Figure 3.  Average spectral ratios of P waves relative to evid 1.  Each curve drawn in this figure is derived from the median spectral ratio of all channels recording both evid 1 and that event.  Most curves have more than 150 degrees of freedom and the scatter in the results is of the less than 6 dB at the 95% level.  The observation of note here is that the spectrum of all sources become nearly indistinguishable above about 25 Hz.