Widespread Failure of Delta Levees in a Hypothetical M7.0 Hayward Fault Earthquake

Session: Forthcoming Updates of the USGS NSHMs: Hawaii, Conterminous U.S. and Alaska [Poster]
Type: Poster
Date: 4/28/2020
Time: 08:00 AM
Room: Ballroom
Description: 

This study presents one possible outcome of a hypothetical M_w 7.0 rupture of the Hayward Fault on the system of levees that protect the 71 named islands in the Sacramento and San Joaquin Delta and Suisun Marsh near the north end of the mainshock rupture. URS Corporation/Jack R. Benjamin & Associates, Inc. prepared the 2009 Delta Risk Management Study (DRMS) for the California Department of Water Resources, which found that “levees in the Delta and Suisun Marsh are at risk of failing due to a variety of factors, including earthquakes and winter storms. Levee failures and the flooding that follow can cause fatalities, destruction of property and infrastructure, interruption of a large portion of California’s water supply, environmental damage and statewide economic impacts.” We used the broadband ground motions modeled by Aagaard et al. in 2010 for a M_w 7.0 rupture of the Hayward North and South segments with an Oakland epicenter. We applied them to the vulnerability functions provided by the DRMS report and found that thousands of levee failures could realistically occur in the scenario earthquake. An estimated 53 islands in the Delta and Suisun Marsh would experience at least one levee failure in the mainshock, a figure that is near the median number of flooded islands estimated by the DRMS authors for a similar (though not identical) scenario earthquake. We do not estimate the outcomes in terms of economic losses, repair durations, loss of life or environmental impacts, but these effects would certainly be catastrophic for the residents and businesses of the Delta and Suisun Marsh and for the lifelines that transect the Delta.

Presenting Author: Keith Porter

Authors