GPS Could Speed Tsunami Warning

wwood_98 writes to tell us that Wired is running a story about how GPS could serve more than its traditional role. From the article: "International organizations like the Pacific Tsunami Warning Center, or PTWC, in Hawaii currently depend on coastal seismic stations to record deep-sea earthquakes that could cause giant waves. But according to Jeff Freymueller, a geophysicist at the University of Alaska Fairbanks, data from GPS receivers could provide quicker, more accurate estimates of the magnitude of a tsunami-causing quake, buying time for evacuation. Freymueller presented his findings at this week's American Geophysical Union conference in San Francisco."

Comments

GPS buys you a head start!

[mister_llah]

Excellent, if you live in a coastal city, you'll get to know that you have 20 minutes left to live...

Re:GPS buys you a head start!

[Mr. Flibble]

Excellent, if you live in a coastal city, you'll get to know that you have 20 minutes left to live...

According to the SAS Survival manual by John Weisman - if a Tsunami is inbound your best defense is to be over 1km inland or 100ft above sea level.

In many (not all) places you would have time to do either of these. You also have the option of quickly heading out to sea as the Tsunami only has effects at shallow depths (right by the coastline). So, an additional 20 min could indeed save a huge number of lives.

I would also add, that you might not be safe even 1km inland if you were withing a natural "funnel" like a trianglar river delta with highlands on each side...

Re:GPS buys you a head start!

[martinX]

No, you have 20 minutes to:

• get dressed (pants at least),
• find the keys,
• grab your wallet,
• look for your cell phone,
• turn off the TV,
• grab the backups you always make,
• where is that cell phone?,
• select a playlist for your iPod,
• grab some cold brewskies
• where is that damned cellphone???,
• don't forget the digital camera

THEN you can drive. If you're not busy blogging the event, telling the other blogophiles you'll be AFK for a while.

Cool stuff

[Sen.NullProcPntr]

I was assuming this would only work if the quake happened under dry land. From The Fine Article;

"GPS receivers measure the static displacement of the earth, and after the first few minutes of a quake, that doesn't change much."

But looks like there may be a way to detect a tsunami caused by an under sea event;

"Quakes that cause tsunamis create deformation on the surface of the water, and that causes an atmospheric 'thump,'" MacDoran said. "A compression wave travels into the upper atmosphere, and that disturbance causes subtle changes in the way GPS signals travel." Digital processing of the changed signals coming from nearby receivers would indicate that a tsunami was imminent.

Sounds promising but is it possible to tell the difference between air movement caused by a tsunami and just a sudden gust of wind? How dense would the sensor array need to be to prevent false positives?

Grade of GPS being used?

[Funakoshi]

Does anyone have any further information regarding what grade of GPS is being used? Based on the price point, I would have to guess that it is Mapping grade GPS equipment, but the problem would be that in order for Mapping grade GPS to update, the person (or mount) holding it, must be moving to get the corrections from the satellite. Survey grade may work, but it wouldn't be under $10k per receiver.

Any help?

Re:Grade of GPS being used?

[kfstark]

This is survey grade GPS units which go for about $6k (quite a bit less in quantity). Generally Ashtech MicroZ, Trimble NetRS and others. The Dorne Margolin choke ring antenna we use costs about $3k. It is possible to put together a survey grade site for about $11k. This was done in Southern California years ago at a cost of $20k/site.

--Keith

Worthwhile - $181 per person in 2004

[Kamiza Ikioi]

The article is interesting in the use of GPS recievers to gather information. Let's look at two datasets.

From Wikipedia: "The accuracy of the GPS signal itself is about 5 meters (16 ft) as of 2005 and has steadily improved over the last 15 years. Using differential GPS and other error-correcting techniques, the accuracy can be improved to about 1 cm (.4 in) over short distances."

