Slip rate and recurrence intervals of the east Lenglongling fault constrained by morphotectonics: Tectonic implications for the northeastern Tibetan Plateau

Abstract

The Lenglongling fault located in the northeast margin of the Tibetan Plateau plays an important role in accommodating the tectonic deformation of the Tibetan Plateau relative to the Gobi-Ala Shan platform to the north and the North China craton to the east. However, little is known about the fault due to a lack of previous research. In this study we use terrestrial light detection and ranging (LiDAR) data combined with high-resolution remote sensing images to survey offset landforms in the east part of the Lenglongling fault. Microtopographic analysis of well-preserved offset terraces, gullies, ridges, and pluvial fans in the highland environment allows evaluation of single-event slip and multievent cumulative slip. Our study provides an important assessment of the horizontal offset associated with the latest earthquake and four paleoearthquakes that were identified from a series of offset bedrock terraces by constructing a morphotectonic evolution model. Terrestrial LiDAR data indicate that the east Lenglongling fault follows a characteristic slip model. The single-event slip of this section is ~9.4 m; 7-8 paleoearthquakes are thought to have occurred during the Holocene, and a left-lateral strike-slip rate of 6.6 ± 0.3 mm/yr is estimated. Combining the slip rate and the single-event slip distribution, we determine a mean recurrence interval of 1430 ± 140 yr for past earthquakes along the east Lenglongling fault. This result is similar to that of the adjacent Gulang fault, but differs slightly from those of other adjacent faults, which may mean that the Lenglongling and Gulang faults compose an integral fault zone. The large number of millennial recurrent active faults in this region heightens the risk of future seismic activity in the northeast Tibetan Plateau.