CRITICAL COMPARISON OF GROUND MOTION ATTENUATION FORMULAE FOR RECENT EARTHQUAKE DATA

Abstract

Earthquake refers to the sudden release of energy in the earth’s crust that creates seismic waves. Earthquakes are unpredictable and their intensity attenuates over long distances. In an idealized situation earth is considered to be elastic and the seismic waves can propagate indefinitely once they are excited. But it is known that the real earth is not perfectly elastic. This causes the waves that are propagating to attenuate with time as they travel. Uncertainties persist in the attenuation equations as they depend on many factors such as epicentral distance, focal depth, geology, fault characteristics, magnitude, topography etc. Many attenuation equations have been developed over the years considering various factors. The present work focuses on validating and critically comparing popular attenuation equations such as Sarma (2000), Smit (2000), Tento(1992), Jacob(1990) etc. for earthquake data of recent times (2005 onwards). An attempt is made to collect as much information as possible from different stations during different earthquakes. The accuracy and effectiveness of different attenuation equations are verified. Also attempt is made to study the sensitiveness of different factors influencing the seismicity. Further it has been inferred that each formula has its own merits and demerits and an attempt is made to identify the most effective attenuation formula for wide range of earthquake data.