Identification and characterization of marine geohazards in the deep water eastern offshore of India: constraints from multibeam bathymetry, side scan sonar and 3D high-resolution seismic data

Abstract

The eastern offshore of India covers a vast stretch of sedimentary tract fed by major rivers like Ganges, Brahmaputra and Mahanadi in the north, Krishna and Godavari in the center, and Cauvery and Palar in the south, which led to variations in shelf-slope characteristics, degree of slope and hence slope instability. The structure as well as seismic attribute maps prepared from multibeam bathymetry and high-resolution 3D seismic data set has been analyzed to identify various geohazards in the deep water offshore regions of the east coast of India. These can be categorized as slope instability, slope canyons, shallow gas, mass transport complexes, sediment waves, gas hydrates, gas chimney, mud volcanoes and shallow faults. The slope instability is primarily related to rapid sedimentation by the active river systems while the other geohazards are often developed in association with shallow gas flows and leakages. The bottom simulating reflectors (BSRs) identified in the seismic sections indicate the presence of gas hydrates. Rapid sedimentation, BSR formation, dissolution and expulsion of water as well as gas and their subsequent vertical migration are responsible for the formation of shallow gas-related hazards. The results from the above analysis are of immense help in minimizing the risk of shallow hazards during exploration, drilling and subsurface installation activities along the eastern Indian offshore.

Crustal structure and rift tectonics across the Cauvery–Palar basin, Eastern Continental Margin of India based on seismic and potential field modelling

“…In the offshore, the shelf is wider north of Pondicherry up to Chennai as well as off Vedaranyam, while the shelf-slope part is seen to be protruding towards the coast between Karaikal and Pondicherry (figure 2a). Presence of submarine canyons off Cuddalore and Pondicherry were reported from earlier bathymetric studies (Varadachari et al 1968;Bastia et al 2011). While major valleys off Pondicherry have formed due to the existence of mega-lineaments (Rao et al 1992), the marine geophysical studies in general Figure 2.…”

Marine Geohazards: A Bibliometric-Based Review

“…Another feature related to fluid seepage is mud volcanoes, which are geological structures formed due to the emission of argillaceous material on the Earth's surface or the seafloor [78,79]. Submarine mud volcanoes occur in both active and passive margins [6,8,10] and are related to the upward migration of over-pressured fluids, which cause liquefaction of mud-rich units, and episodic extrusions of solids, liquids, and gases [80,81]. There are large variations in the size and geometries, as well as the sources, of fluids and sediments expelled by mud volcanoes [78,82].…”

“…Mud volcanoes can have discrete eruptive events or periods of eruption that expel massive amounts of fine-grained sediments in periods that last for hours or centuries [79]. These events are potential geohazards for deep-marine infrastructures [10], as they may affect drilling operations, ring installations, and pipeline routings [4,8].…”

“…Others generally do not cause direct damage to societies but can affect engineered structures. These include pockmarks, mud volcanoes, and mobile bedforms [6][7][8][9][10][11][12][13]. Some manifest themselves on the surface of the seafloor, while others are concerned with processes that occur in the subsurface.…”

Detection and Elimination of Bathymetric Outliers in Multibeam Echosounder System Based on Robust Multi - quadric Method and Median Parameter Model

“…The availability of reliable bathymetry data has been of significant implications for marine applications, such as marine environment protection, offshore development and management, marine navigation, and submarine science [1][2][3][4][5]. Multibeam echosounder system (MBES) is the most widely employed in underwater topographic detection equipment at present.…”