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EARTHQUAKE ›› 2019, Vol. 39 ›› Issue (3): 1-10.

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Paleoearthquake Characteristics of the Eastern Segment of Yumen—Beidahe Fault in the Northern Margin of Qilian Shan

LIU Xing-wang1,2, YUAN Dao-yang1, SHAO Yan-xiu1,2, ZHANG Bo1,2   

  1. 1.Lanzhou Institute of Seismology, China Earthquake Administration, Lanzhou 730000, China;
    2.Lanzhou National Observatory of Geophysics, Lanzhou Gansu 730000, China
  • Received:2017-11-14 Online:2019-07-31 Published:2019-08-09

Abstract: Yumen—Beidahe fault is an important active fault at the south margin of Jiuxi Basin. The fault starts from qingcaowan at west, passes through Yumen, Qingtou Shan, Dahongquan, and ends at the east of Gutouquan. The fault is about 80 km long, strikes NWW , inclines south and dips 20°~60°. Yumen—Beidahe fault is an active thrust fault in Holocene. Earthquake surface ruptures are still preserved at the eastern segment of the fault. Based on the filed fault geomorphological investigation and trench excavation, it is revealed that the rupture zone was formed 1.7±0.3 ka ago. there had been another two paleoearthquakes occurring in (4.1±0.3)~(5.4±0.3) ka and 8.4±1.0 ka, and the magnitudes of the two paleoearthquakes were estimated to be about 7.0 by empirical formulas and existing earthquake cases.

Key words: Yumen—Beidahe fault, Active fault, Paleoearthquake, Holocene

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