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arXiv · 2609.31464

Explaining Ground-Motion Residuals at Two Strong-Motion Stations in Southeastern New York: Sediment Resonance and Topographic Amplification

Aser Abbas·Patrick Daniele·James Kaklamanos·Laurie Baise·Kyle Cannon·Ellie Meyer
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Abstract

Sites hosting strong-motion stations in the Central and Eastern United States are commonly characterized using proxy-based parameters, limiting the ability to identify the physical causes of large ground-motion residuals. This study investigates the amplification mechanisms at two New York strong-motion stations that recorded some of the largest positive 1-Hz pseudospectral-acceleration residuals during the 2024 Mw 4.8 Tewksbury, New Jersey, earthquake. Station N62A is located at Caumsett State Historic Park in the Atlantic Coastal Plain, whereas station PAL is located at the Lamont-Doherty Earth Observatory atop the Palisades cliffs. Detailed geophysical site characterization at both sites combined active-source and ambient-noise surface-wave testing with HVSR measurements. At Lamont-Doherty, additional ambient-noise arrays were deployed across the Palisades ridge to evaluate topographic amplification. At Caumsett, surface-wave testing resolved a thick sedimentary column overlying a major impedance contrast, with a spatially representative fundamental site frequency of 0.93 Hz. Amplification in the same frequency range was also independently evident in observed amplifications computed from site-to-site (S2S) residuals. The fundamental-resonance band also encompasses the 1-Hz frequency at which the large Tewksbury residual was observed, supporting deep sediment resonance as the dominant mechanism. At Lamont-Doherty, surface-wave testing indicated hard-rock conditions with a thin, laterally variable sediment cover. The ambient-noise arrays showed repeatable, directional amplification near 2 Hz at PAL, and the earthquake-based S2S amplifications show a peak between approximately 0.6 and 2 Hz, a pattern reproduced by neither the transfer functions nor the ergodic linear amplification models. These observations support topographic amplification as the primary mechanism at PAL.

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Aser Abbas, Patrick Daniele, James Kaklamanos, Laurie Baise, Kyle Cannon, Ellie Meyer. 2026-09-28. Explaining Ground-Motion Residuals at Two Strong-Motion Stations in Southeastern New York: Sediment Resonance and Topographic Amplification. https://arxiv.org/abs/2609.31464

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