---
title: "Seismic design data (USGS NEHRP 2020)"
method: POST
path: "/api/locus-seismic-design"
tags: ["hazard", "seismic", "earthquake", "design-data", "read-only", "paid", "x402", "category:hazard"]
---

# 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: one of:
  - API key in header `PAYMENT-SIGNATURE`
  - API key in header `Authorization`

Returns USGS NEHRP-2020 values at a US address (Ss, S1, PGA, SDS, SD1, site class, risk category, and seismic design category where USGS has finite values), for engineering agents. Returns the same records as locus_seismic_design. Use this when your client can only call paid x402 routes. Use locus_seismic_design instead when you can call Locus free tools (REST tools/call or MCP).

## 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`

Atomic read result. A substantive result is paid; an empty/out-of-coverage result carries charged:false (x402 settlement suppressed).

- object

## Other responses

- `400`: Invalid request body.
- `402`: Payment Required. For x402 v2, repeat the identical request with a valid PAYMENT-SIGNATURE header (legacy X-PAYMENT is accepted for compatibility), or use Authorization: Payment for MPP Tempo when advertised in x-payment-info.offers.

---

[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)