Place & Population Data
The gazetteer of named places Intensity Lab reports shaking for.
Source: GeoNames cities1000
Every automated intensity report needs a fixed list of named places to evaluate ShakeMap at — otherwise there would be nothing to display but raw coordinates. Intensity Lab uses GeoNames' cities1000 dataset: incorporated places with a population of at least 1,000 residents. This is a widely used, freely licensed open geographic database, not a USGS product — USGS itself does not publish a general-purpose named-places gazetteer.
The population threshold (≥1,000) was chosen because it is consistent with the population cutoff USGS uses in its own earthquake impact reporting, so the set of communities named on Intensity Lab lines up with what a USGS-oriented reader would expect to see — even though the underlying place database itself is GeoNames, not USGS.
Coverage
2,002 gazetteer sites are seeded across the supported region, organized by region tab on the Gazetteer page: California, Nevada, Oregon, Washington, Idaho, and Mexico (Baja California and Sonora).
Every gazetteer site carries a pre-computed site-specific Vs30 value (see ShakeMap vs. GMPE Comparison), so ground motion prediction equations can run for it immediately when an earthquake occurs, without a per-event lookup delay.
Why Population Centers Are Emphasized
Restricting the gazetteer to incorporated places of meaningful population — rather than, say, a dense grid of arbitrary coordinates — means every site named in an intensity report is somewhere a reader can recognize. It also keeps the per-event GMPE and ShakeMap-interpolation workload bounded: 2,002 sites is enough to characterize shaking across the whole region without evaluating an unbounded number of points for every earthquake.
Registered users are not limited to the gazetteer — a custom site anywhere in the supported region can be registered and receives the same ShakeMap interpolation and GMPE comparison as a gazetteer city. See APIs Used & Offered for the on-demand endpoint.
Browse the full list, or search by region: Gazetteer page →