Scripps researchers pinpoint hot spots as earthquake trigger points

Scientists at Scripps Institution of Oceanography at University of California at San Diego have come a step closer to deciphering some of the basic mysteries and mechanisms behind earthquakes and how average-sized earthquakes may evolve into massive ones.

Researchers used a rotary shear apparatus to identify 'melt welts.'

In a paper published in the 30 August issue of the journal Nature, Scripps scientists Kevin Brown and Yuri Fialko describe new information gleaned from laboratory experiments mimicking earthquake processes. The researchers discovered how fault zones weaken in select locations shortly after a fault reaches an earthquake tipping point.

They coined such locations as ''melt welts'' and describe the mechanism akin to an ice skater's blade reducing friction by melting the ice surface. The mechanism may be similar to ''hot spots'' known in automobile brake-clutch components.

''Melt welts appear to be working as part of a complicated feedback mechanism where complex dynamic weakening processes become further concentrated into initially highly stressed regions of a fault,'' said Brown, first author of the study and a professor in the geosciences research division at Scripps.

''The process allows highly stressed areas to rapidly break down, acting like the weakest links in the chain. Even initially stable regions of a fault can experience runaway slip by this process if they are pushed at velocities above a key tipping point,'' Brown adds.