Abstract
The Saurashtra Peninsula and its adjoining regions covered by Deccan Traps (DT) are one of the important parts of the Indian continental lithosphere with interesting geophysical anomalies, tectono-thermal evolution since the Mesozoic times. Knowledge on the deep structure beneath these formations is important for understanding the seismo-tectonics of the region. This region has gained importance after the occurrence of a major earthquake (7.9 Mw) north of Saurashtra, namely Bhuj earthquake during 2001. It is also observed that Saurashtra region has experienced several earthquake swarms limited to small regions. Accordingly, it is important to investigate the deep structure of the Saurashtra region from seismotectonics point of view. In our study, magnetotelluric results of the deep crustal structure along five NS oriented traverses are presented. The five traverses are—Halvad-Rohisa (HR), Sapar-Iswaria (SI), Mota Dahinsara-Bamagadh (MB), Jodiya-Jamkhandorna (JJ) and VavBeraja-Devda (VD). The total length of these 5 traverses is about 670 km. The derived deep geoelectric structure is also compared and correlated with gravity data to get more confidence on the derived results. The 2-D geoelectric section has delineated anomalous high conductivity structure at places extending from 20 km to about 40 km. From the spatial correlation, anomalous high conductive structure derived from MT data with intense localized seismic activity is an interesting observation. In the present study, the results of magnetotelluric studies along with other geophysical results are presented.
Highlights
At the western continental margin of India, a prominent feature—Saurashtra Peninsula (SP)—formed as a unique feature is known to have experienced different faces of stretching, rifting and uplifting during the geological past [1] [2]
The Saurashtra Peninsula and its adjoining regions covered by Deccan Traps (DT) are one of the important parts of the Indian continental lithosphere with interesting geophysical anomalies, tectono-thermal evolution since the Mesozoic times
It is believed that the tectonics of the Saurashtra peninsula is controlled by three major Precambrian trends—Dharwar trend (NNE-SSW), Aravali-Delhi trend (NE-SW) and Satpura trends (ENE-SWS)
Summary
At the western continental margin of India, a prominent feature—Saurashtra Peninsula (SP)—formed as a unique feature is known to have experienced different faces of stretching, rifting and uplifting during the geological past [1] [2]. The region is believed to be influenced by the thermo-tectonic events since the Mesozoic period due to the interactions of the Indian plate with Reunion plume. A huge pile of basalts has erupted during Upper Cretaceous Tertiary boundary and spread over more than 100,000 sq·km [4] Such a large spread of basalts covered the SP. It is believed that due to interaction of Reunion plume with the Indian Plate, a triple junction has been formed with Cambay rift as one of the arms, the Narmada rift as another arm towards the east and the Kachchh rift towards the west. If we detect any deep seated intrusive structures, those locations can be considered as possible occurrence of future earthquakes as they might be reactivated due to tectonic forces It is in this context that magnetotelluric studies have been taken up to understand the seismotectonics of the region. In the following the subsurface section derived along these profiles is presented
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