ELLENSBURG, Wash.--When the earth moves, even atiny bit, even a couple of millimeters, antennas located around the state can detect that movement.
Ten years ago during the Nisqually quake, there were 20 fixed global positioning system antennas available to record that movement.One above the epicenter of the Nisqually quake found the land droppedone-eighth of an inch.
PANGA, which stands for the Pacific Northwest Geodetic Array, can draw information from450 of them.They're all talking tocomputers on the campus of Central Washington University in Ellensburg.
The earth isbeing jerked around, pushed and pulled.Because some pieces of ground are movingmore than others, it builds stress up in the ground. Where there are faults, there's eventually movement.
Everything is moving about an inch a year, on the Washington Coast, said PANGADirectorTom Melbourne, in a northeasterly direction.
Puget Sound is moving northeast too, but much less than the coast.Which means the Olympic Peninsula is being compressed.
This makes the GPS a very powerful tool in terms of forecasting the size and the location of future earthquakes, said Melbourne.
A Southern California native, Melbourneis used to quakes,buthere in Washington, he thinks they will become much more violent.
Computer animations show what would happen when a 9.2 earthquake shakes the subduction zone from southern British Columbia along theWashington and Oregon coastsdown toCape Mendicino, California.
The total amount of shaking in this case is about 380 seconds, which is just over six minutes, said Melbourne.As quakes go, that is as bad as it gets.
It would be like the monster quake that hit Anchorage, Alaska in 1964, or the quake and tsunami that originated off Indonesia in 2004.
Scientists know the last quake likethat happened January 26 in the year 1700 at 9:00 p.m.-- 311 years ago.But when does it hit us again? The lack of timing makes preparing for a big quake so difficult.
To change your behavior in advance of a threat that may not come in your lifetime is a very hard thing to sell, said Melbourne.
Everyone would love to know when quakes are going to hit, and when they're not going to strike.
The GPS network does allow us to say where and it allows us to say how big. As for when, there's no predicting when at those time scales, said Melbourne.
But there is one type of quake that scientists can predict within months, and they happen all the time, 50 miles below our feet and we never feel them.They are slow moving earthquakes that nobody feels because they play out over the course of weeks. They happen almost like clockwork about every 14 months and also show up on GPS. But connectingthem to a violent quake on the surface remains elusive.
So that's given us a whole new window into what this fault is doing, said Melbourne. Where that will lead in terms of predictability remains to be seen.
Scientists do try and forecastthe possibility of quakesalmost like weather forecasts -- like an eight percentchance of a quake within a 50-yearwindow in a certain location. But there's nothing definite about any of it because the time factor remains elusive.Still, there are things we can do to protect lives for when those quakes strike.
If you can be told that this realestate right here has these kinds of earthquakes that are this big, and buildyour buildings appropriately, you will solve most of the death problem, said Melbourne.