A Parametric Evaluation of Qs-Vs Relationships Used in Physics-Based Ground-Motion Earthquake Simulation

Abstract:

The appropriate representation of attenuation effects due to internal friction in the propagating media is an important factor in earthquake ground motion simulation. Inaccuracies in this regard may result in incorrect estimations of the amplification and duration of seismic waves. This is particularly relevant in regions with high dissipative properties. In physics-based simulations, the attenuation of seismic waves is typically introduced using viscoelastic models. Internally, the properties of these models are set based on the quality factor Q. In turn, the values of Q are set based on the seismic velocities Qp and Qs. In the case of shear waves, for instance, Qs is usually defined based on empirical rules that depend on the shear wave velocity, Vs. Typical Qs-Vs relationships are (piecewise) linear or polynomial functions. Several Qs-Vs relationships exist in the literature. There is, however, no consensus about the most appropriate choice. In this study we explore the behavior and effects of different Qs-Vs relationships in ground motion simulations of historical earthquakes. We propose a flexible Qs-Vs relationship and perform a parametric on different forms of the proposed Qs-Vs rule. The different relationship parameters are tested through the validation of synthetics with data from historical events, and through comparisons with intensity measures such as those used in empirical ground motion prediction equations. Our results suggest that there exist a preferred set of parameters for the choice of Qs-Vs relationships, and we provide insights on the selection process.