GNGTS 2014 - Atti del 33° Convegno Nazionale

22 GNGTS 2014 S essione 2.1 Rossini, contemporaneous of Eandi, that says: “La calunnia è un venticello, un’auretta assai gentile… un tremuoto, un temporale… che fa l’aria rimbombar, come un colpo di cannone…”. Rossini was impressed by the chronicles of earthquakes in Val Pellice and the same words of Eandi are present in the lyric aria in “Barbiere di Siviglia”, whose librettist is Cesare Sterbini, that compares the progressive diffusion of slander to a seismic phenomena. In lyric literature this comparison slander-seismic phenomena-volcanic explosion is often present, according to a popular knowledge concerning seismic and pre-seismic phenomena. With reference to rumbles similar to underground rolls of timbals, we must observe another comparison with musical language: these rumbles have a progressive rise in frequencies and intensity, as in a “Beethoven’s crescendo and diminuendo” or as in a “crescendo rossiniano”, we can better observe this characteristic in images of infrasound monitoring, thanks to Spectrum Lab elaborations. Often, in these cases there are contemporaneous earthquakes. Generally, in the case of underground rumbles, there is a contemporaneous little local trembling of the ground, not necessary an earthquake, that often happens 8-15, sometimes 20 hours before earthquakes with epicenter 50-150 km far from Torre Pellice, generally in the area of Cuneo, of Barcelonette or of Brianḉon (France); if there is an important, long storm of shots and rumbles. So we can consider this local trembling following underground rumbles on Vandalino as a phenomenon connected to another future seism with a farther epicentre. In a few cases, rumbles similar to gun shots (observed in Torre Pellice and in a big area of Piedmont and Liguria) happened after earthquakes with magnitude of 4.6 Richter (July 2011), and after a 5.0 Richter (April 2014) in the French Southern Alps, but one time the same rumble happened in Val Pellice 40 minutes before a seism with a magnitude of 0.8 Richter, near Acceglio (July 2012). Sometimes, rumbles and “mistpoeffers” are localized very well in Castelluzzo Peak, in a small underground area of 500-700 m of height: below this area you can hear the rumble above it, while above this area the rumbles can be heard from below. People living near Castelluzzo have the same perception. Often, rumbles, localized in Rorà’s area or in the nearby Frioland Mountain, are followed by a local seism after 50-80 minutes, if there is a sequence of rumbles after the first one. In the consideration of eventual connections between rumbles as pre-seismic or post-seismic phenomena and earthquakes, it is important to take into account the difference of geological micro-zones. Then, it is necessary to distinguish rumbles and brontides where no earthquake follows from the rumble of a seism taking place. In the area of Rorà and Barge there are several gneiss mines, so it is important to differentiate natural rumbles from mine detonations: explosion rumbles of mines have higher frequencies than natural rumbles, they are very short and animals (generally dogs and birds) always cry after these detonations. In the case of natural rumbles and “brontides”, animals cry 70-80 seconds before them, but a wider number of animal species is interested, crying together: dogs, donkeys, cows, cocks, chickens, crows, buzzards, night-birds of prey. Concerning night-birds of prey, they usually scream during the night, but in the case of brontides they cry also during the morning or the afternoon. Amusical sensibility in acoustic perception can assist while considering little differences in the tonal language of animals during their normal life or during situations of alarm. In case of rumbles and brontides followed by earthquakes, vocal animal alarms are like those observed in phase C, before earthquakes (de Liso and Fidani, 2014; de Liso et al. , 2014); vocalizations are more excited and, bearing in mind dog cries, we can hear melodic dissonant intervals. In case of rumbles and brontides without subsequent earthquakes, the shrills are less frequent, but always excited (generally high and with melodic dissonant intervals) and the temporal period of vocal alarm is shorter than in phase A (several hours before earthquakes). Infrasoundmonitoring: instrumentation, monitoringmodality, SpectrumLab’s images of rumbles. Instrumentation. In SPSC an infrasound monitoring by an InfrasoundAetech Meter