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USGS scientist: Bay Area faces elevated earthquake risk; liquefaction a local concern for East Palo Alto
Summary
A USGS scientist told the East Palo Alto City Council there is a high regional likelihood of a major quake before 2043 and highlighted liquefaction and amplified shaking in bay‑mud areas that increase local risk; officials asked staff to bolster retrofit and preparedness efforts.
Belle Filabousian of the U.S. Geological Survey told the East Palo Alto City Council on March 25 that seismic hazard models show substantial earthquake risk across the Bay Area and particular vulnerability for low‑lying, bay‑mud zones in and near East Palo Alto.
Filabousian, a scientist with the USGS Earthquake Science Center, said the agency’s probabilistic models — which combine data on faults, slip rates and historical events — produce a regional estimate that ‘‘there’s a 72% chance of an earthquake above magnitude 7 somewhere in this region before 2043.’’ She noted that this number aggregates many faults across the Bay Area and does not mean a single fault will rupture next week.
Nut graf: The USGS presentation focused on what the hazard numbers mean locally: strong shaking amplified by bay mud, the risk of liquefaction where saturated sediments exist, and the possibility that even lesser‑studied faults can produce damaging events. Council members pressed the presenter for details about a mapped ‘‘San Jose Fault’’ near East Palo Alto and for practical retrofit steps the city can promote.
Filabousian walked through the principal hazards: shaking intensity increases where sediment amplifies seismic waves; fault displacement can sever buried lifelines; and liquefaction can cause buildings and vehicles to sink or tilt. ‘‘Because there is variability, it could also be decades before the next large Hayward Fault earthquake,’’ she said, adding that ‘‘there’s a 13% chance within 30 years of a large earthquake somewhere on one of these lesser known faults’’ and stressing that smaller or unexpected ruptures — like the South Napa event in 2014 — can still cause significant local damage.
Councilors asked technical questions about fault characterization and probability calculations; Filabousian said the 2043 window reflects combined probabilities from many mapped faults and historical slip rates and cautioned that uncertainties remain for less‑studied traces.
Ending: Council members and staff said they would use the USGS briefing as a basis for updating outreach, building‑vulnerability inventories and retrofit priorities discussed later in the meeting.
