ORIGINAL RESEARCH article
Front. Earth Sci.
Sec. Solid Earth Geophysics
This article is part of the Research TopicFaults and Earthquakes Viewed by Networks, Monitoring Systems, and Numerical Modelling Techniques - Volume IIView all articles
Characteristics and Seismogenic Structure of the April 2024 Weishan (Yunnan, China) MS4.1 and MS4.3 Double-Earthquake Sequence
Provisionally accepted
- Yunnan Earthquake Agency, Kunming, China
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According to the China Earthquake Networks Center (CENC), two moderate earthquakes of MS 4.1 and MS 4.3 struck Weishan County, Yunnan Province, at 05:54:10 local time on 19 April 2024 and 13:05:16 local time on 24 April 2024, respectively. Their epicenters are only 2.4 km apart, constituting a typical double-main-shock event. Utilizing the double-difference relocation algorithm, we precisely relocated 115 earthquakes (ML ≥ 0) within the sequence. Focal mechanisms of the two main shocks were further determined via the Cut-and-Paste (CAP) waveform inversion technique. Integrated with regional geological mapping and existing data, we analyzed the spatiotemporal distribution of the sequence and elucidated its seismogenic structure and rupture process. The main findings are as follows: (1) The relocated sequence delineates a dominant northwest-southeast trend (~8 km long) and a subordinate northeast-southwest trend (~4.5 km long); hypocenters concentrate between 3 and 11 km depth. Both main shocks exhibit almost identical rupture styles characterized by normal faulting with a left-lateral strike-slip component. (2) The seismogenic structure is jointly controlled by the NE–SW-striking Bianjiang Fault and the Jijie–Longjie anticline. The Bianjiang Fault served as the primary seismogenic fault for the two main shocks, whereas the axial trace of the Jijie–Longjie anticline dictated the overall NW– SE alignment of the sequence. Vertically, the distribution converges downward, with stronger events preferentially nucleating at greater depths. (3) Within the context of long-term seismicity of the Lanping–Simao accretionary terrane, continuous southeastward extrusion of Tibetan Plateau material has reactivated pre-existing structures to accommodate the prevailing stress field, thereby facilitating the Weishan doublet. This study highlights the interplay between inherited faults and newly stressed structures in generating moderate earthquakes within the terrane and provides a basis for future seismic-hazard assessments.
Keywords: Weishan double-earthquake, Earthquake relocation, Focal mechanism, Seismogenic structure, seismic trend
Received: 10 Sep 2025; Accepted: 28 Oct 2025.
Copyright: © 2025 Hetang, Tianyu, Yuan, Jun, Wenjian, Chengzhu and Wenjian. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Hei Hetang, 854360354@qq.com
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