Surface ruptures of the Myanmar M7.7 earthquake mapped from space
An extremely long rupture is confirmed
ဤစာကို မြန်မာဘာသာဖြင့် ဖတ်ရန် (Google မှ အလိုအလျောက် ဘာသာပြန်သည်) ဤနေရာကို နှိပ်ပါ။
Citation: Bradley, K., Hubbard, J., 2025. Surface ruptures of the Myanmar M7.7 earthquake mapped from space. Earthquake Insights, https://doi.org/10.62481/51b7df8c
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Like our previous post, this discussion is only possible because scientists around the world are rapidly working to produce results and sharing those results with the world. In particular, we would like to acknowledge Zixin Lee, Zhenjiang Liu, Dr. Robert Zinke, Dr. Mary Grace Bato, Dr. Cole Speed, Dr. Eric Fielding, and Dr. Harsha Bhat, whose data and results are shown and discussed below, or who contributed in other ways.
Further notes: The site Mizzima provides Myanmar-specific news, and has a number of stories covering different aspects of the earthquake. The Myanmar Earthquake Committee and Myanmar Engineering Council are organizing efforts to inspect and assess building condition post-earthquake.
Finally, a number of organizations, including the United Nations, Doctors Without Borders, Red Cross, International Rescue Committee, and UNICEF, are raising funds to support rescue and relief efforts.
Edit: The USGS now has a data portal with both satellite imaging products and a downloadable shapefile for the fault trace.
Two days ago, we compiled early seismological analyses suggesting that the deadly M7.7 Myanmar earthquake was produced by a supershear rupture of the Sagaing Fault. Today, new data have been shared by scientists that directly confirm the great length of the rupture.
Mapping of movement of the ground surface from space reveals a clear surface rupture between Penwegon (18.2°N) and Kyauk-Myaung (~22.6°N), a distance of ~500 kilometers.
In the image below, blue pixels moved northward and red pixels moved southward. The surface rupture is indicated by a sharp contrast in the colors (red vs blue) of the images across the fault. We can see a distinct, slightly curved rupture that tracks the Sagaing Fault trace. Because the fault is oriented north-south and is strike-slip, the east-west component of motion (not shown) is much smaller.
The image above is a composite of results from two satellite missions: Sentinel-2, which imaged the central and northern parts of the rupture, and Sentinel-1, which imaged the southern part. In both cases, the movement of the surface is calculated by comparing pre- and post-earthquake images. The sensors on the two satellites are different, but the results match up perfectly where the images overlap. The resolution of the Sentinel-2 image is higher than that of the Sentinel-1 image.
At right on the figure above, we drew some profiles of the displacement across the Sagaing Fault. The sharp drop from positive to negative displacement shows the fault offset along each profile. We have marked the approximate fault location with a dotted line. As researchers begin to grapple with the details of this rupture, they will be looking at the sharpness of this drop to understand how much slip made it to the surface at different parts of the fault, which could tell us more about the overall rupture process.
Soon, new optical images will also be used to make the same kinds of observations of fault slip at the surface, but at a much higher resolution. The higher resolution will allow mapping of details like offset roads and landforms, as well as regions of liquefaction-induced slumping.
A similar image produced by Zixin Lee (National Taiwan University) also includes an estimate for the amount of slip along the length of the fault, reaching up to 4-5 meters, and showing more than 3 meters of slip at the surface along most of the rupture length. The alternating stripes oriented NNE-SSW in this image are just artifacts from the satellite strip geometry and can be ignored. This image shows a cleaner rupture as far south as Penwegon (~18.2°N) than our Figure 1; we are not sure where the difference in the mapping of this southern part of the rupture arises.
The deep rupture on the fault likely extended slightly beyond the area of visible surface rupture. Deep rupture without a surface break would be indicated by a more gradual color shift across the fault, and would be much harder to see in these data.
