Six different things, one phrase
“Seismic risk” in San Francisco is at least six separate questions with six separate answers, kept in different places by different agencies. Conflating them is how a buyer ends up reassured about the wrong thing.
- How hard will it shake here? — the scenario ground-shaking maps.
- What will the ground do? — liquefaction and landslide zones.
- Is there a fault under it? — Alquist-Priolo earthquake fault zones.
- Does this building owe a retrofit? — the Mandatory Soft Story Program.
- Is it an unreinforced masonry building? — the UMB list.
- Will it flood afterwards? — tsunami and dam inundation zones.
The report answers five of them. It cannot answer the sixth, and says so — which is the most important paragraph on this page.
How hard it shakes: the scenario maps
ABAG and the USGS publish scenario maps that assign every parcel in the Bay Area a value for two events: a magnitude 7.8 on the San Andreas and a 7.0 on the Hayward. The report gives both values for the parcel, with ABAG's own legend beside them — 7.5 Strong, 8.5 Very Strong, 9.5 Violent.
Two cautions, and the report prints both. These are published maps from 2013, not a live reading. And the value is the publisher's, on the publisher's scale — Scan the Block does not rate shaking and will not, because a shaking grade of our own invention is exactly the kind of number this product refuses to produce.
The figures do vary meaningfully across the city, which is why they are worth having: the Marina reads 8.2 on the San Andreas scenario where parts of SoMa read 7.6.
What the ground does: liquefaction and landslide
Under California's Seismic Hazards Mapping Act, the state maps zones where liquefaction or earthquake-induced landslide are considered possible enough to require investigation before certain construction. The report names whether the parcel is in either.
A zone is a screening designation, not a prediction about a building. Much of San Francisco's flat, made ground — the Marina, parts of SoMa and Mission Bay — sits in the liquefaction zone. What it means for a specific structure depends on its foundation, and that is a geotechnical question no map answers.
Alquist-Priolo fault zones
A separate state program maps surface-rupture zones along active faults. It is one of the six boxes on California's statutory Natural Hazard Disclosure, and the report answers it.
For San Francisco the answer is No everywhere — the nearest mapped zone lies south of the county line. That is worth printing rather than omitting: a buyer who has seen the box wants to see it answered, and “not in a mapped zone” is a finding.
What the building owes: the soft-story program
This is the one that is an obligation rather than a description. Wood-frame buildings of five or more units and three or more storeys, permitted before 1978, fall under the Mandatory Soft Story Retrofit Program — the classic San Francisco shape of a soft ground floor with garages or shopfronts under living space.
- Tier 1 to 4, which set the compliance deadlines. Tier 4 includes buildings in mapped liquefaction zones, so a Tier 4 listing and a liquefaction hit are related facts rather than two coincidences.
- Work Complete, CFC Issued — done, certificate of final completion issued.
- Non-Compliant — outstanding. A real cost with a real deadline.
- Not listed — the program does not reach it. Not a statement about the structure.
The one this report cannot tell you: unreinforced masonry
San Francisco has a separate, older ordinance covering unreinforced masonry buildings — brick buildings, roughly pre-1948, which behave badly in earthquakes and were required to be retrofitted or placarded under a program from the 1990s.
That list is not published as data. We checked: it is not in the city's open-data catalog, not in its ArcGIS services, and the old Building Inspection PDF now redirects to a landing page. The Department of Building Inspection's Seismic Safety Division holds the list of roughly 2,100 buildings, and it is viewable on a public terminal at 1660 Mission Street or by telephone.
If you are looking at a brick building, this is a question to ask DBI directly. It is exactly the sort of gap that a report which quietly omitted it would let you assume was covered.
Water afterwards
The report names whether the parcel sits in the tsunami inundation zone, a dam or reservoir inundation area, the FEMA flood zone, or the mapped sea level rise areas. The first two are the earthquake-adjacent ones; all four appear together because they are the same kind of fact — a mapped zone, named, with the map it came from.
What none of this says
Not one of these zones or values describes this building's behavior. They describe the ground under it and the programs that reach it. Whether a particular structure is sound is a question for a structural engineer looking at the structure, and no public record substitutes for that.
And the report is not the statutory Natural Hazard Disclosure. It names several of the same zones from the same maps, three weeks earlier. A seller still has to provide the document.