Dynamics of Mikir hills plateau and its vicinity: Inferences on Kopili and Bomdila Faults in Northeastern India through seismotectonics, gravity and magnetic anomalies

Sangeeta Sharma, Jogendra Nath Sarma, Saurabh Baruah

Abstract


he Mikir Hills plateau is encompassed by two prominent faults – Bomdila Fault to the east and the Kopili Fault to the west characterized by strike-slip kinematics. The Kopili Fault has a dip of 75otowards NE. Simultaneously, the Bomdila Fault dips with 50-55otowards the NNE. An integrated approach based on seismotectonics, gravity and magnetic data is utilized to understand the tectonic activity of the Kopili and Bomdila Faults. The bottom of seismogenic zones is inferred to be 45+2 km and 50+2 km for the Kopili Fault and the Bomdila Fault region respectively. So far gravity anomaly is concerned; it varies between -110 to +60 mgals along the Kopili –Bomdila Fault regions from the Belt of Schuppen to the MCT. The low gravity values over the Bomdila Fault area indicate presence of thick alluvial deposits while along Kopili Fault lesser sediment thickness is observed. Simultaneously, basement being at shallower depth, lower magnetic values indicate presence of thick alluvial deposits in and around Bomdila Fault. The curvatures and closures of the gravity contours along the fault lines indicate structures involving basement and indicate influence of Bomdila Fault up to the basement. Simultaneously, it is observed that Kopili and Bomdila faults are neotectonically active. All these are the prime input to the seismic hazard assessment of the region.


Keywords


Mikir Hills; Kopili Fault; Bomdila Fault; Seismotectonics; Gravity contour; Magnetic contour

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References


DOI: https://doi.org/10.4401/ag-7516
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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X