EMPIRICAL PREDICTION OF STRONG GROUND MOTION FROM INTENSITY DATA

Abstract

Estimation of ground shaking due to potentially damaging earthquakes is required for earthquake resistant design of structures. Earthquake intensity is the qualitative estimate of level of shaking and has been traditionally used by seismologists and earthquake engineers to study the attenuation of ground motion with distance from the source. In the present study eight empirical attenuation relations have been developed using MM intensity data of ten Indian earthquakes. The attenuation model I = a + bMW + cr + d logior or I = a + bmb + cr + d logior has been fitted to the MM intensity data and coefficients a, b, c, and d are estimated using one step and two step regression analysis. Distance r is taken as the distance c°e ter of energy release to various idealized isoseismals. After scrutiny and comparison following two attenuation relations are proposed for the northwestern Himalayan region and shield region of India. 1=3.543 +1.1129M~„ — 0.00872r — 2.13350Ioglor I = — 0.3876 + 1.4090Mw - 0.0140r — 0.6273 logior These relations show that in general the shield region is less attenuating as compared to northwestern Himalayan region. The trend and predicted intensities and accelerations from these relations are found to be by and large in agreement with the other reported studies for the regions. The proposed relations can be adopted for estimating the ground shaking hazards for northwestern Himalayan region and Shield region of India.