← Back to Sessions

Near-Surface Attenuation Estimated With Coda Waves: Insights From Numerical Simulations and Empirical Observations

Description: 

Site-specific seismic hazard assessments require appropriate characterizations and quantification of near-surface attenuation, which can be highly affected by local geologic structures – also known as site effects. Site effects are a complex function of both shallow and deep geological conditions, topography and other factors, which cannot be explicitly parameterized by commonly used site parameters like the time-average shear wave velocity for the top 30 m (Vs30). Recently, site-specific k0 has received increasing interest because of its ability to capture the attenuation properties of near-surface materials, but accurate characterization of this parameter has yet to be discovered. In this study, a site-specific k0 is partitioned into a specific-specific increment and a regional contribution characterized by coda waves. Coda waves, which are the backscattering waves of body waves, are expected to be less affected by the shallow soil deposits and more sensitive to the regional variations of hard rock attenuations at depth. Thus, recent studies attempted to measure the regional k0 from surface ground motions. However, the differences between the physics underlying direct body-wave attenuation (i.e., P-wave and S-wave) and coda-wave attenuation are still unclear. The limited understanding of the coda wave propagation mechanism in complex media suggests further investigation is needed. In this work, we firstly examine the applicability to measure regional k0 with coda waves. Using ground motions from the DesignSafe database, no correlations are observed between the S-wave and coda wave k0. One-dimensional simulations are introduced to further study the coda propagation mechanism and associated variability.

Session: How Well Can We Predict Broadband Site-Specific Ground Motion and Its Spatial Variability So Far? -III

Type: Oral

Date: 5/1/2024

Presentation Time: 02:45 PM (local time)

Presenting Author: Chunyang

Student Presenter: No

Invited Presentation: 

Authors