Free Earthquake Risk API
FaultLineMap provides a free, no-authentication JSON API for earthquake risk data covering any location in the United States. Data comes from the USGS Seismic Design Maps API (ASCE 7-22) and the USGS Quaternary Fault Database, queried in real time.
Endpoint
GET https://faultlinemap.com/api/risk?lat={latitude}&lon={longitude}
Parameters
| Parameter | Type | Description |
|---|---|---|
lat | float | Latitude (decimal degrees) |
lon | float | Longitude (decimal degrees, negative for west) |
Example Request
curl "https://faultlinemap.com/api/risk?lat=34.05&lon=-118.24"
Example Response
{
"latitude": 34.05,
"longitude": -118.24,
"hazard": {
"level": "Very High",
"pga": 0.684,
"sds": 1.327,
"sd1": 0.585,
"sdc": "D",
"ss": 1.817,
"s1": 0.683
},
"nearby_faults": 12,
"recent_earthquakes_100km": 47,
"source": "USGS Seismic Design Maps API (ASCE 7-22)",
"report_url": "https://faultlinemap.com/lookup?q=34.05000,-118.24000"
}
Response Fields
| Field | Description |
|---|---|
hazard.level | Risk category: Very Low, Low, Moderate, High, or Very High |
hazard.pga | Peak Ground Acceleration (g) — risk-targeted |
hazard.sds | Design spectral acceleration at short periods |
hazard.sd1 | Design spectral acceleration at 1 second |
hazard.sdc | Seismic Design Category (A through F) |
hazard.ss | Maximum spectral acceleration at short periods |
hazard.s1 | Maximum spectral acceleration at 1 second |
nearby_faults | Number of known faults within 100 km |
recent_earthquakes_100km | Earthquakes within 100 km in the past year |
report_url | Link to the full interactive report on FaultLineMap.com |
Rate Limits
No API key is required. Please limit requests to a reasonable rate (a few per second). Data is cached for one hour. For bulk lookups, please space your requests. If you need high-volume access, contact us.
Embeddable Risk Badge
Want to show earthquake risk on your site? Use our badge endpoint to display a risk level indicator with a link back to the full report:
<a href="https://faultlinemap.com/lookup?q=34.05,-118.24"><img src="https://faultlinemap.com/badge?lat=34.05&lon=-118.24" alt="Earthquake Risk"></a>
The badge is a small SVG image showing the earthquake risk level for the given coordinates. It works great in blog posts, real estate listings, property reports, and insurance content.
Attribution
This API is free to use. We appreciate (but don't require) a link back to FaultLineMap.com when displaying data from this API. All underlying data comes from the USGS Earthquake Hazards Program.