Seismologist Ross Stein urges Portola Valley to fold earthquake prep into wildfire and flood plans

Ross Stein, a seismologist formerly with the U.S. Geological Survey and founder of the Timblor app, told the Portola Valley Town Geologic Safety Committee that residents in the town face a substantial lifetime chance of strong shaking and should leverage existing flood and wildfire preparations to improve earthquake readiness.

Stein opened the presentation with historical context from the 1906 San Francisco earthquake and argued that living memory of large quakes has faded in California. "The earthquake kit is basically the fire kit," he said, recommending that communication plans, emergency kits and evacuation routes designed for fire and flood be emphasized as earthquake preparations as well.

Why this matters: Stein presented hazard maps and metrics showing a roughly 1% per year chance of very strong shaking in the local area, which he framed as translating to a more-than-50% chance of such shaking for someone who lives to about 85. He said the magnitude residents are most likely to experience in their lifetime is near 6.8, and that local site conditions — bay muds that amplify shaking and ridge areas prone to landslides — shape neighborhood risk.

In the meeting’s technical discussion, committee members previewed a July presentation by researcher Kim (transcript shows variant spellings including "Kim Blizzard" and "Kim Blisnuk") who is using cosmogenic dating (beryllium-10) at Sanborn County Park. Simon explained the research method and said the new results could indicate a slip rate near 24 millimeters per year at that site, compared with earlier trenching estimates of about 14–17 mm/yr. "I believe that Kim Blisnuk is using beryllium-10 to date the surfaces of boulders," Simon said, describing why that approach may yield different local slip-rate estimates. Committee members said Kim is scheduled to speak to the group in July.

Stein stressed that slip rates can vary along a fault and that higher local values do not automatically imply a uniform increase along the entire San Andreas. He recommended that residents and the town focus on actions within local control: retrofit or strengthen homes, maintain an emergency kit and communications plan, and organize neighbors to help in the hours after an event.

Committee members asked about insurance, FEMA response and utility resilience. Stein noted that earthquake insurance uptake is low and that reinsurance availability constrains broader adoption. He also said local utilities such as Pacific Gas and Electric (PG&E) have expertise on infrastructure resilience and recommended the committee invite utility representatives to brief the group. On gas safety, Stein advised homeowners to know their domestic shutoff valves and asked residents to consult PG&E about area shutoffs and automatic shutoff valves.

On questions about recent small earthquakes and landslide seasonality, Stein said felt smaller quakes make hazard real for residents but do not change the long-term statistics: "little earthquakes like that just remind us that the faults are ratcheting up the stress." He also said landslides and earthquake hazards can compound, particularly after heavy rain years.

The meeting included extended public Q&A on trees and slope stability, insurance and federal response, and neighborhood-level preparedness. The committee confirmed the next guest speaker arrangements for July 13 and noted that the May meeting was canceled for lack of a quorum. The session concluded without formal votes.