Main Himalayan Thrust

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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[1] fault in the world.[2]

Overview[edit]

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[edit]

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[edit]

References[edit]

  1. ^ Sieh, Kerry (2007). "The Sunda megathrust - Past, present and future" (PDF). Journal of Earthquake and Tsunami. 1. California Institute of Technology: 1-19. doi:10.1142/S179343110700002X. ISSN 1793-4311.
  2. ^ Liu, Y.; Hubbard, J.; Almeida, R.V.; Foster, A.; Liberty, L.; Lee, Y.S.; Sapkota, S.N. (2020). "Constraints on the Shallow Deformation Around the Main Frontal Thrust in Central Nepal from Refraction Velocities". Tectonophysics. 777: 228366. doi:10.1016/j.tecto.2020.228366. hdl:10356/143621 – via Boise State University.
  3. ^ a b Hubbard, J.; Almeida, R.; Foster, A.; Sapkota, S.N.; Bürgi, P.; Tapponnier, P. (2016). "Structural segmentation controlled the 2015 Mw 7.8 Gorkha earthquake rupture in Nepal". Geology. 44 (8): 639–642. doi:10.1130/G38077.1. hdl:10220/50430.
  4. ^ Ader, Thomas, et al. “Convergence Rate across the Nepal Himalaya and Interseismic Coupling on the Main Himalayan Thrust: Implications for Seismic Hazard.” Journal of Geophysical Research: Solid Earth, vol. 117, no. B4, 2012, doi:10.1029/2011jb009071.
  5. ^ Le Roux-Mallouf, R.; Godard, V.; Cattin, R.; Ferry, M.; Gyeltshen, J.; Ritz, J.–F.; Drupka, D.; Guillou, V.; Arnold, M.; Aumaitre, G.; Bourlès, D.L.; Keddadouche, K. (2015). "Evidence for a wide and gently dipping Main Himalayan Thrust in western Bhutan" (PDF). Geophysical Research Letters. 42 (9): 3257–3265. doi:10.1002/2015GL063767. S2CID 30608419.
  6. ^ Hubbard, J. "Geometry and Kinematics of the Main Frontal Thrust, Himalaya". Earth Observatory of Singapore. Retrieved 27 October 2020.
  7. ^ a b "M 7.8 - 36km E of Khudi, Nepal". US Geological Survey. Archived from the original on 2020-08-13.
  8. ^ Duputel, Z.; Vergne, J.; Rivera, L.; Wittlinger, G.; Farra, V.; Hetényi, G. (2016). "The 2015 Gorkha earthquake: A large event illuminating the Main Himalayan Thrust fault" (PDF). Geophysical Research Letters. 43 (6): 2517–2525. doi:10.1002/2016GL068083. S2CID 53463752.
  9. ^ National Geophysical Data Center / World Data Service (NGDC/WDS): NCEI/WDS Global Significant Earthquake Database. NOAA National Centers for Environmental Information (1972). "Comments for the 1255 Earthquake". NOAA. National Geophysical Data Center, NOAA. doi:10.7289/V5TD9V7K. Archived from the original on 2017-12-16. Retrieved 2020-10-17.
  10. ^ Pierce, I.; Wesnousky, S.G. (2016). "On a flawed conclusion that the 1255 A.D. earthquake ruptured 800 km of the Himalayan Frontal Thrust east of Kathmandu". Geophysical Research Letters. 43 (17): 9026–9029. doi:10.1002/2016GL070426.
  11. ^ a b c Bollinger, L.; Tapponnier, P.; Sapkota, S.N.; Klinger, Y. (2016). "Slip deficit in central Nepal: omen for a repeat of the 1344 AD earthquake?". Earth Planets Space. 68 (12). doi:10.1186/s40623-016-0389-1. hdl:10220/39981. S2CID 32078899.
  12. ^ Jha, Madan Kumar (2010). Natural and Anthropogenic Disasters: Vulnerability, Preparedness and Mitigation. New Delhi: Springer. pp. 25–26. ISBN 978-90-481-2497-8.
  13. ^ Bilham R.; Ambraseys N.N. (2005). "Apparent Himalayan slip deficit from the summation of seismic moments for Himalayan earthquakes, 1500–2000" (PDF). Current Science. 88 (10): 1658–1663. JSTOR 24110492. Archived from the original (PDF) on 2016-03-04. Retrieved 2015-08-21.
  14. ^ Rajendran, C.P.; Rajendran, K.; Sanwal, J.; Sandiford, M. (2013). "Archeological and Historical Database on the Medieval Earthquakes of the Central Himalaya: Ambiguities and Inferences" (PDF). Seismological Research Letters. 84 (6): 1098–1108. doi:10.1785/0220130077.
  15. ^ Zhao, Y.; Grujic, D.; Baruah, S.; Drukpa, D.; Elkadi, J.; Hetényi, G.; King, G.E.; Mildon, Z.K.; Nepal, N.; Welte, C. (2021). "Paleoseismological Findings at a New Trench Indicate the 1714 M8.1 Earthquake Ruptured the Main Frontal Thrust Over all the Bhutan Himalaya". Frontiers in Earth Science. 9. doi:10.3389/feart.2021.689457. hdl:10026.1/18289.
  16. ^ Chaulagain, H.; Gautam, D.; Rodrigues, H. (2018). "Chapter 1 - Revisiting Major Historical Earthquakes in Nepal: Overview of 1833, 1934, 1980, 1988, 2011, and 2015 Seismic Events". In Gautam, D.; Rodrigues, H.F.P. (eds.). Impacts and Insights of the Gorkha Earthquake. Elsevier. pp. 1–17. ISBN 9780128128091.
  17. ^ 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.
  18. ^ "M 8.0 - Nepal-India border region". US Geological Survey. Archived from the original on 2020-10-18.
  19. ^ "M 8.6 - 1950 Assam-Tibet Earthquake". US Geological Survey. Archived from the original on 2020-10-19.
  20. ^ P. N. Agrawal (1969). "Structural response results during the June 27, 1966 earthquake in Nepal-India border region". Bulletin of the Seismological Society of America. 59 (2): 771–775. doi:10.1785/BSSA0590020771.
  21. ^ "M 6.5 - 40 km NNE of Dipayal, Nepal". earthquake.usgs.gov. U.S. Geological Survey. Retrieved 10 January 2022.
  22. ^ Zahid Ali; Muhammad Qaisar; Tariq Mahmood; Muhammad Ali Shah; Talat Iqbal; Leonello Serva; Alessandro M. Michetti; Paul W. Burton (2009). "The Muzaffarabad, Pakistan, earthquake of 8 October 2005: surface faulting, environmental effects and macroseismic intensity". Special Publications. 316. The Geological Society of London: 155–172. doi:10.1144/SP316.9. S2CID 128469925.
  23. ^ "M 6.1 - Bhutan". US Geological Survey.
  24. ^ Mukhtar Ahmad (1 May 2013). "Moderate earthquake kills 1, injures 59 in eastern Kashmir". CNN. Retrieved 10 January 2022.
  25. ^ "M 5.1 - 19km WSW of Murree, Pakistan". US Geological Survey. Archived from the original on 2020-10-28.
  26. ^ Sreejith, K.M.; Jasir, M.C.M.; Agrawal, R.; Rajawat, A.S. (2021). "The 2019 September 24, Mw = 6, Mirpur earthquake, NW Himalaya: Geodetic evidence for shallow, near-horizontal décollement rupture of the Main Himalayan Thrust". Tectonophysics. 816 (229013). Elsevier. doi:10.1016/j.tecto.2021.229013.
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