Holocene paleoearthquakes activity in the Nieru graben, southern Tibet

Abstract

The Yadong-Gulu Rift (YGR) is the longest and most prominent rift in southern Tibet. While 14 large historical earthquakes have occurred on the northern-central segment of the YGR, historical or paleoearthquake records along the southern segment remain poorly understood. The spatial discrepancy of large earthquakes has significant implications for assessing seismic hazards along the entire YGR. To address this knowledge gap, this study presents the paleoseismic events for the first time in the Nieru graben located along the southern segment of the YGR. The excavation of a paleoseismic trench reveals two Holocene earthquakes with calibrated radiocarbon dates constraining the timing of the two events to be after 4084-3954 cal yr BP. The paleoearthquake had a magnitude of M 7. The study shows that the southern segment of the YGR experienced strong paleoseismic events, except for the Relong graben. Considering the high present extension rate of the southern rifts and the magnitude of the paleoseismic events along the Nieru graben, the southern segment of the YGR holds the potential for producing large earthquakes. Furthermore, the ongoing tectonic deformation in the area, coupled with stress changes from large earthquakes on Himalayan thrust faults, may increase the likelihood of future rupture along the active faults in the Nieru graben.