| Abstract Submission No. | ABS-3.1-0174 |
| Title of Abstract | Mud volcanism and overpressured systems as drivers of recent submarine slope failure in the Krishna-Godavari basin, Bay of Bengal |
| Authors | Pawan Dewangan*, G. Sriram, R. Komal, V. Mahale |
| Organisation | CSIR-National Institute of Oceanography, Goa |
| Address | Sr. Principal Scientist, CSIR-NIO Dona Paula, Goa, India Pincode: 403004 E-mail: pdewangan.nio@csir.res.in |
| Country | India |
| Presentation | Oral |
| Abstract | CSIR-NIO identified a recent submarine slope failure in the shelfal region of the Krishna-Godavari (KG) Basin, Bay of Bengal, through integrated analysis of geophysical datasets spanning over two decades. The failure scarp reveals erosion of ~160 m of sedimentary strata, displacing an estimated ~11 km³ of sediments and representing one of the largest documented submarine slope failures through time-lapse geophysical surveys. Repeat surveys constrain the event between January 2009 and December 2015, with Cyclone Helen (November 2013), a Category-1 storm that passed directly over the slump head, emerging as a likely trigger. To investigate preconditioning factors, we analyzed pre-failure 3D seismic data (2004) provided by the Directorate General of Hydrocarbons (DGH). Seismic attributes indicate that the failure surface was controlled by the geomorphology of a paleo-submarine canyon intersected by multiple active faults, forming a zone of pronounced weakness. Subsurface layers below the canyon exhibit enhanced amplitudes with negative polarity, indicative of gas-charged sediments and the layers underneath this horizon show enhanced attenuated with low-frequency shadows. A central mud volcano confirms the presence of an overpressured system in the study area. Post-failure multibeam and water-column surveys aboard RV Sindhu Sankalp (2022, 2025) detected numerous gas flares within the slumped area, consistent with gas release triggered by reduced overburden pressure. We propose that subsurface overpressured system, active faulting, pre-existing canyon geomorphology, and mud volcanism are key pre-conditioning factors that facilitate the slope failure, rendering the region highly susceptible even with low-to-moderate external triggering forces. This study highlights a potential risk associated with submarine slope failure for offshore operations in narrow-shelf basins with gas-charged, paleo-canyon systems and shows the importance of long-term geophysical monitoring, structural mapping, and real-time slope stability assessment of gas charged, hydrocarbon-bearing continental margins. |
| Keywords | Mud volcanism, slope stability, KG basin, geohazards, overpressured system, slumping/sliding |