The Sentinel-1 images covering the southern end of the rupture have also now been used for InSAR, a method that can sense much smaller displacements of the surface than pixel tracking, and is sensitive to vertical as well as horizontal motions of the Earth’s surface. (See here for a description how InSAR works.) The image below, from Zhenjiang Liu, shows the InSAR fringes, which are sort of like contours of motion. Each band of repeating color represents one cycle of the radar wave, representing movement towards or away from the satellite by 2.8 centimeters. By adding up the number of fringes between the stable areas away from the fault and the fault itself, it is possible to estimate the amount of displacement. We expect to see “unwrapped” InSAR images — converting these fringes into displacement — soon.
Slip clearly extended southward to just north of Myo-Chaung, although the southernmost lobe is isolated from the main slip region to the north. The area of continuous large slip seems to reach as far south as ~18.5°N. This compares well with the southerly aftershocks as far south as ~18°N seen by the Thai seismic network, which we discussed in our last post.
We can expect that a lot more work and modeling will be done on both the pixel tracking and InSAR, aimed at mapping the slip along the fault and associated surface deformation. From these preliminary maps, we can already see that the pixel tracking and InSAR data both show that permanent ground displacement was concentrated along the fault line. This narrow zone is where the highest MMI (shaking) intensities also occurred during the earthquake.
The USGS slip model has also been updated. The new model incorporates estimates of surface slip of pixel tracking from Sentinel-2, and two strong motion seismic stations in Myanmar. We show the model below, roughly aligned with the surface offset data:
We note that the current slip model is in part inconsistent with the surface displacement of the fault: the slip model shows low slip south of Nay Pyi Taw, while the surface trace is still quite clear in the pixel tracking. The USGS says:
The apparent gap in rupture toward the south end of the model is likely due to the gap in observations south of the Sentinel-2 imagery and north of the MM site, YGN. Forthcoming observations are expected to confirm slip in that area. Updates are expected.
We expect that the Sentinel-1 mapping in the south will soon be incorporated into the slip model.
This highlights the great challenge of making fault rupture models when there is a possibility of supershear rupture: the usual scaling relationships that give good results for most earthquakes just don’t work very well, at least in this case. As a result, as new data have become available, both the slip model and the shaking estimates have gone through significant revisions.
Comparisons of rupture length
Overall, it is clear that the rupture is unusually long for a M7.7 event. The plot below, from Wells and Coppersmith (1994), shows a comparison of earthquake magnitude with surface rupture length for a large dataset of earthquakes.
How unusual is the rupture length?
More updated studies of continental strike-slip earthquakes (Hanks and Bakun, 2002, 2008) included 12 additional events between M7 and M8.1 (compared to Wells and Coppersmith). In that compilation, rupture lengths range from 40 km for the 1999 M7.1 Ducze earthquake in Turkey to 400 km for the Mw7.8 2001 Kokoxili earthquake. Last week, we also discussed two historical 8+ earthquakes in Mongolia that ruptured 350 km (1905 Mw8.1 Bolnay) and 260 km (the 1957 M8.1 Gobi-Altai Mongolia earthquake 260 km). Magnitude may be related to rupture length, but there is clearly a lot of variation!
The 2012 Mw8.6 Wharton Basin earthquake was the largest strike-slip event ever recorded, releasing ~20 times as much energy as the recent M7.7 in Myanmar. During that event, a cascade of ruptures probably broke over 800 kilometers of fault (probably; the uncertainties remain high for this remote event). However, that earthquake was sourced by a very complex rupture of multiple faults, some triggered by the first event, and does not represent slip on a single fault. The location of the event in the oceanic lithosphere also makes it impossible to compare usefully to earthquakes in continental regions.
We note that satellite imaging of the rupture has captured not just deformation due to the mainshock, but also integrated deformation due to aftershocks and to potential slow continuing slip on the fault after the main rupture. The largest aftershock so far was a M6.7, about 11 minutes after the mainshock. Because this earthquake occurred just south of the epicenter, it could not have contributed to the overall rupture length. The remaining aftershocks so have remained at or below M5.1, and so their impact on surface deformation must have been minimal.
