Earthquakes: Love and stress
Non-volcanic tremor and slip along a plate boundary can be triggered by shear stress, rather than fluid movement.The analysis of seismic data has revealed long-duration, low-amplitude tremor, similar to that seen below active volcanoes, but associated with plate tectonic boundaries, rather than volcanoes. Episodes of tremors and slow slip have been observed to last up to months, and can be associated with as much deformation as a magnitude-7 earthquake. Although observations of this type of tremor are increasing, the mechanism behind it remains unclear, with some researchers pointing towards slip along the plate interface, and others the movement of fluids.
Justin Rubinstein and colleagues examined seismic recordings associated with the 2002 Denali earthquake and found clear evidence of bursts of tremor having been triggered within the Cascadia subduction zone near Vancouver Island, Canada. These episodes seem to be triggered when the Love wave (surface seismic wave) displacements were to the southwest — parallel to the direction of plate convergence. They conclude that the tremor and possibly slow-slip events can be induced by shear stress increases along the subduction interface.
CONTACT
Justin Rubinstein (University of Washington, Seattle, WA, USA)
Tel: +1 206 685 7563; E-mail: justin@ess.washington.edu