| Abstract Submission No. | ABS-3.1-0139 |
| Title of Abstract | Coseismic liquefaction during M6.0 2021-Assam earthquake and paleoliquefaction features in the Brahmaputra Plain, India: implications on boundary conditions and paleoseismicity |
| Authors | Shibu Rajkhowa*, Nilesh K. Jaiswara, Prabha Pandey, Anand K. Pandey |
| Organisation | CSIR-National Geophysical Research Institute, Hyderabad-500007 |
| Address | CSIR NGRI Hyderabad, Telengana, India Pincode: 500007 E-mail: srajkhowa92@gmail.com |
| Country | India |
| Presentation | Poster |
| Abstract | Extensive coseismic liquefaction features, such as sand dykes and vents, ephemeral sand-water springs, and lateral spreadings, have developed along the river banks in the mesoseimic area of the M6.0 (April 28, 2021) earthquake in the northern Kopili Fault Zone (Brahmaputra Plain, Himalayan Piedmont zone). In order to explore their stratigraphic and structural expressions, we mapped and excavated shallow trenches across the coseismic liquefaction features in the sediment profile of the point-bar deposits. The paleoliquefaction features, suggesting the occurrence of a past event, were also observed in the sediment profile. The subsurface architecture of sand boils/blows, feeder-dykes, soft-sediment deformation (SSD) structures, depth of liquified sand bed, thickness of confining cover bed, and depth of water table helped establishing the boundary conditions for the SSD. We dated the sediment profile using the OSL dating technique to constrain the age of the present and paleoliquefied sediments. The analysis of results suggests the 1714-Bhutan paleoseismic trigger event was responsible for the observed SSD structures. The study also highlights the significance of favorable boundary conditions for the occurrence of liquefaction features at moderate magnitude events and the importance even of a shallow sediment profile as a paleoseismic repository. |
| Keywords | Liquefaction, Soft sediment deformation (SSD), Trigger mechanism, Boundary conditions, OSL dating; Kopili Fault Zone |