June 22, 2009
KTLA
PASADENA -- A new NASA radar project could help uncover clues to the timing of a mega-earthquake hitting Southern California. In other words, they hope to be able to predict "the big one."
Photo: The discovery could provide clues as to when the next earthquake along the San Andreas fault will occur (NASA)
Scientists at the Jet Propulsion Laboratory in Pasadena are using a very precise radar, strapped to the bottom of a jet flying 45,000 feet over California, to measure exact surface elevations along the southern-most section of the San Andreas fault.
For the first time, scientists will get an extremely accurate picture of the earth's surface near the fault. As earthquake-inducing stress builds up, they expect to be able to detect changes in elevations by overflying the area and taking new measurements.
Scientists say they'll map the San Andreas and adjacent faults, segment by segment. Then, periodically, they'll repeat the same radar observations. Scientists hope to be able to measure deformations in the crust that might occur between observations.
A special NASA jet will begin the overflights soon, and will eventually map some 600 miles of San Andreas fault and its related splinters, from north of San Francisco to Yuma, Arizona.
Scientists use a broad of array of tools to "listen" to the San Andreas and other faults in an effort to detect changes on or below the earth's surface. They dig trenches and place instruments such as seismographs, creep meters and stress meters into the ground. And scientists have long known that Los Angeles, San Diego and Riverside are creeping north at 1.4 inches per year past San Bernardino, Lancaster and the rest of North America. This slippage occurs regularly along some parts of the San Andreas, but it has been locked up in southern-most California for more than 320 years.
Some scientists believe that because there has been no major movement in such a long period of time, earth movement in the jammed-up faults could inflict servere damage in Los Angeles, San Diego, and even as far east as Phoenix.
Other studies have already indicated that strands of the fault in the Salton Sea area are extremely overstressed. A recent chain of small earthquakes east of Borrego Springs and north of El Centro was feared to have over-stressed the main fault, according to JPL.
Space technology is increasingly being used to determine earth movements. The new airborne tool from JPL is called the Unihabited Aerial Vehicle Synthetic Aperture Radar, or UAVSAR. UAVSAR flies aboard a modified NASA Gulfstream III aircraft which is equipped with an advanced navigation system so it can fly quite precisely over the same path -- to an accuracy of within 15 feet.
Over time, scientists will be able to measure the the slow surface deformations involved in the buildup and release of strain along earthquake faults.
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