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  Analysis on the mechanical causes of the complex seismicity in Changning area, China

Hu, X., Cui, X., Zhang, G., Wang, G., Zang, A., Shi, B., Jiang, D. (2021): Analysis on the mechanical causes of the complex seismicity in Changning area, China. - Chinese Journal of Geophysics - Chinese Edition, 64, 1, 1-17.
https://doi.org/10.6038/cjg2021O0232

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Item Permalink: https://gfzpublic.gfz-potsdam.de/pubman/item/item_5005579 Version Permalink: https://gfzpublic.gfz-potsdam.de/pubman/item/item_5005579_4
Genre: Journal Article

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 Creators:
Hu, XingPing1, Author
Cui, XiaoFeng1, Author
Zhang, GuangWei1, Author
Wang, GanJiao1, Author
Zang, A.2, Author              
Shi, BingXin1, Author
Jiang, DaWei1, Author
Affiliations:
1External Organizations, ou_persistent22              
22.6 Seismic Hazard and Risk Dynamics, 2.0 Geophysics, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum, ou_146032              

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 Abstract: The Changning MS6.0 earthquake and its moderate to strong aftershocks, which occurred in the axial area of Changning anticline, exhibit different features with the moderate to strong earthquakes that occurred in the southern syncline area nearby, although these two areas are only a dozen kilometers away. Whether this difference is only caused by different fault structures, or caused by local change is still a matter of debate. In order to answer this question, basing on the correction of small earthquake location and seismic velocity structure through double-difference tomography inversion, this paper determined the fine structure of the crustal stress field by using comprehensive focal mechanism solutions, and analyzed its mechanical consistency with the focal mechanism solutions of moderate to strong earthquakes. It is found that for the different subareas of Changning area, the maximum principal stress remains horizontal, and its azimuth remains almost East-West oriented although it has a small clockwise rotation from north to south; meanwhile, the stress regime exhibit a significant local change, which is thrust stress regime for the axial area of Changning anticline, against strike-slip stress regime for the southern syncline area. The stress fields in these two subareas highly accord with the focal mechanism solutions of moderate to strong earthquakes in the corresponding area, but poorly accord with, or even contradict that in the non-corresponding area, which indicates that the local stress change of stress field is the necessary mechanical basis for the complex seismicity behavior in Changning area. Additional rock mechanics analysis points out that lateral difference of Poisson's ratio of rock is probably the main cause of this local change of stress field. This paper also discusses the seismogenic fault structure of Changning MS6.0 earthquake sequence, and suggests the activation of the basement fault(s) in the depth range of 6 to 9 km in the axial area of Changning anticline driven by regional stress field is the potential cause of the occurrence of Changning MS6.0 earthquake sequence.

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Language(s): zho - Chinese
 Dates: 2021
 Publication Status: Finally published
 Pages: 17
 Publishing info: -
 Table of Contents: -
 Rev. Type: -
 Identifiers: DOI: 10.6038/cjg2021O0232
GFZPOF: p4 T3 Restless Earth
GFZPOF: p4 T8 Georesources
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Title: Chinese Journal of Geophysics - Chinese Edition
Source Genre: Journal, SCI, p3
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Pages: 17 Volume / Issue: 64 (1) Sequence Number: - Start / End Page: 1 - 17 Identifier: CoNE: https://gfzpublic.gfz-potsdam.de/cone/journals/resource/journals74
Publisher: Chinese Geophysical Society