Word: paleoseismologist
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Thanks to the efforts of USGS paleoseismologist Carol Prentice and her colleagues, however, residents of the Bay Area will have a much better sense of the precise path the earthquake took. Working with old photographs, Prentice has found a number of the missing signs of 1906--abrupt jogs in fences that once straddled the rupture zone, for example--and located them on aerial photos. Among the communities bisected by the fault break is San Bruno, a city of 40,000 that borders San Francisco international airport...
...principle, this cycle of stress accumulation and release should be fairly regular, but scientists are finding it is not. Paleoseismologist Tina Niemi of the University of Missouri--Kansas City, for example, is studying a stream-fed marsh near Tomales Bay that has preserved evidence of past earthquakes in its sedimentary layers. By trenching through those layers to a depth of 15 ft., she has uncovered buried fissures formed by recurrent earth movements along the San Andreas. On average, that pattern repeats every 250 or so years, but "average" in this case covers a wide range. In one instance there appears...
...fault experienced only one earthquake of magnitude 5.8 or higher.* Since then there have been seven, including the Landers quake, which weighed in at an impressive 7.5. Moreover, this surge in seismicity appears to be occurring on a worrisome schedule. Excavations of old lake-bed sediments by Caltech paleoseismologist Kerry Sieh in the mid-1980s indicate that large earthquakes have roared through this section of the San Andreas at not quite 300-year intervals. The last such quake took place circa 1680. "It's just a gut feeling," ventures Sieh, who is 41 years old, "but I think...
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