Constraining the Seismic Potentiality Analysis for Andaman Arc System, NE Indian Ocean

• Published in: Journal of the Geological Society of India 2018-05, Vol.91 (5), p.523-534
• Main Authors: Mukhopadhyay, Basab, Mukhopadhyay, Manoj, Mishra, Om Prakash, Sengupta, Diptansu, Dasgupta, Sujit, Elawadi, Eslam, Mondal, Prabir Kumar, Gonnade, Ghanshyam Dharamchand
• Format: Article
• Language: English
• Subjects: Anomalies; Asperity; Crustal structure; Earth and Environmental Science; Earth Sciences; Earthquakes; Geological surveys; Geology; Gravitation; Gravity; Heterogeneity; Hydrogeology; Lava; Magma; Magma chambers; Oceanic crust; Plate boundaries; Plates (structural members); Seismic activity; Seismic analysis; Seismic surveys; Seismic tomography; Seismic zones; Spatial distribution; Surveys; Tomography; Velocity
• ISSN: 0016-7622; 0974-6889
• DOI: 10.1007/s12594-018-0900-3

Seismic-potential for the Andaman Arc System (AAS) is evaluated using a three-tier approach: (i) the seismic b-values derived using a revised and homogenized earthquake catalog for Mw ≥ 4.7, with uniform Mw, for the period 1964–2013 created from ISC Data, (ii) Free-air gravity-anomalies for AAS and their geologic interpretation and (iii) deep crustal structure from seismic reflection surveys and 3D seismic tomography results. Both long-term spatial b-value anomalies for the period 1964-2013 and temporal b-value anomalies for a shorter period (2002–2013) have been estimated. The b-value maps are interpreted in terms of the stress regime acting across AAS and stressed asperities inferred along the strike of AAS. Eight distinguishable seismic-zones are identified and their seismic potential is examined by temporal bvalue anomalies in producing moderate to large earthquakes. The latter demonstrates ‘low-high’ or ‘high-low’ couplet over years, and that a variation in b-value more than 20% compared to the previous year value is likely to produce an earthquake event with Mw ≥ 6.0. Some support to this interpretation comes from the regional Free-air gravity-anomalies and deep crustal structure interpreted from hypocentral distribution of earthquakes. The high b-values are seemingly associated with magma chambers or low velocity crust; creating asperity zones due to multiple batholithic intrusions at plate boundary. This geologic interpretation is evidenced by 3D P-wave seismic tomography and velocity heterogeneity study for AAS reported by us elsewhere.