Abstract

Earthquakes in India occur in the plate-boundary region of the Himalayas as well as in the intraplate region of peninsular India (PI). Devastating events have occurred in PI in the recent past, which is a warning about the possibility of such earthquakes in the future. But very limited recorded data are available about ground motion in PI for engineers to rely upon. The present paper, after a review of available data, develops an attenuation relationship based on a statistically simulated seismological model. The proposed equation for peak ground acceleration (PGA), under bed rock conditions, is of the form  
\[\ \mathrm{ln}(\mathrm{PGA{/}g})=c_{1}+c_{2}(M-6)+c_{3}(M-6)^{2}-\mathrm{ln}(R)-c_{4}R+\mathrm{ln}{\varepsilon},\]
(1)
with c1 = 1.6858, c2 = 0.9241, c3 = -0.0760, c4 = 0.0057, and σ(lnϵ) = 0.4648. Correction factors for other site conditions are also computed. In the absence of a robust database of strong-motion records, seismological modeling is a rational alternative until sufficient instrumental records become available in PI. It is observed that attenuation of strong motion in PI is similar to that in other intraplate regions of the world.
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