GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 3.1 553 Beamforming method was applied to check the isotropy of seismic noise recorded in the band of interest during the entire analysed period. The analysis was performed using the daily signals - vertical component - recorded by the network stations and the results show that the seismic noise is isotropic in the range 1.5-2.0 Hz during the entire analysed time window. Acknowledgements. This work was partially funded by the European Union’s Horizon 2020 research and innovation program under grant agreement n. 764810 (S4CE – Science for Clean Energy). References Bensen G. D., Ritzwoller M. H., Barmin M. P., Levshin A. L., Lin F., Moschetti M. P., Shapiro N. M. and Yang Y.; 2007: Processing seismic ambient noise data to obtain reliable broad-band surface wave dispersion measurement. Geophys. J. Int., 169, 1239–1260, DOI: 10.1111/j.1365-246X.2007.03374.x. López Comino J.A., Cesca S., Jarosławski J., Montcoudiol N., Heimann S., DahmT., Lasocki S., GunningA., Capuano P. and Ellsworth W. L.; 2018: Induced seismicity response of hydraulic fracturing: results of a multidisciplinary monitoring at the Wysin site, Poland. Scientific Reports, DOI:10.1038/s41598-018-26970-9. Obermann A., Kraft T., Larose E. and Wiemer S.; 2015: Potential of ambient seismic noise techniques to monitor the St. Gallen geothermal site (Switzerland). J. Geophys. Res. Solid Earth, 120, 4301–4316, DOI: 10.1002/2014JB011817. Shapiro N. M., Campillo M., Stehly L. and Ritzwoller M.H.; 2005: High-Resolution surface wave tomography from ambient seismic noise. Science, 307, 1615-1618. Vassallo M., Festa G., Bobbio A. and M. Serra; 2016: Low shear velocity in a normal fault system imaged by ambient noise cross correlation: The case of the Irpinia fault zone, Southern Italy. J. Geophys. Res. Solid Earth, 121, 4290–4305, DOI: 10.1002/2015JB012410. Weaver R. L. and Lobkis O. I.; 2001: On the emergence of the Green’s function in the correlations of a diffuse field. J. Acoust. Soc. Am., 110, 3011 – 3017. SPECTRAL ANALYSIS OF POTENTIAL FIELD DATA FOR DEPTH ESTIMATION: CHALLENGES AND APPLICATIONS Y. Kelemework 1 , M. Fedi 1 , N. Pajola 2 1 University of Naples Federico II, Department of Earth, Environment and Resources Sciences, Naples, Italy 2 Eni s.p.a, Milan, Italy Spectral analysis is among the most old and common techniques for the processing and interpretation of potential field data. This is related to the decay properties of the field power spectra which allows an easy estimation of the depths to the top and to the bottom of the sources of magnetic and gravity field anomalies. Depending on the aim of the study, both the depth to the top and bottom of the magnetic sources are important parameters to know. Information about the depth to the top of the magnetic source might help to know the depth to basement rocks and basin analysis in general. An estimate of the depth to the Curie temperature isotherm based on magnetic anomalies can help to understand the general geothermal setting of a region. There is no doubt about the usefulness of power spectrum techniques for potential field data analysis, but it is ambiguous whether deterministic, random uncorrelated, fractal or mixed approaches have to be used for its interpretation (Quarta et al. , 2000). The mathematical formulation of these methods is based on different types of assumptions: a statistical ensemble of blocks (Fig. 1a), flat layers with random and uncorrelated magnetization or fractal/scaling source (Fig. 1b) distribution models. In general, the depth to the top of the shallow source bodies can be computed without major difficulties from the slope of the power spectrum assuming either a statistical ensemble