http://www.lcsun-news.com/ci_7874144
LOS ALAMOS, N.M.â??Aftershocks from earthquakes can happen minutes, hours or even days after the sound waves that radiate from them pass, but the cause of the delay remains a mystery, a group of researchers said.
In a letter that appeared Thursday in the science journal Nature, Los Alamos National Laboratory researcher Paul Johnson and his colleagues show how energy can be stored in certain types of granular materials like those found along fault lines worldwide.
Johnson said the experiment conducted with the help of researchers at the University of California-Santa Cruz, the University of Wisconsin, the U.S. Geological Survey and the University of Washington has helped confirm that earthquakes are periodic events and that sound can disrupt them.