From NASA: "Large earthquakes often cause permanent movement of the Earth's surface, a result of the motion that occurs deep underground. The tsunamis spawned by the magnitude 9.0 earthquake on December 26, 2004, were the result of motions of the sea floor above the earthquake fault. Seismic measurements and computer models show that the Burma Plate slipped up to 20 meters (66 feet) at the location of the earthquake, 18 kilometers underground. The sea floor above moved less, up to 5 meters (16 feet) vertically and 11 meters (36 feet) horizontally."

So, the practical uses of this, even without error-correction, are theoretically viable for creating an early warning system for Tsunamis.

The article states that it should only really take 70 seconds for "a good idea of the final deformation". Linking this data to website and government run servers, the early warning system for Tsunamis would be far greater and accurate that say, tornado early warning systems. Consider the following exerpt from PBS's NewsHour: Developing a Global Tsunami Warning System: "STUART WEINSTEIN, Geophysicist, Pacific Tsunami Warning Center: I think the 'holy cow' moment didn't occur until we started getting the first preliminary reports over the wire services that, in fact, a damaging wave struck Phuket, Thailand and Sri Lanka.

BETTY ANN BOWSER: Were you frustrated?

Stuart WeinsteinSTUART WEINSTEIN: Very frustrated. Frustrated and to a certain extent humiliated. It's humiliating for me as a geophysicist working for a tsunami-warning program to learn first of a tsunami from a wire service than from a tide gauge. That -- it doesn't get any worse than that, quite frankly.

BETTY ANN BOWSER: Thousands of miles away at NOAA's Pacific Marine Research Lab in Seattle, tsunami researcher Vasily Titov was also frustrated. It took him until 4 a.m. in the morning of the next day to run this computer model, because he didn't have tsunami readings either."

Considering the earthquake hit at 00:59 GMT, and the wave first makes landfall at Sumatra 01:30 GMT, then 02:30 GMT in Thailand, then 03:00GMT in Sri Lanka and India... having a result from this system at 01:00GMT (70 seconds) automatically piped to the national emergency centers of governments, could have at least mobilized aid faster in Sumatra, and could have evacuated thousands in Thailand, Sri Lanka, and India.

A total of approximately 275,000 died in the Indian Ocean Tsunami of 2004. At a cost of even $10,000 per detector, 5000 detectors for $50million USD would have only cost $181 for every person that died.

A better use for GPS?

[thisjustin]

I think this article (and the researcher) missed the point of a far more profound, yet more far-off, use of GPS in earthquake detection. Spectrum recently ran a story describing how the GPS system among other things could sense impending earthquakes days, weeks, and even months in advance of an earthquake. The basic concept is the cracking of rocks in the crust leading up to an earthquake frees electrons which rush downward creating positvely charged holes. These holes also appear at Earth's surface and attract electons out of the ionosphere. The phase difference of the two signals the GPS satelites transmit is affected by this change and the change from normal values can be detected. This is still a long way off, and the use of GPS to measure this phenomena is only one and definitely not the best. But it sounds better than the couple hours mentioned in the article.

Re:GPS Accuracy?

[kfstark]

A single frequency GPS receiver that you use in a car would be worthless for this application.

Check out the Southern California Integrated GPS Network for an example of highly accurate (sub millimeter) uses of GPS over a large area. The receivers being used in this network are 10 years old and still returning excellent data which we can use to compute annual tectonic plate motion. In 1999, after the Hector mine earthquake, we were able to determine 17cm of slip at a sight 40km away from the epicenter. This was done in a few hours.

Also, take a look at the Plate Boundary Observatory which is being built now.

--Keith

But

[Catmeat]

More accurate seismometers would be nice. But one thing about sea-floor earthequakes is that some generate tsunamis and some do not. That's why NOAA spends a bucket-load of money maintaining a network of deep-ocean pressure sensors on the bed of the Pacific (link) These work because a tsunami in deep ocean has a wavelength vastly greater than the depth of water so it produces a small, but characteristic and detectable, pressure pulse as it passes over the sensor.

If this GPS idea works as advertised, it'll be a very useful incremental improvment to the tsunami warning networks. But it'll hardly be revolutionary. Being able to determine which events will produce a tsunami just from the seismic data - that would be revolutionary.