How Much Warning Time Will California’s Earthquake App Give?

The farther you are from the epicenter, the more warning time you'd probably have. San Francisco is 60 miles away from the epicenter of the 1989 earthquake, which was in the Santa Cruz Mountains.

by Rong-Gong Lin II, Los Angeles Times / October 17, 2019

(TNS) — California Gov. Gavin Newsom is set to unveil the state's new earthquake early warning app, MyShake, at 11 a.m. Thursday, available on iOS and Android on the 30th anniversary of the magnitude 6.9 Loma Prieta earthquake. The announcement will be streamed live.

How much warning would MyShake have provided if an earthquake warning system were available in 1989?

Here are some estimates, according to Richard Allen, director of the Berkeley Seismology Lab:

· San Francisco's Marina District: 20 seconds

· Candlestick Point: 15 seconds

· San Jose: A few seconds

· Santa Cruz: No warning

The farther you are from the epicenter, the more warning time you'd probably have. San Francisco is 60 miles away from the epicenter of the 1989 earthquake, which was in the Santa Cruz Mountains.

San Francisco suffered considerable damage from that earthquake; in the Marina District, vulnerable wood apartments with flimsy first stories collapsed and burst into flames as gas lines broke, killing at least three; workers heading home from a brick office building in the South of Market area were crushed to death when a brick wall collapsed on cars in a parking lot.

People too close to the epicenter won't get a warning.

When does the MyShake alert app begin having the capability of sending alerts?

Officials will switch the alerts on around 11 a.m. Thursday.

Where do you have to be to get the alerts if you've downloaded the app?

Anywhere in the state of California.

Do you have to download the app on a smartphone to get the warnings?

That's the best move if you have a smartphone. State officials will also send out quake warnings through text message on the Amber Alert-style Wireless Emergency Alert system. Recent tests show it may be quick enough to get the warning before shaking begins, but it could also be too slow, and you might get the alert after the shaking has started.

So if you have a smartphone, officials urge you to download the app.

How does this compare to the ShakeAlertLA earthquake early warning app that became available in January?

The ShakeAlertLA app, created by the city of Los Angeles, sends alerts right now only to users physically in Los Angeles County.

Can I have both ShakeAlertLA and MyShake on my phone?

Yes. If you're in L.A. County, you might get two alerts.

Under what circumstances would I get an alert with the MyShakeApp?

The U.S. Geological Survey has hundreds of seismic sensors around California under its backbone ShakeAlert earthquake early warning detection system, which has been built in recent years, thanks to considerable support from Congress and elected officials in Sacramento.

When an earthquake of magnitude 4.5 or greater hits, computers instantly analyze what areas of the state are expected to see an intensity of shaking described as "felt quite noticeably by persons indoors, especially on upper floors of buildings," and causing standing cars to rock slightly, with many people thinking the vibrations are similar to a truck passing by.

That's known as intensity Level 3 on the Modified Mercalli Intensity Scale. If you're in a zone that's forecast to get this level of shaking, the system is designed to give you an alert on the MyShake app. (The criteria is the same as ShakeAlertLA's.)

Is that threshold different after many people in L.A. County were mad about not getting warnings from the Ridgecrest quakes in July?

Yes. Experts had thought people wanted to be warned only in advance of damaging shaking.

They now recognize people want warnings when the shaking is scary, even if there is no damage.

Is the warning threshold different for people who do not download the MyShake app?

Yes. If you don't download the app, you might still get alerts via text message from the Wireless Emergency Alert system, similar to an Amber Alert message.

In that case, warnings will go out only to people in places where intensity Level 4 shaking is expected. That's a level of shaking described as "light," in which many are aware of the shaking, walls make cracking sounds, and doors and windows and dishes are disturbed.

How reliable is the MyShake app?

You should expect there will be false alarms and missed alarms. That's part of the deal with earthquake early warnings when they've operated in countries like Japan and Mexico. But the public consensus in other countries is that the system is worth the trouble because of the profound benefit you can have when the warning is correct.

What can you do with a few seconds of warnings?

You can drop, cover and hold on. That will help you prevent getting injured by falling objects and help you protect your head and other parts of your body when the shaking is bad. In a serious shaking situation, you may be knocked to the ground, and so sheltering yourself is the prudent thing to do; that's why schoolchildren across California are taught this in elementary school.

I see there's a version of MyShake that's been around since 2016. What's that?

The first version of MyShake was designed in part as a research experiment to allow users to send shaking data from their smartphones' motion sensors to researchers.

Starting Thursday at 11 a.m., the capability of MyShake to issue earthquake early warnings will be turned on.

How long has earthquake early warning been in development in California?

Tom Heaton, a Caltech professor of engineering seismology, is credited with writing up the first serious proposal of an earthquake early warning system in the United States when he was with the USGS.

One of the first practical tests of the concept in California came after the Loma Prieta quake, which caused a section of the double-decker Interstate 880 to collapse in Oakland, which ultimately killed 42 people and caused 108 injuries.

A system was devised to place sensors near the epicenter of the quake in the Santa Cruz Mountains and issue alerts by radio to rescuers working in Oakland on the damaged freeway, 60 miles away. The idea was to get the rescue workers an alert about a significant aftershock that began in the Santa Cruz Mountains to Oakland before the shaking arrived at the freeway. The system worked for six months and sent 12 warnings.

How did a similar earthquake warning system in Tokyo work during the 2011 magnitude 9 earthquake?

During the 2011 magnitude 9 earthquake in Japan, viewers in Tokyo watching an NHK television channel that blared the early warning had more than a minute of notice before the strongest shaking arrived.

Will the earthquake early warning system be expanded to other West Coast states?

The USGS is working on expanding the system to Oregon and Washington state. Some officials in Nevada have expressed interest in joining the system.


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