The October 26, 2015 M 7.5 earthquake near the Hindu Kush region of
Afghanistan (SW of Jarm) occurred as the result of reverse faulting
at intermediate depths, approximately 210 km below the Hindu Kush
Range in northeastern Afghanistan. Focal mechanisms indicate rupture
occurred on either a near-vertical reverse fault or a shallowly
dipping thrust fault. At the latitude of the earthquake, the India
subcontinent moves northward and collides with Eurasia at a velocity of
about 37 mm/yr. Active faults and their resultant earthquakes in northern
Pakistan and adjacent parts of India and Afghanistan are the direct result
of the convergence between the India and Eurasia plates. This collision
causes uplift that produces the highest mountain peaks in the world including
the Himalayan, the Karakoram, the Pamir and the Hindu Kush ranges.
Earthquakes such as this event, with focal depths between 70 and 300 km,
are commonly termed "intermediate-depth" earthquakes. Intermediate-depth
earthquakes represent deformation within subducted lithosphere rather than
at the shallow plate interfaces between subducting and overriding tectonic plates.
They typically cause less damage on the ground surface above their foci than is
the case with similar magnitude shallow-focus earthquakes, but large intermediate-depth
earthquakes may be felt at great distance from their epicenters. "Deep-focus" earthquakes,
those with focal depths greater than 300 km, also occur beneath northeastern part of Afghanistan.
Earthquakes have been reliably located to depths of just over 300 km in this region.
Seven other M 7 or greater earthquakes have occurred within 250 km of this event over
the preceding century, the most recent being a M 7.4 earthquake in March 2002 just 20
km to the west of the October 26, 2015 event, and with a similar depth
and thrust fault orientation.