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EARTHQUAKE ›› 2020, Vol. 40 ›› Issue (3): 83-98.doi: 10.12196/j.issn.1000-3274.2020.03.007

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Study of the Activity Since Late Pleistocene of West Section of Cixian-Daming Faults Zone

ZHANG Lu, XIE Xin-Sheng, GUO Hui   

  1. Key Laboratory of Crustal Dynamics, Institute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China
  • Received:2019-08-13 Online:2020-07-31 Published:2020-07-28

Abstract: A M71/2 earthquake occurred in Cixian County, Hebei Province, in 1830, in the west section of the Cixian-Daming fault zone. Seismic rupture and the activity of this fault have been concerned by earthquake researchers. Previous studies focused on the surface rupture of the Cixian earthquake in 1830. The focus of this paper is on the fault activity since the late Pleistocene in the whole west section of the Cixian-Daming fault zone. The satellite interpretation, aerial photo interpretation, and field seismic geological surveys were applied to conduct researches, and trench excavation or exfoliation of field geological sections and sampling dating were performed at important locations, to determine the time of occurrence of ruptures in various sections of the fault. The western section of the fault is divided into three fault sections, in which F2 is the Cixian-Fengfeng section, F3 is the Dongtianjing-Taoquan section, and F4 is the Hanjiagou-Ganquan section. The F2 fault, an early-middle Pleistocene fault, is buried mostly. The eastern end of the F3 fault cuts off the 22 ka strata in the south of Dongtianjing Village, being late Pleistocene fault. The F3 fault section in the Nanshan Village, Gushan, is a Holocene fault, and the section is a suspected Holocene active fault from Zhangjialou Village to Taoquan Township. The main rupture in the F4 fault is the Holocene fault. The fault section of F4 is all located in the mountainous area of the bedrock, where many fault fractures such as bedrock sections, seismic trenches, and fault eyebrown ridges can be found. Lichens (Xanthoria) were developed on some of the ruptured surfaces. Lichen dating methods were used to determine these ruptured surfaces as the surface earthquake remnants of the Cixian earthquake in 1830. The Cixian-Daming fault zone ends at the western end of F4. A comprehensive analysis of the rupture events in each section of the fault zone was made to get the spatial and temporal distribution map of active events in the west section of the Cixian-Daming fault zone. It is estimated that the late Pleistocene earthquake recurrence period in the west section of the Cixian-Daming fault zone is about 6000 years.

Key words: West section of Cixian-Daming faults zone, Fault activity, Trench, Lichen dating, Recurrence interval

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