A recent study on the March 28, 2025 magnitude 7.8 earthquake in Myanmar suggests that a section of its fault rupture occurred at supershear velocity, reaching speeds of up to 5-6 kilometers per second. This phenomenon is rare and offers valuable insights into the earthquake’s behavior.
Researchers analyzed seismic and satellite imagery data to conclude that the rupture had a large slip of up to seven meters that extended over 85 kilometers north of the epicenter near Mandalay. The southern portion of the rupture showed a patchy slip, ranging from 1-6 meters. The researchers’ findings confirm initial reports suggesting supershear rupture in some parts.
Measurements taken at a seismic station near Nay Pyi Taw provided clear evidence for supershear rupture. Strong ground motion was recorded just 12 seconds after the initial weak P wave arrival, indicating fast fault movement. This observation is significant, as it allows seismologists to study the rupture passage up close.
The strong directivity of the rupture and supershear velocity may have contributed to the earthquake’s damaging impacts felt in distant areas like Bangkok. The researchers note that several large earthquakes along the Sagaing Fault have occurred before, but this event ruptured a previously quiet section of the fault.
Further research is needed to understand the characteristics of the “seismic gap” preceding the 2025 earthquake. However, the study suggests that long histories and better understanding of fault segmentation are required for accurate predictions. The researchers believe that another major event in the central area may not occur before a long period of rebuilding strain energy.
Source: https://phys.org/news/2025-07-myanmar-earthquake-fault-rupture-exceeded.html