Using “Did You Feel It?” Data to Map Spatially Variable Site Amplification in the Central and Eastern United States: Lessons From the 2024 M 4.8 Tewksbury, New Jersey, Earthquake
Description:
Seismic hazard is strongly influenced by site-specific geologic conditions. In the Central and Eastern United States (CEUS), strong impedance contrasts (with sediments overlying hard intact bedrock) can lead to significant amplifications of ground motions. The inclusion of site effects in ground-motion models (GMMs) requires residual analysis to examine trends in the residuals with site-specific variables, such as the time-averaged shear-wave velocity in the upper 30 m (VS30), sediment thickness, and basin terms such as Z1.0 (the depth to shear-wave velocity of 1 km/s). This residual analysis is particularly challenging in the CEUS, where station coverage is sparse and many stations are situated on bedrock, leading to minimal observations of true sediment amplification. Macroseismic intensity data, such as the U.S. Geological Survey “Did You Feel It?” (DYFI) program, can be used to provide much denser spatial coverage of earthquake ground motions in the CEUS than from seismic recording stations alone. The 2024 M 4.8 earthquake in Tewksbury, New Jersey, had the highest number of DYFI reports of any earthquake in history, because of the dense population centers near the epicenter and the lower rates of attenuation seen in the CEUS. This work uses over 180,000 DYFI responses from the 2024 M 4.8 New Jersey earthquake to examine site effects in the CEUS. We use the Atkinson et al. (2014) intensity prediction equation to predict Modified Mercalli Intensity (MMI) for each 1-km grid square using the New Jersey earthquake, and compute residuals between the observed and predicted MMI. These event-specific residuals are compared with residuals from strong motion recordings from the earthquake and examined to search for high-resolution spatial trends in site and basin terms at a 1-km resolution. We hypothesize that the broad spatial coverage of DYFI data can be used to better understand site and basin effects at a higher resolution in the CEUS.
Session: Macroseismic Intensity: Past, Present and Future [Poster]
Type: Poster
Date: 4/17/2025
Presentation Time: 08:00 AM (local time)
Presenting Author: Elise
Student Presenter: Yes
Invited Presentation: Yes
Poster Number: 20
Authors
Elise Meyer Presenting Author Corresponding Author elise.meyer@tufts.edu Tufts University |
Laurie Baise laurie.baise@tufts.edu Tufts University |
James Kaklamanos KaklamanosJ@merrimack.edu Merrimack College |
Shiyang Nie shiying.nie@tufts.edu Tufts University |
Maggie Roberts maggie.roberts@tufts.edu Tufts University |
Weiwei Zhan Weiwei.Zhan@ucf.edu University of Central Florida |
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Using “Did You Feel It?” Data to Map Spatially Variable Site Amplification in the Central and Eastern United States: Lessons From the 2024 M 4.8 Tewksbury, New Jersey, Earthquake
Session
Macroseismic Intensity: Past, Present and Future