The seismological characteristics of the 15 February 2013 Chelyabinsk bolide explosion are investigated based on seismograms recorded at 50 stations with epicentral distances ranging from 229 to 4324 km. By using 8–25 s vertical-component Rayleigh waveforms, we obtain a surface-wave magnitude of 4.17±0.31 for this event. According to the relationship among the Rayleigh-wave magnitude, burst height and explosive yield, the explosion yield is estimated to be 686 kt. Using a single-force source to fit the observed Rayleigh waveforms, we obtain a single force of 1.03×1012 N, which is equivalent to the impact from the shock wave generated by the bolide explosion.
Low-rise buildings are susceptible to high-frequency ground motion. The high-frequency ground motions at regional distances are mainly controlled by crustal Lg waves whose amplitudes are typically much larger than those of body waves. In this study, we develop a Lg-wave Q model for the Sichuan and Yunnan region in the frequency band of 0.3–2.0 Hz using regional seismic records of 1166 earthquakes recorded at 152 stations. Comparison between the observed pattern of ground motion from real earthquake and model prediction demonstrates the robustness and effectiveness of our Lg-Q model. Then, assuming that the Lg-wave Q structure is the main factor affecting the propagation of the high-frequency ground motions, we calculate the spatial distributions of high-frequency ground motions from scenario earthquakes at different locations in the region using the average Lg-wave attenuation model over the frequency band of 0.3–2.0 Hz. We also use the Lg-Q model to estimate the distribution of cumulative energy of high-frequency ground motions based on the historical seismicity of the Sichuan and Yunnan region. Results show that the Lg-Q model can be used effectively in estimating the spatial distribution of high-frequency seismic energies and thus can contribute to the assessment of seismic hazard to low-rise buildings.