THE PREDICTION OF EARTHQUAKE PEAK GROUNDACCELERATION IN KOYNA REGION, INDIA

摘要

The quantitative evaluation of earthquake hazard for critical structures, such as dams and nuclear powerplants, requires an estimate of the ground motion from an earthquake having specified magnitude,epicentral distance and focal-depth. To obtain these estimates, one requires development of empiricalequations to arrive at the ground motion parameters as a function of magnitude, source distance and soilconditions. From the characteristics of the worldwide strong motion records, it is seen that attenuationrelations developed for peak ground acceleration for same type of site condition in different parts of theworld differ widely. It is, therefore, necessary to develop attenuation relations, specific to each region,and, if possible, from the recorded strong motion data of the region, to make more realistic prediction ofground motion for given design earthquake specifications. Peninsular India is an area of low to moderate,infrequent seismicity, typically of an Intra-plate region. In peninsular India, strong motion records ofengineering importance are available from Koyna region. A set of 31 three-component accelerograms fromKoyna region having magnitude ranging 3.5 to 6.5 and hypocentral distance varying from 3.5 km to 25.0km have been used to develop an attenuation relation for PGA. The results are of direct engineeringimportance, as these strong motion records provide near-field estimate of ground motion in an intra-plateregion, which can be used in earthquake-resistant design of critical facilities in the geological environmentsimilar to Koyna region.