Satellite System Will Speed Up Tsunami Warnings

ananyo writes "NASA and a group of universities known as the READI network have begun testing an earthquake-warning system based on satellite data from the Global Positioning System. The method could have allowed Japanese officials to issue accurate warnings of the deadly March 2011 earthquake and tsunami ten times faster than they did, say scientists. The system is currently being tested using the U.S. Pacific Northwest Geodetic Array: hundreds of GPS receivers placed along the North American coast between Northern California and British Columbia in Canada. While conventional seismometers provide similar information, they run into trouble with earthquakes of magnitude 7 or higher. This is partly because in big quakes, the ground may shake for longer, but not significantly harder. GPS has no such problem, because it directly measures the movement of the ground."

Comments

Nice

[masternerdguy]

Now the panic can start a few hours earlier. Unless evacuation plans are improved this won't help much.

Re:Nice

[icebike]

Actually, BOTH the size and the location of the earthquake (which was centered off-shore) was known fairly quickly.
What wasn't know was whether or not a tsunami would result.

So issuing an accurate warning ten times faster (they had to have meant 1/10th the time) would have meant little, since the actual ground uplift movement was 80 miles out to sea, where no GPS meters would have been available. The actual quake itself was already known to be very large the instant it happened and the location was pin-pointed within minutes of the quake itself.

There is nothing GPS could have added to speed things up. They don't work underwater. Existing ocean buoy based sensors detected the tsunami as soon as the wave approached shallow waters where it could be distinguished from a normal wave.

So for the last several big quakes which happened off shore, these GPS detectors would not have helped speed the location or magnitude information at all. And as we have seen in recent weeks, large quakes more often then not do not trigger tsunamis.

Since quake magnitude and location are already known with minutes (generally within seconds of P wave arrival at a few sensors), I fail to see how this cuts down warning time. Since the quake is felt simultaneous with P wave arrival, the only thing left to warn about is a tsunami, and that determination is based almost solely on quake epicenter location, which is determined very very quickly by computer.

Re:Nice

[ananyo]

Right - Yes GPS doesn't work underwater but that doesn't matter. The detectors are mostly close to shore - they detect the seismic waves. As tsunamis are caused by earthquakes out to sea (as one commenter notes) the tsunami follows some time later - depending on how far from shore the earthquake happened.
According to the source story, GPS measurements of the ground movement (close to shore) is MORE accurate than the seismometer readings. Seismometers detect the amount of shaking but struggle with the duration - which is a key part of what makes big earthquakes big.

Quoting from the source:
"But seismometers have limitations. "They do a beautiful job discriminating among magnitude 2, 3, 4, 6, earthquakes," says Melbourne. "But they run into trouble where you have to distinguish a magnitude 8 from a magnitude 9." This is partly because in big quakes, the ground may shake for longer, but not significantly harder.

Melbourne and Allen use the Japan earthquake as an example. In March 2011, Japanese officials relying on seismometer data were able to issue earthquake warnings within eight seconds of detecting that something major was going on. "But they thought it was magnitude 7.1," says Allen. The estimate increased to 8.1 within 2 minutes, but it took another 20 minutes to reach the final value of magnitude 9.

Funding

[Oxford_Comma_Lover]

Yes. The Pacific Tsunami Warning System is already fast. I can get earthquake info almost as fast from the USGS as I can from a million people on facebook live-reporting the earthquake.

So this project, while cool, sounds more like a way to get funding than anything else.

If only tsunamis were caused by ground movement

[Anonymous Coward]

Only problem with that proposal is that tsunamis are not caused by dry land moving, they are caused by earthquakes underneath the ocean.... measuring how much the land moves only works for earthquakes (at sea) that occur close to shore. Typically the quakes that have caused the large tsunamis we have been seeing of late have been further off shore.

Thats the reason the current tsunami buoys are located *in the ocean* http://www.bom.gov.au/tsunami/about/detection_buoys.shtml ... The problem there is there just aren't many buoys so the amount of data they get is small. more funding should be spent on increasing the number of buoys. (their locations + data are shown here: http://www.ndbc.noaa.gov/dart.shtml )

In Australia (for an earth quake in Chile) it's typical for a tsunami alert to be issued, then retracted nine hours later when the expected wave finally reaches the one buoy closer to Australia. If there were five or more buoys along the way they could retract the alert sooner, or delay issuing the alert until a couple of buoys had been passed and they had accurate data.

Nonsense

[fullback]

"The method could have allowed Japanese officials to issue accurate warnings of the deadly March 2011 earthquake and tsunami ten times faster than they did, say scientists."

The tsunami was known almost instantaneously and warnings issued where they could be. The METHOD of warning was affected since many loudspeakers didn't work because of the widespread power outage.

We see tsunami warnings almost instantly on Japanese TV immediately after a quake, or the information that there is no tsunami warning. For large quakes, we actually get a warning on TV before the quake is felt if it's far away. Quake warning -> quake is felt within 2 seconds.

well duh

[Gravis Zero]

of course they are going to know when there is going to be a tsunami when the satellites start shooting lasers off the coast of small islands.

"We can provide protection from tsunamis by tellin' yous guys when they gonna hit. it would be a shame if something were to happen to this nice unprotected island. Isn't that right Tony?"
"Yeah boss, it'd be a real shame."

Using GPS latency

[AmiMoJo]

Japanese universities have been working on a system that measures the latency of GPS signals to detect earthquakes before they happen. Apparently in the time before a quake there are changes in the atmosphere which affect the transmission of signals from the satellites to receivers on the ground, resulting in the time delay changing. By detecting the changes they can give up to half an hour of warning.

There was some coverage on Japanese TV and I think the BBC picked up on it too, but I can't find the link right now.