How a 2.5-Meter Fault Slip Is Revolutionizing Earthquake Science

Ground Shifting in Real Time: A Breakthrough in Earthquake Science

A remarkable video captured the movement of the ground along Myanmar’s Sagaing Fault, offering an unprecedented glimpse into the mechanics of earthquake ruptures. Within just 1.3 seconds, the ground on either side of the fault shifted 2.5 meters sideways, recorded by a security camera. This footage, analyzed by researchers from Kyoto University, provides direct and quantitative evidence of coseismic fault slip, challenging previous assumptions and validating long-standing theories in seismology.

The breakthrough came from the use of pixel cross-correlation, a digital image correlation technique that allowed scientists to measure the displacement of the fault frame by frame. By tracking objects in the video, the team reconstructed the slip path with high precision. Their findings revealed that the fault moved at a maximum speed of 3.2 meters per second, with all 2.5 meters of displacement occurring in a single burst—a phenomenon known as a pulse-like rupture. As co-author Jesse Kearse explained, “The brief duration of motion confirms a pulse-like rupture, characterized by a concentrated burst of slip propagating along the fault, much like a ripple traveling down a rug when flicked from one end.”

Technical Methodology: Precision in Motion Tracking

The methodology used in this study was highly detailed. Scientists divided the video into 25 overlapping 26 × 26 pixel subsets, focusing on features located 70–80 meters from the camera. By isolating the displacement of stable features from those over the moving fault block, they eliminated artifacts caused by camera shake and ground motion. The team then calibrated the data using known-spaced fence posts, corrected for lens distortion and parallax, and converted pixel shifts into actual ground measurements. Using a 0.2-second moving average, they smoothed and differentiated the slip function, resulting in a high-resolution velocity profile of the rupture process.

The results suggest that the slip on the Sagaing Fault occurred as a smooth ramp-like function, with an amplitude of 2.5 ± 0.5 meters and a duration of 1.3 ± 0.2 seconds.

Curved Slip Path: A New Insight into Earthquake Dynamics

One of the most significant discoveries was the explicit visualization of a curved slip path. While geological records have long suggested that curved slickenlines and fault plane striations indicate dynamic, non-linear slip during earthquakes, such evidence has typically been interpreted after the fact. This video, however, provides real-time confirmation: the slip path initially began obliquely, with a rake as high as 35°, before transitioning to nearly pure strike-slip motion as the rupture slowed.

Kearse noted, “Instead of things moving straight across the video screen, they moved along a curved path that has a convexity downwards, which instantly started bells ringing in my head, because some of my previous research has been specifically on curvature of fault slip, but from the geological record.”

This curvature is not an anomaly but a key element of rupture mechanics. Dynamic rupture simulations have predicted that transient stresses within the cohesive zone ahead of the rupture front can cause oblique slip at the beginning, with the slip path becoming straighter as velocity peaks and subsides. This behavior aligns with observations from other major earthquakes, such as the 2025 Myanmar and 2016 Kaikōura events.

Implications for Seismological Models

The study also has practical implications for testing seismological models. By comparing on-fault slip velocity with near-fault ground velocity measured at a strong-motion station 2.7 kilometers away, the researchers found excellent consistency in amplitude, length, and character. This suggests that near-fault ground motion can serve as a reliable proxy for on-fault slip during large earthquakes.

However, there was a notable discrepancy in the estimation of the slip-weakening distance: 2.4 meters from strong-motion data versus 1.2 meters from on-fault observations. This difference is likely due to the complexity of off-fault effects and underscores the importance of on-fault measurements.

Advancements in Geophysical Monitoring

The broader context of this research lies in the development of digital image correlation (DIC) and remote sensing for geophysical monitoring. What were once laboratory experiments are now being applied in the field, enabling real-time, high-precision tracking of displacement. The application of DIC algorithms to monitor earth flows’ displacement is a growing area of study.

The reliability of these techniques, down to pixel-by-pixel accuracy, places them on par with, and often ahead of, traditional methods like GNSS or robotic total stations, especially in cases involving rapid or complex motion.

A New Standard for Earthquake Source Physics

This research bridges the gap between geological records, numerical models, and instrumental observations, establishing a new standard for earthquake source physics. “We did not anticipate that this video record would provide such a rich variety of detailed observations,” said Kearse. “Such kinematic data is critical for advancing our understanding of earthquake source physics.”

The next phase of the research will involve applying physics-based rupture models and dynamic friction laws to investigate the underlying controls on pulse-like, curved slip—now supported by direct observation rather than inference.