© Reuters/Robert Galbreath
Water shapes California powerfully, deluging the state with El Niño - generated rainfalls and drying it out with punishing droughts. Now, a new study suggests that water may play yet another role: triggering earthquakes.
Scientists for decades have tried to understand how different natural forces, pressing on Earth's surface, might help explain changes in earthquake rates, with mixed results. The pulsing of the tides
has been one long-standing suspect, but their effect is weak or nonexistent. In the Himalayas, rains from the annual monsoon season have also been found
to affect quake frequency. And in California, criss-crossed with faults and at the center of grinding tectonic plates, quake activity seems to increase regularly in the autumn along part of the San Andreas fault—during the driest time of year.
To find out whether precipitation was playing a role, geophysicist Christopher Johnson, a recent Ph.D. graduate from the University of California, Berkeley, set out with colleagues to gather data from a network of 661 GPS sensors scattered around the state. The units are sensitive enough to detect when the ground rises or sinks by a few millimeters because of water weight, groundwater pumping, and tides, among other things.
Comment: Perhaps there is a rational design that remains to be learned. For more information, see: The Cs Hit List 09: DNA, Rational Design and the Origins of Life