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      https://www.ias.ac.in/article/fulltext/jess/123/08/1907-1918

    • Keywords

       

      Magnetotelluric; Uttarakhnad Himalayan region; geoelectric strike; crustal structure.

    • Abstract

       

      Geoelectric strike and resistivity structure of the crust have been estimated from 37 magnetotelluric (MT) data sites along a profile from Roorkee to Gangotri in Uttarakhand Himalaya. Impedance decomposition schemes based on Bahr’s, Groom Bailey and Phase tensor were implemented in a MATLAB code for the average strike estimation. Geoelectric strike direction varies with period as well as in different lithotectonic units along the profile. In the period band from 1 to 100 s average geoelectric strike in the southern end of the profile (Indo-Gangetic Plains) is N79°W, which is slightly rotated to the north in the Lesser Himalayan region and becomes N68°W whereas it is N81°W in the Higher Himalayan region. However, average strike is stabilized to N77°W for the entire profile in the long period band (100–1000 s). Geoelectrical structure of the crust has been obtained along the profile by 2D inversion of MT data. Major features of 2D resistivity model are: (i) southern part of the model is a low resistivity (> 50 𝛺m) zone at shallow depth (5–7 km) representing the loose sediments of the Indo-Gangetic Plains (IGP), whose thickness increases in the south; (ii) highly resistive (>1000 𝛺m) layer below the IGP sediments is the basement rock, representing the resistivity of the top of the subducting Indian Plate; (iii) the Main Boundary Thrust (MBT) and the Main Central Thrust (MCT) zones can be seen in the electrical image. However, the Himalayan Frontal Thrust (HFT) could not be resolved and (iv) a low resistivity (> 10 𝛺m) feature in the MCT zone extending to the depth of 30 km is delineated. This low resistivity could be due to fluid-filled fractured rock matrix or partial melt zone. Hypocenters of many earthquakes are concentrated along the boundary of this low resistivity zone and relatively high resistivity blocks around it. The resulted model supports flat-ramp-flat geometry of the Main Himalayan Thrust along which the Indian Plate is subducting.

    • Author Affiliations

       

      Rohit Miglani1 M Shahrukh1 M Israil1 Pravin K Gupta1 S K Varshney2 Sokolova Elena3

      1. Indian Institute of Technology Roorkee, Roorkee 247 667, India.
      2. Department of Science and Technology, New Mehrauli Road, New Delhi 110 016, India.
      3. Institute of the Physics of the Earth, Russian Academy of Sciences, Moscow, Russia.
    • Dates

       
  • Journal of Earth System Science | News

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