Rakshit, R., D. Bezbaruah, F. Zaman, B. Bharali and S. Saikia (2022): Locked crustal faults associated with the subducting Indian Lithosphere and its implications in seismotectonic activity in the Central Indo-Burmese Ranges,
Northeast India.
Northeast India is a geodynamic hotspot for tectonic activities where three
different plates viz., Indian, Eurasian and Burma Plates collide and deform with
respect to each other. Northeast moving Indian Plate subducting transversely
beneath Burma Plate results in the formation of the Indo-Burmese Ranges
(IBR). In central IBR, the north-south trending Churachandpur-Mao Fault
(CMF) is situated in the east of the Mizoram-Tripura Fold belt. The northwestsoutheast
trending Mat River Fault or Mat Fault (MF), which is another major
crustal-scale strike-slip transverse fault, upholds the movement of the CMF. In
this work, seismotectonic analysis of these two active intra-plate faults which
are related to the June–September 2020 earthquake series, have been discussed.
It is observed from satellite imageries, earthquake data and confirmed by the
field investigation that these faults are not directly involved in the generation
of the earthquakes; rather epicenters are distributed in the junction between
the MF and CMF. It is evident from the seismotectonic analysis that this stress
is distributed through some northwest-southeast synthetic faults, located north
of MF and parallel to it, close to the junction with the CMF. The focal solution
of the strongest of the 2020 earthquakes, the 5.5 Mw Champhai earthquake (on
22nd June 2020 at 04:10 IST) in Mizoram shows that the principal nodal plane
was aligning along MF. Therefore, it is these synthetic faults that are responsible
for the earthquakes rather than the locked zone between intra-plate MF
and CMF crustal faults. This juxtaposition has caused a major shift in the
geodynamic regime in the central IBR. Champhai earthquake might not be the
only large devastating earthquake in the region and could be followed by more
major earthquakes in the future.
Keywords: locked plate, Indo-Burmese Range, seismotectonics, Mizoram [
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