M 6.6 - northern Qinghai, China

Tectonic Summary

The January 7, 2022 M6.6 earthquake in north-central China occurred as a result of strike-slip faulting at shallow depth. The earthquake occurred on either an east-west striking left-lateral fault, or a north-south striking right-lateral fault. The location and mechanism of the earthquake are consistent with the earthquake having occurred on or near the Haiyuan fault system, which is a major left-lateral fault system on the northern margin of the Tibetan Plateau.

The region where the January 7 earthquake occurred is an intraplate (i.e., not at a plate boundary) region located on the northern margin of the Tibetan Plateau. The Tibetan Plateau is a high topographic region north of the Himalaya Mountains that developed in response to ongoing collision between the India and Eurasia plates. Because of the high topography of the plateau, the plateau undergoes extension oriented in an approximately east-west direction. This extension is accommodated through combination of normal faulting and strike-slip faulting. Strike-slip faulting is additionally caused by complex interactions at the edges of the plateau introduced by the oblique motion between the India and Eurasia plates. In most examples, the major strike-slip faults of the Tibetan Plateau accommodate left-lateral motion similar to that associated with the January 7 earthquake, and many of these faults (such as the Kunlun and Altan Tagh faults) are capable of producing M7 or larger earthquakes. The Haiyuan fault system in the vicinity of the January 7 earthquake is a ~1000 km long fault system that accommodates approximately 3-5 mm/yr of left-lateral slip.

In the last fifty years there have been about 20 earthquakes magnitude 5.5 and larger within 200 km of the January 7 earthquake. In 1927 an M7.7 earthquake occurred in the Haiyuan fault system about 150 km to the east of the January 7 earthquake. The 1927 earthquake caused more than 40,000 deaths and extreme damage in the Gulang-Wuwei area. Landslides buried a town near Gulang and dammed a stream in Wuwei County, creating a new lake. Large fissures and sandblows occurred in the area. Damage occurred from Lanzhou through Minqin and Yongchang to Jinta. An M8.3 earthquake also occurred in the eastern-most Haiyuan fault system on December 16, 1920, approximately 300-400 km from the January 7 earthquake. The 1920 earthquake infamously caused over 200,000 fatalities, with around half of those fatalities caused by earthquake-triggered landslides.