Hazard Lingers After South Napa Earthquake

Alexandria, VA - After the Aug. 24, 2014, Napa Valley earthquake, movement continued along the principal fault to the north of the epicenter, according to a report released by the U.S. Geological Survey. Such “afterslip” is known from previous quakes, but this is the first time that strong afterslip has been observed in a populated residential community.

While the majority of shaking on the main strand of the West Napa Fault Zone occurred in rural fields, approximately 20 homes were immediately affected. The fault runs under Napa’s Browns Valley neighborhood and is expected to slip between 5 and 15 centimeters in the next three years, followed by reduced slip until 2024.

Follow the discussion in this month’s issue of EARTH as California legislators and scientists determine if it’s safe for people to rebuild in the fault zone.

For more stories about the science of our planet, check out EARTH magazine online or subscribe at www.earthmagazine.org. The March issue, now available for download features stories on the asbestos controversy unfolding in Nevada, new satellite maps of carbon dioxide sources, and how geoscience is being used to hunt for treasure in the Rocky Mountains.