A public earthquake
warning system could be used to reduce damages and injuries on services
like BART commuter trains in California.
minute you're sitting at your desk on solid ground, the next the floor
slips out from underneath you and things start to rattle off the
shelves. Earthquakes seem to come out of nowhere and can cause widespread devastation.
Building codes and safety videos provide only so much protection.
governments in some earthquake-prone countries, including Japan and
Mexico, institute early warning systems to alert the public to expect
potentially hazardous shaking. (Read up on some earthquake safety tips.)
This week, California followed suit, adopting a new law that requires the Office of Emergency Services to institute a public early warning system for earthquakes.
We spoke to seismologist Richard Allen,
director of the Seismological Laboratory at the University of
California, Berkeley, to understand how an earthquake early warning
system works and what one might look like for the Golden State.
How can you have an early warning system for something no one can predict?
when people talk about prediction, they're talking about when an
earthquake will occur—when rocks in a fault slip past each other.
Most seismologists say we won't be able to predict this for the foreseeable future.
We're predicting the shaking that comes from when the earthquake ruptures. So basically, an earthquake has already started.
think of an earthquake as being an instantaneous occurrence. It's not.
The energy that radiates out from an earthquake is what causes the
shaking that people feel.
P waves come first, and our instruments can detect that. S waves come next, and they carry most of the energy and do most of the damage.
You can estimate how strong the shaking that's carried by the S waves will be, and that's the basis for the early warning.
How far in advance could these warnings be?
talking about tens of seconds. The best case on the U.S. West Coast, in
California, you could have up to a minute of warning. If you're in
Seattle, you could have up to five minutes.
Why is there a timing difference between California and Seattle?
warning time is a function of your distance from the [earthquake's]
epicenter. And the most warning time actually occurs for the bigger
In California, the biggest magnitude
you could get is an 8. So you could get up to a minute warning. For the
Cascadia Subduction Zone, the biggest magnitude is about a 9, and you
could get a five-minute warning.
It's because bigger
earthquakes rupture over a much larger area, and it takes time for that
earthquake to propagate over the area. And that gives more time for
If you're right next to the epicenter, you
might get no warning at all. The shaking at the epicenter occurs about a
second after the P waves. If you're right at the epicenter, you
probably will not get a warning.
What can you do with a few seconds of warning?
is what can people do for themselves? The idea of early warning is that
you can get under a sturdy table before the shaking begins. It's about
getting mentally ready for the shaking, and then essentially waiting for
the earthquake to pass.
The second area is automated
response. And that's really about automated systems that can be slowed,
stopped, put into a safe mode to reduce damage.
example is trains. If you can brake a train so it slows down, you can
significantly reduce the chances it will derail during the earthquake.
The BART [Bay Area Rapid Transit public transportation system in San
Francisco] already has an early warning system.
rush hour, there are about 75 BART trains running. Each train is
carrying about a thousand people. At any given point there are about 45
trains traveling at 70 miles per hour [113 kilometers per hour]. A
derailment could result in a lot of injuries.
example comes from the Oki computer chip manufacturer in Japan. They had
$15 million worth of damage during two moderate earthquakes. They
implemented an early warning system that would isolate hazardous
chemicals and put chip-manufacturing robots into safe mode.
The next time, they only had $600,000 worth of damage in two similar earthquakes.
All four were in the magnitude 6 range.
What would an early warning system look like in California?
We—meaning the California Integrated Seismic Network,
a federation of groups that run the seismic network in the state—have
been working on developing a proof of concept of an early warning
For the last two years we've had a demonstration system running using the existing seismic network.
issues an alert to a small group of users: scientists both internal and
external to the project, as well as industry partners. BART gets the
alert, San Francisco emergency response, Los Angeles city and county
emergency response, and then private companies [that] have been testing
this system over the last two years.
We're in the process of creating a prototype system that would be a blueprint for California's public early warning system.
envision that it would build on the prototype system we have. We
already have 400 seismic stations all around the state, but they vary in
their coverage. Some areas have more than others.
We would need to add some more stations so that we have more coverage over the state.
envision that the public portion of the system would issue the alerts,
but we would need the private sector to distribute them to users.
could be apps that people could create for smartphones. [Alerts] could
also be distributed over the Internet so you could have an app pop up on
Can you predict where the shaking will go?
detect where the earthquake starts, the magnitude, and create a
prediction map as an estimate of ground shaking. When you get the alert,
we can tell you what we expect the shaking to be at your location.
How much would the entire system cost?
cost of building and operating this system for the first five years is
about $80 million in California. If you wanted to do this for the West
Coast as a whole, it would be $120 million for the first five years.
To operate it beyond those first five years, it's about $16 million per year.
It's approximately doubling what's currently spent for earthquake monitoring on the West Coast.
How long have Japan and Mexico had their systems?
[Mexico's] was the first public warning system. It went online in 1991, so it's actually been around for a very long time.
City gets more than 60 seconds worth of warning, because the [usual]
source of their earthquakes is about 300 kilometers [186 miles] from the
Last year in March there was a magnitude 7.4 that
caused a large amount of shaking, fairly serious shaking in Mexico
City, and the system issued a warning and people evacuated buildings.
Japan's is by far the most sophisticated early warning system. They turned on their public, nationwide system in 2007.
really big test was in the magnitude 9 earthquake in 2011. And they
successfully issued a warning for that earthquake for the largest nearby
city, Sendai. They had about 15 seconds of warning.