Seismologist Ross Stein tells Portola Valley residents to prepare now for likely strong shaking

Seismologist Ross Stein told the Portola Valley Town geologic safety committee on April 16 that residents should treat earthquake readiness as part of the same preparedness people already do for flood and fire hazards.

Stein opened by reading a passage about the 1906 San Francisco earthquake to stress how quickly urban disasters erase infrastructure and memories. He said living in the Bay Area carries a roughly 1% per year chance of very strong shaking — which translates to a greater-than-50% chance of such shaking over a typical lifetime — and estimated that the quake many residents are most likely to experience in their lives would be about magnitude 6.8.

That local hazard picture, Stein said, combines areas of amplified shaking where bay muds and delta sands exist (raising liquefaction risk) with ridge areas that are more landslide-prone. "A building could be structurally sound, but if it sinks or tilts, it's a total loss," he said, urging homeowners to retrofit when possible and to insure properties that cannot be strengthened.

Nut graf: Stein argued officials and residents can improve community resilience by "hijacking" existing concern about fire and flood — promoting the same emergency kit, communications plan and egress routes — rather than asking people to adopt a separate earthquake-only set of behaviors. He also compared U.S. and Japanese approaches, saying Japan’s frequent large events and cultural response make preparedness more embedded there.

On insurance and policy: an attendee noted that only a minority of homeowners buy earthquake insurance. Stein replied that Japan’s insurance uptake is not dramatically higher than California’s and warned that a sudden large increase in insured properties could strain reinsurance markets. He also said Japan pioneered earthquake early warning systems and that wider adoption of early-warning apps helps public awareness.

Q&A highlights: Participants asked practical questions about landslides after wet years, tree removal and slope stability, recent small shocks (a magnitude 4.6 in the Santa Cruz Mountains), and gas-line safety. In response to a question about trees, Stein said roots can help stabilize steep slopes but that tree-removal decisions are typically driven by fire risk and species survival. Regarding gas safety, Stein advised consulting Pacific Gas & Electric on the resilience of local facilities and recommended that households know the location of domestic gas shutoff valves; another participant noted some homes have automatic seismic shutoff valves but utilities historically weighed trade-offs about their use.

Stein also raised broader concerns about science capacity, saying the U.S. Geological Survey "has lost almost 20% of its workforce in the last year alone," and called for protecting scientific institutions that inform hazard planning.

The meeting closed after about 20 participants joined on Zoom and organizers thanked Stein and the committee for the discussion. The committee did not take formal votes or adopt policy during the session.