Earthquakes
Understanding earthquake hazard at a national scale enables you to anticipate and mitigate potential threats to the built environment and community. Proactive risk management based on accurate hazard predictions safeguards physical assets and ensures sustainable development in the face of evolving environmental challenges. The UrbanFootprint Enhanced Earthquake Hazard Risk Model enables you to assess localized earthquake risk across the United States by combining the U.S. Geological Survey (USGS) National Seismic Hazard Model (NSHM) with a machine learning-derived Vs30 map of the contiguous United States (CONUS) (Geyin et al. (2022).
The USGS National Seismic Hazard Model (NSHM) forecasts the chance of experiencing low- and high-ground shaking intensities and frequency of earthquakes at various magnitudes based on peak ground acceleration (PGA) and peak ground velocity (PGV). Varying ranges are mapped to very low, low, moderate, high, and very high-risk hazard categories. USGS produces eight NSHM maps, one per National Earthquake Hazards Reduction Program (NEHRP) site class. A NEHRP site class represents the time-averaged shear-wave velocity of the top 30 meters of soil (Vs30). It is a key index adopted by the earthquake engineering community to account for seismic site conditions. At the local scale, these individual maps are useful resources where the site class for the area is known. However, for their data across the contiguous United States (CONUS), USGS aligns on a single soil type (site class BC or firm rock) to represent a seismic hazard. In reality, soil type varies quite a bit across the country’s surface, and assuming one site class for the nation has the potential to greatly over- or under-estimate the seismic hazard of a specific location.
Rather than assuming a single site class for the entire United States, we use a machine learning-derived Vs30 map of CONUS (Geyin et al. (2022) to inform where to use data from each respective seismic hazard map. For example, in locations where the Vs30 value is between Site Class AB and Site Class B, we interpolate between the peak ground acceleration (PGA) and peak ground velocity values (PGV) for Site Class AB and Site Class B. Our methodology produces a single, enhanced seismic hazard map for CONUS that accounts for variability in Vs30.
Having the site class-appropriate PGA and PGV values in a single map enables analysis at scale and removes the need for cross-referencing multiple maps. Furthermore, this model offers high-resolution downscaled earthquake hazard assessments that reveal nuanced risk features beyond USGS data – leading to meaningful differences in hazard risk. For example, by applying our earthquake risk model to California, we found that risk is being under-reported by approximately 2,000,000 people.
Availability: Location Insights | Climate & Hazard Insights