The 14 November 2001, Mw = 7.8 Kokoxili Earthquake in Northern Tibet (Qinghai Province, China)

Abstract

On 14 November 2001, at 5:26 pm local time (9:26:10.3 GMT), a great earthquake ( Ms = 8.1) struck the Kokoxili region of the northwest part of Qinghai Province, China (Figure 1). Although this earthquake was felt in Sichuan Province, more than 1,000 km away from the epicentral area, it did not attract much media attention because it shook a thinly populated area on the northern margin of the Tibetan Plateau. The preliminary epicenter (U.S. Geological Survey-National Earthquake Information Center [NEIC]) is located near 90.5°E, about 300 km west of the Golmud-Lhasa road (Figures 2 and 3), across which surface rupture has been reported near Kunlun Pass. As mentioned in several Chinese newspapers, the famous milestone statue at Kunlun Pass broke and fell because of the earthquake, and the construction of the Golmud-Lhasa railroad has been put on hold since the occurrence of this unexpected event. The earthquake appears to have ruptured the left-lateral Kunlun Fault (Tapponnier and Molnar, 1977) or Kusai-Dongxi-Maqu Fault (Cui and Jiang, 1979; Jia et al. , 1988), which extends roughly east-west for about 1,600 km in north Tibet. This event follows, nearly four years later, the 8 November 1997, Mw = 7.6 Manyi earthquake, which broke another segment of the same active fault system farther west (Figure 2). The centroid (Harvard CMT Catalog), at 35.5°N 92.7°E, lies about 200 km east of the USGS (NEIC) and China Seismological Bureau (CSB) preliminary epicentral locations and about 35 km south of the fault, consistent with a south-dipping fault plane (Figure 3). Eighteen of the twenty-two aftershocks with magnitude Mb ≥ 3.8 that occurred during the first week are located another 100 km farther east, between 93°E and 94.7°E. The easternmost ones are located east of Kunlun Pass. Two focal mechanisms, one from the …