Study faults a ‘runaway’ mechanism in intermediate-depth earthquakes
Nearly 25 percent of earthquakes occur more than 50 kilometers below the Earth’s surface, when one tectonic plate slides below another, in a region called the lithosphere. Scientists have thought that these rumblings from the deep arise from a different process than shallower, more destructive quakes. But limited seismic data, and difficulty in reproducing these quakes in the laboratory, have combined to prevent researchers from pinpointing the cause of intermediate and deep earthquakes. Now a team from MIT and Stanford University has identified a mechanism that helps these deeper quakes spread. By analyzing seismic data from a region in Colombia with a high concentration of intermediate-depth earthquakes, the researchers identified a “runaway process” in which the sliding of rocks at great depths causes surrounding temperatures to spike. This influx of heat, in turn, encourages more sliding — a feedback mechanism that propagates through the lithosphere, generating an earthquake. German Prieto,...