How an ‘ancient landslide’ keeps threatening a railroad, homes in San Clemente
SAN CLEMENTE, Calif. — Two earthquakes struck in the same area almost simultaneously on a hot afternoon in 2011, killing an Amtrak train passenger and killing at least 15 people.
The first quake, a 5.3-magnitude tremor, was felt across much of Southern California and was followed by a 2.7-magnitude aftershock more than 5 hours later. The shaking continued for 13.5 hours.
It’s the deadliest earthquake in US history.
But the area — a fault zone that had been dormant for three centuries — re-awakened in the 1990s, when a geologic anomaly known as the San Andreas fault moved to its present position, according to The New York Times. The fault is thought to have ruptured at least twice within the past 2,300 years and moved to its current position along the fault.
The area is now subject to what may be the most active fault in the world, experts say, and a recent study found strong evidence that the San Andreas fault is shifting again.
The earthquake hit just as a new government earthquake-preparedness report was being released by the Federal Emergency Management Agency. The report said that the most significant earthquake that has struck the region for more than a century was still unfolding.
The area, which includes Malibu and parts of Ventura and Santa Barbara counties, could be vulnerable to a major earthquake, said David Smith, a geologist at Caltech who has studied the San Andreas fault.
The 2011 temblor is only the sixth in the last 100 years. The most powerful earthquake was a magnitude 8.2 quake in 1960, when it hit off the coast of Chile and damaged the cities of Concepcion and Talcahuano, killing more than 300 and causing more than $1 billion in damage.
The 2011 quake comes at a time when the area is feeling increasingly more seismic activity, based on measurements made by the U.S. Geological Survey. The California Geological Survey reported last week that it expects