Crustal Thickness and Composition Variation along the Western Ghats of India through Teleseismic Receiver Function Analysis

Abstract

The crustal thickness and composition variation along the Western Ghats using analysis of the teleseismic receiver functions calculated on the 36 broadband seismic stations in and around the Western Ghats is presented. The results show that the crustal thickness is mostly 36 – 40 km beneath the Western Ghats. The seismic stations falling in the Western Ghats however, imaging the mid-Archean Nucleus of the Western Dharwar Craton and Nilgiri hills (ca. 2.2 km elevation) show a crustal thickness of 45 – 50 km beneath these regions. In general, the calculated Vp/Vs ratio is varying between 1.66 and 1.82 all along the Western Ghats. Most of the seismic stations show higher Vp/Vs ratio (> 1.8), an indicative of mafic composition, may be due to magmatic underplating below the Western Ghats. The lower value of Vp/Vs ratio (< 1.70) at few stations can be due to local heterogeneity beneath those stations. Based on calculated crustal properties, the portion of the Western Ghats falling in the Deccan Volcanic region is different from the remaining; and we believe that the portion of the Western Ghats falling in the Deccan Volcanic Province was probably modified by the crust-mantle interaction during tectono-magmatic event related with the Deccan volcanism.