So, we can pretty confidently say that the Mw7.7 is an exceptional earthquake.
Damage, death tolls, and ways to help
As we noted in our previous post, this unusually long surface rupture means two things. First, many people were very close to the rupture, meaning that many people and buildings experienced extremely high shaking intensities. The USGS PAGER now estimates that more than seven million people experienced intensity VIII or IX shaking (severe to violent); images of damage from around the rupture area certainly capture the effects of that shaking. In addition, the rupture passed within 1 kilometer of both Nay Pyi Taw and Mandalay airports, caused damage to both and hindering rescue efforts. The unfortunate locations of these airports has long been noted by earthquake scientists familiar with Myanmar. However, at least the fault trace didn’t run directly beneath the runways!
Examples of damage to buildings, due to both shaking and ensuing fires, are emerging online as people begin to analyze high-resolution satellite imagery. The following images were highlighted by Nathan Ruser on X, using Planet’s SkySat products.
Second, as we discussed in our previous post, the earthquake must have propagated very quickly, at speeds well above the speed at which shear waves typically travel through the crust. This confirms that the earthquake was a supershear rupture, and areas south of the epicenter may have experienced stronger shaking as a result, including potentially some regions well so the south (like Bangkok).
Dr. Harsha Bhat, an earthquake source physicist at the Centre National de la Recherche Scientifique (CNRS, France) wrote to us with a useful note about supershear ruptures:
One note to keep in mind is that the word shock front evokes dramatic
images of a supersonic aircraft and its sonic boom. Supershear shocks
are much milder. They do faithfully carry fault radiation with minimal
attenuation to large distances. But the impact on a structure from a
supershear Mach front is not clear as this is a very short part of the
rupture duration itself.
A final note: The danger of AI summaries of earthquakes
We were curious what the longest recorded strike-slip rupture was in the Wells and Coppersmith database, so we searched Google for the term “longest strike-slip earthquake rupture.” Much to our dismay, the Google AI results that were returned looked like this:
The super-geniuses at Google say that the March 28 Mw7.7 earthquake rupture was 1,200 kilometers long! The last earthquake rupture that long was the 2004 Sumatra-Andaman earthquake, a subduction event with a magnitude of 9.1.
Where could they have come by such wrong information? Surprise, surprise — it’s us! Our first post about the Myanmar earthquake is cited as a source for this wildly incorrect information.
We assume that digital brains can’t yet tell the difference between the length of a fault (~1,200 kilometers for the on-land part of the Sagaing Fault) and a fault rupture. The data sources to the right suggest that the AI is even confusing the Sagaing Fault with the San Andreas Fault, because they are roughly the same length, despite being located on opposite sides of the Earth. We hope our readers will understand these differences, even if their personal computing apparatus is low wattage and a bit soggy.
Amazingly, disappointingly, and disconcertingly, AI has also already been used to create false images and videos of damage following the earthquake, some of which have been been circulating on social media. We encourage our readers to vet their sources carefully. The use, and misuse, of AI in these situations is extremely troubling.
While we try to ignore AI Overviews in general, we have noticed that they tend to be particularly awful for earthquake and tectonics subjects. We strongly suggest that anyone interested in this topic avoid these AI summaries.
To end on a more positive note, further sleuthing (not using Google AI) eventually revealed that the longest rupture in the Wells and Coppersmith database was the 432 km-long rupture that produced the Mw7.9 1906 San Francisco earthquake. That event also suspected of being a supershear rupture, but of course there are no data that can test the idea.
As always, we solicit corrections, additions, or other perspectives in the comments!
References:
For references to the data images above, see the caption text.
