Tuesday, April 19, 2016

What You Need to Know About Earthquakes After Ecuador, Japan and on San Francisco's Anniversary

Three deadly earthquakes have struck in the past week -- twice in Japan and once in Ecuador -- leaving many wondering if quakes in the two countries separated by the Pacific Ocean could be connected.
But two earthquake experts debunked that theory.
"The occurrence of earthquakes in time is more or less a random process," said Jonathan Stewart, a professor of civil and environmental engineering in the UCLA Henry Samueli School of Engineering and Applied Science.
"There's absolutely no link," said Mark Benthien, director for outreach for the Southern California Earthquake Center. "There are times when large earthquakes do trigger an earthquake somewhere else. The Japan earthquake was certainly not large enough to trigger an earthquake in Ecuador." He said a quake would need to be roughly a 9.0 magnitude to trigger another one a large distance away.

When's the Next Quake in California?

While these recent quakes hit internationally, people in the U.S. -- specifically the West Coast -- are at risk for one any time, experts said.
"We certainly can have large earthquakes at any time," Benthien told ABC News. "There's ... no information we have that would say one is imminent. But we have expectations for up to an earthquake the size of the Ecuador earthquake [7.8 magnitude] ... on the San Andreas fault [in Southern California] and it could happen today ... or may not happen for 50 years. But we expect it to happen."
Benthien explained that the long-term average for a large earthquake in Southern California is every 150 years -- the last large one in Southern California was Fort Tejon in 1857 -- so now we've just past that mark.
But "it could be another 50 to 100 years, because it's an average," Benthien said, noting that if there were a quake about 7.0 magnitude -- like this week in Japan -- in the Los Angeles area now, "that would certainly be devastating -- but it wouldn't be 'the big one.'"
"If a 'big' earthquake [over a 7.0 magnitude] happens in Southern California today, scientists would not be surprised," Benthien added.
Stewart, who explained that it's possible to predict probabilities of large earthquakes over long term -- like decades -- but not short term, said up to a magnitude 8 quake could hit in Southern California and up to a magnitude 9 could hit in Oregon or Washington.
Stewart said it's not just West Coasters who experience it -- earthquakes also happen on the East Coast and in the Central U.S., like a 2011 quake in Virginia. "They tend to be smaller. ... They occur much less often but they do occur," he said. "And it will happen eventually."
Stewart said Californians' fear of the imminent "big one" is in reference to Southern California's San Andreas fault, which he said is very active and moving quickly -- about 2.5 or 3 centimeters per year.
"The situation we have with San Andreas ... is that it hasn't ruptured in a long time. ... It's overdue," Stewart said. "If you don't have an earthquake ... you're building up more and more strain in the earth and then eventually it gets released as an earthquake."
Benthien said that his long-term 150-year average measurement for a large Southern California earthquake applies separately in Northern California. The last earthquake on that scale there was the 1906 quake in San Francisco -- and today marks the 110th anniversary of that deadly 7.8 quake, which killed more than 3,000 people and ignited fires throughout the city.

Are We Prepared?

Since the San Francisco quake, the way buildings are built have changed significantly, Stewart said.
"There really was no earthquake engineering up until the 1930s," Stewart said. "Starting after the Long Beach earthquake in the 1930s going up to the present, we've progressively learned how to build buildings that are more resilient."
San Francisco and Los Angeles have started to put policies in place that can upgrade buildings at risk of collapse, he said, noting, "Once those policies have a chance to play out over time, that will appreciably reduce the risk of building collapses and loss of life."
While timing remains unpredictable, Stewart does have predictions for the aftermath if a big quake hits Southern California -- he said it would sever several major water lines, dramatically reduced water service. He said there could also be fatalities, older concrete buildings could be destroyed and there would be huge economic losses.
Benthien said what's really key is being prepared -- "both to survive and recover when the earthquake happens." He said you can prepare by storing water and securing items and furniture that could fall and break.
"Most people by far will survive any earthquake that we get in Southern California. Just like in [Japan and Ecuador] while there are deaths ... it's a very small percentage of the population," Benthien said. "Most people will survive and have survived these earthquakes."
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