HIMALAYAN FRONTAL THRUST

Subject: Geography

Context: Recently, several houses and buildings were damaged after an earthquake of magnitude 6.4 on the Richter scale hit Assam.

The preliminary analysis shows that the events are located near to Kopili Fault closer to Himalayan Frontal Thrust (HFT).

Concept:

Himalayan Front Thrust (HFT)

It is also known as the Main Frontal Thrust (MFT).
It is a geological fault along the boundary of the Indian and Eurasian tectonic plates.
It demarcates a sharp physiographic and tectonic boundary between the Himalayan foothills and the Indo-Gangetic Alluvial Plains.
It represents a discontinuous zone of active faulting between the Sub-Himalaya and the alluvial plain.

About Kopili Fault

The Kopili is the main river of the Kopili Valley.
Geologically, Kopili Valley area comprises Neogene-Quaternary sediments which were deposited directly over the Archean basement.
The Kopili Fault is a 300-km northwest-southeast trending fault from the Bhutan Himalaya to the Burmese arc.
The Kopili Fault is a NW–SE trending strike-slip fault where intense seismic activity occurs down to a depth of about 50 km beneath the Kopili Fault, and the activity continues to the Main Central Thrust (MCT) in the Bhutan Himalaya.

What is a Fault?

The United States Geological Survey (USGS) defines a fault as a fracture along which the blocks of crust on either side have moved relative to one another parallel to the fracture.
According to the USGS, when an earthquake occurs on one of these faults, the rock on one side of the fault slips with respect to the other.
The fault surface can be vertical, horizontal, or at some angle to the surface of the earth.

Types of Fault

Normal fault: It is a dip-slip fault in which the block above the fault has moved downward relative to the block below.
Thrust fault: It is a dip-slip fault in which the upper block, above the fault plane, moves up and over the lower block.
Strike-slip fault: It is a fault on which the two blocks slide past one another.