13th International Conference on Fracture June 16–21, 2013, Beijing, China -9- 60 km 80 km 100 km 1 week 0.0254 0.0732 0.1437 2 weeks 0.0357 0.1196 0.2629 3 weeks 0.0371 0.1509 0.3362 4 weeks 0.0371 0.1652 0.3732 5 weeks 0.0371 0.1665 0.3768 Table 2. Cumulative Probability C-: AE as Aftershock from May 9, 2011 to June 16, 2011 60 km 80 km 100 km 1 week 0.0075 0.0278 0.0846 2 weeks 0.0184 0.0552 0.1896 3 weeks 0.0239 0.0833 0.3222 4 weeks 0.0346 0.1040 0.3841 5 weeks 0.0498 0.1210 0.4435 6 weeks 0.0557 0.1268 0.5130 7 weeks 0.0557 0.1268 0.5497 8 weeks 0.0557 0.1268 0.5607 9 weeks 0.0557 0.1268 0.5657 Table 3. Cumulative Probability C+: AE as Precursor from July 5, 2011 to September 5, 2011 60 km 80 km 100 km 1 week 0.0045 0.0298 0.1192 2 weeks 0.0132 0.0465 0.1916 3 weeks 0.0234 0.0717 0.2592 4 weeks 0.0301 0.0970 0.3251 5 weeks 0.0313 0.1114 0.3737 6 weeks 0.0313 0.1246 0.4164 7 weeks 0.0313 0.1299 0.4283 8 weeks 0.0313 0.1336 0.4333 9 weeks 0.0313 0.1341 0.4338 Table 4. Cumulative Probability C-: AE as Aftershock from July 5, 2011 to September 5, 2011 Comparing the probability values obtained for the period May-June, it can be seen that, regardless of the distance and of the correlation time, the probability that a seismic event follows a peak of Acoustic Emission is always greater than the probability that the same AE peak is an effect of the damage caused by the earthquake (Tables 1,2). In practice, we see that the monitored structure behaves as a good seismic receptor. It is interesting to note that, for both monitoring periods, within a radius of 60 km from the monitored site, the AE signal still plays its role as a seismic precursor. On the contrary at 80 km and 100 km, the AE behavior follows the variation of the time windows (Tables 3,4). In particular, we can observe a clear reversal of the AE signal behavior from precursor to aftershock for the second
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