← Back to Sessions

Comparison of the Spatial Correlation of Non-Ergodic Terms in GMMs Utilizing Empirical and Simulation Data From Diverse Regions

Description: 

Recent studies, such as those by Sung et al. (2023) and Lavrentiadis et al. (2023), have developed non-ergodic GMMs, which incorporate the spatial distribution behavior of source, path, and site. These studies utilized the varying coefficient model (VCM) approach to account for the source, path, and site effects on ground-motion scaling for a specific site and source pair. The VCM considers the non-ergodic terms as spatially correlated random variables following assumed prior distributions, and it incorporates two hyperparameters derived from the posterior distribution: the correlation length and variance for each non-ergodic term. The hyperparameters aid in predicting the spatially correlated non-ergodic terms to adjust the ergodic model at a specific site. In recent studies, the hyperparameters have been estimated for six specific regions (California, France, Japan, Taiwan, Utah, and Cascadia) based on empirical data or simulation data. The non-ergodic terms include two site terms (one region site term that is spatially correlated and one uncorrelated site term), two path terms (one related to Q effects and one related to the 3-D velocity structure effects), and one source term. We compare the correlation lengths for the four spatially correlated terms for these six regions. Within the frequency range of 0.2-20 Hz, the correlation lengths from the VCM for the non-ergodic source, path, and site terms are in the ranges of 20-50 km, 15-45 km, and 10-30 km, respectively. A consistent result is that the correlation lengths for the source and site terms at frequencies higher than 10Hz are large (10s of km), which seems counterintuitive, but this may reflect regional kappa differences related to regional geology. In regions without enough data to estimate region-specific hyperparameters, the sets of hyperparameters from the six regions can be used in the forward prediction of the non-ergodic effects using the available region-specific ground-motion data.

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

Type: Oral

Date: 5/1/2024

Presentation Time: 11:30 AM (local time)

Presenting Author: Chih-Hsuan

Student Presenter: No

Invited Presentation: 

Authors