EarthquakesWorries in southern California: San Andreas fault “locked, loaded, and ready to roll”

Published 9 May 2016

Top seismologists have warned residents of southern California that the region is overdue for a major earthquake. The San Andreas fault is “locked, loaded and ready to go,” said Thomas Jordan, director of the Southern California Earthquake Center. Meanwhile, in the Pacific Northwest, Mount St Helens is waking up, with  as many as 130 small earthquakes detected beneath the mountain in recent weeks.

Top seismologists have warned residents of southern California that the region is overdue for a major earthquake. The San Andreas fault is “locked, loaded and ready to go,” said Thomas Jordan, director of the Southern California Earthquake Center.

Jordan, speaking at a seismology conference, said that “The San Andreas fault is locked, loaded and ready to roll. The springs of that fault have been wound pretty tightly and the situation is there where we could have major earthquakes in California.”

The Earthquake Center has released a graphic which simulates how far the shaking would travel if, as he suggests, it is of 8.0 magnitude.  

The Daily Mail reports that there has been a growing concern among experts that the San Andreas fault may be close to a new, major ruction if only because the length of time since it happened last. In 1857 the southern portion of the fault was struck by a 7.9 tremor.

In the intervening 159 years, the tectonic plates which meet at the fault have been moving at a rate of about two inches per year – meaning that there has been a shift of about twenty-six feet, with the Pacific plate moves in a northwesterly direction relative to the American continental plate.

Seismologists note that an 8.0 magnitude shake in southern Carolina would likely be far more destructive than the 1994 Northridge earthquake. That earthquake hit a different fault northwest of Los Angeles, killing sixty people.  

In 2008 the the US Geological Survey (USGS) warned that even a 7.8 magnitude earthquake on the southern portion of the San Andreas Fault would cause more than 1,800 deaths, 50,000 injuries, $200 billion in damage. In addition to the physical damage to infrastructure, there would be serious health risks as sewage systems would be destroyed.

In October, Los Angeles mayor Eric Garcetti persuaded the City Council to pass legislation requiring as many as 15,000 buildings be reinforced, including concrete buildings considered brittle and apartment blocks built mostly from timber.

Jordan praised the city for taking steps to mitigate the risks. “It’s remarkable that this happened,” he said. “We know politically how difficult it is to make these kinds of changes.”

While California is worried about the Big One, Washington State is worried about a swarm of as many as 130 small earthquakes in recent weeks under Mount St. Helens, signaling increasing dangers of a volcanic eruption. 

USGS said, however, that at this point, “there is absolutely no sign that it will erupt anytime soon, but the data we collect tells us that the volcano is still very much alive.”

USGS said that the tremors began on 14 March and now reach as many as forty a week. In 1980, a major eruption of the volcano blew a 1,000 feet off the top of the mountain, ignited forest fires, and killing fifty-even people.

“The earthquakes are volcano-tectonic in nature, indicative of a slip on a small fault. Such events are commonly seen in active hydrothermal and magmatic systems,” USGS said. Most of the earthquakes now being detected are of 0.3 magnitude or less, with the largest at 1.3 magnitude.