Analysis of crustal deformation and strain characteristics in the Tianshan Mountains with least-squares collocation

Abstract. By fitting the observed velocity field of the Tianshan Mountains from 1992 to 2006 with least-squares collocation, we established a velocity field model in this region. The velocity field model reflects the crustal deformation characteristics of the Tianshan reasonably well. From the Tarim Basin to the Junggar Basin and Kazakh platform, the crustal deformation decreases gradually. Divided at 82° E, the convergence rates in the west are obviously higher than those in the east. We also calculated the parameter values for crustal strain in the Tianshan Mountains. The results for maximum shear strain exhibited a concentration of significantly high values at Wuqia and its western regions, and the values reached a maxima of 4.4×10⁻⁸ a⁻¹. According to isogram distributions for the surface expansion rate, we found evidence that the Tianshan Mountains have been suffering from strong lateral extrusion by the basin on both sides. Combining this analysis with existing results for focal mechanism solutions from 1976 to 2014, we conclude that it should be easy for a concentration of earthquake events to occur in regions where maximum shear strains accumulate or mutate. For the Tianshan Mountains, the possibility of strong earthquakes in Wuqia–Jiashi and Lake Issyk-Kul will persist over the long term.