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Earthquake early-warning system gave 10-second alert before Napa quake felt

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Re: Earthquake early-warning system gave 10-second alert before Napa quake felt

#11

Post by w00kie »

freditup wrote: post #8
waiwai933 wrote: post #4

Earlier quoted context omitted.

If the system were relatively reliable, 10 seconds is actually a lot of time. During the day, it's enough time for many people to take cover. During the night, it's enough time to at least get people up and semi-oriented. The other thing to note is that earthquakes are much shorter than most people think, usually about a minute long. 10 seconds is quite a bit of time compared to that.

But there's no way to reliably get information to all people within ten seconds. Even if a text message alert was sent out as soon as the system was triggered, that time, plus the time for even the most phone-ready people to pull out their phone and do the necessary steps to read a message leads to basically no warning at all.

In Japan, all phones (even the iPhone) are setup to emit a loud alarm sound when an earthquake warning is sent, whether your phone is on manner mode or not. The alarm sound is very distinctive and the same for all phones as well as all TV channels.

Re: Earthquake early-warning system gave 10-second alert before Napa quake felt

#12

Post by wtallis »

byteCoder wrote: post #10

Of course, we never hear about all the times the system has given false positives.

Given the design of this system (it's an early warning system, not a prediction system), the false positive rate could easily be zero so far.

Re: Earthquake early-warning system gave 10-second alert before Napa quake felt

#13

Post by Steuard »

bigiain wrote: post #7

"The system works because while earthquakes travel at the speed of sound ..." That sounds like a somewhat misleading simplification or a complete misunderstanding. Presumably "the speed of sound in the earth" and "the speed at which earthquakes travel" is by definition the same - earthquakes just being "sound vibrations" in the earth with macro level amplitudes. I'd be very surprised if that was particularly close to…

Sure, and the warning signal doesn't travel at the full vacuum speed of light, either: part or all of its path goes through electronics, and electrical signals travel only something like 0.5c.

But this is a really short article aiming to give readers the gist of how the system works. Referring to "the speed of sound" without specifying the material is still probably within an order of magnitude or so of being accurate, and I don't know how valuable greater precision would be in this context.

(In any case, I'll wager that the number of people who 1) have a solid, intuitive understanding of the 350m/s speed of sound in air, but also 2) don't understand that earthquake wave speeds in rock are also essentially sound waves but travel significantly faster, is pretty low.)

Re: Earthquake early-warning system gave 10-second alert before Napa quake felt

#14

Post by hendzen »

rdl wrote: post #2

A few seconds warning seems like it might be kind of useless for humans, especially at 3am, but it would be cool to have this feed into automatic systems to automatically put them in a "safer" state before an earthquake hits. It might even be that 10 false positives a day are worth it to catch one real event, if the "safing" operation is relatively non-disruptive.

Yep - kind of like active hard-drive protection [0].

I could imagine stop-lights turning red at major intersections, elevators stopping and opening at the nearest floor, BART trains coming to a stop, etc.

[0] - http://en.wikipedia.org/wiki/Active_hard-drive_protection

Re: Earthquake early-warning system gave 10-second alert before Napa quake felt

#15

Post by Scoundreller »

w00kie wrote: post #11
freditup wrote: post #8

Earlier quoted context omitted.

But there's no way to reliably get information to all people within ten seconds. Even if a text message alert was sent out as soon as the system was triggered, that time, plus the time for even the most phone-ready people to pull out their phone and do the necessary steps to read a message leads to basically no warning at all.

In Japan, all phones (even the iPhone) are setup to emit a loud alarm sound when an earthquake warning is sent, whether your phone is on manner mode or not. The alarm sound is very distinctive and the same for all phones as well as all TV channels.

This is what I could find: The sound: https://www.youtube.com/watch?v=lPDvAYF8Q-I Wikipedia article in bad need of proof-reading: http://en.wikipedia.org/wiki/Earthquake_Early_Warning_(Japan...

Re: Earthquake early-warning system gave 10-second alert before Napa quake felt

#16

Post by ssclafani »

w00kie wrote: post #11
freditup wrote: post #8

Earlier quoted context omitted.

But there's no way to reliably get information to all people within ten seconds. Even if a text message alert was sent out as soon as the system was triggered, that time, plus the time for even the most phone-ready people to pull out their phone and do the necessary steps to read a message leads to basically no warning at all.

