M 7.8 - Southern Qinghai, China

Tectonic Summary

The November 14, 2001, M 7.8 earthquake in southern Qinghai province of China occurred as the result of shallow strike-slip faulting in the crust of the Tibetan Plateau, northeast of the Himalaya Mountain Range. Focal mechanism solutions, finite-fault modeling of globally recorded seismic data, and geological field observations all indicate that rupture occurred on a left-lateral east-west-striking fault known as the Kunlun fault, which extends roughly east-west for about 1,600 km in north Tibet. This earthquake occurred several hundred kilometers north of the convergent India:Eurasia plate boundary, where the India plate is moving northward with respect to Eurasia at a rate of approximately 46 mm/yr. This convergence drives the uplift of the Himalaya Mountains and the Tibetan Plateau, which is an extremely broad region of thickened and uplifted crust sitting above 4.5-5 km, at a rate of approximately 10 mm/yr. The uplifted Tibetan Plateau is spreading to the east and, as a result, is an area of east-west extension and eastward crustal motion within a larger region of generally north-south convergence. The Kunlun earthquake, as this event has been named, likely reflects the interplay among these major tectonic forces, dominated in this location by the eastward motion of Tibet, with respect to Eurasia farther north. Farther to the north, the large intra-continental Altyn Tagh fault system also helps to accommodate this motion.

While commonly plotted as points on maps, earthquakes of this size are more appropriately described as slip over a larger fault area. Strike-slip events of the size of the November 14, 2001, earthquake are typically about 185x20 km (length x width); modeling of this earthquake implies dimensions of about 300x30 km, directed from the hypocenter eastward.

In November 1997, a M 7.5 strike-slip faulting earthquake occurred along another segment of the same active fault system about 300 km to the southwest of the November 2001 event. It was the only other local earthquake of M 7+ in the past 40 years; however, eight earthquakes above M 6 have occurred within 400 km of the November 2001 event. The only historical earthquake that has caused damage in the vicinity of the November 14th event was a shallow M 6.0 earthquake in January 1977, 200 km to the north, which resulted in at least two fatalities and four injuries.

Hayes et al. (2016) Tectonic summaries of magnitude 7 and greater earthquakes from 2000 to 2015, USGS Open-File Report 2016-1192. (5.2 MB PDF)