One-month earthquake forecast for western Myanmar following the devastating magnitude 7.7 Mandalay shock

Our short-term forecast suggests that between now and May 1, between 1 and 4 shocks greater than or equal to magnitude 4.0 are expected — fortunately a low rate. Much larger shocks are possible, but unlikely.
 

By Shinji Toda (Tohoku University) and Ross S. Stein (Temblor, Inc.)
 

Citation: Toda, S. and Stein, R. S., 2025, One-month earthquake forecast for western Myanmar following the devastating magnitude 7.7 Mandalay shock, Temblor, http://doi.org/10.32858/temblor.360
 

On March 28 at 12:51 p.m. local time (6:21 a.m. GMT), a magnitude 7.7 earthquake struck near Mandalay, Myanmar (Figure 1). The focal mechanism reported by the U.S. Geological Survey indicates that this earthquake was strike-slip, which means that one side of the fault moved horizontally past the other. About 11 minutes later, a magnitude 6.7 aftershock struck to the south. As of this writing, more than 3,000 deaths have been reported. A high-rise building under construction in neighboring Thailand also collapsed, 1,000 kilometers away.
 

 

The Mandalay earthquake struck on the right-lateral Sagaing fault, along a section with a slip rate of 24 millimeters per year based on GPS data (Tin et al., 2022). In 1946, a magnitude 7.7 earthquake struck just to the north of (or slightly overlapping) the rupture of the March 28 quake.

Here, we present a one-month earthquake forecast for western Myanmar. This analysis follows from a calculation by Xiong et al. (2017) that demonstrated that the section of the Sagaing fault that ruptured on March 28 had the highest accumulated stress. We extend this approach to make a short-term forecast of the likely number of shocks greater than or equal to magnitude 4.0, and find it to be 2.5 ± 1.0 earthquakes.
 

A catastrophe, but not a surprise

The documented toll of this earthquake continues to increase. Satellite imagery and ground photographs reveal massive damage, including numerous building collapses and fires that spread along a 400-kilometer-long band slicing through the country, encompassing its two largest cities, Mandalay, and Myanmar’s capital, Naypitaw.

Although no one predicted the Mandalay shock, it was not unforeseen. The Saigang fault’s very high slip rate of 24 millimeters per year was established by GPS data (Tin et al., 2022), and a comprehensive seismic hazard model and map for Myanmar identified the entire 1,200 kilometer length of the Sagaing fault as having among the highest shaking likelihood in the country (Yang et al., 2023). The Sagaing fault is matched only by the Sumatra-Java subduction zone that lies just off the west coast, site of a 1762 megathrust shock of about magnitude 8.8 (Cummins, 2007). Hubbard and Bradley (2025) and Bradley and Hubbard (2025) have reviewed much of this evidence, including the satellite evidence of at least a 350 kilometer long rupture.

But perhaps the most prescient analysis was a calculation of the cumulative Coulomb stress imparted by the ten shocks along the Sagaing fault that have occurred since 1906 with magnitudes greater than or equal 6.5 (Xiong et al., 2017). The ‘Coulomb stress hypothesis’ posits that failure on a fault is promoted when a nearby earthquake causes the shear stress on the fault to increase and the fault to be unclamped; when the shear stress decreases and the fault is further clamped, failure is inhibited (start here in the Coulomb stress video to understand what these stresses are and why they matter).

Back in 2017, Xiong et al. identified the section of the fault that ruptured on March 28 as the most promoted toward failure (Figure 2). Of course, there are large uncertainties in these calculations because the slip and rupture length of the historical quakes are not well known. But Xiong et al. (2017) serves as one among many successful prospective tests of the Coulomb hypothesis of earthquake interaction, a scientific advance wrested from a human catastrophe.
 

 

Quiet before the storm

If the section of the Sagaing fault that ruptured was indeed close to failure, one might expect it to show a higher rate of small shocks on or near the fault, but that’s not what we see. Instead, most of the future magnitude 7.7 rupture was quiet over the past three decades (Figure 3). This seems to be typical of the half-dozen earthquakes of similar or greater magnitudes that have occurred on continental strike-slip faults like the Sagaing. At the very least, this means we cannot expect foreshocks to reveal the proximity to failure. But the observation also suggests that these long strike-slip ‘transform’ faults can rupture when the shear stress is well below the shear stress expected for failure (Stein and Bird, 2024).
 

 

What next?

The Coulomb stress imparted by the magnitude 7.7 Mandalay shock includes good news — stress shadows where the quake rate should ultimately drop — and bad news — the stress trigger lobes where the quake rate should immediately rise (Figure 4). The top panel in Figure 4 is easier to understand, but oversimplifies the geometry of the faults that receive the stress transferred by the earthquake. In reality, the receiver faults are not parallel and right-lateral, as assumed in this calculation; the mapped faults are shown as thin green lines, and they are far from parallel.

The lower panel of Figure 4, offers a more realistic but patchier representation of stress transfer. The beachballs are ‘focal mechanisms,’ which depict the actual, rather than idealized, geometry of the surrounding faults. Where beachballs are red, fault failure is promoted (more likely); where blue, failure is inhibited (less likely). The map annotation next to the dotted ellipses indicate that the patterns generally resemble the simple version depicted in the top panel, with three zones of shadowed (blue) faults, and three of triggered (yellow-red) faults.
 

