| Abstract Submission No. | ABS-1.2-0183 |
| Title of Abstract | Seismotectonic Analysis and Volcanic-Tectonic Interactions in the Andaman-Nicobar Subduction Zone |
| Authors | Sunanda Manneela* |
| Organisation | INCOIS |
| Address | INCOIS, Pragathi Nagar (BO), Nizampet (SO) Hyderabad, Telangana, India Pincode: 500090 E-mail: sunanda@incois.gov.in |
| Country | India |
| Presentation | Poster |
| Abstract | The Andaman-Nicobar region experiences frequent earthquake swarms that reflect a complex interplay between tectonic deformation and magmatic activity. Comprehensive seismotectonic analyses from 1960 to 2024 show that most swarm sequences are concentrated around the Andaman Sea back-arc basin and the Alcock Rise. Focal mechanism solutions indicate predominantly normal faulting with occasional strike-slip components, consistent with extensional deformation in a back-arc tectonic setting. Calculated b-values range from 1.09 to 2.17, with higher b-values and normal faulting events interpreted as indicators of magmatic or volcanic influence, supported by the presence of active and dormant submarine volcanoes in the region. Recent studies provide strong geophysical evidence for subsurface magmatic processes, suggesting that ascending magma from deep reservoirs interacts with the regional fault system to generate swarm-like seismicity. The March 2014 Nicobar swarm, for example, exhibited both tectonic and volcanic signatures, right-lateral strike-slip faulting, elevated b-values (~1.39), and shallow crustal sources, further supporting the hypothesis of magma-driven fault activation. These observations suggest that earthquake swarms in the Andaman-Nicobar arc result from the interplay between stress perturbations induced by major tectonic events and episodic magmatic intrusions. The regional sliver fault system likely serves as a conduit for ascending magmatic fluids, promoting swarm activity along zones of pre-existing crustal weakness. Distinct spatio-temporal migration trends, bimodal b-value distributions, and the close association with volcanic centers collectively point to a dual volcano-tectonic origin for these swarms. This integrated interpretation contributes in understanding of crustal deformation and seismo-volcanic coupling within subduction-related back-arc systems, also, strengthens the scientific basis for regional seismic and tsunami hazard assessments. |
| Keywords | earthquake, swarm, magma, b-value |