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Development of a Physics-Guided Non-Ergodic Ground Motion Model for the Groningen, Netherlands Region

Description: 

We present the development of a non-ergodic ground motion model (GMM) for the Groningen natural gas field in the Netherlands. Non-ergodic GMMs are a promising development in probabilistic seismic hazard analysis as they offer the potential to reduce the aleatory variability that controls the seismic hazard, especially in larger return periods. This reduction in aleatory variability is accompanied by epistemic uncertainty in regions with sparse observation or a systematic shift in the median ground motion in regions with dense recordings. In order to further reduce the range of epistemic uncertainties, a series of 3D wave propagation simulations on a 3D velocity model for Groningen were performed, illuminating seismic wave propagation paths not represented in the empirical datasets. These simulations are currently limited to a maximum frequency of 5 Hz with plans to extend them to 10 Hz. The non-ergodic model is formulated as a Gaussian Process where the systematic source and site effects are expressed as spatially varying coefficients that depend on the event and site coordinates. A physics-informed kernel function is developed to describe the systematic path effects that takes into account the correlation between entire rays. Assimilating large sets of empirical and simulated data necessitated the development of efficient sparse approximations and the use of high-performance computing. Using the Sparse Cholesky Factorization following the procedure described by Schafer et al. (2021), we were able to reduce the memory and computational complexity from O(N²) and O(N³) to O(N log(N)^d) and O(N log(N)^2d), respectively. While the use of the open-source coding language Julia, which is optimized for parallel computing scalability, allowed us to take advantage of the additional resources in HPC environments for the GP regression.

Session: Regional-Scale Hazard, Risk and Loss Assessments - II

Type: Oral

Date: 5/2/2024

Presentation Time: 02:00 PM (local time)

Presenting Author: Grigorios

Student Presenter: No

Invited Presentation: 

Authors