Coupling of regional geophysics and local soil-structure models in the EQSIM fault-to-structure earthquake simulation framework

Abstract

Accurate understanding and quantification of the risk to critical infrastructure posed by future large earthquakes continues to be a very challenging problem. Earthquake phenomena are quite complex and traditional approaches to predicting ground motions for future earthquake events have historically been empirically based whereby measured ground motion data from historical earthquakes are homogenized into a common data set and the ground motions for future postulated earthquakes are probabilistically derived based on the historical observations. This procedure has recognized significant limitations, principally due to the fact that earthquake ground motions tend to be dictated by the particular earthquake fault rupture and geologic conditions at a given site and are thus very site-specific. Historical earthquakes recorded at different locations are often only marginally representative. There has been strong and increasing interest in utilizing large-scale, physics-based regional simulations to advance the ability to accurately predict ground motions and associated infrastructure response. However, the computational requirements for simulations at frequencies of engineering interest have proven a major barrier to employing regional scale simulations. In a U.S. Department of Energy Exascale Computing Initiative project, the EQSIM application development is underway to create a framework for fault-to-structure simulations. This framework is being prepared to exploit emerging exascale platforms in order to overcome computational limitations. This article presents the essential methodology and computational workflow employed in EQSIM to couple regional-scale geophysics models with local soil-structure models to achieve a fully integrated, complete fault-to-structure simulation framework. The computational workflow, accuracy and performance of the coupling methodology are illustrated through example fault-to-structure simulations.

Predicament of the 1d Assumption in Site Response Analysis and Implication on Vertical Ground Motion Assessment

“…To achieve optimal efficiency for solving plane waves propagating in a single large computational domain or processing multiple sites in parallel, the calculation process for each frequency is parallelized with the multiprocessing module [23] and further speedup is obtained through the translation to machine code at run time by the Numba just-in-time (JIT) compiler [24]. Although plane waves are 2D motions by nature (i.e., motions are independent of the spatial location in the out-of-plane direction), seismic motions in 3D space can be obtained by specifying appropriate coordinate system transformation in Site2D when applied to 3D engineering systems [25,26].…”

Transformational Regional-Scale Earthquake Simulations with the DOE EarthQuake SIMulation (EQSIM) Exascale Framework

“…The EQSIM framework (Ref. [8][9][10][11], an application development under the DOE Exascale Computing Project (ECP), has focused on creating a rigorous multidisciplinary workflow for fault-to-structure simulations starting from the release of energy along the rupture of the causative fault, the subsequent propagation of seismic waves radiating away from the fault and finally the interaction of the seismic waves with soil/structure systems, as shown schematically in Figure 3.…”

Applicability of 1D site response analysis to shallow sedimentary basins: A critical evaluation through physics‐based 3D ground motion simulations

“…Complex seismic wave propagation in 3D heterogeneous geological structures across a broad frequency band can be captured through this deterministic approach 42 . In contrast to the continuing limited ground motion recordings from real earthquakes, spatially dense ground motions can be simulated at any location within the regional‐scale computational domain 43 . Since the geological structure employed in the simulation is fully known, this approach provides a unique opportunity to evaluate the applicability of the 1D approximation technique while avoiding the uncertainties in subsurface characterization and input motion selection that are commonly observed in existing field site response investigations.…”

“…42 In contrast to the continuing limited ground motion recordings from real earthquakes, spatially dense ground motions can be simulated at any location within the regional-scale computational domain. 43 Since the geological structure employed in the simulation is fully known, this approach provides a unique opportunity to evaluate the applicability of the 1D approximation technique while avoiding the uncertainties in subsurface characterization and input motion selection that are commonly observed in existing field site response investigations. In this article, based on high-fidelity physics-based ground motion simulations, we perform extensive evaluation of the applicability of 1D SRA for both the horizontal and vertical motions when applied to realistic 3D seismic wavefields.…”