Bradley, K. and Hubbard, J., 2025. Moderate M5.1 earthquake in Mongolia. Earthquake Insights, https://doi.org/10.62481/eb69363e
Bradley, K. and Hubbard, J., 2025. Updates on the Myanmar earthquake. Earthquake Insights, https://doi.org/10.62481/9e49eb4a
Hanks, T.C. and Bakun, W.H., 2002. A bilinear source-scaling model for M-log A observations of continental earthquakes. Bulletin of the Seismological Society of America, 92(5), pp.1841-1846. https://doi.org/10.1785/0120010148
Hanks, T.C. and Bakun, W.H., 2008. M-log A observations for recent large earthquakes. Bulletin of the seismological society of America, 98(1), pp.490-494. https://doi.org/10.1785/0120070174
Hill, E.M., Yue, H., Barbot, S., Lay, T., Tapponnier, P., Hermawan, I., Hubbard, J., Banerjee, P., Feng, L., Natawidjaja, D. and Sieh, K., 2015. The 2012 Mw 8.6 Wharton Basin sequence: A cascade of great earthquakes generated by near‐orthogonal, young, oceanic mantle faults. Journal of Geophysical Research: Solid Earth, 120(5), pp.3723-3747. https://doi.org/10.1002/2014JB011703
Hubbard, J. and Bradley, K., 2025. Catastrophic M7.7 earthquake caused by rupture of Sagaing Fault in Myanmar. Earthquake Insights, https://doi.org/10.62481/9250a38a
Hubbard, J. and Bradley, K., 2023. Did the High Atlas really grow 20 cm in the Moroccan earthquake?. Earthquake Insights, https://doi.org/10.62481/9cb23fd9
Wells, D.L. and Coppersmith, K.J., 1994. New empirical relationships among magnitude, rupture length, rupture width, rupture area, and surface displacement. Bulletin of the seismological Society of America, 84(4), pp.974-1002. https://doi.org/10.1785/BSSA0840040974
Seismotectonics is certainly being helped along by this newsletter. I was stimulated to try to understand the concept of "supershear". After a while I found this helpful work "CRACKS FASTER THAN THE SHEAR WAVE SPEED" by A.J. Rosakis, 0. Samudrala and D. Coker in 1998. They suggest supershear requires a mode II rupture in a material with a preloaded planar weakness, with the zone of stress accumulation coinciding with the alignment of the future fracture plane. Just as a jet can break the sound barrier, and create a sonic boom, the physics of rupture propagation does not intrinsically limit the velocity of the rupture tip to the speed of wave propagation. However, once the 'sonic boom' takes place, a distal observer experiences the effect of wave interference. In this case, estimates of moment magnitude seem weirdly low, suggesting destructive interference, or perhaps even that estimation methods should not infer point source emanation of the radiating energy patterns.
The question of why a supershear rupture can be so long is an even more interesting one . An earthquake rupture harvests stored elastic strain energy. How much energy an earthquake rupture is therefore capable of releasing depends on: i) the 3D geometry of the energy patches being harvested; and on: ii) the ability of the expanding rupture to track that geometry. If the rupture propagation direction should diverge from the alignment of the energy patches, that earthquake comes to a halt. The rupture becomes no longer capable of continuing the harvest.
Supershear therefore depends on two factors: i) the existence of a long smoothly curving fault without significant splays; and ii) overall orthogonal to the strike-slip fault, the existence of an extensional regime that swings σ1 (the axis of principle compressive deviatoric stress) towards parallelism with the wrench system. This single factor overall controls the morphology of the fault network, and the wrench system in Myanmar is a classic example of the simplifying effects on fault geometry that result from an overall transtensional regime. In this case the extensional regime is distal, driven by "collapse over" in the foreland, as the crust moves to follow a retreating subducting transform fault, in a direction orthogonal overall to relative plate motion.
This paper claims there is evidence of the 1906 San Francisco earthquake rupture being supershear:
"teleseismic body-wave data can be reconciled with the geodetically derived slip model by allowing supershear rupture."
https://pubs.geoscienceworld.org/ssa/bssa/article-abstract/98/2/823/350136/A-Unified-Source-Model-for-the-1906-San-Francisco