Background
The United States Geological Survey (USGS) develops and maintains seismic hazard maps for the United States (U.S.) and its territories using a probabilistic seismic hazard analysis (PSHA) framework. The USGS also developed seismic hazard maps as part of a United States Agency for International Development (USAID) effort (e.g., Haiti and Afghanistan).
When USGS develops and publishes seismic hazard maps, the underlying map data is publicly released in the USGS Data Releases section. The map data is released as gridded data (on latitude and longitude) for various ground motion intensity measures and site classes.
Modern datasets have gridded data available for eight National Earthquake Hazards Reduction Program (NEHRP) site classes (Federal Emergency Management Agency [FEMA] 2020 [?]) and twenty-two ground motion intensity measures, excluding peak ground velocity (PGV) (Petersen et al. 2020) [?]. Legacy data sets generally have gridded data available only for NEHRP site class boundary B/C (very dense soil and soft rock) and three ground motion intensity measures: peak ground acceleration (PGA), 0.2-second spectral acceleration, and 1-second SA. Depending on the legacy dataset, additional site classes or SAs may be available. The grid spacing varies by model to provide adequate resolution.
The USGS-developed web-based tools are used to extract site data, such as the USGS Earthquake Hazard Toolbox. While the web-based tools are very helpful in the quick visualization of the seismic hazard at a site, they are often cumbersome when extracting the data for further processing. This toolbox provides a convenient means for importing USGS data into Microsoft Excel for further processing and plotting.