Research on paleoearthquakes in Jiuxian trenches across Nankou-Sunhe fault zone in Changping County of Beijing plain |
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| Authors: | Wali Jiang Zhihua Hou and Xinsheng Xie |
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| Institution: | Institute of Crustal Dynamics, China Seismological Bureau, Beijing 100085, China |
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| Abstract: | An abundance of the phenomena of tectonic deformation and paleoseismic events of different times and their recurrent interval,
as well as coseismic vertical displacements is exposed in Jiuxian trenches across the Nankou-Sunhe fault zone in Changping
County. The research result shows three paleoearthquakes occurring during the Holocene. They were dated as 10643 ± 250 a B.P.—9706
± 1235 a B.P., 7894±150 a B.P.—7640 ± 650 a B.P, and 3987+100 a B.P.—3670 ± 310 a B.P, respectively. The coseismic vertical
displacements are 1.0 m, 2.0 m, and 2.0 m, respectively. From a statistical formula of relation between historic earthquake
magnitudes and surface seismic dislocations in North China, the magnitudes of these paleoearthquakes are inferred to be in
a range fromM 7.7 toM 7.9. The research shows that the Holocene fault activity in the plain can be traced in the trenches according to the micro-geomorphic
features. Many micro-structural phenomena are also found in these trenches. Identification of the paleoearthquakes in the
Nankou-Sunhe fault zone during the Holocene time is of significance for assessment of future seismic risk in Beijing area.
The important item of the Ninth Five-Year Program of China Seismological Bureau. Contribution No.2001A0002, Institute of Crustal
Dynamics, China Seismological Bureau. |
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| Keywords: | trench excavation Holocene fault activity paleoearthquake Nankou-Sunhe fault zone Beijing plain |
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