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Geologic Safety Committee reports drone and field surveys, asks council for GIS support
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Summary
The Geologic Safety Committee described drone magnetic surveys and follow‑up ground studies at Hawthorns and other sites, outlined plans to map unmapped historic hazards and asked council for GIS, digitization and budget support to make geotechnical records publicly accessible.
The Geologic Safety Committee told the council it has begun geophysical work — starting with drone magnetic surveys — and intends to follow up with ground‑level magnetics, gravity and seismic reflection testing to locate unmapped faults and other hazards.
A committee member described December drone flights and subsequent January field surveys conducted by Stanford students under the supervision of a Stanford geophysics professor. "The first survey was just by drone, and they found enough interesting data to continue the ground work," the committee said, describing gravimeter and magnetometer use and seismic reflection tests that rely on controlled impacts.
Committee members said their work is motivated by historically documented hazards from the 1906 earthquake and by concerns that new building could occur over unmapped hazards. They also flagged wildfire‑after‑earthquake evacuation planning as a priority and proposed neighborhood‑level geologic hazard summaries that would supplement the townwide evacuation map.
The committee requested council support for finding and digitizing older geotechnical and geologic reports (some of which staff and county consultants hold), and for a GIS budget item to make maps and reports more accessible to the public. The council thanked the committee and offered to facilitate coordination with county GIS and Cotton Shires as the committee produces scoping and cost estimates.
