GNGTS 2014 - Atti del 33° Convegno Nazionale

GNGTS 2014 S essione 2.1 25 more intense than during other rumbles with or without earthquakes. Perhaps the increasing in frequency and intensity gives the animals the sensation of a terrific danger, that pounce as a predatory on a quarry. Generally animals begin to cry when the frequency values are around 3-3.5 Hz, but only when these low frequencies rapidly rise. In fact, when natural (creek noises) or anthropic noises or sounds with low frequency values are rather constant, animals are calm. It is interesting to observe some circular and oval figures in spectrum analysis of rumbles when the increase and the following decrease in intensity and frequency are rather uniform. In Fig. 2b we can observe a spectrum figure as a Moorish arc. Animals (those mentioned in chapter 1) always shrill before the rumbles just mentioned above, whatever they may be, but rumbles having a spectrum elaboration with geometrical forms similar to circles, ovals or Moorish arches, when are not followed by a seism, infuse in animals a great fear that expresses itself in anomalous behaviors with high shrills preceding the rumbles. In this instance, animals start to shrills when the frequency of such rumbles is between 3 and 5 Hz. Instead other typologies of rumbles, underground or in air borne, always preceded by animal high cries, induce animal to seek safety by taking to flight, if this is possible. Perhaps, regarding other typologies of rumbles there is a greater association with earthquakes and landslides. Rise in Radon emission, eventual seismic events and rumbles increasing. In an area rich in augen-gneiss, of eruptive origin, and in pechblenda, with also emission of gases, often warm before seism, a continuous Radon 222 monitoring can provide good information about underground gases or water shifting, eventual seismic precursor (de Liso, 2010; de Liso et al. , 2011). The instrument for the Radon monitoring is a Radon-meter detector (Geoex, model 1027), located in SPSC basement, as we can see in Fig. 1. To this day, we have often observed before local earthquakes a rise in Radon mean values, two, three days, sometimes one week before. In the case of earthquakes with magnitude over 3.5 Richter we have sometimes observed a few variations of water-course of creeks in Val Pellice, this happened also for Biglione creek. In these cases, a remarkable variation of Radon mean values was recorded in SPSC. For example, one week before the seism of April 7, 2014, with magnitude 5.0, depth of 5 km and with epicenter distance of 25 km from Torre Pellice, we recorded in SPSC Radon values inferior to the average, contemporaneously to a sudden reduction in the flow of Biglione creek (near SPSC). A reconnaissance on the area above SPSC by the first Author has shown her a variation of the water flow of Biglione creek above Castelluzzo: the creek became hollow in a large transversal crack, and the noise of the water was similar to the one of a waterfall. During the same time, Biglione’s water flow near SPSC was much reduced despite the rains just occurred, Radon mean values in SPSC basement were 81,4 Bq/m 3 , lower than the average local values before a seism. We can suppose that creeks that became hollow in cracks, can create cavities, which can changes Radon carriers, underground movements of gases and the production of different typology of rumbles. For example, in the week before the earthquake of April 7, 2014, a new Radon monitoring (with Geoex Radon dosimeters) in a second house 300 m from SPSC, that had showed for the two months before Radon mean values of 14.8 Bq/m 3 , recorded mean values of 181.4 Bq/m 3 . During this same week, this latter house had the basement flooded, so also two houses located nearby. The inverted situation of Radon mean values between SPSC and this house persists at this day, even if in SPSC basement Radon mean values are gradually returning at higher average values, luckily not as in December 2013 (Fig. 3). In this instance, together with the anomalous emission recorded in the basement of SPSC (1517 Bq/m 3) , an important increase in temperature occurred together with numerous rumbles (more than 50) a day before a local seism (2.6 Richter).