GNGTS 2017 - 36° Convegno Nazionale

GNGTS 2017 S essione 1.2 107 transformed to obtain a ( t ) and b ( t ). This allows, via Eq. (2), the computation of the residual signal r ( t ). We have applied the described procedure to the tilt signal resulting from the vectorial sum of the E-W and N-S components of the ground tilt. In the Fig. 2 (left) the total contribution to the tilt of the temperature and pressure changes is shown together its spectral content (right). In the Fig. 3 the spectra of the signal, before and after the application of the procedure, are represented. In the right plot of the same figure, the residual tilt depurated of the contribution given by the temperature and pressure is shown. Here the red line represents the average trend of the tilt, mainly in the north-south direction (immersion southward), on which fluctuations of variable amplitude are superimposed. An average decrease of the tilt is observable till the end of 2013, reaching a total of 11 µrad; later the observed trend remains constant. The fluctuations around the average trend result randomly distributed with an average amplitude of 9 µrad. Two points of conclusion. The proposed algorithm seems efficiently able at the removal from the ground tilt records of the combined influence of the atmospheric temperature and pressure. A slow significant ground tilt affects the site where the station is located. Attempts of understanding the geophysical meaning of the observed trend require analogous observations to be carried at sites near that being monitored. References Albano A., Corrado G., Gervasi A., Guerra I., 2011. La stazione gravimetrica registratrice dell’Università della Calabria. 30° Conv. Ann. GNGTS, Trieste. AlbanoA., Corrado G., Gervasi G., Guerra I., 2013. ���������� ������� ��� ���� ������������ �� �������� Continuous gravity and tilt observations in Calabria . 32° Conv. Ann. ������ �������� GNGTS, Trieste. Albano A., Corrado G., Gervasi A., Guerra I. ;2015. Continuous gravity and tilt observations in an active g��������� eodynamic area of Southern Italy: the Calabria Arc System. ����� ������� ����� ������ ��� ����� Boll. Geofis. Teor. Appl., 56, 1-18. Berger J.; 1975. A note on thermoelastic strains and tilts . J. Geophys. Res., 88, 2. Hannan E. J., 1970. Multiple Time Series. J. Wiley & Sons, .536 pag. Fig. 3 - Spectra of the tilt, before (left) and after (centre) the application of the procedure and the residual tilt (right) (starting time of the plot is 2011, May 9 at 4 h 00 m 00 s GMT). The red line represents the average trend.