Supershear Earthquakes: Their Occurrence and Importance for Seismic Hazard, Early Warning, and Design Standards

Strike-slip faults—where tectonic plates grind past each other horizontally—are a defining feature of many densely populated continental seismic zones worldwide, including the San Andreas fault system in California, the North and East Anatolian faults in Türkiye, and the Sagaing fault in Myanmar (Burma). Although their lateral motion has long been recognized, a growing body of global evidence is now highlighting a more hazardous aspect of these systems: supershear earthquakes—fast propagating ruptures that exceed the speed of shear waves and can cause disproportionately intense shaking and destruction. Four of the last six Mw 7.0+ earthquakes on strike-slip faults have been recognized as supershear events, including the damaging Mw 7.7 Myanmar and the Mw 7.8 Pazarcik earthquakes, highlighting the need to confront the potential implications of such future events.