Californians have been hearing for decades that an enormously powerful earthquake called the Big One could strike at any time, and a recent study by Caltech shows that such a quake could reach farther than previously thought, potentially including both San Francisco and Los Angeles.
Although the state is well-known as earthquake country, there are some areas with relatively stable ground, or tectonic plates that "creep" instead of slip quickly. One such area acts as a barrier between Northern and Southern California, but a new Caltech quake model published Wednesday in the journal Nature challenges that notion.
"What we have found, based on laboratory data about rock behavior, is that such supposedly stable segments can behave differently when an earthquake rupture penetrates into them. Instead of arresting the rupture as expected, they can actually join in and hence make earthquakes much larger than anticipated," said study coauthor Nadia Lapusta, professor of mechanical engineering and geophysics at Caltech.
The study draws on data from the magnitude-9.0 Tohoku-Oki earthquake in Japan, which generated a massive tsunami and caused a nuclear reactor meltdown in 2011. That quake confounded seismologists because some areas where the quake struck were previously thought to be more stable.
The new models suggests that seismic hazard may have to be re-evaluated in many areas, including an earthquake on the San Andreas fault that extends far beyond its epicenter.