Myanmar Earthquake: Supershear Rupture Causes Devastation
Myanmar Earthquake Ruptured at Supersonic Speeds, Scientists Reveal
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A recent earthquake in Myanmar has provided seismologists with compelling evidence of a rare phenomenon: a fault rupturing at speeds exceeding that of sound. Teh March earthquake, which struck along the Sagaing Fault, exhibited characteristics that Thorne Lay, a seismologist at UC Santa Cruz, described as “promptly convincing of supershear rupture.”
The Science Behind Supersonic Earthquakes
Supershear rupture occurs when a fault breaks at a velocity faster than the shear wave velocity of the surrounding rock. This means the rupture is moving faster than the seismic waves it generates, a phenomenon that was once thought to be impractical.
“That was unusually clear and convincing evidence for supershear rupture relative to other long strike-slip events that I have worked on,” Lay stated in a Seismological Society of America statement. He explained that the ground motion data showed a distinct time gap between the initial, weak P-wave arrival and the arrival of notable shear offset at a seismic station. An offset, in seismological terms, refers to the displacement of the ground along a fault line during an earthquake.
lay and his team believe that this supershear velocity, combined with the earthquake’s strong directivity, may have contributed to the widespread damage observed. Directivity refers to the phenomenon where seismic waves pile up in the direction of fault rupture, leading to more intense shaking in that specific area. In this case, the rupture’s directivity was towards the south.
The Sagaing Fault: A History of Activity
The Sagaing Fault is a major geological feature known for frequently generating large earthquakes. Though, the March event involved a segment of the fault between the cities of Mandalay and Nay Pyi Taw that had been seismically quiet as 1912.
“Longer histories and better understanding of fault segmentation and geometry are needed to have any guidance for future event activity,” Lay commented.He added that he wouldn’t expect this central area of the fault to experience another major rupture for a considerable time, allowing for the rebuilding of strain energy.
Advancements in Earthquake Early Warning
While predicting earthquakes with pinpoint accuracy remains elusive, earthquake early-warning (EEW) systems offer a critical last-minute alert. These systems transmit electronic alerts that travel faster than seismic waves, providing precious seconds or minutes of warning before the most intense shaking arrives.
Many seismically active regions lack the necessary infrastructure for conventional EEW systems. Though, the smartphone-based Android Earthquake Alerts (AEA) system has recently emerged as a highly efficient choice, proving to be as effective as established seismic networks in detecting and alerting people to earthquakes.