Estimation of source characteristics, site effects and path attenuation in the Sichuan Basin, China, using a non-parametric generalized inversion technique

Abstract

Summary A nonparametric generalized inversion technique for the S-wave amplitude spectrum on both the horizontal and vertical components was adopted to calculate the source parameters, site effects, and path attenuations. In this scheme, 1647 three-component records corresponding to 78 earthquakes with Ms values of 2.9–6.0 recorded by 58 strong-motion stations in the Sichuan Basin were used. In the nonparametric generalized inversion technique, a reference station was adopted to remove the trade-off between the site and source terms. Then, the simple model R−0.5 was selected to describe the geometric spreading characteristics of the Sichuan Basin region. The frequency-related quality factor models for the horizontal and vertical components are estimated as Q(f) = 129.9872f1.1119 and Q(f) = 132.54f1.1236, respectively. In addition, the inverted source spectra are well matched with Brune's model, in which the stress drop values range between 0.3 and 3.5 MPa with a mean value of 1.36 MPa. In addition, a comparison between the site effects estimated from horizontal-to-vertical and nonparametric generalized inversion methods shows that the geological environment significantly amplifies the vertical component of ground motion. Finally, a residual related to distance and magnitude indicates that there is no obvious dependence of the scatter on distance or magnitude. The source, path, and site parameters estimated in this inversion can be adopted in ground motion simulations, which could aid in the study of seismic disasters and risk assessment in the Sichuan Basin.