Study on crustal deformation characteristics before Xinjiang Yutian M_S7.3 earthquake in 2014

This paper calculates the principal strain rate, plane strain rate and maximum shear strain rate in Xinjiang and its vicinity by using the least squares method with GPS data set during 1999—2007 and 2009—2013. The crustal tectonic deformation characteristics in this area before 2008 and 2014 Yutian M_S7.3 earthquakes are also analyzed comprehensively. The dynamic results of velocity field and strain rate field indicate that the crust shortening decreases gradually from south to north and from west to east, suggesting that the sinistral shear deformation in the eastern side is significantly greater than that in the western side around focal area. The source areas of 2008 and 2014 M_S7.3 Yutian earthquakes are located in the transitional zone of the tensile and compressive deformation, which is prone to occurrence of a great earthquake. The surface rupture in 2008 Yutian earthquake, which is mainly tensile with little shear component, strengthened the sinistral shear deformation of Altyn Tagh fault. The GPS velocity profiles show that the deformation width of western side is greater than that of the east in the hypocentral region before 2014 Yutian M_S7.3 earthquake, consistent with the degree of shear strain accumulation. In conclusion, this difference between two sides in strain accumulation are easy for the nucleation process of 2014 Yutian earthquake. And it is inferred that the 2008 Yutian M_S7.3 earthquake may play a role in promoting the 2014 Yutian M_S7.3 earthquake.