Contemporary tectonic stressing rates of major strike-slip faults in the Tibetan Plateau from GPS observations using Least-Squares Collocation

Abstract

Abstract We invert the stressing rates of major strike-slip faults in the Tibetan Plateau using GPS measurements by the method of Least-Squares Collocation. From the comparison results of the influence of different distance intervals and covariance functions on the fit to GPS velocity field and the statistics of variance and covariance, we choose 40 km as the distance interval and exponential function as the covariance function to calculate the stressing rates. The results show that the root-mean-square error of GPS observations is only 0.061 cm. The stressing rates of the faults in the eastern Tibetan Plateau are generally higher than those in the west. The faults, whose maximum stressing rates are larger than 2.0 kPa/yr, account for about 41.4% of selected faults. Specifically, the stressing rate of the northwest segment of the XSHF is the highest with a value of 7.05 kPa/yr. Our stressing rates of the KLF and XSHF are consistent with published values or deduced results from published stress drops and earthquake recurrence intervals. The comparison results of stressing rates with fault slip rates show that the ratios of the stressing rates to the slip rates range broadly from 0.4 to 7.5 bar/m, which may be due to different kinds of data and methods used to calculate the slip rates besides varying petrophysical properties in the Tibetan Plateau. However this variation of the same fault is less distinct than that in different faults. The GYFF, HYF, JLF, LCRF and RRF with low slip rates and high stressing rates may be located in brittle shear zones. Inversely, the ATF, KLF, KRKRF and KRKXF may be located in ductile zones. Additionally, the statistical results between the stressing rates and the seismicity rates show that the seismicity roughly grows with the tectonic stressing rates. And we deduce that the KRKXF and MCRCF with high seismicity rates and low stressing rates are the strike-slip faults mostly prone to rupture in the Tibetan Plateau.