Land–ocean tectonics (LOTs) and the associated seismic hazard over the Eastern Continental Margin of India (ECMI)

Abstract

The South Indian (Peninsular) Shield which includes both the Eastern and Western Continental Margins of India is not as stable as it was originally thought of. The importance of intraplate seismicity within this Shield has recently been realized with some devastating earthquakes that occurred during the last few decades. It is also significant to note that most of the Precambrian tectonic lineaments in this Shield are oriented in either a NW-SE or W-E direction, joining the eastern offshore. In contrast, the western margin has an elevated coast, associated with a linear coast parallel escarpment, particularly on the southern side, superimposed by Deccan Trap volcanics on the northern side. The fault reactivation and the associated seismicity are hence more predominant on the east coast. Recent geophysical studies delineated land-ocean tectonics (LOTs) over the eastern margin, in some cases associated with moderate seismicity as a result of the compressional stress acting on the Indian Plate. Though the Eastern Continental Margin of India (ECMI) is considered as a passive margin, coastal seismicity due to the reactivation of the pre-existing tectonic lineaments extending offshore represents a potential natural hazard. In this context, the ECMI appears to be much more vulnerable compared to its counterpart on the west.

A seismotectonic study of the 21 May 2014 Bay of Bengal intraplate earthquake: evidence of onshore-offshore tectonic linkage and fracture zone reactivation in the northern Bay of Bengal

“…2), the Eastern Ghat Mobile Belt (EGMB), major shear zones and the rocks belonging to the Southern Granulite Terrain (SGT) at the Indian shield margin, have close linkages with a similar geology along East Antarctica (Yoshida et al 1999). Geophysical studies (Venkatarengan and Ray 1993;Subrahmanyam et al 1995Subrahmanyam et al , 2008Bastia et al 2010;Murthy et al 2010) at the coast revealed the extension of major Precambrian structural trends, basin scale faults/fractures into the offshore areas (Fig. 2).…”

“…Details of the focal mechanisms are given in Table 1. Blue dots represent the location of micro-tremors in the coastal areas (Murthy et al 2010). Dashed lines across the east coast of India indicate the lineaments extending from onshore to offshore (after Murthy et al 2010).…”

Geomorphic History and Landscapes of India

“…10 The Luni River downstream of Tilwara, east of Barmer, Rajasthan. The Luni (meaning salty) is the only well integrated river system in the Thar Desert breakup resulted in the eastward tilt of the Peninsula and establishment of the easterly drainage (Murthy et al 2010). During its northward journey the western continental passive margin of India was impacted by two major hotspots (Marion and Réunion) and has experienced two episodes of separation-Madagascar-Greater India *80-90 Ma and Seychelles-India *65 Ma (Norton and Sclater 1979;Storey et al 1995).…”

Source rock analysis, thermal maturation and hydrocarbon generation using rock-eval pyrolysis in parts of Krishna–Godavari basin, India: a case study

“…The basin is dominated by deltaic plains near the sea-land boundary. From the study of gravity anomalies, three basins have been characterized separated by the two basement horsts namely, Bapatla and Tanuku (Venkatarangan and Ray 1993;Murthy et al 1995;Subrahmanyam et al 2008;Murthy et al 2010). The basin has significant hydrocarbon potential both in the Tertiary delta as well as in the channel-levee-overbank play types in the deepwaters (Saxena et al 2011).…”