Geologists are recording continuous tremors deep under theSan Andreas Fault, according to an article published in thisweek’s edition of Science Magazine.
A cluster of these tremors was observed before a significantquake last September, raising the possibility that they maybe precursors of larger events, and therefore a possiblepredictive tool for future earthquakes. During September,clusters of these deep tremors were measured before aSeptember 28 earthquake measuring 6.0 on the Richter Scaletook place in the Parkfield segment of the San Andreas fault.
The tremors are taking place at a depth of 12 to 15 milesbeneath the surface of the earth. Normal earthquakes rarelystart deeper than 9 miles. The quakes are not noticeable onthe surface.