Session: Empirical Modeling of Site Effects [Poster]
Type: Poster
Date: 10/12/2023
Time: 07:00 AM
Room: Stanley Park Ballroom
Geometric Parameters for Seismic Site Response in Sedimentary Basins
Site response in sedimentary basins is governed by mechanisms associated with three-dimensional features. This includes the generation of propagating surface waves due to trapped (reflected and refracted) seismic waves, focusing of seismic energy due to basin shape and size, and resonance of the entire basin sediment structure. These mechanisms are referred to as basin effects and they lead to a significant increase in the amplitude and duration of the observed ground motions from earthquake events. Currently, ground motion models (GMMs) incorporate basin effects using the time-averaged shear-wave velocity in the upper 30 m (𝑉S30), and the isosurface depths (depth to a particular shear wave velocity horizon, 𝑧x). This approach captures site response features associated with the basins but uses parameters that are one-dimensional in nature and therefore are limited in their description of the lateral and other three-dimensional (3D) contributing effects. This work explores geometric features as predictive parameters in the development of site-specific models to improve the characterization of site response in sedimentary basins. In this work basin shape is constrained using depth to subsurface geologic formation interfaces associated with the oldest sedimentary deposits (depth to a particular shear wave velocity horizon i.e., 𝑧1.5 and z2.3) and depth to crystalline basement (zcb) which are derived and validated using a systematic exploration of geological cross sections and Community Velocity Model (CVM) profiles in the Los Angeles Basin (LAB). Finally geometric parameters such as basin centroid, area of basin, distance from basin margin, and basin eccentricity are computed based on finalized shape. Residual analysis is employed to evaluate these derived geometric parameters for their ability to reduce bias and uncertainty in basin site response analysis.
Presenting Author: Rashid Shams
Additional Authors
Rashid Shams rashidshams1998@gmail.com University of Southern California, Los Angeles, California, United States Presenting Author
Corresponding Author
|
Chukwuebuka C Nweke ccnweke@usc.edu University of Southern California, LOS ANGELES, California, United States |
Grace A Parker gparker@usgs.gov U.S. Geological Survey, Moffett Field, California, United States |
Geometric Parameters for Seismic Site Response in Sedimentary Basins
Category
Empirical Modeling of Site Effects
Description