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Electrical structure of the Himalaya of central Nepal: High conductivity around the mid‐crustal ramp along the MHT
Author(s) -
Lemonnier Carole,
Marquis Guy,
Perrier Frédéric,
Avouac JeanPhilippe,
Chitrakar Gyani,
Kafle Basantha,
Sapkota Som,
Gautam Umesh,
Tiwari Dilliram,
Bano Maksim
Publication year - 1999
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/1999gl008363
Subject(s) - magnetotellurics , geology , seismology , crust , foreland basin , tectonics , lithosphere , basement , depth sounding , geomorphology , geophysics , electrical resistivity and conductivity , oceanography , civil engineering , engineering , electrical engineering
Twelve broadband magnetotelluric (MT) soundings were performed across the Himalaya of Central Nepal in 1996 in order to determine the electrical structure of the crust and its relation to geological structures and active tectonics. The MT impedance tensors were obtained for frequencies between 0.001 and 500 Hz. The 2‐D section, derived from joint inversion of TE‐ and TM mode after RRI and Groom/Bailey decomposition, shows high conductivity in the foreland basin (∼30 Ω.m) that contrasts with the resistive Indian basement (>300 Ω.m) and Lesser Himalaya (>1000 Ω.m). In addition, our MT sounding reveals a major conductive feature beneath the front of the Higher Himalaya, also characterized by intense microseismic activity, and the position of a mid‐crustal ramp along the major active thrust fault (MHT). This high conductivity zone probably reflects metamorphic fluids, released during underthrusting of the Indian basement and pervading well connected microcracks induced by interseismic stress build‐up, or distributed brittle deformation around the ramp.