13th International Conference on Fracture June 16–21, 2013, Beijing, China -7- 5. AE as seismic precursors in The Sacred Mountain of Varallo 5.1. AE monitoring periods The AE collected data are grouped into two different time windows. The first time window starts from May 9, 2011 and finishes June 16, 2011. The second time window starts July 5, 2011 and finishes September 5, 2011. Both time windows shown in the following involve the monitoring of the vertical crack and of the frescos detachment [2,3]. 5.2. Recognizing impending earthquakes by means of AE In this section, referring to the theories introduced above, we obtain a correlation between seismic and acoustic events through the application of the modified integral of Grassberger-Procaccia. The data series of AE analyzed are those related to the time periods listed above. The seismic events, taken from the website http://iside.rm.ingv.it/iside/standard/result.jsp?page=EVENTS#result (seismic catalog of INGV, National Institute of Geophysics and Volcanology), are selected introducing search parameters relating to the defined AE monitoring periods and to a radius of 100 km, close to the site of Sacred Mountain of Varallo (Fig.7). Looking at the temporal distribution of earthquakes in relation to the cumulative AE trend, it can be seen a certain correspondence between AE peaks and earthquake events (Fig.8,9). By applying to the data series the modified correlation integral of Grassberger-Procaccia, we obtain the cumulative probabilities, depending on the radius of interest r and on the interval of occurrence t, considering the peak of Acoustic Emission both as earthquake precursor and as aftershock (Tables 1,2,3,4). Fig.7. Seisimic Events around Varallo (Italy) from May, 2011 to September, 2011.
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