More Than 200 Earthquakes Just Rattled California | WIREDLos Angeles residents should brace themselves for a big earthquake, Nasa has warned.The space agency says it is 99.9 per cent sure that LA will be hit by a 5.0 magnitude earthquake in the next three years.It's basing its prediction on a study of the La Habra earthquake that shook Greater Los Angeles last year.But in a rare public disagreement, the US Geological Survey (USGS) has said Nasa's analysis is wrong, and there's only 85 per cent chance this could happen.
Several earthquake swarms have struck the Calaveras since the 1970s, and none of them have triggered a big earthquake. If history is any indication, says Kaven, the swarm is likely to last another two weeks with the total number of quakes going into the hundreds. The longest recorded swarm in the area lasted 42 days.NASA warning: '99.9 percent chance' of California earthquake | AL.com
The particular geology of the Calaveras fault makes it prone to earthquake swarms. The fault is creeping along at a more or less constant rate, and it has many different secondary faults branching perpendicularly from the main Calaveras fault, like twigs coming off a branch. When one of those secondary faults gets critically stressed, it could set off a swarm. The quakes in swarms are small, usually 4.0 or below, because those secondary faults are small; not much energy is stored in them in the first place.
NASA's has a warning for California: Get ready for an earthquake.
A new study from the space agency's Jet Propulsion Laboratory in California said there was a 99.9 percent chance that Los Angeles will experience an earthquake of at least 5.0 magnitude in the next 2 ½ years.
The study was published in the journal Earth and Space Science.
The determinations were made by using GPS and airborne radar to measure stress in tectonic fault lines following the 2014 La Habra earthquake that had a magnitude of 5.1.
"If you think of pulling on a rubber band, you stretch it and stretch it, and if you pull on it hard enough, it's going to break," NASA geophysicist Andrea Donnellan told The Huffington Post, comparing the rubber band to the earth's crust. "The earthquakes are the breaking rubber band. So what we did in this study is we showed what stored potential was still in the northeast LA basin and northern Orange County."
A 5.0 earthquake is considered moderate but an event of that size in Los Angeles could result in millions of dollars of damage. The LaHabra earthquake caused an estimated $12 million in damages; a 2013 quake near Napa, California in 2015 killed one person and caused an estimated $300 million in damages. That earthquake measured 6.1.