Abstract

We deployed a temporary passive ocean‐bottom seismometer (OBS) network from 25 December 2013 to 15 May 2014 to understand the local seismicity pattern in the Andaman region. A total of 559 local earthquakes are identified from the OBS network. The data are integrated with the available earthquake data from the Andaman ISLANDS (Investigation of Seismicity and Lithospheric Structure beneath the Andaman–Nicobar Subduction Zone) network and some global seismic stations. The minimum 1D velocity model and station corrections are estimated using the VELEST algorithm (Kissling et al., 1994). Our derived velocity model suggests the presence of Moho at a depth of 30 km and the station corrections suggest that the model is acceptable beneath the Andaman and Nicobar Islands. The joint hypocenter determination (JHD) is carried out using the minimum 1D velocity model and station corrections. The configuration of the Wadati–Benioff zone is observed from the intermediate‐depth earthquakes, and the dip of the subducting Indian plate increases from 26° in the Nicobar segment (NS) to 53° in the Andaman segment (AS). A seismic gap is observed in the subducting Indian plate between 7.5° N and 9.5° N at depths greater than 100 km, which may be due to partial subduction of the Ninetyeast ridge (NER).

The shallow‐depth local seismicity is similar to that observed after the 2004 Aceh earthquake and the shallow seismicity occurs along the trench, Andaman back‐arc spreading center (ABSC), Andaman–Nicobar fault (ANF), and Seulimeum strand of Sumatra fault (SF) system. Some extent of shallow seismicity is also observed on the Eastern Marginal fault (EMF) and Diligent fault (DF) to the south of 10° N. Some seismicity is observed to the west of the trench along the presumed extension of east‐northeast–west‐southwest‐oriented faults of the NER.

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