GNGTS 2017 - 36° Convegno Nazionale

GNGTS 2017 S essione 1.2 105 GROUND TILT OBSERVATIONS IN AN ACTIVE GEODYNAMIC AREA OF SOUTHERN ITALY: THE CALABRIA ARC SYSTEM A. Albano 1 , A. Gervasi 2,3 , I.Guerra 3 , G. Corrado 3 1 Istituto Statale di Istruzione Superiore, Baronissi (SA), Italy 2 Istituto Nazionale di Geofisica e Vulcanologia, CNT, Sede di Rende (CS), Italy 3 Università della Calabria, Dip. di Biologia, Ecologia e Scienze della Terra, Arcavacata (CS), Italy In the past years we presented at the GNGST meetings the results obtained progressively by elaborating the continuous recordings of gravity and ground tilt at the ad hoc station activated in 2011 inside the Calabria University settlements ��� � ���������� �� � � ���������� �� � � ( � ���������� �� � � ���������� �� � � = 39°.359005 N; λ = 16°.226858 E; h = 221 m asl), limiting ourself to the time variations of g (e.g. Albano et al. , 2011, 2013). A quite detailed description of the station and the models of the gravity tide and of the tidal field in northern Calabria were reported and discussed by Albano et al. (2015). Long term aim of these activities is the improved knowledge of the overall geophysical frame that will be the scenery of possible medium and high energy earthquakes expectable in the region on the basis of its past history and geodynamical features. With this in mind, the Geophysics and Seismology Laboratory of the Calabria University developed in the last decades a multidisciplinary system of scientific monitoring devices. We report here the results obtained by the analysis of four years (May 2011 - May 2015) of continuous tilt observations at the Calabria University site.��� ������� ������� �� ������� The Earth’s surface is feeling changes of the atmospheric temperature and pressure spanning a wide spectrum both in space and time. ��� ������� �������� ��� ��� ������� ������ �� ��� ����� ��� ������� �� ������������ �� The diurnal rotation and the orbital motion of the Earth are sources of fluctuations of the air temperature and pressure at the surface with main daily and annual periods. Moreover random fluctuations (weather continuum) are superimposed to these fundamental frequencies, associated with the changes of the weather patterns. ����� �� ��� ����������� �� ��� ������� Owing to the propagation of the thermal wave through the Earth’s surface, stresses and ground tilts are induced in the rocks of the upper crust by thermo-elastic effect. A model of the temperature induced tilt and strain at the Earth’s surface was provided by Berger (1975). Changes of the atmospheric pressure also induce deformations in the Earth’s crust. The size of such effects are considerably influenced by the physical parameters of the surface rocks ����� ��� ����� �������� ��� ������� ���� �� ���� ��� (e.g. the water content) and depends also on ���� ��� both the space and time patterns of the thermal and baric fields. Strain and tilt of thermo-baric origin at the Earth’s surface can be considered as a noise masking or distorting the effects of other Fig. 1 - Changes versus time of the air temperature and atmospheric pressure (left) and of the tilt components (right) at the Calabria University station.