Broadband ground motion simulation of the 2013 Lushan earthquake considering source uncertainties and small earthquake diversity

With the continuous improvements in comprehensive earthquake monitoring capabilities over the past few decades, large amounts of seismic data, especially for earthquakes below M_S 5.0, have been recorded in China. These earthquake data should have great value in the application of strong motion seismology, such as for synthesizing the ground motions of large earthquakes. In this study, we propose an approach for synthesizing the high-probability ground motions for broadband rupture scenarios the 2013 Lushan earthquake by using data from a collection of small earthquakes as empirical Green’s functions. To obtain more refined broadband ground motions, we consider the multiple uncertainty characteristics of the source parameters and simplify the combined scenarios of source models through sensitivity analysis methods. We also analyzed the reliability and rationality of the estimation results for seismic motions from indirect perspectives. This study verified that earthquakes of M_S 4.0–4.9 without considering whether the focal mechanisms is consistent with the mainshock can be used as Green’s functions to synthesize the strong motions of large earthquakes at the same station with the same propagation paths and site environments. We found that the statistical peak ground acceleration and peak ground velocity results for all earthquake scenarios at each station are preliminarily in agreement with the Gaussian distributions or the Chi-Square (χ²) distributions. This approach can also provide ground motion inputs that are more representative of the local area, which can be valuable for designing earthquake-resistant buildings as well as earthquake engineering.