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On March 28, 2025, a magnitude 7.7 tremor hit the Southeast Asian nation of Myanmar along the Sagaing Fault, leading to the deaths of thousands and extensive destruction. A recent investigation from Caltech utilizes satellite imagery of the Sagaing Fault’s movement to enhance models predicting future fault behavior. The research suggests that strike–slip faults, such as the Sagaing and San Andreas, could produce earthquakes that differ markedly from previously recorded events and may be considerably larger.
The investigation was mainly conducted in the laboratory of Jean-Philippe Avouac, the Earle C. Anthony Professor of Geology and Mechanical and Civil Engineering, who is also the director of the Center for Geomechanics and the Mitigation of Geohazards. Postdoctoral researcher Solène Antoine serves as the principal author of the study. The findings are detailed in a paper published in the journal Proceedings of the National Academy of Sciences on August 11.
The Sagaing Fault extends in a relatively straight north-south direction throughout Myanmar. As its two sides gradually shift against each other in opposing directions, stress builds up along the fault. When this stress accumulates to a breaking point, the fault slips swiftly, resulting in an earthquake. Given their similarities—both are relatively straight strike-slip faults extending hundreds of kilometers—the 2025 Myanmar quake provides insights into potential future seismic events on the San Andreas Fault.
“This earthquake proved to be an excellent case for applying image correlation techniques [methods for comparing images before and after a geological occurrence] developed by our research team,” Antoine states. “These techniques enable us to assess ground displacements at the fault, where the alternative method, radar interferometry, fails due to phenomena like decorrelation [a process to separate signals] and limited sensitivity to north-south shifts.”
From the analysis of historical earthquakes along the Sagaing Fault, scientists predicted that a significant earthquake would occur on a 300-kilometer stretch that had not experienced a large event since 1839. This theory is referred to as the seismic gap hypothesis: sections of a fault that are immobilized are expected to slip to “catch up.” While this section did rupture during the 2025 quake, the fault actually slipped over a total of more than 500 kilometers, indicating that it made up the shortfall in slip and additional movement besides.
In their recent study, the team employed correlation of satellite optical and radar images of the fault—a technique initially created in the Avouac laboratory and now widely adopted in seismology—and its surroundings to determine that the 500-kilometer segment shifted a net of 3 meters after the quake, meaning the eastern side moved south by 3 meters in relation to the western side.
Current models employed for seismic hazard evaluation primarily rely on earthquake statistics and are time-independent, signifying they can only project probabilities of an earthquake within a selected timeframe. For instance, these models might estimate, for any specified 30-year period in a given area, the likelihood that an earthquake would surpass a predetermined magnitude. However, it is essential for models to consider how recently a fault has moved, where the movement took place, and the magnitude of that slip in order to provide truly informed estimates of potential seismic hazards for defined time intervals—such as the upcoming 30 years.
“The research indicates that future earthquakes may not merely replicate previously recorded quakes,” Avouac remarks. “Subsequent ruptures of a particular fault, even as straightforward as the Sagaing or San Andreas faults, can differ significantly and can release more than the shortfall of slip since the last event. Furthermore, historical documentation is generally far too brief for statistical models to capture the full spectrum of possible earthquakes and eventual recurrence patterns. Physics-based models offer an alternative approach, with the advantage that they could, in principle, be calibrated to observations and utilized for time-dependent forecasting.”
The paper is titled “The 2025 Mw7.7 Mandalay, Myanmar, earthquake reveals complex earthquake cycle with clustering and variable segmentation on Sagaing fault.” Besides Antoine and Avouac, Caltech co-authors include graduate student Rajani Shrestha, postdoctoral researcher Chris Milliner, and senior research scientist Kyungjae Im. Additional co-authors are Chris Rollins (PhD ’18) from GNS Science Te Pu Ao in New Zealand, Kang Wang of EarthScope Consortium Inc., and Kejie Chen of Southern University of Science and Technology in China. Funding has been provided by the Center for Geomechanics and Mitigation of Geohazards, the Statewide California Earthquake Center, the National Science Foundation, and the US Geological Survey.
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