Building Distance to a mapped seismic fault

Is there a code or standards section that identifies a minimum building setback from a mapped or active fault for typical privately funded buildings such as the UBC once identified? Any direction would be helpful.

Original Post

Presuming you are in California: there are two sources, not in the codes:

Alquist Priolo Act (long time ago) established special study zones for CA major earthquake faults and keep clear zones. Planning Departments usually have the old original maps for CEQA review use.

ASCE 7; referenced in chapter 16 CBC: has minimum building separation to fault rupture lines.

 

There is an old 11x17 seismic fault map published for the '94 UBC that shows the known major active faults in California (& USA). This is a good reference that can be used to locate the building in relation to the fault.

 

If you know the building is located near or in a fault zone, CBC has requirements for geotechnical and geologic investigation for seismic hazards that should include (given a proper standard of care by the Geotechnical Engineer) keep clear distance to the fault rupture zone. If the project Owner is balking about getting geotech/geologic report, or says they cannot afford the report fees, then they cannot afford the project. Without geotech/geologic study/report for a new building, casualty insurance is near impossible to obtain and mortgage financing will be in jeopardy without insurance.

 

If this is for an existing building, existing non-conforming can remain until additions or alterations are proposed. Then good luck with getting a geotech/geologic report.

 

Check local ordinances; there may be a requirement in either building code or construction chapters or in Public Works related grading, drainage, & excavation for geotech/geologic study/report being required. Many cities and counties in CA have adopted ordinances for seismic hazards, hopefully your jurisdiction has one.

 

You can also contact other cities and counties in seismic active areas such as the Bay Area to get some background info on how the plan reviews and project approvals are handled by those jurisdictions.

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