Present-day movement characteristics of the Qinghai Nanshan fault and its surrounding area from GPS observation

Abstract

The Qinghai Nanshan fault is a larger fault in the Northeastern Xizang Plateau. In previous studies, its movement characteristics are mainly investigated with geological and seismic observations, and the tectonic transformation role of the fault on its east is not yet clear. This study uses data fusion to obtain denser GPS observations near the Qinghai Nanshan fault. Based on tectonic characteristics, we establish a block model to investigate the fault slip rate, locking degree, and slip deficit. The results show that the Qinghai Nanshan fault slip rate is characterized by sinistral and convergent movement. Both the sinistral and convergent rates display a decreasing trend from west to east. The locking degree and slip deficit are higher in the western segment (with an average of about 0.74 and 1.1 mm/a) and lower in the eastern segment. Then, we construct a strain rate field using GPS observations to analyze the regional strain characteristics. The results indicate that along the fault, the western segment shows a larger shear strain rate and negative dilation rate. Regional earthquake records show that the frequency of earthquakes is lower near the fault. The joint results suggest that the western segment may have a higher earthquake risk. In addition, the insignificant fault slip rate in the eastern segment may indicate that it does not participate in the tectonic transformation among the Riyueshan, Lajishan, and West Qinling faults.