GNGTS 2014 - Atti del 33° Convegno Nazionale

46 GNGTS 2014 S essione 3.1 disturbances. As we want to focus the study on microseismic events related to fracture processes we temporarily don’t deepen the distinction and the research of their specific source mechanisms. The comparison between event rate and meteorological data can give further information about microseismic source mechanisms and related temporal distribution. The correlation between temperature recorded by an automatic data logger placed on the southern cliff of Madonna del Sasso and the cumulative curve of probable microseismic events is shown in Fig. 3a. At a first sight a relationship between sudden accelerations in the number of microseismic events and abrupt changes (negative or positive) in the air temperature values can be observed. The largest number of probable microseismic events in a day (7) was recorded on 30 November 2013, when temperatures rapidly decreased under 0°C. Fig. 3 – First comparisons between event rate and meteorological data for the period November 2013 - February 2014. (a) Temperature recorded by a probe on the southern cliff of Madonna del Sasso and probable microseismic event cumulative curve. Black rectangles point out the steeper parts of the cumulative curve in agreement with abrupt temperature changes. (b) Daily rainfalls measured at the Arpa Piemonte station of Cesara (VB) compared with the daily total number of events and the daily number of probable microseismic events. The coloured rectangles overlap periods in which signal recording was lacking and only event count was available.