Paleoseismic activity on Wujiahe segment of Serteng piedmont fault, Inner Mongolia

Abstract

Geomorphic study on Wujiahe segment of Serteng piedmont fault, Inner Mongolia is made. Through analysis of the available data in combination with the results of predecessors’ studies it can be obtained that average vertical displacement rate is 0.48–0.75 mm/a along the Wujiahe segment since the late Pleistocene (14.450–22.340 ka BP) and 0.56–0.88 mm/a since the early-middle Holocene (5.570–8.830 ka BP). Analyzing paleoseismic phenomena revealed in the excavated 5 trenches in combination with the results of predecessors’ studies of paleoearthquakes on the fault, we determine five paleoseismic events on the Wujiahe segment of Serteng piedmont fault since 27.0 ka BP and the recurrence interval to be about 4.300–4.400 ka. A cluster of paleoearthquakes occurred probably during 8.000–9.000 ka BP and two paleoseismic events in 10.000–20.000 ka BP may be missed. A comparison between height of fault scarps and sum of displacement caused by paleoseismic events revealed in trenches, and recurrence interval of paleoseismic events obtained from average displacement rate along the fault and the dislocation by one event suggest that three paleoseismic events are absent in Alagaitu trench. Two paleoseismic events may be absent on the whole active fault segment.