Super-intense earthquakes more prevalent, some scientists say. Does it heighten San Andreas risk?

"Scientists have increasingly observed how the rupturing of a fault during an earthquake can be even faster than the speed of another type of damaging seismic wave, theoretically generating energy on the level of a sonic boom. These shock waves - created during "supershear" earthquakes - can worsen how bad the ground shakes both side to side and up and down along an affected fault area, scientists at USC, Caltech and the University of Illinois Urbana-Champaign wrote in a recent opinion article for the journal Seismological Research Letters."

"It is imperative that we update these scenarios to account for supershear rupture,"

"We must also reassess the vulnerability of infrastructure and update the relevant building code provisions - especially for critical facilities."

Supershear earthquakes occur when a fault rupture travels faster than shear waves, producing shock waves analogous to sonic booms. Those shock waves can amplify both horizontal and vertical ground motion along the affected fault. Observations indicate supershear ruptures are more common than previously believed, raising potential risk across California, including regions near the San Andreas Fault. Supershear effects could increase infrastructure vulnerability and intensify shaking beyond traditional forecasts. Some disagreement exists about whether supershear ruptures are inherently more destructive, yet seismic scenarios, hazard forecasts, and building-code provisions—especially for critical facilities—require reassessment to improve preparedness and resilience.

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