System Will Monitor Minute Southland Earth Movements
A $20-million network of 250 research stations to measure minute ground movements in Southern California was dedicated Friday as a new tool to understand the mechanics of earthquakes and, perhaps much later, forecast them.
Linked to space satellites, the Global Positioning System stations are designed, for the next 50 years, to detect virtually all tectonic shifts in the Earth’s crust in the region, measuring the accumulating strains leading to quakes.
When a large temblor does occur, the data assembled will show the patterns both preceding and following it. Scientists hope that will help them better comprehend processes that up to now have been mysterious.
With the new network, “Southern California becomes the premier national laboratory for earthquake research,†Ghassem Asrar, associate administrator for Earth science at NASA, said at a ceremony Monday at the Glendale Civic Auditorium.
The stations have been gradually installed over the last decade. They are located from Parkfield on the San Andreas fault in Central California south into Baja California and east into the deserts, but there is a particular concentration in the Los Angeles Basin. The final one was completed Monday in Joshua Tree National Park.
Many of the stations are in schools or other public facilities such as those operated by Caltrans or the Metropolitan Water District. Very few are on private property, and it was essential for them to have a clear view from the sky to facilitate signals from satellites.
Most earthquake research stations up to now have been confined to recording the amplitude and pinpointing the location of quakes. Some have recorded the ground motions of temblors.
But this network will try to measure the underlying stress--the crustal movements or deformation--believed to cause earthquakes.
An array of officials from the National Aeronautics and Space Administration, the U.S. Geological Survey, the National Geodetic Survey, the National Science Foundation and other institutions that are participating in the research joined in the dedication.
But it was Ed Stone, an official of the W.M. Keck Foundation--which contributed $5.6 million toward assembling the network--who perhaps best expressed the hopes and uncertainties of those who joined in the collaboration.
“A new kind of information†will now be obtained, Stone said. “But there are no guarantees what will be learned. This is the first, but not the last, step in a new direction.â€
He noted that the new Southern California Integrated GPS Network, its formal name, will measure “with unprecedented precision, down to 1 millimeter,†the movements that are continually taking place along tectonic plate boundaries such as the San Andreas fault.
Officials expressed hope Friday that the network eventually will be expanded to cover the West Coast from Alaska to southern Mexico.
But, already, there is concern that money just to maintain the Southern California stations may be difficult to obtain.
Ken Hudnut, the Geological Survey geophysicist who has directed much of the work along with the Southern California Earthquake Center, said it will cost $1.8 million a year just to maintain the system.
The Geological Survey is putting up $650,000 of that and there is some money left over from the original budget, but beyond that funding is uncertain, he said.
John Filson, a national program coordinator for the Geological Survey, and Margaret Leinen, an assistant director of the National Science Foundation, expressed strong hope for future federal funding Friday.
Besides the Keck Foundation, those who funded the installation were NASA, the National Science Foundation and the Geological Survey.
The major research objectives of the network are fourfold, according to a joint statement of participants. They are:
* To measure crustal movements to better estimate earthquake potential.
* To identify active blind thrust faults (faults that do not come to the surface).
* To measure local variations in strain rates that might reveal the way earthquake faults work.
* In the event of a temblor, to measure permanent deformation not detectable by seismographs, as well as the response of major faults.
These are ambitious goals and not all of them will be realized soon, scientists emphasized. But gradually, they hope, the patterns of crustal movements will become evident.
“And this information will give us new questions to ask,†said Lucy Jones, scientist in charge of the Geological Survey office in Pasadena.
As part of the project, another new earthquake monitoring device called a laser strainmeter has been installed along the east side of the Glendale Freeway north of Glendale with the support of Caltrans.
There a laser beam will travel back and forth inside a 1,800-foot-long pipe to precisely measure the distance between both ends of the pipe. Any change will indicate deformation of the Earth’s crust at that point.
This device will be able to make measurements down to about three parts in 10 trillion, hundreds of times more precise than the ordinary stations.
There are two other laser strainmeters in Southern California. They are independent of the ordinary stations and are used to add further validity to their findings.
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Understanding Earthquakes
A new network of earthquake research stations was dedicated Friday in Southern California. The stations will record crustal movements as small as 1/25th of an inch.
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What the System Does
A Global Positioning System satellite transmits a signal to a 5- to 6-foot-tall sensor on the ground, pictured at right. The sensor’s antenna decodes the signal and records any crustal movement that has taken place over a particular period of time. The sensors will be used to measure crustal movements, to identify active blind thrust faults, and in the event of an earthquake, to measure crustal deformation not detectable by seismographs.
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Source: Southern California Earthquake Center
