GNGTS 2019 - Atti del 38° Convegno Nazionale

214 GNGTS 2019 S essione 1.4 whose mean duration is more that 14 years from 15 superconducting gravimeters (Rosat et al. , 2017). Moreover, to our best knowledge we provide the first experimental constraints on resonance parameters related to horizontal displacement Love numbers, through suitable uncorrelated combinations of both real and immaginary parts. This work represents a forward step with respect to Amoruso et al. (2012). References Amoruso A. and Crescentini L.; 2009: The geodetic laser interferometers at Gran Sasso, Italy: Recent modifications and correction for local effects. J. Geodyn., 48 , 120-125, DOI 10.1016/j.jog.2009.09.025. AmorusoA., Botta V. and Crescentini L.; 2012: Free Core Resonance parameters from strain data: Sensitivity analysis and results from the Gran Sasso (Italy) extensometers. Geophys. J. Intern., 189 , 923-936, DOI 10.1111/j.1365- 246X.2012.05440.x. Amoruso A., Crescentini L., Bayo A., Fernández Royo S. and Luongo A.; 2018: Two High-Sensitivity Laser Strainmeters Installed in the Canfranc Underground Laboratory (Spain): Instrument Features from 100 to 0.001 mHz. Pure Appl. Geophys., 175 , 1727-1737, DOI 10.1007/s00024-017-1553-7. Rosat S., Lambert S. B., Gattano C. and Calvo M.; 2017: Earth’s core and inner-core resonances from analysis of VLBI nutation and superconducting gravimeter data. Geophys. J. Int., 208 , 211-220, DOI 10.1093/gji/ggw378. THE COLLOCATION APPROACH TO MOHO ESTIMATE AND EVALUATION OF DIFFERENT GRAVIMETRIC METHODS TO MOHO RECOVERY IN IRAN R. Barzaghi 1 , L. Biagi 1 , C. De Gaetani 1 , S. Ebadi 2 , A. Safari 2 , A. Bahroudi 3 1 Politecnico di Milano, Dipartimento di Ingegneria Civile e Ambientale, Milan, Italy 2 School of Surveying and Geospatial Engineering, Research Institute of Geoinformation Technology (RIGT), College of Engineering, University of Tehran, Iran 3 Exploration department, School of Mining Engineering, University of Tehran, Tehran, Iran The transition layer between the upper mantle and the lower part of the crust is defined as the Mohorovicic discontinuity (Moho) and ideally considered as a surface (Turcotte and Schubert 1982). On a global scale, this surface has sharp variations, ranging from over 60 km to less than 5 km depth. The density variation occurring across the Moho between the upper mantle and the lower crust is generally set at 0.5 g/cm3, based on the assumption that the upper mantle density is 3.4 g/cm3 and the lower crust density is 2.9 g/cm3 (Anderson 1989). The Moho transition layer causes seismic wave refraction and reflection and the related gravity signal as measured on the Earth surface can have a standard deviation ranging from 50 to 100 mGal. Moho depths can be estimated using both seismic and gravimetric inversion methods (Parker 1972, Lebedev et al. 2013). Seismic methods can give more accurate estimates that are not however homogeneously distributed over the Earth. On the contrary, gravity is quite homogeneously distributed over the entire Earth and only relatively small areas are un-surveyed (Pavlis and Rapp 1990). Furthermore, satellite dedicated gravity missions (Reigber et al. 1999, Albertella et al. 2002, Tapley et al. 2004) have made available a large amount of data that can be profitably used in combination with ground based gravity data (Shin et al. 2007). In this work, the gravity estimation of the Moho based on the collocation method is presented (Krarup 1969, Moritz 1989, Barzaghi et al. 1992) which also allows integration of gravity and seismic information available in the investigated area. The basic idea of this method is to propagate the covariance structure of the Moho depth to the covariance of the observed gravity. Given gravity observations and Moho depth information (e.g. from seismics), the Moho collocation estimate can be obtained as a linear combination of these data. Also, collocation allows the computation of the variance of the estimation error that can be used as an indication of the estimated depth precision. This approach has been devised for a two layers model and