In Japan, all phones (even the iPhone) are setup to emit a loud alarm sound when an earthquake warning is sent, whether your phone is on manner mode or not. The alarm sound is very distinctive and the same for all phones as well as all TV channels.

People in Tokyo had a 60 second warning for the 2011 quake. Here's a good translation of the TV alerts from that day: https://www.youtube.com/watch?v=24KfBwkMw_M Phone alert: https://www.youtube.com/watch?v=bAAIcqI_0Jk Warning countdown: https://www.youtube.com/watch?v=n-FMpNBfna8

Re: Earthquake early-warning system gave 10-second alert before Napa quake felt

#17

Post by Scoundreller »

argonaut wrote: post #6
waiwai933 wrote: post #4

Earlier quoted context omitted.

If the system were relatively reliable, 10 seconds is actually a lot of time. During the day, it's enough time for many people to take cover. During the night, it's enough time to at least get people up and semi-oriented. The other thing to note is that earthquakes are much shorter than most people think, usually about a minute long. 10 seconds is quite a bit of time compared to that.

I think the point is that 10 seconds of warning really translates to 0-5 seconds of warning given the time it takes to send out the warning (text, radio, emergency broadcast). Then add in time to wake and get oriented.

Which might mean getting to a safe place 20 seconds into the earthquake instead of 30 seconds into it. I wouldn't downplay this.

Re: Earthquake early-warning system gave 10-second alert before Napa quake felt

#18

Post by thatswrong0 »

w00kie wrote: post #11
freditup wrote: post #8

Earlier quoted context omitted.

But there's no way to reliably get information to all people within ten seconds. Even if a text message alert was sent out as soon as the system was triggered, that time, plus the time for even the most phone-ready people to pull out their phone and do the necessary steps to read a message leads to basically no warning at all.

In Japan, all phones (even the iPhone) are setup to emit a loud alarm sound when an earthquake warning is sent, whether your phone is on manner mode or not. The alarm sound is very distinctive and the same for all phones as well as all TV channels.

In the US, amber alerts hijack phones and emit an alarm. Had it happen in the middle of a college lecture.. although some phones received it 5 minutes later than others. I'm guessing this functionality could be used for earthquakes.

Re: Earthquake early-warning system gave 10-second alert before Napa quake felt

#19

Post by idlewords »

melling wrote: post #5

To be clear, the detectors in Napa felt the tremors then transmitted the data to Berkeley. They got a 10 second warning because the tremors travel much slower than the speed of light. Being 10 seconds away means the quake is much less intense. This is helpful, but what we need is a warning for people within a few seconds of the epicenter.

The various types of seismic waves travel at different speeds. Luckily the most damaging are slowest, which travel at about half the speed of the fastest (~5 km/s). You can detect the fast waves and trigger warnings immediately, without having to wait for the damage to start.

California is a little bit of a special case, in that quake damage falls off rapidly with distance (the rock is kind of broken up here and doesn't transmit energy well). Earthquakes east of the rockies, while rarer, also have a much bigger radius of damage. In areas like the New Madrid Seismic Zone you could get useful warning times on the order of minutes.

Any early warning system is worth its weight in gold if it's automatically linked to infrastucture like gas mains and train signals (or data centers!). Even a few seconds warning can save lives. Unfortunately, like any other kind of public infrastructure besides roads, getting a decent warning system in place is politically impossibe in the US.

Re: Earthquake early-warning system gave 10-second alert before Napa quake felt

#20

Post by mhurron »

thatswrong0 wrote: post #18
w00kie wrote: post #11

Earlier quoted context omitted.

In Japan, all phones (even the iPhone) are setup to emit a loud alarm sound when an earthquake warning is sent, whether your phone is on manner mode or not. The alarm sound is very distinctive and the same for all phones as well as all TV channels.

In the US, amber alerts hijack phones and emit an alarm. Had it happen in the middle of a college lecture.. although some phones received it 5 minutes later than others. I'm guessing this functionality could be used for earthquakes.

That system is really poorly implemented in the US. I've received alerts for things happening in different states and haven't received alerts for things I know are happening in the county.

I would expect if they used it for earthquakes as it is I would get the alert on the East Coast and someone in California wouldn't.

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