Preprints
https://doi.org/10.5194/nhess-2021-21
https://doi.org/10.5194/nhess-2021-21

  05 Mar 2021

05 Mar 2021

Review status: this preprint is currently under review for the journal NHESS.

The Effect of the Wenchuan and Lushan Earthquakes on the Size Distribution of Earthquakes along the Longmenshan Fault

Chun Hui1,2,3, Changxiu Cheng1,2,3,4, Shi Shen1,2,3, Peichao Gao1,2,3, Jin Chen1,2, Jing Yang5, and Min Zhao1,2,3 Chun Hui et al.
  • 1Key Laboratory of Environmental Change and Natural Disaster, Beijing Normal University, China, 100875
  • 2State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, China, 100875
  • 3Faculty of Geographical Science, Center for Geodata and Analysis, Beijing Normal University, China, 100875
  • 4National Tibetan Plateau Data Center, Beijing, China, 100101
  • 5College of Data Science, Taiyuan University of Technology, China, 030024

Abstract. Changes in the stress state of faults and their surroundings is a highly plausible mechanism explaining earthquakes interaction. These stress changes can impact the seismicity rate and the size distribution of earthquakes. However, the effect of large earthquakes on the earthquake size distribution along the Longmenshan fault has not been quantified. We evaluated the levels of the b value for the stable state before and after the large earthquakes on 12 May 2008 (Wenchuan, MS 8.0) and 20 April 2013 (Lushan, MS 7.0) along the Longmenshan fault. We found that after the mainshocks, the size distribution of the subsequent earthquakes shifted toward relatively larger events in the Wenchuan aftershock zone (b value decreased from 1.03 to 0.84), and generally remained invariable in the Lushan aftershock zone (b value remained at 0.76). The time required for the b value to return to stable states after both mainshocks were entirely consistent with the time needed by the aftershock depth images to stop visibly changing. The result of the temporal variation of b values show decreasing trends for the b value before both large earthquakes. Our results are available for assessing the potential seismic risk of the Longmenshan fault as a reference.

Chun Hui et al.

Status: open (extended)

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Chun Hui et al.

Chun Hui et al.

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Short summary
This article quantify the effect of the Wenchuan MS 8.0 and Lushan MS 7.0 earthquakes on the size distribution of earthquakes along the Longmenshan fault. The results depict the decreasing trends of b values before the two large earthquakes in the study region. The major aftershock active periods of the Wenchuan MS 8.0 and Lushan MS 7.0 earthquakes were less than one year and ten months. Moreover, both large earthquakes do not change the pattern of high in the north, low in the south.
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