Research on slow earthquakes by Carnegie Fellow Teh-Ru Alex Song is featured in the 24 April issue of Science. Song and colleagues have found that a layer of anomalously low seismic velocity at the top of a subducting plate coincides with the locations of slow earthquakes and non-volcanic tremors. The presence of such a layer in similar settings elsewhere could point to others regions of slow quakes.

The group analyzed 20 years of seismic data for southern Mexico, where the Cocos plate is slipping beneath the North American plate. “We can tell a lot about the material inside the Earth by the speed, strength, and interferences of different seismic waves,” Song commented. “Typically, P-waves are the fastest, followed by scattered waves associated with variations in seismic wave speed within the medium. We used local observations recorded within 100 to 150 miles to map the structures at the top of the subducting plate.” Click here for the CIW press release.