Site Characterizations and Linear Site Responses at Selected Borehole Strong-Motion Arrays From the United States and Japan
Description:
The increase of shear-wave impedance (ρVs) with depth leads to site response: the modification of ground motion in terms of spectral content, amplitude, and duration. Site response can be quantified by the borehole transfer function (TF) and characterized by two parameter pairs of primary importance: the fundamental-mode (i.e., first mode) frequency (f0) and its associated amplification (A0) and peak-mode frequency (fp) and its associated amplification (Ap). To explore the relationship between site characteristics and site response, we characterized the Vs profile using the shear-wave impedance ratio (IR) and velocity ratio (VR). IR is defined as the ratio of the layer impedance below the interface j (ρjVsj) to the average impedance above the interface (ρjaVsja). ρja is the average density above the interface, and ρj is the layer density below the interface j. VR is defined as the ratio of the layer shear-wave velocity below the interface j (Vsj) to the average shear-wave velocity above the interface (Vsja). In this study, we selected 54 borehole arrays penetrating bedrock from the United States and Japan and calculated IRs and VRs for all the Vs profiles. We also derived linear empirical and theoretical TFs for all selected arrays using the weak ground motions and 1D site-response analyses. Our results demonstrated that site response is controlled predominantly by each site’s Vs profile, the IRs or VRs distribution and maximum impedance or velocity ratio (IRmax or VRmax) in particular. Our results also demonstrated that the Vs profiles can be characterized by 1) resonant dominance having IRmax≥3.8 or Rmax≥3.3, 2) complex or weak resonance having 3.5≤IRmax<3.8 or 2.9≤ Rmax<3.3, and 3) weak or non-resonance having IRmax<3.3 or Rmax<2.9. This site characterization has a practical application in engineering because site resonance is of primary interest. Thus, it is essential to obtain a reliable Vs profile down to bedrock for accurate site response quantification.
Session: From Sensors and Networks to Site Characterization and Site Response: Coming Full Circle [Poster]
Type: Poster
Date: 4/18/2023
Presentation Time: 08:00 AM (local time)
Presenting Author: Zhenming Wang
Student Presenter: No
Invited Presentation:
Authors
Zhenming Wang Presenting Author Corresponding Author zmwang@uky.edu University of Kentucky |
Seth Carpenter seth.carpenter@uky.edu University of Kentucky |
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Site Characterizations and Linear Site Responses at Selected Borehole Strong-Motion Arrays From the United States and Japan
Category
From Sensors and Networks to Site Characterization and Site Response: Coming Full Circle