Kancheepuram was carried out under the aegis of an Indo-Italian Significant Bilateral Project on seismic vulnerability of historic centers in Southern India between the University of Pavia, Italy, and the Indian Institute of Technology Madras, India. The scope of the hazard study was the definition of the seismic input in terms of horizontal/vertical UHS for structural analysis of the heritage structures in Kancheepuram. The standard Cornell-McGuire method and the Zone-Free approach by Woo (1996) have been used for hazard computation after the compilation of a composite earthquake catalogue for Kancheepuram. To make the catalogue statistically consistent with the Poisson's model of earthquake occurrence, the declustering process was carried out by using a dynamic spatial-temporal windowing technique.Completeness analysis of the catalogue was performed by both the Visual Cumulative, Mulargia (1987) and Stepp (1973) methods. Ground Motion Prediction Equations (GMPEs) developed for Peninsular India and three other shallow crustal earthquake models have been used to estimate ground motion attenuation. Epistemic uncertainty in the seismic hazard was addressed by using a logic tree framework assuming completeness analysis, maximum cut-off magnitude, seismogenic zoning and attenuation relations as separate branches of the logic tree. The computed seismic hazard at Kancheepuram is slightly higher than that specified by the current seismic code, IS-1893 (2002). Deaggregation of the seismic hazard for peak ground acceleration predicts low seismicity at Kancheepuram controlled by weak to moderate earthquakes with sources located at short distances from the site.