Video: How prepared or unprepared are you for an earthquake?
A pair of significant earthquakes last week in Southern California sent shock waves through the state – both literally and figuratively, as the temblors evoked concern over preparedness, fault proximity and the likelihood of the “Big One” causing mass destruction.
Some Sacramento-area residents took to social media to say they felt the 7.1-magnitude earthquake last Friday evening, with reports of swimming pool water bobbing within minutes of the quake striking near Ridgecrest, almost 400 miles away.
About a month ago, The Bee examined the Sacramento area’s earthquake risk in response to a reader question posed as part of our “Beyond Sacramento” series. Seismology experts and a professor who studies earthquake engineering told The Bee that the region’s earthquake risk is minor compared to the Bay Area or Los Angeles.
Data and modeling support that idea. Maps and hazard forecasts by the U.S. Geological Survey and California Department of Conservation provide a good look at the greater Sacramento area’s fortunate seismological position.
USGS seismic hazard maps – both recent 1-year short-term models and the 50-year long-term model released in 2014 – show California’s only “green” zone and the region of lowest seismic hazard in the entire state is a small pocket roughly between south Sacramento County and the Stockton-Modesto area.
However, as experts told The Bee last month, a major (6.8 magnitude or higher) earthquake on Bay Area’s Hayward Fault would likely shake buildings, wake residents and possibly break some dishes or windows.
A quake near that magnitude has happened only once since 1800 on the Hayward Fault, according to the California Department of Conservation: the 1868 Hayward earthquake, which shook at a magnitude of about 6.7.
A map of all significant earthquakes statewide from 1800 to 1999 shows there were no earthquakes magnitude 5 or higher with epicenters in the greater Sacramento area: Sacramento, El Dorado, Placer and Yolo counties. The closest came in Solano County with 1892’s Vacaville-Winters earthquake, which is recorded at 6.4.
You can thank a lack of active faults running under Sacramento for this good fortune.
We’re not without nearby faults, though. Surrounding Sacramento is the Cleveland Hill Fault to the north, near Oroville; the Sierra Nevada Fault to the east, near the mountain range; the San Joaquin Fault south of the Sacramento Valley; and the aforementioned Hayward Fault to the west.