M 6.7 - 29 km W of Imph?l, India

Tectonic Summary

The January 3, 2016 M 6.7 earthquake near Imphal, India occurred as the result of strike slip faulting in the complex plate boundary region between India and the Eurasia plate in southeast Asia. Focal mechanisms for the event indicate slip occurred on either a right-lateral fault plane dipping moderately to the east-northeast, or on a left-lateral fault dipping steeply to the south-southeast. In the region of the earthquake, the India plate is moving towards the north-northeast with respect to Eurasia at a velocity of approximately 48 mm/yr; the regional plate boundary in eastern India – the Indo-Burmese Arc - is oriented approximately south-southwest-north-northeast.

The tectonics of southeast Asia are broadly dominated by the collision of the Indian subcontinent with Eurasia, which causes uplift that produces the highest mountain peaks in the world, including the Himalayan, the Karakoram, the Pamir and the Hindu Kush ranges. In northeast India, the ~east-west oriented Himalayan Front takes a southward turn towards Burma (Myanmar), and plate boundary deformation is more broadly distributed over a series of reverse and strike-slip structures in the Indo-Burmese Arc system, including the Sagaing, Kabaw and Dauki faults. The January 3, 2016 earthquake occurred in this region of broad deformation, at a depth of close to 50 km within the lithosphere of the India plate. The causative fault is unknown, but is broadly related to this plate boundary deformation. Farther south, plate motions are accommodated by northeast-oriented subduction of the India plate beneath the Sunda plate and the Burmese Arc.

Moderate-to-large earthquakes in this region are fairly common; 19 other M 6+ earthquakes have occurred within 250 km of the 2016 event over the preceding century. The largest was a M 8.0 earthquake in 1946, 220 km to the southeast of the 2016 earthquake on the Sagaing Fault. Other nearby damaging events include a M 7.3 earthquake 150 km to the east of the 2016 event in August 1988, which caused several fatalities and dozens of injuries, and a M 6.0 earthquake 90 km to the southwest in December 1984 that caused 20 fatalities and 100 injuries.