5. Crustal Structure of Seismically Active Regions by
Non-seismic
Methods
5.1 Himalaya
5.1.1 Seismotectonics of the Sikkim Himalaya
The
occurrence of deep crustal strike-slip earthquakes in the Sikkim
Himalaya is indicative of the ongoing transverse tectonic deformation of
the Indian plate, in addition to the N-S convergence related deformation
within the Himalayan wedge. The two dominant tectonic forces operating
in this region could lead to a complex variable spatial deformation
within the Indian lithosphere. Two-dimensional modeling of
magnetotelluric data incorporating the NW-SE transverse tectonic trend
within the Main Central Thrust zone (MCTZ) yields a lithospheric
electrical resistivity structure of the region down to 100 km. By
integration of these results with other geophysical information,
seismological data and in conjunction with a kinematic wedge model,
Pavankumar and Manglik (2021) proposed a comprehensive tectonic model
for the Sikkim Himalaya that highlights the complex nature of the
lithospheric structure (Fig.8). A major contact beneath the MCTZ
separating two geologically and compositionally distinct blocks of the
underthrusting Indian plate is suggested to be a NW-SE trending
lithospheric-scale fault in this segment of the Himalaya. The tectonic
model also demonstrates another crustal-scale tectonic feature beneath
the Main Frontal Thrust that demarcates a transition zone of moderately
conductive crust of the Ganga Foreland Basin and a resistive crustal
block beneath the Sub-Himalaya.