Investigations on the Kappa Parameter Using Empirical and Numerical Approaches and Application for Site-Specific Ground Motion Assessment

Date: 4/24/2019

Time: 04:30 PM

Room: Pine

Anderson and Hough (1984) defined the Kappa parameter κ as frequency-independent attenuation of the S-wave at high-frequency. Based on observations, they decomposed κ in local (κ₀) and regional attenuation (κ_R), respectively. In the last years, this parameter has become important in engineering seismology, in particular to take into account local site conditions in ground motion prediction studies. However, the link between κ and attenuation, traditionally represented in seismology by the 1/Q factor and composed of intrinsic 1/Q_i and scattering 1/Q_sc regimes, is still under study. In this project funded by the French strong-motion network (RESIF-RAP), we propose empirical and numerical approaches to improve the understanding of the link between κ and Q and we explore the influence of the uncertainties related to κ in a site-specific study.

We present results on both κ and 1/Q_i results at stations located in areas of small-to-moderate seismic activity in mainland France. Secondly, we look at the dependency of κ to 1/Q_i and 1/Q_sc through numerical simulations of 2D and 3D wave propagation. Wave scattering is generated by random velocity perturbations in the propagation medium. To do so, we model point sources at depth and study the waves recorded at the free surface. At last, a host-to-target exercise is carried out in the Nice area, southeast of France, where we compute site-specific response spectra using different GMPEs and compare to the ones obtained from recorded earthquake data.

Presenting Author: Celine Gelis

Authors