Full-Wavefield, Full-Domain Deterministic Modeling of Shallow Low-Magnitude Events for Improving Regional Ground-Motion Predictions

Abstract

ABSTRACT At the fundamental level, seismic risk analysis relies on good modeling tools for predicting the ground motion resulting from hypothetical earthquake events, which is traditionally approximated using many variations of ground-motion prediction equations (GMPEs). The main benefit of these equations lies in their low computational cost, allowing one to run Monte Carlo simulations in which event probabilities are dictated by regional catalogs comprising historical observations. These equations, however, rely on approximations that are only accurate in a statistical sense. In this study, we consider cases in which regional high-resolution 3D earth models are available from exploration reflection seismology. These high-fidelity velocity models allow us to perform deterministic elastic ground-motion simulations at local distances, given a prescribed synthetic earthquake event, and compare the results with those predicted by GMPEs. This full-wavefield full-domain modeling approach is significantly more costly and particularly challenging due to the slow shear-wave velocity at the near surface, which requires fine spatial and temporal discretizations. With the aid of powerful computational resources, we use an adaptive mesh generator and an efficient wave solver to model the 3D elastic and anelastic wave propagation from the hypocenter all the way to the ground surface. This approach can simultaneously account for 3D subsurface structures, near-surface site effects, topographic relief, and the radiation pattern of the source. In areas where observations are sparse, the modeling results can fill the gap between stations and provide a test bed that can be used for improving the development and accuracy of GMPEs. This approach is well suited for areas where shallow low-magnitude-induced seismic events can occur. Lastly, to demonstrate our approach, we consider an observed seismic event at the Groningen gas field and compare the recorded ground motions with both—those predicted by our approach and those predicted by GMPEs.