GNGTS 2015 - Atti del 34° Convegno Nazionale

The data at different heights, for the synthetic case, were generated in two different ways. The first approach, i.e. theoretical approach, consists in measuring the field response at different altitude, the second one, uses a property of the potential field that allows calculating the data at different heights starting from a fixed base level, i.e. the upward continuation. However, the upward continuation introduces an error in calculated field values that can be removed using a third-order polynomial in the inversion process. For the synthetic case, for both calculated and continued data, the inverse models represent the correct position and the true magnetization contrast of the anomaly source. The inversion of the continued data did not provide a good definition of the bottom of the source probably because of the upward continuation errors. For the real case the obtained result are in good agreement with those retrieved by Phelps and Graham (2002). In both cases, even if the algorithm is dealing with a mono-dimensional vertical inversion, we are able to obtain a really good fitting among the measured and the estimated data along the horizontal profile. References Barbosa V. C. F. & Silva J. B. C. , 1994. Generalized compact gravity inversion, Geophysics, 59, 57–68. Barbosa, V.C.F. & Silva, J.B.C., 2006. Interactive 2D magnetic inversion: a tool for aiding forward modeling and testing geological hypotheses, Geophysics, 71 (5), 43–50. Barnes G. & Barraud J., 2012. Imaging geologic surfaces by inverting gravity gradient data with depth horizons. Geophysics, 77, G1–G11. Bott M. H. P., A Simple Criterion for Interpreting Negative Gravity Anomalies, Geophysics, VOL. XXVII, No. 3 (JUNE 1962); P. 376-381 Castaldo R., Fedi M., Florio G., Multiscale estimation of excess mass from gravity data, Geophys. J. Int. (2014) 197, 1387–1398 Fedi, M., & Florio, G. (2001). Detection of potential fields source boundaries by enhanced horizontal derivative method. Geophysical Prospecting, 49(2001), 40–58. Fedi, M., Rapolla, A., 1993. I metodi gravimetrico e magnetico nella geofisica della Terra solida, Liguori Editore, 322 pp. Fedi, M., Rapolla, A., Vertical Gravity an Magnetic Soundings: forward problem formulation and data inversion, Bollettino di GeofisicaTeoricaedApplicataVol.XXXVII, N.147 – September 1995 Fisher, N. J., and Howard, L. E., 1980, Gravity interpretation with the aid of quadratic programming: Geophysics, 45, 403-419. Menke, W., 1984. Geophysical Data Analysis: Discrete Inverse Theory, Academic Press (Elsevier), 260 pp. Guillen A. & Menichetti V., 1984. Gravity and magnetic inversion with minimization of a specific functional, Geophysics, 49, 1354–1360. Last B.J. & Kubik K., 1983. Compact gravity inversion, Geophysics, 48, 713–721. Li Y., and Oldenburg D., 1996, 3D inversion of magnetic data: Geophysics, 61, 394-408. Li Y., and Oldenburg D., 1998, 3D inversion of gravity data: Geophysics, 63, 109–119. Li Y., and Oldenburg D., 2003, Fast inversion of large-scale magnetic data using wavelet transform and logarithmic barrier method: Geophysical Journal International, 152, 251-265. Phelps G. A. & Graham S. E., 2002. Preliminary gravity inversion model of Frenchman Flat basin, Nevada Test Site, Nevada, U.S. Geological Survey Open-File Report 02-363 Pilkington, M., 1997, 3-D magnetic imaging using conjugate gradients: Geophysics 62, 1132-1142. Pilkington M., 2009, 3D magnetic data-space inversion with sparseness constraints: Geophysics 74, L7-L15 Portniaguine, O., and Zhdanov, M. S., 1999, Focusing geophysical inversion images: Geophysics 48, 713-721. Portniaguine, O., and Zhdanov, M. S., 2002, Magnetic inversion and compression: Geophysics 67, 1532-1541. Safon, C., Vasseur, G., and Cuer, M., 1977, Some applications of linear programming to the inverse gravity problem: Geophysics, 42, 1215-1229. Silva J.B.C. & Barbosa V.C.F., 2006. Interactive gravity inversion, Geophysics, 71, J1–J9. Vadim A. Litinsky, Concept of effective density: Key to gravity depth determinations for sedimentary basins, Geophysics, Vol. 54, No. 11 (NOVEMBER 1989); P. 1474-1482 Wijns, C. & Kowalczyk, P., 2007. Interactive geophysical inversion using qualitative geological constraints, Exploration Geophys., 38, 208–212. 172 GNGTS 2015 S essione 3.3