Although not everyone agrees that supershear earthquakes are inherently more destructive than other types, the potential implications are massive and need to be accounted for in seismic forecasts, the scientists contend. <\/p>\n
\u201cIt is imperative that we update these scenarios to account for supershear rupture,\u201d scientists wrote in the opinion article. \u201cWe must also reassess the vulnerability of infrastructure and update the relevant building code provisions \u2014 especially for critical facilities.\u201d<\/p>\n
Earthquakes are the result of one block of earth moving away from another. This action starts at an epicenter and moves in one or more directions down a fault, sometimes for hundreds of miles over a matter of minutes. On a fault like the San Andreas<\/a>, the earthquake moves like a train barreling full speed down the tracks. <\/p>\n Traditionally, it was thought that the rupturing of a fault moved slower than another type of damaging seismic wave, known as a shear wave. Generally speaking, shear waves cause a great deal of the destructive shaking power in an earthquake. <\/p>\n But in the last few decades, scientists have increasingly observed how the rupturing of a fault during an earthquake can be even faster in some cases. <\/p>\n \u201cThis generates something similar to the sonic boom, when an aircraft exceeds the speed of sound,\u201d said Ahmed Ettaf Elbanna, the lead author of the opinion piece and a USC professor of earth science and civil engineering.<\/p>\n Not everyone agrees on the implications, however. <\/p>\n \u201cI don\u2019t think we know yet whether supershear ruptures really are more destructive,\u201d said U.S. Geological Survey research geophysicist Brad Aagaard, who wasn\u2019t involved in the opinion article. <\/p>\n \u201cThe opinion piece calls out for more effort to really try and understand both where supershear ruptures are likely to occur and the implications,\u201d Aagaard said. <\/p>\n The idea that the rupture on a fault can move even faster than the seismic shear wave was theorized as early as the 1970s, said Elbanna, who is set to become director of the Statewide California Earthquake Center next year.<\/p>\n But by the turn of the century, there had been only one earthquake globally that some scientists suspected was a supershear event \u2014 the magnitude 6.4 Imperial Valley earthquake of 1979.<\/p>\n It was only in the late 1990s that the idea of supershear earthquakes began to be taken more seriously. Lab experiments at Caltech showed they were physically possible. And in the last quarter-century, a growing number of earthquakes of magnitude 7 or greater have been determined to be supershear, observations that have been assisted by the installation of monitoring devices around the world. <\/p>\n A key breakthrough came during the magnitude 7.9 earthquake in Alaska in 2002, where a sensor station happened to be close enough to the ruptured Denali fault to record data confirming what scientists would expect from a theoretical supershear earthquake, Elbanna said. <\/p>\n Since then, scientists have identified more earthquakes as such events. <\/p>\n \u201cWe\u2019re getting better data, and so now we see this,\u201d said seismologist Lucy Jones, a Caltech research associate. <\/p>\n In just the last 15 years, 14 of 39 large strike-slip earthquakes have exhibited features of supershear ruptures, the opinion article said. <\/p>\n Among them were the magnitude 7.7 earthquake in Myanmar<\/a> in March, which killed more than 3,700 people; as well as the dual magnitude 7.8 and 7.5 earthquakes that killed more than 58,000 people across Turkey<\/a> and Syria in 2023<\/a>; and the magnitude 7.5 earthquake and tsunami of 2018<\/a> in Indonesia, which killed at least 2,000 people.<\/p>\n Scientists also now consider a magnitude 7.6 earthquake that struck Turkey in 1999<\/a> to be a supershear earthquake. That quake killed at least 17,000 people.<\/p>\n \u201cWe are detecting them more frequently than before,\u201d Elbanna said. <\/p>\n A look back at the massive 1906 earthquake that destroyed much of San Francisco suggests a likely supershear event too, the opinion piece said, citing a report<\/a> published in 2008 in the Bulletin of the Seismological Society of America.<\/p>\n In California, supershear earthquakes would be expected on the straightest of \u201cstrike-slip<\/a>\u201d faults \u2014 in which one block of earth slides past another \u2014 like the San Andreas and perhaps the Garlock, which runs through the Mojave Desert along the Tehachapi Mountains, Aagaard said. <\/p>\n There are a number of communities directly on top of the San Andreas fault. Among them are Coachella, Indio, Cathedral City, Palm Springs, Desert Hot Springs, Banning, Yucaipa, Highland, San Bernardino, Wrightwood, Palmdale, Gorman, Frazier Park, San Juan Bautista, Palo Alto, Portola Valley, Woodside, San Bruno, South San Francisco, Pacifica, Daly City and Bodega Bay.<\/p>\n![\"\"](\"https:\/\/www.newsbeep.com\/us-ca\/wp-content\/uploads\/2025\/10\/1760523547_848_hqdefault.jpg\")
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