Wikipedia

Main Boundary Thrust

TheMain Boundary Thrust (MBT),also known as theMain Boundary Fault,is a discontinuous series of seismicfaultsin theHimalayaswhich form the structural boundary between theOuter HimalayasandLower Himalayan Range.The MBT is itself part of a series of thrusts which helped to accommodate the deformation when theIndian Platecollidedwith theEurasian Platein theCenozoic.The MBT fault system began forming in theMiocene.The MBT consists of multiple segments, and is composed from west to east of the Murree and Drang thrust faults, the Krol thrust fault, the Surkhet-Ghorahi thrust fault, the Kathmandu thrust, and the Gondwana/Garu thrust. Despite originating as a thrust fault in the collision ofIndiaandEurasia,the MBT system has reactivated as a normal faulting system.

Main Boundary Thrust
Main Boundary Fault
LocationHimalayas
CountryIndia,Nepal,Pakistan,Bhutan
Characteristics
RangeHimalayan Mountains
Length2,400 km (1,500 mi)
Tectonics
TypeThrust(formerly),Normal(present)
AgeMiocene-Holocene
OrogenyHimalayan

Tectonic setting

edit
Main article:India-Asia collision

The MBT was formed as a result of thecollision of the Indian continent with Asia.It developed to relieve stresses from thecompressionof thecontinental collision.When the MBT initially formed around 10-25 million years ago,[1]it was a system of thrust faults which accommodated stresses from thecompressionof thecontinental collisionwhich led to Himalayan uplift. TheMain Himalayan Thrustis the rootDécollementstructure, and results in similar fault system splays such as theMain Himalayan Thrust,Main Central Thrust,and theSouth Tibetan Detachment.These faults accommodated stresses parallel to the MBT and helped the Himalayan mountains grow.[2]Each of these faults served as the primary reliever of strain in the Himalayan Orogeny until being abandoned in a successive chain of intracontinental thrust faults.[3]Currently, theMain Frontal Thrustis the main thrust fault in the system.[4]

Segments

edit

The Main Boundary Thrust consists of multiple segments spanning 2,400 km (1,500 mi) in theHimalayas.

Murree/Drang thrust

edit

The Murree fault is athrust faultwhich lies inKashmir.To its southeast, the Drang thrust continues as an extension of the Murree thrust inHimachal.[5]

Krol thrust

edit

To the southeast of the Murree and Drang faults, the Krol thrust is the main strand of the MBT and has "caused great shattering, inversion and imbricate thrusting".[6]

Surkhet-Ghorahi fault

edit

The Surkhet-Ghorahi thrust fault is a northwest trending fault in CentralNepal.[7]It stretches fromSurkhettoGhorahiin over an extent of 90–120 km (56–75 mi).[8]At the western bank of theBheri River,the fault slips at a rate of 0.75 mm (0.030 in)/yr.[9]The fault shows verticalfault scarpof 30 m (98 ft).[10]

Kathmandu thrust

edit

The Kathmandu thrust runs from east of the Surkhet-Ghorahi fault nearKathmanduto west ofThimphu.[5]

Gondwana/Garu thrust

edit

The Gondwana thrust fault system runs from west ofThimphupassing throughBhutanbefore terminating inWest Kameng.In the east it is termed the Garu thrust, though it is a part of the Gondwana thrust.[11]

Modern reactivation

edit

After acting as a thrust fault initially, the Surkhet-Ghorahi may have reactivated as a normal fault—moving the opposite direction of a thrust fault.[12]

References

edit
  1. ^Meigs, Burbank & Beck 1995,p. 423, 425.
  2. ^Thiede et al. 2017,p. 716, 717.
  3. ^Meigs, Burbank & Beck 1995,p. 423.
  4. ^Patra & Saha 2019.
  5. ^abValdiya 1980,p. 329.
  6. ^Valdiya 1980,p. 329, 331.
  7. ^Malinconico, Lillie & Nakata 1989,p. 253-254.
  8. ^Mugnier et al. 1994,p. 200;Malinconico, Lillie & Nakata 1989,p. 253.
  9. ^Malinconico, Lillie & Nakata 1989,p. 256.
  10. ^Riesner, Bollinger & Hubbard 2021.
  11. ^Valdiya 1980,p. 329, 334.
  12. ^Mugnier et al. 1994,p. 205, 210.

Sources

Retrieved from "https://en.wikipedia.org/w/index.php?title=Main_Boundary_Thrust&oldid=1261744827"