GIS Data

Copy page

Seismic Design Parameters

The Calcs.com GIS API provides access to seismic design parameters for the United States via the USGS web services.

Overview

Seismic data is sourced from the USGS Seismic Design Web Services, which provide spectral acceleration values based on:

• Geographic location (latitude/longitude)
• Building code standard (ASCE 7-16 or ASCE 7-22)
• Risk category (I through IV)
• Site class (soil classification)

Response Parameters

The seismic endpoint returns USGS design parameters per ASCE 7:

Parameter	Description	Units
ss	Mapped spectral acceleration at short periods (0.2 sec)	g
s1	Mapped spectral acceleration at 1-second period	g
sms	Site-modified spectral acceleration at short periods	g
sm1	Site-modified spectral acceleration at 1-second period	g
sds	Design spectral acceleration at short periods	g
sd1	Design spectral acceleration at 1-second period	g
tl	Long-period transition period	seconds
sdc	Seismic Design Category	A-F
siteClass	Site classification used for calculation	A-E
riskCategory	Risk category used for calculation	I-IV

Site Classes

Site class represents soil conditions at the building site. Available options depend on the standard:

ASCE 7-22 Site Classes

Class	Description
A	Hard rock
B	Rock
BC	Soft rock / very dense soil (boundary)
C	Very dense soil and soft rock
CD	Dense sand / stiff soil (boundary)
D	Stiff soil (default)
DE	Stiff to soft soil (boundary)
E	Soft clay soil

ASCE 7-16 Site Classes

Class	Description
A	Hard rock
B	Rock
C	Very dense soil and soft rock
D	Stiff soil (default)
E	Soft clay soil

Note: ASCE 7-22 introduced intermediate site classes (BC, CD, DE) for more precise soil classification.

Risk Categories

Category	Description	Typical Buildings
I	Low hazard	Agricultural, minor storage
II	Standard occupancy (default)	Most buildings, residences
III	Substantial hazard	Schools, jails, power plants
IV	Essential facilities	Hospitals, fire stations, emergency shelters

API Endpoints

Endpoint	Use Case	API Reference
/gis/seismic	Recommended - Get seismic parameters for a location	Seismic API
/gis/environmental_loads	Get all environmental data (wind, tornado, snow, seismic) in one call	Environmental Loads API

Quick Example

Get seismic parameters for Los Angeles (using defaults):

Code
 
curl "https://api.calcs.com/gis/seismic?latitude=34.0522&longitude=-118.2437" \
  -H "Authorization: Bearer YOUR_API_KEY"

Response:

Code
 
{
  "location": {
    "latitude": 34.0522,
    "longitude": -118.2437,
    "country": "United States",
    "countryCode": "US",
    "standard": "ASCE 7-22"
  },
  "values": [
    {
      "ss": 2.25,
      "s1": 0.72,
      "sms": 2.28,
      "sm1": 1.66,
      "sds": 1.52,
      "sd1": 1.11,
      "tl": 8,
      "sdc": "D",
      "siteClass": "D",
      "riskCategory": "II"
    }
  ],
  "_metadata": {
    "source": "USGS"
  }
}

With custom parameters (essential facility on rock):

Code
 
curl "https://api.calcs.com/gis/seismic?latitude=34.0522&longitude=-118.2437&riskCategory=IV&siteClass=B" \
  -H "Authorization: Bearer YOUR_API_KEY"

Default Values

When parameters are not specified, the following defaults are used:

Parameter	Default Value
standard	ASCE 7-22
riskCategory	II
siteClass	D

Country Coverage

Country	Seismic Data Available	Source
US	Yes	USGS
Sweden	No	-
Norway	No	-
Denmark	No	-
UK	No	-
Spain	No	-
Kenya	No	-

Note: Seismic data is currently only available for the United States. Other countries will return null for seismic values.

Data Source

Seismic data is retrieved in real-time from the USGS Seismic Design Web Services:

• USGS Seismic Design Maps
• Data is authoritative and always current

Related Documentation

• Seismic API - Recommended for seismic data
• Environmental Loads API - All environmental data in one call
• Wind Data - Wind speed datasets
• Snow Data - Ground snow load datasets