STRESS ACCUMULATION AND RELEASE IN THE XIANSHUIHE FAULT ZONE

In this paper, on the basis of historical data of earthquakes with magnitudes M6, the seismicity in the Xianshuihe fault zone has been studied, and the stress accumulation and release in the fault zone has been further studied by using dislocation model of the fault. The results show that in Daofu, the activity of strong earthquakes along the fault is divided into two active segments: the northwestern and southeastern segments. Strong earthquakes occurred alternately on these active segments. The seismic energy release seems to be quasi-periodic, and the average recurrence period of earthquakes with magnitude M7 is 27.6 years. This paper has shown the patterns of stress release due to the strong earthquakes occurring in three different time spans (1700-1811, 1816-1967, 1816-1982), and has discussed the effect of the stress fields due to the strong earthquakes in the former two time intervals on the occurrence of the first large earthquake that follows. The stress accumulation in the southeastern segment of the fault since 1893 has been calculated, and the corresponding contours of maximum shear stress and hydrostatic stress are shown. Finally, according to the stress accumulation, the additional stress changes and the seismicity as well as the characteristics of strain release curves, we have estimated the seismic trend, and believe that a coming earthquake with magnitude 7.1 to 7.7 may occur in (1) the segment between Kangding and Moxi or (2) the segment between Daofu and Qianning or (3) the segment between Qianning and Kangding in the Xianshuihe fault by the end of this century.