The latest U.S. National Seismic Hazard Model (NSHM) reveals that approximately 230 million people in the United States are at risk of experiencing damaging earthquakes within the next 100 years. This is an increase of about 40 million people compared to previous estimates. The NSHM is based on data from 130,000 seismic events and the geological record, as well as nearly 500 new active faults. It also incorporates new ground motion models to estimate the shaking during an earthquake. These updates have led to an overall increase in earthquake hazard across the country, as reported in Earthquake Spectra on December 29 by Petersen and colleagues.
One significant improvement in this update is the enhanced characterization of shaking in sedimentary basins, which can amplify earthquake waves, particularly affecting tall buildings and long bridges. This amplification has raised the ground shaking hazard for such structures in major cities like Seattle, Los Angeles, Salt Lake City, and Portland, Oregon. The new NSHM also includes updated ground shaking models for subduction zones in the Pacific Northwest and southern Alaska, notorious for generating large quakes. Overall, the changes in the new NSHM have increased the hazard close to the subduction zone and decreased it further away.
2024-02-06 09:00:00
Original from www.sciencenews.org
