2014 Yutian Ms7.3 earthquake: Structural response of the Bayankala tectonic-block to eastward extrusion

The Bayankala tectonic-block, located in the north of the Tibetan Plateau, is the most active area of strong earthquakes in recent years. A series of strong earthquakes occurred around the block since 1997. The Yutian M(s)7. 3 earthquake of 2014 occurred in the southern margin of the Xiaoerkule basin, which is located on the west boundary of the Bayankala tectonic-block. This area is the intersection site of the Altyn Tagh fault, the Karakax fault and the Eastern Kunlun fault, which are all large strike-slip active fault zones in different directions. The sudden change in direction and rate distribution of the Altyn Tagh fault lead to the formation of local tensile stress characteristics in the region, forming sinistral-normal fault with NE and SN strike. By analyzing the aftershocks distribution and focal mechanism solution results, we conclude that the seismogenic structure of this earthquake is the Xiaoerkule fracture, a secondary fault of the Altyn Tagh faiult southwest segment. The earthquake rupture is characterized by sinistral strike slip normal fault. The north and east boundaries of the Bayankala tectonic-block have shown block eastward extrusion displacement of about 7 m during the strong earthquakes, but the amount of stretch of the west boundary of the block is apparently inconsistent. The Yutian Ms7. 3 earthquake is the structural response and strain adjustments of the Bayankala tectonic-block to the eastward extrusion.