Regional spectral decay model for the Sichuan, China: Application in ground motion simulation of the Ms 6.0 Changning earthquake

Abstract. 4260 recordings of 165 events by 168 stations were used to calculate the spectral decay kappa parameter. The kappa values of the two horizontal components were similar and generally larger than those of the vertical component. The impact of magnitude and site condition on the κ₀ value was also investigated, which showed that κ₀ increased with magnitude, indicating that κ₀ is influenced by source effects. In addition, the results showed that softer sites have higher κ₀ values, indicating that site conditions significantly affect κ₀ estimates. The single-station κ₀ values showed little difference between the two horizontal components, both of which were significantly greater than the κ₀ value of the UD component. Furthermore, the relationships between κ₀ and Vs30 were derived, which indicates that κ₀ value decreases with increasing parameter Vs30. Moreover, the logκ₀-logf₀ correlations estimate the κ₀ better than the lnVs30-κ₀ correlation does. Finally, we performed ground motion simulations at 16 stations to validate the derived site-based kappa model. Ground motion simulations at 16 stations demonstrate that both site- and event-related κ₀ mainly affect high-frequency amplitudes. These findings provide a basis for seismic attenuation study and refined ground motion simulation in the study region.