If L.A.'s Saber-Tooth Cats Could Talk Long before the La Brea tar pits were a tourist attraction, when saber-tooth cats and mastodons roamed the area that is now metropolitan Los Angeles, frequent major earthquakes shook the ground. There is now strong scientific evidence, funded through a grant from the USGS, that downtown L.A. has been the site of several greater than magnitude 7 earthquakes in the past 11,000 years raising the expected hazard for the City of Angels significantly higher than previously thought. And while it might seem a rare occurrence, a large earthquake every 2,000 years is relatively frequent at least geologically speaking. In the 1970's when many buildings were built, scientists thought the largest earthquake that would occur directly beneath the city would be in the magnitude 5 range. A magnitude 7 earthquake would produce much more significant damage. The USC and Harvard researchers, under an earthquake hazards grant from USGS, drilled boreholes southeast of LA to determine the earthquake history of the Puente Hills fault using a technique called paleoseismology that looks at geologic evidence to tell the story of past earthquakes. (Kathleen Gohn, 703-648-4242, kgohn@usgs.gov)

Revealing Bulges in Mother Earth With a powerful new tool called Interferometric Synthetic Aperture Radar or (mercifully) InSAR for short, scientists are using radar signals from satellites to measure the up and down movement of the Earth's crust at an unprecedented level of accuracy. Under ideal conditions, it is possible to measure changes in elevation on the order of 0.2 to 0.4 inches over areas of hundreds of square miles. What's cool to scientists about InSAR is that it doesn't need equipment on the ground so it can tell them stuff like the movement of magma that is related to earthquakes and volcanoes even in the remotest areas of the planet. InSAR can also map land subsidence the sinking of
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Contact: USGS Office of Communications
703-648-4460
United States Geological Survey
7-Apr-2003