Tides in earth's crust can cause earthquakes!

San Andreas Fault in California

Scientists have just discovered some new information about what can causes earthquakes! In class we learned that the movements of earth's crust causes pressure to build up along fault lines which triggers earth quakes. Scientists working out of the University of California have discovered that the same forces which cause ocean tides also can cause "tides" in earth's crust which can trigger small deep quakes along some fault lines. Scientists analyzed a data from Cholame, California, a town located on the southeastern end of the San Andreas fault. The scientists looked into the 1700 minor earthquakes that occured in a 110 kilometer square area around the town. What they found is pretty cool. They discovered that the small deep earthquakes were more likely to occur at the time when the tidal stresses pulled the Pacific tectonic plate north-northwest in relation to the North American plate. However, when the tidal stress switched directions and lessened the stress on the San Andreas fault the number of small quakes dropped. These studies help support the theory that even tiny changes in stress along faults can cause earthquakes.

http://www.sciencenews.org/view/generic/id/51459/title/Tides_in_Earths_crust_trigger_small%2C_deep_quakes