GNGTS 2016 - Atti del 35° Convegno Nazionale

254 GNGTS 2016 S essione 1.3 For the Mount Etna case study (Fig. 3), we waited for the scientific publications about this eruptive period, in order to get new parameters related to the eruptive activity. The scientific production about an eruptive volcano is faster, so in a few years we could gather some multidisciplinary data (for example Bombrum et al. , 2016; Bonaccorso and Calvari, 2013; Bencke et al. , 2013), independently acquired, well interpreted, revised and then widely accepted by the scientific community. Fig. 3a shows the position of our monitoring station (TBL), on the opposite flank with respect to the direction of last pyroclastic falls and flows emitted by the New South East Crater, 4 km to South. The exposed ground surface actually shows a wide temperature range, as shown in the �� ����� ����� �� ��������� ����� ������ � ������ ��� ���� �������� ������ ���� IR image taken in September 2016, during a cloudy day with rainfall (18-41 °C). During the monitoring period (September 2009-2012) the surface heat flux ���� ��� ������ from the ground registered ������� �������� ������� �� ��� �������� �������� ��� �� ����� ��� ���� �������� changes directly related to the volcanic activity and no delay has been observed between the changes of eruptive rate and the relative change of surface heat flux (Fig. 2b). The monitoring site, located on the opposite flank, was about � �� ���� ���� ��� ��� �������� 4 km away from the new eruptive center, located on the SE flank. In 2010, few months after a seismic swarm at the pernicana fault, a new eruptive cycle started at SE crater and a new cone formed. The new vent, named “New SE Crater” was already 240 m high in spring 2013. Magma rising in new conduits keept its gases up to the surface and eruption of this period were more explosive than before. �� ���� In Fig. 2b the ����� ������ ����� �������� ��� ������ ����������� �� ��� ���� ���� ���������� �� ���� white arrows (1-4) indicate the ranges represented by the mean term variations of heat flux during the pre-eruptive phase (1); during low emission rate (2), high emission rate (3) periods, and the after the eruptive period (4). In Fig. 3c the distal heat flux from the ground (HFD) show an inverse relationship with the Total Radiant Energy (T RE, scale on the right axis) retrieved for lava fountain episodes and strombolian explosions at the New South East Crater (data from Bombrum et al. , 2016). Moreover, in the same figure, the continuous heat release monitored in distal position (HFD) showed in the short term (±1 day) around the explosive activity interesting correlations with the Radiant Energy evaluated by Bombrun et al. (2016) by analyses of IR imaging. The different datasets under consideration showed that, in case of stress-induced changes in the vapor pressures, the meteorological noise has a negligible effect and the time variations of heat release from fumaroles areas; The heat flux from the ground has been related to many other geophysical parameters, such as deformations, seismic release, or increase of magmatic component in the fluid release. On the contrary, the local heat flux from soil resulted essentially modulated by external variations (like sun radiation, rainfall, atmospheric pressure) during phases of stationary convection, when the steady state pressure field appeared less perturbed by volcano-tectonic activity. Starting from these monitoring evidences, the fumaroles areas should be considered as indicators of geodynamic instability, and the implementation of multidisciplinary observation systems by a new network of monitoring stations able to highlight the main variations of surface heat flux by these particular observational sites, and their surroundings, would be convenient. By adding the geochemical perspective to a well established geophysical monitoring network we could successfully address the interpretation of observed phenomena and a timely evaluation of volcanic hazard. A volcano, as well as geothermal area, are characterized by a thermal transients higher than the surroundings. In these areas the fluid circulation is a form of work easily to monitor in continuous, as the expression of extensive andwidely diffuse energy flux toward the earth surface, even if the intensity is lower than those associated to the episodic paroxysms characterizing the main eruptive vents. The right perspective for interpreting all the observational data could came comparing dataset acquired on a very long term period at an adequate sampling rate, to avoid wrong interpolations of time-series. Interpretation can be correctly addressed only in the framework of a multidisciplinary observation system, keeping in mind that the preparatory stages of earthquakes and volcanic eruptions/unrests are deeply linked by mutual cause-