 

The forecast

We furnish a short-term forecast for two reasons: It is testable, and it could have societal value. We make the forecast (upper panel of Figure 5) by combining the Coulomb stress transfer in the lower panel of Figure 4 with the theory of ‘rate/state friction’ (Dieterich, 1994). Even though the stress changes are permanent, rate/state friction accounts for the decaying effect of seismicity. Further, rate/state friction holds that areas with a high background seismicity rate are most responsive to the stress imparted by a mainshock; in contrast, in areas with a low background seismicity rate, stress increases and decreases have almost no impact. For the background — or longterm — seismicity rate (lower panel of Figure 5), we use the Global Earthquake Activity Rate (GEAR1) model of Bird et al. (2015). Our forecast strategy is explained in Toda and Stein (2018) and Toda and Stein (2020).

We anticipate 2.5 ± 1.0 shocks by May 1. In other words, we expect between 1 and 4 shocks greater than or equal to magnitude 4 in the next month in western Myanmar. We also specify where that likelihood is greatest (along the rupture, shown as red pixels) and where it is least likely (the 50 to 100 kilometer-wide white area just west of the rupture). The forecast can later be objectively evaluated on both these criteria.

It’s important to emphasize that our use of magnitude 4.0 is not diagnostic. Rather, shocks much larger than magnitude 4.0 are possible, but less likely. You can think of this likelihood as 2.5 shocks of magnitude 4.0 being roughly equal to 0.25 magnitude 5.0 shocks (or one chance in four of experiencing an earthquake of magnitude 5.0). That’s because as magnitudes increase by one unit, their frequency generally drops by a factor of ten.

What is the greatest weakness of our forecast? The more irregular and patchy the slip in the rupture, the more stress spikes or ‘asperities’ remain on the fault, potentially triggering quakes. Slip models (also known as ‘finite fault models’) are over-smoothed, so one could regard our forecast as a lower bound. Though unlikely, the off-fault stress triggering lobes in the top panel of Figure 4 could also be the sites of much larger (say, magnitude 7) events. We hope this will not be so.
 

 

What can be learned?

Worldwide, there are forty named continental transform (major strike-slip) faults like the Sagaing fault, so what we can learn from the Mandalay quake has wide applicability.

The Sagaing and San Andreas, for example, share the same length (1,200 kilometers), the same slip rate (20-24 millimeters per year) and similar earthquake histories (three shocks greater than or equal to magnitude 7.6 since 1906 on the Saigang; two shocks greater than or equal to magnitude 7.8 since 1857 on the San Andreas). In that spirit, we offer this forecast to test our understanding of how earthquakes on these great faults interact. We will later report how the forecast fared, and what it taught us.

 

References

Bird, P., Jackson, D. D., Kagan, Y. Y., Kreemer, C., & Stein, R. S. (2015). GEAR1: A global earthquake activity rate model constructed from geodetic strain rates and smoothed seismicity. Bulletin of the Seismological Society of America, 105(5), 2538-2554.

Bradley, K., Hubbard, J. (2025). Surface ruptures of the Myanmar M7.7 earthquake mapped from space. Earthquake Insights. https://doi.org/10.62481/51b7df8c

Cummins, P. R. (2007). The potential for giant tsunamigenic earthquakes in the northern Bay of Bengal. Nature, 449(7158), 75-78.

Dieterich, J. (1994). A constitutive law for rate of earthquake production and its application to earthquake clustering. Journal of Geophysical Research: Solid Earth, 99(B2), 2601-2618.

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



Stein, R. S., & Bird, P. (2024). Why do great continental transform earthquakes nucleate on branch faults?. Seismological Research Letters, 95(6), 3406-3415.

Toda, S., & Stein, R. S. (2020). Long‐and short‐term stress interaction of the 2019 Ridgecrest sequence and Coulomb‐based earthquake forecasts. Bulletin of the Seismological Society of America, 110(4), 1765-1780.

Toda, S., & Stein, R. S. (2018). Why aftershock duration matters for probabilistic seismic hazard assessment. Bulletin of the Seismological Society of America, 108(3A), 1414-1426.

Tin, T. Z. H., Nishimura, T., Hashimoto, M., Lindsey, E. O., Aung, L. T., Min, S. M., & Thant, M. (2022). Present-day crustal deformation and slip rate along the southern Sagaing fault in Myanmar by GNSS observation. Journal of Asian Earth Sciences, 228, 105125.

Xiong, X., Shan, B., Zhou, Y. M., Wei, S. J., Li, Y. D., Wang, R. J., & Zheng, Y. (2017). Coulomb stress transfer and accumulation on the Sagaing Fault, Myanmar, over the past 110 years and its implications for seismic hazard. Geophysical Research Letters, 44(10), 4781-4789.

Yang, H. B., Chang, Y. K., Liu, W., Sung, G. Y., Gao, J. C., Thant, M., … & Chan, C. H. (2023). Probabilistic seismic hazard assessments for Myanmar and its metropolitan areas. Geoscience letters, 10(1), 48.
 

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