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Site Response High-frequency Frontiers and the Added-value of Site-Specific Earthquake Record-based Measurements of Velocity and Attenuation

Description: 

One-dimensional ground response analyses based on 1D velocity profiles and generic relationships between damping and velocity are frequently employed with the assumption that they can provide a reliable assessment of site effects. According to this hypothesis, epistemic uncertainty in site response primarily stems from unconstrained soil properties, and this uncertainty rises sharply with increasing frequency in all Fourier-based ground-motion models. Our results show that the inversion of the spectral ratio of the horizontal-to-vertical components of strong motions based on the diffuse field concept accounting for the site-specific damping profile allows to capture significantly more site-specific features in site response, especially at high frequencies where both the deep sedimentary structure and the damping profile above the seismological bedrock have a strong influence on the disparity between observed and predicted ground motion. While the use of refined velocity and generic damping profiles for testing sites of the Japanese KiK-net already provides a reduction in the high-frequency residual and corrected site-to-site variability (and then the accuracy of predictions), the inclusion of site-specific damping allows this value almost to be halved. These results show that many sites are indeed too complex to be modelled by classical 1D ground-response analysis relying on generic damping relationships, while only site-specific record-based models allow a significant reduction in the bias with respect to coarse and generic site models.

Session: Challenges and Opportunities in Constraining Ground-motion Models from Physics-based Ground-motion Simulations - II

Type: Oral

Date: 4/17/2025

Presentation Time: 11:15 AM (local time)

Presenting Author: Marco

Student Presenter: No

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