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Why Los Angeles' Early Warning System For Earthquakes Was Not Activated On Thursday

MARY LOUISE KELLY, HOST:

The Fourth of July was a little shakier than expected for people in Southern California. A 6.4-magnitude earthquake hit near Ridgecrest, Calif. One person who felt the effects was California Institute of Technology seismologist Lucy Jones.

LUCY JONES: I was sitting at home - it was the Fourth of July - and felt it quite effectively, and jumped up and ran into work.

KELLY: The effects of the earthquake were felt as far away as Los Angeles. That's about 150 miles away. But a recently rolled out early alert system known as ShakeAlertLA was not triggered. That's because the shaking in LA reached an intensity level of three, below the level required to activate a warning. Jones says that is exactly how things should have worked.

JONES: It was intensity three in Los Angeles, and the system worked as it was supposed to and did not send an alert. Now, we have to say, is that really what people want? And I think one of the disconnects that happened is the scientists look at this and try to do a cost-benefit ratio. And there's no benefit to notifying people at this low level of shaking - physically.

What's being missed, perhaps, is the psychological benefit of, if we had given out the warning - you know, be aware there's low shaking expected - people would have known it was going to stay small. And they would have had the reassurance that the system was working as it should.

KELLY: So for people who were sitting in LA yesterday, had this alert gone out, how many minutes in advance of actually feeling the quake might it pop up on the screen of your phone?

JONES: For this particular earthquake, there was 48 seconds to downtown Los Angeles as the warning time. And of course that goes along with having a low level of shaking.

KELLY: And I guess the question is, what can a reasonable person do in 48 seconds or a minute to prepare and help change the outcome for them or their belongings?

JONES: For the situation where you are getting it - a shaking level that's actually doing some damage, the alert times will almost always be shorter. But five seconds gives you plenty of time to start undertaking drop, cover, hold on and get into a safer place before the shaking gets to you.

You could hook this up to elevator controls and move the elevator to the nearest floor and open the door, so if the electricity goes out, you weren't stuck in the elevator. You could ring an alarm in operating rooms and dentists' offices so the scalpel gets taken out of your chest before the surgeon's hand gets jerked around.

KELLY: Oh, wow. Yeah.

JONES: You don't need much time to have some pretty important things to be done.

KELLY: Are systems like these widely used in other cities and other places?

JONES: It's interesting. As you look around the world, every other system has been built after a large earthquake killed at least 2,000 people. So for all the struggles we're having in California, I appreciate the fact that we've been able to do it before we kill a lot of people. The most active ones are in Mexico, Japan, Taiwan and China. I think Italy is getting forward on it, too.

Probably Japan is the one where it is most effectively integrated into society. You know, the magnitude 9 that they had in 2011 - no trains derailed because every train had already come to a stop before the earthquake shaking got to it. And there's another time where the month after the earthquake saw a million downloads of the phone apps because people wanted to get the reassurance that the aftershock was going to stay small.

KELLY: And what about elsewhere on the West Coast, which is prone to earthquakes - and San Francisco, other big cities?

JONES: Here in America, it's one system that's being created for the whole West Coast - so Washington, Oregon and California. Los Angeles County is the only one that has an operational public version - and obviously still in prototype mode - because Los Angeles put up the money to greatly densify seismic stations down here quite a few years ago. And therefore, Southern California is the - has the densest distribution of seismometers, which is what's needed to keep the system going.

KELLY: Lucy Jones. She's a seismologist at the California Institute of Technology. Thanks so much for speaking with us.

JONES: Oh, thanks for having me. Transcript provided by NPR, Copyright NPR.