Main Himalayan Thrust
Main Himalayan Thrust | |
---|---|
Location | Himalayas |
Characteristics | |
Length | >2,000km |
Strike | northwest-southeast |
Tectonics | |
Status | Active |
Type | Thrust fault |
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[1] fault in the world.[2]
Overview
The MHT accommodates crustal shortening of India and Eurasia as a result of the ongoing collision between the Indian and Eurasian plates.[3] 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.[4] 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).[5][6] 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.[7][8]
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. | [9][10] | ||
1344-09-14 | Nepal | - | [11] | ||||
1408 | Nepal | - | [11] | ||||
1505-06-06 | Nepal, India and China | 8.2–8.8[12][13] | - | Killed 30% of the Nepalese population. | [14] | ||
1680 | Nepal | <7.5 | - | [11] | |||
1714-05-4 | Bhutan | 7.6–8.6 | - | IX | "Many" | Ruptured the whole Bhutan section of the Main Frontal Thrust. | [15] |
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. | [16] |
1905-04-04 | India | 7.9 | - | X | 20,000+ | [17] | |
1934-01-05 | Nepal and India | 8.1 | 15.0 | XI | 12,000 | Ruptured to the surface via the Main Frontal Thrust. | [18] |
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. | [19] |
1966-06-27 | Nepal and India | 6.1 | 37.0 | 80 | [20] | ||
1980-07-29 | Nepal and India | 6.5 | 17.5 | VIII | 200 | [21] | |
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 | [22] | |
2009-09-21 | Bhutan | 6.1 | 14.0 | VI | 11 | [23] | |
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. | [24] |
2015-04-25 | Nepal | 7.8 | 8.2 | VIII | 8,964 | [7] | |
2015-05-12 | Nepal | 7.3 | 18.5 | VIII | 218 | Aftershock of the April 2015 earthquake .
|
[3] |
2015-07-24 | Pakistan | 5.1 | 17.0 | V | 3 | [25] | |
2019-09-24 | Pakistan | 6.0 | 10.0 | VII | 40 | [26] |
See also
- Geology of the Himalaya
References
- ISSN 1793-4311.
- hdl:10356/143621– via Boise State University.
- ^ hdl:10220/50430.
- .
- S2CID 30608419.
- ^ Hubbard, J. "Geometry and Kinematics of the Main Frontal Thrust, Himalaya". Earth Observatory of Singapore. Retrieved 27 October 2020.
- ^ a b "M 7.8 - 36km E of Khudi, Nepal". US Geological Survey. Archived from the original on 2020-08-13.
- S2CID 53463752.
- doi:10.7289/V5TD9V7K. Archived from the originalon 2017-12-16. Retrieved 2020-10-17.
- .
- ^ S2CID 32078899.
- ISBN 978-90-481-2497-8.
- JSTOR 24110492. Archived from the original(PDF) on 2016-03-04. Retrieved 2015-08-21.
- .
- hdl:10026.1/18289.
- ISBN 9780128128091.
- ^ Pant, C.C.; Pathak, V.; Joshi, S. (2016). "Extant Seismicity and Regional Tectonic Interpretation: An illustration from Kumaun Himalaya, Uttarakhand, India". In Singh, S.P.; Khanal, S.C.; Joshi, M. (eds.). Lessons From Nepal's Earthquake For The Indian Himalayas And The Gangetic Plains (PDF). Central Himalayan Environment Association. p. 31.
- ^ "M 8.0 - Nepal-India border region". US Geological Survey. Archived from the original on 2020-10-18.
- ^ "M 8.6 - 1950 Assam-Tibet Earthquake". US Geological Survey. Archived from the original on 2020-10-19.
- .
- U.S. Geological Survey. Retrieved 10 January 2022.
- S2CID 128469925.
- ^ "M 6.1 - Bhutan". US Geological Survey.
- ^ Mukhtar Ahmad (1 May 2013). "Moderate earthquake kills 1, injures 59 in eastern Kashmir". CNN. Retrieved 10 January 2022.
- ^ "M 5.1 - 19km WSW of Murree, Pakistan". US Geological Survey. Archived from the original on 2020-10-28.
- .