GNGTS 2014 - Atti del 33° Convegno Nazionale

The presence of a very shallow aquifer seem to have the control on the behavior and composition of the fumaroles. The �������� �� ����� ��� ������ ��� �������� �� ������������ emission of gases and fluids are affected by near-surface secondary processes of seasonal character that seem to mask the deeper signals related to the temperature-pressure changes occurring in the hydrothermal system, clearly observed, instead, inside the Solfatara crater at the BG and BN fumarole vents (Chiodini et al. , 2011). �� ��� ������� In the January 2013 the disappearance of the main fumarole recently opened and the appearance of a vent that emits high-pressure steam and liquid water up to 3-4 meters high were observed. It could be a phenomenon partly due to heavy rains during the last week of January (���� � ������������ INGV – Osservatorio Vesuviano)� ���� ��������� ����� �� ����� ������� ������� ��������� ����������� ������� ������ . This fumarolic field is still largely unknown regarding geophysical ������� ������ surveys mainly because of its limited space, surrounded on the eastern side by intense urbanization inside the large Agnano crater (Troiano et al., 2014). Currently it �� ������ �������� �� ������������ is mainly affected by geochemical, thermal and seismic monitoring which may not fully explain the behaviour of fluids surface. The geophysical characterization of the Pisciarelli structure is a crucial step for improving our capability to forecast pre-eruptive scenarios. In particular, electrical and electromagnetic (EM) methods are among the most suitable tools in volcano-geothermal areas (e.g., Di Maio et al. , 1997; 1998; Legaz et al. , 2009; Zeyen et al. , 2011; Fikos et al. , 2012). The resistivity parameter has, indeed, a so large variability as to allow the great majority of buried structures of volcanological interest to be distinguished. To enhance the resolution power, great help is provided by the Electrical Resistivity Tomography (ERT) approach, which implies handling of Fig. 1 – a) The Phlegraean Volcanic District; b) the ERT profiles at Pisciarelli. GNGTS 2014 S essione 1.3 213 a b