Before the collapse experiment, an array of broad-band seismometers was deployed around the anticipated collapse area on the surface to record the seismic signals from the collapse and subsequent aftershocks. Figure 2 illustrates the array layout relative to the mine and the collapsed panel.
Ground motion from the collapse was recorded by the array and the data were transformed into vertical, radial and transverse components. Instrument response was removed from the data. An example of the data set and the spectra are presented in Figure 3.
To facilitate the analysis, the velocity model of the mine site was investigated by analyzing the aftershock P and S arrivals. The model was deduced based on the analysis results and the results of a previously conducted reflection and refraction survey. Figure 4 shows the model.