---
title: "Seismic design data (USGS NEHRP 2020)"
method: POST
path: "/api/locus_seismic_design"
tags: ["hazard", "seismic", "earthquake", "design-data", "read-only", "free", "free"]
---

# Seismic design data (USGS NEHRP 2020)

`POST /api/locus_seismic_design`

## Request

- Base URL: `https://api.locus.report`
- URL: `https://api.locus.report/api/locus_seismic_design`
- Auth: none required

Returns USGS NEHRP-2020 / ASCE 7 parameters at a point (Ss, S1, PGA, SDS, SD1, and Seismic Design Category) for an assumed default site class, for engineering agents. Cited hazard data for a design check. Not a safety, risk, or safe/unsafe judgment. National. Read-only.
Use this when you can call Locus free tools (REST tools/call or MCP).
Use locus-seismic-design instead when your client can only call paid x402 routes; it returns the same records. Direct flat-body route for this one free resource; no API key, payment, or catalog wrapper. Return only the cited bounded evidence described here; this route never produces a paid brief or full report.

## Request body

- object
  - `address` string: Optional US street address or place; NC uses AddressNC first, other areas use the national geocoder fallback when latitude/longitude are not provided.
  - `latitude` number: Optional decimal latitude; provide with longitude to skip address geocoding.
  - `longitude` number: Optional decimal longitude; provide with latitude to skip address geocoding.

## Response `200`

Free cited evidence response.

- object

## Other responses

- `400`: Invalid request body.
- `429`: Rate limited.

---

[API](https://skmtc.dev/locus/apis/locus-api.md) · [All operations](https://skmtc.dev/locus/apis/locus-api/llms.txt) · [OpenAPI document](https://skmtc.dev/locus/apis/locus-api/revisions/ba7786b74adb?raw)