Preprints
https://doi.org/10.5194/egusphere-2023-1119
https://doi.org/10.5194/egusphere-2023-1119
07 Jun 2023
 | 07 Jun 2023

The crustal structure of the Lomgmenshan fault zone and its implications for seismogenesis: New insight from aeromagnetic and gravity data

Hai Yang, Shengqing Xiong, Qiankun Liu, Fang Li, Zhiye Jia, Xue Yang, Haofei Yan, and Zhaoliang Li

Abstract. Although many geophysical models have been proposed in the Longmenshan fault zone (LFZ) and its surrounding areas, the deep structure of the seismic gap and its constraint of the Wenchuan and Lushan earthquakes remain uncertain. Based on the compiled aeromagnetic data and Bouguer gravity data, we have tried to create a more detailed and visible magnetic and density model beneath the LFZ using 2D forward modeling and 3D inversion. The research shows that structure heterogeneities are widely distributed beneath the LFZ. The earthquake epicenters show high magnetic anomalies and the edge of high Bouguer gravity anomalies that consist of rigid blocks where apt to accumulate stress. However, the seismic gap shows low magnetic anomalies and transition of Bouguer gravity anomalies related to a weak zone. The Sichuan Basin has two NE-trending banded high magnetic blocks extending beneath the LFZ that firmly support the crust of the Sichuan Basin was downward subduction toward the LFZ. More importantly, the basement subducts to approximately 33 km west of the Wenchuan-Maoxian fault with a low dip angle beneath the middle segment of the LFZ, whereas the distance decreases to approximately 17 and 19 km under the southern segment. Thus, the crust of the Sichuan Basin beneath the middle segment extends farther than that beneath the southern segment with the seismic gap as the transition zone. Therefore, we propose that the structural heterogeneity of the basement on the western margin of the Sichuan Basin may be the main reason for the different focal mechanisms and geodynamics of the Wenchuan and Lushan earthquakes.

Journal article(s) based on this preprint

21 Dec 2023
The crustal structure of the Longmenshan fault zone and its implications for seismogenesis: new insight from aeromagnetic and gravity data
Hai Yang, Shengqing Xiong, Qiankun Liu, Fang Li, Zhiye Jia, Xue Yang, Haofei Yan, and Zhaoliang Li
Solid Earth, 14, 1289–1308, https://doi.org/10.5194/se-14-1289-2023,https://doi.org/10.5194/se-14-1289-2023, 2023
Short summary

Hai Yang et al.

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1119', Chuntao Liang, 03 Sep 2023
    • AC1: 'Reply on RC1', Hai Yang, 02 Oct 2023
  • RC2: 'Comment on egusphere-2023-1119', Anonymous Referee #2, 04 Sep 2023
    • AC2: 'Reply on RC2', Hai Yang, 02 Oct 2023

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1119', Chuntao Liang, 03 Sep 2023
    • AC1: 'Reply on RC1', Hai Yang, 02 Oct 2023
  • RC2: 'Comment on egusphere-2023-1119', Anonymous Referee #2, 04 Sep 2023
    • AC2: 'Reply on RC2', Hai Yang, 02 Oct 2023

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Hai Yang on behalf of the Authors (28 Oct 2023)  Author's response   Author's tracked changes   Manuscript 
ED: Publish as is (05 Nov 2023) by Nicolas Gillet
ED: Publish as is (05 Nov 2023) by Susanne Buiter (Executive editor)
AR by Hai Yang on behalf of the Authors (10 Nov 2023)

Journal article(s) based on this preprint

21 Dec 2023
The crustal structure of the Longmenshan fault zone and its implications for seismogenesis: new insight from aeromagnetic and gravity data
Hai Yang, Shengqing Xiong, Qiankun Liu, Fang Li, Zhiye Jia, Xue Yang, Haofei Yan, and Zhaoliang Li
Solid Earth, 14, 1289–1308, https://doi.org/10.5194/se-14-1289-2023,https://doi.org/10.5194/se-14-1289-2023, 2023
Short summary

Hai Yang et al.

Hai Yang et al.

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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

Short summary
In 2008 and 2013, the Wenchuan (Ms 8.0) and Lushan (Ms 7.0) earthquakes successively struck the Longmenshan fault zone (LFZ) in the eastern margin of the Tibetan Plateau. The two earthquakes show different geodynamic features and form a 40~60 km gap area void of aftershocks for both earthquakes along the fault zone. The magnetic and density models indicate that the genesis of the gap area is closely related to structural heterogeneity along the LFZ.