| Abstract Submission No. | ABS-3.1-0164 |
| Title of Abstract | Characterization of Recent Earthquakes in the Kopili Fault Zone, Northeast India, and its seismotectonic implications. |
| Authors | Velugula Mahalakshmi naidu*, Dr. Himangshu paul, Dr. M. Ravi Kumar, Dr. Naba K. Borah, Dr. Prakash Kumar |
| Organisation | CSIR-NGRI |
| Address | csir-ngri, quarters, habsiguda hyderabad, telangana, India Pincode: 500007 E-mail: vmngeo@gmail.com |
| Country | India |
| Presentation | Poster |
| Abstract | The Kopili Fault zone, situated within the Assam Valley of Northeast India, constitutes one of the most prominent intraplate fault systems in the region. Bounded by the Himalayan Collision Zone to the north and the Burmese Arc to the southeast, it accommodates complex strain resulting from oblique India⿿Eurasia plate convergence. Historical records and paleoseismological analyses reveal a pattern of recurrent large-magnitude seismic events in the region, including the 1869 Cachar earthquake (Mw 7.5) and the 1943 Hajo earthquake (Ms 7.2). Geodetic measurements indicate slip rates of approximately 2⿿3 mm/yr along the Kopili Fault, coupled with shallow locking depths estimated at ~3±2 km. These parameters suggest substantial strain accumulation. However, any earthquake occurring in the region may not necessarily be related to the Kopili fault zone, as other active structures exist in the region. Understanding the characteristics of moderate to major earthquakes in the region may provide insights into the associated fault systems and their seismic potential. We investigate the Mw 6.0 mainshock that occurred in 2021, followed by three earthquakes exceeding magnitude 5 within the past three years within the Assam Valley. The earthquakes occurred between 26.5-26.7 °N and 92.2-92.4°E at ~30 km depths. They are within 10-20 km of the centre of the Kopili fault zone. Focal mechanism solutions for the events exhibit strike-slip motion on steeply dipping faults. The results are consistent with the presumed geometry of the Kopili Fault zone and indicate that seismic events are consistently occurring within the Kopili fault zone. Additionally, major thrust components are identified in nearby seismic events⿿particularly those intersecting the Kopili Fault and adjacent structures⿿indicating the coexistence of strike-slip and compressional deformation. These observations reinforce the Kopili Fault⿿s role as a significant seismogenic structure within the Indo-Burman⿿Himalayan transitional zone, with the potential to generate future large-magnitude earthquakes (Mw > 7). |
| Keywords | kopili fault zone, seismotectonics, geodetic |