Slip rate and paleoseismicity of the Minle-Damaying Fault, middle of the Hexi Corridor, Northwest China

Abstract:

The Minle-Damaying Fault (MDF) is a segment of the north frontal fault of the Qilian Mountains, and the southern boundary fault of the Zhangye Basin in the middle of Hexi Corridor, a foreland basin system in the northern margin of the Qinghai-Tibet Plateau. Many faults around this area have been studied in detail during the past decade, but there are few researches on the slip rate and paleoseismicty of the MDF. In the west part of the MDF, it is found that gully floor and terraces were offset around 2m and 6 m vertically, a trench on the terrace indicates 3 paleoseimic events. In the east part of the MDF, it is found that the river terraces of a branch the Dongdahe River were vertically offset by the MDF with dislocations of 15m, 10m, 7.5m, and 5m from higher to lower. Trench study on the lowest terraces indicate 2 paleoseismic events, the earlier event offset the strath of the terrace 2.5m vertically, and over thrust Carboniferous System on the late Holocene alluvium 7m horizontally, while the later event offset the strath of the terrace 2.5m vertically and 9m horizontally. According to the ages of the terraces and the ration of the vertical to horizontal dislocation of the faulting events, it is calculated that the vertical slip rate of the fault is 1.1 mm/a, and the horizontal shorting rate is 3-3.4 mm/a.