Source Complexity and Faulting Heterogeneity of the 2024 Mw 4.8 Zhongdian Earthquake, Yunnan, China
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1.
China Earthquake Administration
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2.
Yunnan University
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3.
Southern University of Science and Technology
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4.
California Institute of Technology
Abstract
Earthquakes in stable continental regions occur less frequently than those at plate boundaries, and their seismic hazards remain poorly understood. In this study, we analyze the source complexity of the Mw 4.8 Zhongdian earthquake in southeastern Tibet, which occurred in an area where no major faults were previously mapped. Notably, the focal mechanism solutions differ significantly between the different approaches: whereas the centroid moment tensor (CMT) indicates oblique-normal faulting, the first-motion (FM) solution suggests purely dip-slip faulting. This discrepancy points to a complex rupture process involving multiple slip modes. Using multi-point-source inversion, we identify two near-simultaneous subevents. The first aligns with the FM dip-slip mechanism, and the second is dominated by strike-slip motion; together, they are consistent with the overall CMT solution. However, source spectral ratio analysis and displacement records show no distinct temporal separation between the subevents. On the other hand, structural complexities are revealed by relocated aftershocks and spatially diverse focal mechanisms, which enable the observed rupture behavior. We further compare the stress fields across multiple scales and find no significant differences in principal stress orientations between the Zhongdian source region and the broader western Chuandian block. Nevertheless, the two subevent areas display contrasting faulting styles, highlighting the influence of localized strain or deformation heterogeneity. These findings suggest that the moderate-size Zhongdian earthquake was governed by both complex fault geometry and heterogeneous faulting behavior.
Copyright and License
© 2025 Seismological Society of America.
Acknowledgement
The authors thank the Seismological Research Letters (SRL) editor, the Eastern Section editor, and two anonymous reviewers for their constructive comments on this work. The authors thank the International Earthquake Science Data Center of the Institute of Geophysics, China Earthquake Administration for providing seismic waveforms; Peizhen Su for providing his focal mechanism dataset (Su et al., 2024); and Zhenyue Li and Zhenjiang Liu for their discussions on focal mechanisms, stress field inversion, and Coulomb failure stress change calculation. The maps in this study are primarily generated using the Generic Mapping Tools software package (Wessel et al., 2019). This work is supported by the National Natural Science Foundation of China (Grant Numbers 42374079 and 42074053) and the Basic Research Fund of the Institute of Geophysics, CEA (Grant Numbers DQJB19B30 and JY2024Z01).
Data Availability
The seismic waveforms used in this study can be obtained by contacting the International Earthquake Science Data Center available at http://www.esdc.ac.cn (last accessed December 2024; doi: 10.11998/IESDC). The HypoInverse and HypoDD programs used for earthquake location can be accessed at https://www.usgs.gov/software/hypoinverse-earthquake-location and https://www.ldeo.columbia.edu/∼felixw/hypoDD.html, respectively (both last accessed December 2024). The Phase picking, Association, Location, and Matched‐filter (PALM) workflow used in this study is available at https://github.com/YijianZhou/PALM (last accessed April 2025). The module used for source spectra analysis can be found at https://github.com/YijianZhou/Manual-Analysis-Helper (last accessed December 2024). The hashpy2 code used for focal mechanism calculation is available at https://github.com/wasjabloch/hashpy2 (last accessed December 2024). The cut‐and‐paste (CAP) program can be found at https://www.eas.slu.edu/People/LZhu/home.html (last accessed December 2024). The STRESSINVERSE program for stress field inversion is available at https://www.ig.cas.cz/en/stress-inverse (last accessed December 2024). The Coulomb 3.3 program for Coulomb failure stress change (ΔCFS) calculation is available at https://temblor.net/coulomb (last accessed December 2024). The seismic catalog of the Zhongdian sequence constructed in this study is available at https://github.com/YijianZhou/Seismic-Catalog (last accessed April 2025). The Global Centroid Moment Tensor (Global CMT) webpage is available at https://www.globalcmt.org. IEF, CEA website can be accessed at https://www.ief.ac.cn/1068/info/2020/21375.html (last accessed November 2025). The supplemental material for this article includes additional tests on focal mechanism inversion, aftershock location, Coulomb stress calculation, and spectral ratio analysis.
Supplemental Material
srl-2025259_supplement- pdf file
Files
srl-2025259_supplement.pdf
Additional details
Funding
- National Natural Science Foundation of China
- 42374079
- National Natural Science Foundation of China
- 42074053
- Institute of Geology and Geophysics
- DQJB19B30
- Institute of Geology and Geophysics
- JY2024Z01
Dates
- Available
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2025-12-02First online
Caltech Custom Metadata
- Caltech groups
- Division of Geological and Planetary Sciences (GPS) , Center for Geomechanics and Mitigation of Geohazards (GMG)
- Publication Status
- Published