Seismic waves can trigger aftershocks

LOS ALAMOS, N.M., Jan. 4 (UPI) -- U.S. researchers say seismic waves radiated from earthquakes can spur aftershocks long after the quake has occurred.

Paul Johnson and colleagues at Los Alamos National Laboratory in New Mexico said in a letter in the journal Nature that wave energy stored in granular materials found along certain fault lines can suddenly be released as an earthquake when hit by relatively small seismic waves far beyond the traditional "aftershock zone" of a main quake, the Energy Department said Thursday in a release.

The researchers found that the release of energy can occur minutes, hours, or even days after the sound waves pass.

Earthquakes release seismic waves that can trigger aftershocks in a zone several to tens of miles away from the radiating main earthquake, known as a "mainshock." Most aftershocks usually occur within hours to days after the mainshock, although new research has shown that seismic activity sometimes increases thousands of miles away after an earthquake, the report said.