Monitoring the horizontal movement along the Shanxi fault zone by GPS measurement

Abstract

Based on the data from 4 times of repeated measurements (1996–1999) of GPS monitoring network arranged along Shanxi fault zone, the current horizontal movement of Shanxi fault zone and its relationship with Yang-yuan-Hunyuan earthquake (M=5.6; 39.8°N, 113.9°E; November 1, 1999) which occurred at the north part of the monitoring network is analyzed. The results from the analysis indicate: 1 The horizontal movement along Shanxi fault zone was not obvious from 1996 to 1997; 2 The intensity of horizontal movement along Shanxi fault zone increased at the period of 1997 to 1998, and there are three areas with relatively higher strain (1×10−6) appeared, i.e., the source region, Xinzhou region and northeastern part of Jiexiu; 3 Although the dominant movement direction of Shanxi fault zone in the period of 1998 to 1999 was consistent with the fault striking direction, but as compared with the movement in the passed year, the direction was almost reversed, while the absolute value of the movement was close each other; 4 The accumulated horizontal movement along Shanxi fault zone from 1996 to 1999 became obvious gradually. It can be divided into three parts by considering its tendency: (a) the dominant direction of movement in north of Xinzhou is NNE (0.8 cm); (b) in south of Quwo it is SSW (1 cm); (c) in the central area it is rather complicated, the deformation in the southern part is little more large, but in the view of whole area there is no dominant movement exist. Generally speaking, Shanxi fault zone is mainly controlled by the NNE-SSW-trending extension stress field, but there is no strike-slip movement. In the period of 1997 to 1998, there might be a clear stress disturb and it was essentially recovered in 1999. Then the Yangyuan-Hunyuan earthquake occurred. Very possible, this disturb is the triggering to the earthquake.