Word: faults
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...those faults, the most feared is the San Andreas, which slashes its way along the California coast for 750 miles. Many scientists believe that after decades of quietude, the pressure on sections of the San Andreas is reaching the point at which something will have to give. Researchers have been rushing to instrument the fault--"setting out traplines," as Ken Hudnut, a geophysicist with the U.S. Geological Survey (USGS), puts it--to catch the faintest movements and seismic mutterings...
...largest quakes in U.S. history and another segment characterized by snail-like creep and small, quiet microquakes. Here, amid rolling hills and golden pastureland, scientists with a National Science Foundation initiative called EarthScope are building a remarkable underground observatory known as SAFOD, or the San Andreas Fault Observatory at Depth...
Just last week SAFOD's giant Texas-style drill bored to an inclined depth of 11,000 ft., coming to within 1,000 ft. of the San Andreas. Around July 4, the giant drill's steel teeth should chatter through to the fault itself, reaching the far side of the San Andreas later this summer. At that point, Stanford University geophysicist Mark Zoback and his colleagues will finish casing the perimeter of their borehole with steel and start packing it with instruments...
...question. "This is a new window on the earthquake process," says Stephen Hickman, a senior scientist at the USGS in Menlo Park, Calif. SAFOD could also help settle a number of long-simmering disputes. Although the basic cause of earthquakes on the San Andreas is well understood--the fault marks the major interface between two sections of the earth's crust that are grinding past each other--scientists argue endlessly about the details. Among the most pressing questions are whether the rock in the fault zone is intrinsically strong or weak and whether an increase in fluid pressure helps trigger...
...instruments over the area, hoping to catch the next iteration. The last quake occurred in 1966, so scientists figured the next would come around 1988. Instead, the 1966 quake was followed by a 38-year pause. Some speculate that another earthquake, which occurred on a nearby thrust fault in 1983, reset the seismic clock by altering the local stress field...