Certain sections of strike-slip faults, known as restraining bends, are sites of unusual tectonic activity because they undergo more contractional motion than surrounding areas.

These bends can be the site of major contraction-dominated earthquakes that are difficult to characterize using traditional means. Over millions of years, these earthquakes build substantial mountain ranges, such as the site of the present study, the Santa Cruz Mountains, California.

This study tests a method for estimating where and how fast these tectonic motions build mountains based on rates of river erosion at various points in the mountain range. The faster a mountain is uplifted, the steeper it will become, causing rivers to erode it more rapidly -- thus high erosion rates should occur where uplift rates are high. We calculate erosion rates by measuring chemical changes that occur in rock as it reaches the Earth's surface and is exposed to radiation from outer space. Using erosion rates calculated from these chemical changes, we are able to replicate known variations in the rate at which the Santa Cruz Mountains are being uplifted.

This technique has the potential to reveal areas of rapid mountain-building, which might be particularly prone to hazardous earthquakes.

 Paper: Maria H. Gudmundsdottir et al., Department of Geological and Environmental Sciences, Braun Hall, Building 320, 450 Serra Mall, Stanford University. DOI: 10.1130/G33970.1.