Paleoearthquakes and the latest active age of Jinghe segment of Bolokenu-Aqikekuduk fault

Bolokenu-Aqikekuduk fault is located at the northernmost end of the NW-trending dextral strike-slip fault system in the west Tianshan mountain, and is also the longest active fault extending in China. The latest active ages of both faults are determined to be Holocene based on the relation between the optically stimulated luminescence age of sediments and earthquake colluvial wedges. In this paper, two trenches were excavated on the latest surface deformation in the west of Aibi lake and southeast of Jinghe county. According to activity difference, the fault can be divided into the Aibi lake segment and the east Jinghe segment. The results show that the latest active times of the two segments are determined to be Holocene, and the latest earthquake events occurred on 3.7−4.86 ka BP respectively. According to the results of gully dislocation and pluvial fan dating, the activity rate in the east Jinghe segment is more than 4 mm/a. Furthermore, it is deduced that the Aibi Lake segment may be the seismogenic structure of M6¹/₂ Jinghe earthquake in 1765, and its magnitude is likely to be underestimated. According to the rupture length of Aibi lake segment more than 60 km, the magnitude is likely to be more than M7.0.