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Seismogenic structure and mechanism of the 1954 M7(1/4) Shandan earthquake, Gansu Province, western China

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Authors:Zheng Wenjun; Zhang Zhuqi; Zhang Peichen; Liu Xingwang; Guo Xiao; Pang Jianzhang; Ge Weipeng; Yu Jingxing
Author Affiliations:Primary:
China Earthquake Administration, Institute of Geology, Beijing, China
Volume Title:Diqiu Wulixue Bao Acta Geophysica Sinica
Source:Diqiu Wulixue Bao = Acta Geophysica Sinica, 56(3), p.916-928. Publisher: Science Press, Beijing, China. ISSN: 0001-5733
Publication Date:2013
Note:In Chinese with English summary. 51 refs.
Summary:Located in the front margin of the northeastern Tibetan Plateau, the Longshoushan fault zone is one of the boundary faults between the Hexi corridor and the Alxa Block. Although the resolution of observation is limited, the 1954 M71/4 earthquake on the Longshoushan fault zone is a rare big event in this zone with modern seismological observation and documentation. During this earthquake, one continuous dextral-normal rupture occurred with a length of only 7 km along a transfer fault connecting two secondary faults of the Longshoushan fault zone. However, the dextral-normal sense of this surface rupture is contrary to the tectonic kinematics in this area. Based on recent field investigation and mapping, two phenomena were discovered. Firstly, except the one appeared on the transform fault, no surface rupture zone is found on the branches of the Longshoushn fault zone. Secondly, the main damage caused by earthquake is distributed on the region between the northern and the southern branches of the Longshoushan fault zone. These two findings indicate that the 1954 earthquake was caused by the main faults rather than the transfer fault of the Longshoushan fault zone, and the co-seismic surface rupture on the transfer fault is only a form of stress release at local portion. According to calculation of static co-seismic Coulomb stress change, the surface rupture could be triggered by an earthquake on the southern branch of the Longshoushan fault zone. Furthermore, in consideration of the possibility of dynamic triggering along the northern branch of the Longshoushan fault zone, the surface rupture should be the co-seismic response to the earthquake occurred on the main branches of the Longshoushan fault zone. Relocation of the small earthquakes also shows that a narrow inverted north-extending triangle about 10 km wide was formed between the northern and the southern faults of the Longshoushan fault zone.
Subjects:Earthquakes; Faults; Focal mechanism; Neotectonics; Rupture; Seismicity; Seismotectonics; Strike-slip faults; Tectonics; Transfer faults; Asia; China; Far East; Gansu China; Hexi Corridor; Alxa Block; Longshoushan fault zone; Shandan China; Shandan earthquake 1954; Western China
Coordinates:N384234 N384234 E1012004 E1012004
Record ID:759114-14
Copyright Information:GeoRef, Copyright 2021 American Geosciences Institute.
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