Land-ocean tectonic signatures of the Krishna-Godavari Basin, a qualitative evaluation

Abstract

The bathymetry data of Krishna-Godavari Offshore Basin reveal that the water depths in the area vary from 40 m (near shore) to 3000 m (offshore). The data indicate high gradient tightly packed contours over offshore Krishna Basin between 40 and 1000m water depth whereas between Krishna and Godavari Rivers, the pattern shows relatively wider shelf from 40 m to slope regions up to 2500 m water depth. The band of depth contours ranging from 1000 to 2400 m appears to be sheared and bounded by fault lineaments. The NW-SE trending topographic rise of 500meters from the adjacent seafloor of 1750 meters observed in multi-beam bathymetry study. The landward extension of this topographic rise, well depicted in the multibeam bathymetry contours probably abuts trend of the Bhimavaram-Tanuku ridge at the coast. The total intensity magnetic anomaly map exhibits two major trends in NE-SW and NW-SE directions. . The NE-SW trending wide curvilinear anomaly zone approximately runs parallel to the coast within the water depths of 1000 -2500 meters off Ongole to Kakinada. This Anomaly Zone is sheared and block shifted by an intervening NW–SE trending anomaly zone bounded by two fault lineaments which may be the offshore extension of on land river lineaments off Vasishta Godavari and off Krishna River. The NW-SE trending contour pattern of zone clearly depicts that there is a marked change in the coastal tectonics as evidenced from concavity of the coast. It is surmised from our studies that it is highly essential to link coastal and offshore lineaments from geophysical data vis-a-vis earthquake activity of entire Eastern Continental Margin of India (ECMI) in order to understand the factors responsible for the recent seismic activity over coastal and near shore regions.