Published August 11, 2025 | Version Published
Journal Article Open

The 2025 Mw 7.7 Mandalay, Myanmar, earthquake reveals a complex earthquake cycle with clustering and variable segmentation on the Sagaing Fault

  • 1. ROR icon California Institute of Technology
  • 2. Earth Sciences New Zealand, Lower Hutt 5011, New Zealand.
  • 3. Department of Earthquake Physics and Statistics, EarthScope Consortium Inc., Washington, DC 20005.
  • 4. ROR icon Southern University of Science and Technology

Abstract

We use remote sensing observations to document surface deformation caused by the 2025 Mw 7.7 Mandalay earthquake. This event is a unique case of an extremely long (~510 km) and sustained supershear rupture probably favored by the rather smooth and continuous geometry of this section of the structurally mature Sagaing Fault. The seismic rupture involved the locked portion of the fault over its entire depth extent (0 to 13 km) with a remarkably uniform slip distribution that averages 3.3 m, and an average stress drop of 4.7 MPa. No shallow-slip deficit is observed. The rupture extent challenges usual scaling laws relating earthquake magnitude, fault length, and slip. The fault ruptured along a known seismic gap that last ruptured in 1839 and tailed off into sections that ruptured during large earthquakes in 1930 and 1946. The amplitude and spatial distribution of fault slip in the 2025 event conform only approximatively to the slip-predictable model and the segmentation inferred from the fault geometry and past ruptures. Plausible sequences of earthquakes with variable magnitude, segmentation, and return periods, including events similar to the 2025 earthquake are produced in quasidynamic simulations using a simplified but nonplanar fault geometry. Based on this simulation, Mw >7.5 events return irregularly with an interevent time of ~141 y on average and a SD of ~40 y. The simulation is consistent with the historical seismicity and with the maximum magnitude ~Mw 7.9 and return period (~250 y) derived from moment conservation. Data assimilation into such simulations could provide a way for time-dependent hazard assessment in the future.

Copyright and License

© 2025 the Author(s). Published by PNAS. This article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).

Acknowledgement

This work was carried at the California Institute of Technology with support from the center for Geomechanics and Mitigation of Geohazards, from the Statewide California Earthquake Center (SCEC; award 25232), the National Key R&D Program of China (Grant 2024YFC3012803), and the National Natural Science Foundation of China (Grant 42474046). This is SCEC contribution nº14228. SCEC is funded by the NSF Cooperative Agreement EAR-2225216, and the United States Geological Survey Cooperative Agreement G24AC00072-00. We thank Kerry Sieh and Gilles Peltzer for providing detailed and thoughtful comments and suggestions which helped improve the manuscript substantially.

Data Availability

Sentinel2 images were accessed at https://dataspace.copernicus.eu/ (68). Detailed information on the image dates is provided in the SI Appendix, Table S1. COSI-Corr https://github.com/SaifAati/Geospatial-COSICorr3D (69), StackProf https://github.com/IPGP/stackprof (70), Quake-DFN https://github.com/limkjae/Quake-DFN (71), and ISC-GEM catalog https://www.isc.ac.uk/iscgem/request_catalogue.php (72) are open source. Supplementary figures and text provide additional details on the methodology and the results of this study. Surface displacement maps, offset measurements, and finite slip model are publicly available at https://doi.org/10.6084/m9.figshare.29430056.v2 (73). All other data are included in the manuscript and/or SI Appendix.

Supplemental Material

Appendix 01 (PDF)

Additional Information

This contribution is part of the special series of Inaugural Articles by members of the National Academy of Sciences elected in 2025.

Files

antoine-et-al-the-2025-mw7-7-mandalay-myanmar-earthquake-reveals-a-complex-earthquake-cycle-with-clustering-and.pdf

Additional details

Funding

Southern California Earthquake Center
25232
Ministry of Science and Technology of the People's Republic of China
National Key R&D Program 2024YFC3012803
National Natural Science Foundation of China
42474046
National Science Foundation
EAR-2225216
United States Geological Survey
G24AC00072-00

Dates

Accepted
2025-07-03

Caltech Custom Metadata

Caltech groups
Center for Geomechanics and Mitigation of Geohazards (GMG), Seismological Laboratory, Division of Geological and Planetary Sciences (GPS)
Publication Status
Published