Water seen as earthquake fault factor

Strange variations in earthquake activity along the San Andreas Fault in California may be due to saltwater seeping into the rocks, researchers say. Scientists from the GFZ German Research Center for Geosciences at Potsdam found seismic activity varied significantly along a 30-mile stretch of the fault between Parkfield and Cholame, with earthquakes in some segments of the fault while other portions stay relatively steady, LiveScience.com reported Friday. The researchers theorized the differences might be due to liquid seeping into rock at some places and weakening it, enabling faults to slip. They scanned for signs of underground fluid by measuring variations in electrical conductivity along the San Andreas that would indicate water in the rock. "It was most exciting to see all these electrically conductive zones, which we interpret in terms of the presence of fluids," GFZ geophysicist Michael Becken said. While the salty liquid isn't present in anything like large pools or streams, the researchers said, its presence in even small amounts could affect movement along the fault. "The fluid is contained in the pore space of the rocks and makes up only a few percent, but if the pores are interconnected, the fluid can make an entire rock volume conductive," Becken said of the measurements recorded by the researchers.