A new statewide shaking-intensity map released by the California Geological Survey shows that several major metropolitan areas are at considerable risk of disastrous earthquake shaking. The map illustrates "earthquake shaking potential" for California over time, indicating that while the highest expected shaking is concentrated near fault zones, damaging tremors are possible anywhere in the state.
San Francisco and the surrounding Bay Area appear to be the most vulnerable, according to the map. The region is traversed by the San Andreas and Hayward Faults. San Francisco and Oakland are categorized under class "XI," a level that predicts "devastating shaking" capable of destroying most structures, collapsing bridges, causing ground fissures, breaking pipes, and triggering damaging landslides.
Los Angeles is also projected to experience considerable shaking, although in the lesser "X" category, described as "extreme shaking." This level of shaking could result in the destruction of most masonry and frame structures, cracked ground, and landslides. The Los Angeles area last experienced a major earthquake during the 1994 Northridge disaster, a magnitude 6.7 event that caused numerous deaths, thousands of injuries, widespread structural collapse, and billions of dollars in damage.
Federal scientists had previously estimated a 74.1% probability of Bay Area residents experiencing an earthquake of magnitude 6.7 or stronger within the next 30 years. The new map's findings align with these long-standing concerns about seismic activity in the region.
In contrast, areas such as the Sierras are shown to have minimal earthquake risk in the coming years, and the Sacramento area is expected to experience less severe effects. The map uses data from the 2023 National Seismic Hazard Model.
Conversations about a potential "Big One" have persisted for years, with particular anxiety surrounding a rupture of the San Andreas Fault. A recent study has intensified these concerns, with experts suggesting that a catastrophic earthquake on this fault may occur sooner than previously anticipated. Caltech seismologist Dr. Lucy Jones, who developed a scenario for a magnitude 7.8 San Andreas rupture, has warned that such an event would have far-reaching and devastating consequences across California. Simulations indicate that such a quake could generate nearly two minutes of intense, continuous shaking, leading to severe traffic gridlock and crippling essential infrastructure, including water systems that cross the fault line.