Abstract

Seismic waveform data, recorded by short-period instruments of the Cooperative New Madrid Seismic Network (CNMSN), and a temporary aftershock deployment for the 2001 Bhuj MW 7.6 earthquake are corrected to the theoretical Wood-Anderson response, and the horizontal peak amplitudes are used to determine local magnitude scales for the Mississippi embayment of the central United States and the Kachchh basin of western India, with a focus to understand the distance attenuation in these two regions. Results show that the distance-correction function for the Mississippi embayment of the central United States is  
\[-\mathrm{log}{\,}A_{0}=1.2362{\,}\mathrm{log}\frac{r}{17.0}-0.005437(r-17.0)+2.0,\]
showing a weak distance attenuation within 17.0–100.0 km. The distance-correction function for the Kachchh basin of western India is  
\[-\mathrm{log}{\,}A_{0}=1.6213{\,}\mathrm{log}\frac{r}{17.0}-0.002940(r-17.0)+2.0,\]
showing a relatively stronger distance attenuation within 17.0–100.0 km. Kachchh basin distance attenuation is closer to southern California than to the central United States suggesting fundamental differences in local wave propagation between these two intraplate regions.
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