The M S7.1 Yushu earthquake surface rupture and large historical earthquakes on the Garzê-Yushu Fault

Abstract

As revealed by field investigations, the co-seismic surface rupture zone of the 2010 M S 7.1 Yushu earthquake, Qinghai is a characteristic sinistral strike-slip feature consisting of three distinct sinistral primary ruptures, with an overall strike of 310°-320° and a total length of 31 km. In addition, an approximately 2-km-long en-echelon tensile fissure zone was found east of Longbao Town; if this site is taken as the north end of the rupture zone, then the rupture had a total length of ~51 km. The surface rupture zone is composed of a series of fissures arranged in an en-echelon or alternating relationship between compressive bulges and tensile fissures, with a measured maximum horizontal displacement of 1.8 m. The surface rupture zone extends along the mapped Garzê-Yushu Fault, which implicates it as the seismogenic fault for this earthquake. Historically, a few earthquakes with a magnitude of about 7 have occurred along the fault, and additionally traces of paleoearthquakes are evident that characterize the short-period recurrence interval of large earthquakes here. Similar to the seismogenic process of the 2008 Wenchuan earthquake, the Yushu earthquake is also due to the stress accumulation and release on the block boundaries resulting from the eastward expansion of Qinghai-Tibet Plateau. However, in contrast with the Wenchuan earthquake, the Yushu earthquake had a sinistral strike-slip mechanism resulting from the uneven eastward extrusion of the Baryan Har and Sichuan-Yunnan fault blocks. M S 7.1 Yushu earthquake, surface rupture, large historical earthquakes, Garzê-Yushu Fault Citation: Chen L C, Wang H, Ran Y K, et al. The M S 7.1 Yushu earthquake surface rupture and large historical earthquakes on the Garzê-Yushu Fault. At 7 : 49 on April 14, 2010, an M s 7.1 earthquake occurred in Yushu County, Yushu Tibetan Autonomous Prefecture, Qinghai Province, China. The earthquake left more than 2200 people dead and destroyed more than 80% of the buildings in Jiegu Town. It was one of the largest earthquakes experienced in the region since the 2008 M s 8.0 Wenchuan earthquake, causing huge losses of life and property in China. The seismotectonic setting and earthquake surface rupture characteristics for this earthquake and the recurrence pattern of major earthquakes on the seismogenic faults in this area are major concerns of community and a focus of research activity. *Corresponding author (email: ykran@263.net)The investigation and discussion of such issues as soon as possible after an earthquake occurs can provide important reference information for post-earthquake reconstruction and delineate key surveillance and protection regimes for future large earthquakes. Based on the first field survey to be conducted in the area after the earthquake, we aim to depict the co-seismic surface ruptures of the Yushu earthquake and to analyze the seismogenic structures and earthquake recurrence characteristics in combination with historical earthquake records and paleoseismology surveys.

Earthquake deformation field characteristics associated with the 2010 Yushu M s7.1 earthquake

“…The rupture map has been confirmed by field observations made by Chen et al [25], and also by its agreement with the interpretation of SPOT satellite imagery. Additionally, QukckBird data were used in seismic disaster assessment.…”

Possible thermal brightness temperature anomalies associated with the Lushan (China) M S7.0 earthquake on 20 April 2013

“…Xianshuihe fault is the southern boundary of Bayan Har block. Great earthquakes in Tibetan Plateau mainly have occurred along these Block boundaries (Deng et al 2003;Chen et al 2010). And the Ya'an earthquake occurred at the joint area of the two faults Earthq Sci (2015) 28 (1):37-47 39…”

The Evolution of Stress and Strain around the Bayan Har Block in the Tibetan Plateau

“…Large displacement along these strike-slip faults adjusts the substance movement from the strong Indo-Asian collision [58]. High strain rate along the faults allows the crust to move southeastward in the eastern Tibetan Plateau [69]. In the block interior, the strain rate is relatively uniform and small.…”