Why quakes occur even in stable faults

Science News : A new simulation may explain why fault segments that are considered stable can sometimes rupture catastrophically. Nadia Lapusta of Caltech and Hiroyuki Noda of the Japan Agency for MarineâEarth Science and Technology in Yokohama created the simulation based on the properties of borehole samples collected along a fault line in Taiwan. Generally, stable faults are found where two tectonic plates “creep” past each other steadily without building up much strain. However, seismic activity on one segment of the fault can generate enough heat to cause water in the ground to expand into pores in the rocks of a nearby segment. As the water pressure builds, it increases the strain of the tectonic plates against each other until the fault ruptures. The model could explain the magnitude-9 earthquake that struck off the east coast of Japan in March 2011, although seismologists don’t know for certain whether the Tohoku fault was creeping or locked prior to the quake.