A large earthquake can trigger distant smaller earthquakes throughout the world, independent of geologic setting, reports a study published online this week in Nature Geoscience. The study suggests that earthquake triggering ? caused by deformation of the Earth’s crust as a result of the passage of surface seismic waves ? is a common and widespread phenomenon.
Tom Parsons and colleagues analysed global and regional earthquake catalogues to identify small earthquakes indicative of triggering. They found that 12 out of 15 large earthquakes that had occurred since 1990 generated surface waves that in turn set off smaller quakes around the world. For example, the December 2004 mega-earthquake at the Sumatra?Andaman islands triggered small earthquakes as far away as Alaska, California and Ecuador.
This study identifies triggered earthquakes around the world that would otherwise have escaped attention. The variety of tectonic settings and triggering waves observed in relation to this phenomenon implies that many different physical mechanisms are involved.