Main Himalayan Thrust

Main Himalayan Thrust
LocationHimalayas
Characteristics
Length>2,000km
Strikenorthwest-southeast
Tectonics
StatusActive
TypeThrust fault
A geological map of the Himalaya region. The Main Himalayan Thrust underlies the rock units.
Diagram showing a décollement

The Main Himalayan Thrust (MHT) is a décollement under the Himalaya Range. This thrust fault follows a NW-SE strike, reminiscent of an arc, and gently dips about 10 degrees towards the north, beneath the region. It is the largest active continental megathrust fault in the world.

Overview

The MHT accommodates crustal shortening of India and Eurasia as a result of the ongoing collision between the Indian and Eurasian plates. The MHT absorbs around 20mm/yr of slip, nearly half of the total convergence rate. This slip can be released from small scale earthquakes and some plastic deformation, but the MHT still accumulates a deficit of moment of 6.6*10^19 Nm/yr. The MHT also remains locked with the overlying Eurasian plate from its surface expression to the front of the higher Himalayas, nearly 100km. This locking mechanism combined with the rapid accumulation of deficit of moment are concerning as some professionals estimate that earthquakes up to the size of 8.9 on the Richter scale could be in order for regions such as western Nepal. Earthquakes of this magnitude are estimated to have a return period of over 1000 years in this region. Deformation of the crust is also accommodated along splay structures including the Main Frontal Thrust (MFT), Main Boundary Thrust (MBT), Main Central Thrust (MCT) and possibly the South Tibetan Detachment. The MHT is the root detachment of these splays. At this present moment, the MFT and MHT accounts for almost the entire rate of convergence (15-21 mm/yr). This fault defines where the India subcontinent is underthrust beneath the Himalayan orogenic wedge.

In April 2015, a section of the MHT produced a blind rupture earthquake, killing nearly 9,000 Nepalese.

Associated seismicity

The Main Himalayan Thrust and its splay branches has been the source of numerous earthquakes, including some that are indirectly related.

Date Country Magnitude Depth (km) MMI Deaths Comments Source
1255-06-07 Nepal 8.0+ - Rupture length uncertain but possibly in the hundreds of kilometers. Killed one-third of Nepal's population.
1344-09-14 Nepal -
1408 Nepal -
1505-06-06 Nepal, India and China 8.2–8.8 - Killed 30% of the Nepalese population.
1680 Nepal <7.5 -
1714-05-4 Bhutan 7.6–8.6 - IX "Many" Ruptured the whole Bhutan section of the Main Frontal Thrust.
1803-09-01 India 7.8–7.9 - IX 300 Damage as far as New Delhi.
1833-08-26 Nepal 7.5–7.9 - IX 500 Severely damaged Kathmandu and was felt as far as Calcutta.
1905-04-04 India 7.9 - X 20,000+
1934-01-05 Nepal and India 8.1 15.0 XI 12,000 Ruptured to the surface via the Main Frontal Thrust.
1947-07-29 China 7.3 20.0 V
1950-08-15 India, China and Myanmar 8.6 15.0 XI 4,800 Ranks among the largest Strike-slip earthquake ever instrumentally recorded.
1966-06-27 Nepal and India 6.1 37.0 80
1980-07-29 Nepal and India 6.5 17.5 VIII 200
1988-08-21 Nepal 6.9 57.4 VIII 700-1400
1991-10-20 India 6.8 10.3 IX 2000 Main Central Thrust.
1999-03-29 India 6.8 21.0 VII 103
2005-10-08 Pakistan 7.6 26.0 XI 87,400
2009-09-21 Bhutan 6.1 14.0 VI 11
2011-09-18 India 6.9 50.0 VII 111 Intraplate strike-slip.
2013-05-01 Pakistan and India 5.7 15.0 VII 1 Additional 59 injured.
2015-04-25 Nepal 7.8 8.2 VIII 8,964
2015-05-12 Nepal 7.3 18.5 VIII 218 Aftershock of the April 2015 earthquake.
2015-07-24 Pakistan 5.1 17.0 V 3
2019-09-24 Pakistan 6.0 10.0 VII 40

See also


This page was last updated at 2023-12-26 07:45 UTC. Update now. View original page.

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