Archivio della ricerca di Triestehttps://arts.units.itIl sistema di repository digitale IRIS acquisisce, archivia, indicizza, conserva e rende accessibili prodotti digitali della ricerca.Fri, 27 Nov 2020 22:36:35 GMT2020-11-27T22:36:35Z1051A new methodology to estimate the EM velocity from Common Offset GPR: Theory and application on synthetic and real datahttp://hdl.handle.net/11368/2848300Titolo: A new methodology to estimate the EM velocity from Common Offset GPR: Theory and application on synthetic and real data
Abstract: We implemented and validated a new method to estimate the velocity distribution from CO GPR data by using the reflection amplitudes and traveltimes picked on the interpreted interfaces in a GPR profiles. Since the method assumes the picked amplitudes to be related only to the reflection coefficients, an accurate data processing is essential before any amplitude picking, the most important steps being the amplitude recovery and the removal of scattering effects. The method also requires as input: 1) the value of the offset, 2) the velocity of the EM wave in the shallow layer, 3) the peak amplitude of the wavelet incident at the first interface. The error associated to the velocities in the first layer has the major influence on the uncertainties of the final results. Nevertheless, this error can be reduced by combining different independent measurements, like CMP gathers, TDR measurements, or dedicated trans-illumination experiments. The assumption of 1-D model in the proximity of each trace position, as well as the small spread approximation used in the algorithm, are acceptable for most of the real GPR applications. In fact, given the small offsets normally used for CO GPR surveys, the incident angles on the various interfaces are small even for shallow targets. The method assumes the subsurface material as lossless and non-dispersive. The latter assumption is satisfied for most practical applications, but most geological media are characterized by high intrinsic attenuation. In such conditions, the procedure could be still valid if applied on data properly corrected for dissipation effects. Further research must address this topic for a better understanding not only of the kinematic, but also of the dynamic behavior of the EM waves in real media at practical field conditions.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/11368/28483002013-01-01T00:00:00ZAutomated reflection picking and inversion: Application to ground and airborne GPR surveyshttp://hdl.handle.net/11368/2882397Titolo: Automated reflection picking and inversion: Application to ground and airborne GPR surveys
Abstract: We apply an automated picking and inversion algorithm to ground-based and airborne glaciological GPR surveys, in order to recover the internal stratigraphy, density distribution, and water content of alpine glaciers. Current glacier monitoring techniques encompass topographic mapping, direct measurements, and GPR surveys. However, the resulting models strongly depend on the assumptions made about the glacier's internal EM velocity and density distributions, which are usually set either constant or slow-varying, with the only constraints given by locally sampled values. Our inversion procedure uses amplitudes and timespace positions of the recorded reflections to recover the EM velocity and thickness of each layer by reconstructing the travel path of each reflected wavelet. The internal density distribution of glaciers is then recovered using well-known empirical formulas. The input reflections are automatically picked using an algorithm designed to detect and track any recorded event characterized by lateral phase continuity. Such a procedure is mostly independent of the interpreter and only requires a few input parameters and thresholds. High data densities lead to accurate and statistically sound models, while 4-D GPR surveys allow monitoring of the temporal variations of a glacier and the estimation of its mass balance.
Fri, 01 Jan 2016 00:00:00 GMThttp://hdl.handle.net/11368/28823972016-01-01T00:00:00ZFirst surveys in an ice cave of the Monte Canin Massif, Alpi Giulie (Italy)http://hdl.handle.net/11368/2859161Titolo: First surveys in an ice cave of the Monte Canin Massif, Alpi Giulie (Italy)
Sun, 01 Jan 2012 00:00:00 GMThttp://hdl.handle.net/11368/28591612012-01-01T00:00:00ZQuantitative 3-D GPR analysis to estimate the total volume and water content of a glacierhttp://hdl.handle.net/11368/2928590Titolo: Quantitative 3-D GPR analysis to estimate the total volume and water content of a glacier
Abstract: We apply an automated picking and inversion algorithm to a 3-D GPR data set acquired on an alpine glacieret, to study its internal stratigraphy, density distribution, total volume, and water content. GPR surveys are particularly useful for glaciological studies, since the transmitted signal can propagate efficiently through the entire glacier volume, while the large number of recorded traces makes any quantitative analysis statistically sound. The applied auto-picking algorithm is designed to accurately and objectively identify the main reflections within a GPR data set, and to characterize them in terms of their peak amplitudes, travel times, and polarities. The inversion algorithm then uses these quantities to recover the subsurface stratigraphy and EM velocity distribution along each GPR profile. In air-ice mixtures, the EM velocity is linked to the density through well-known empirical formulas. Therefore, our inversion algorithm is able to recover the density distribution within a glacier, and combine it with the internal stratigraphy to estimate its water content. By applying this procedure to a 3-D GPR data set, we can obtain an accurate model of an entire glacier, while 4-D surveys can be used to monitor its temporal changes and estimate its annual and seasonal mass balances.
Mon, 01 Jan 2018 00:00:00 GMThttp://hdl.handle.net/11368/29285902018-01-01T00:00:00ZThe cryosphere in the Julian Alps: the case study of Monte Canin massif.http://hdl.handle.net/11368/2377395Titolo: The cryosphere in the Julian Alps: the case study of Monte Canin massif.
Sat, 01 Jan 2011 00:00:00 GMThttp://hdl.handle.net/11368/23773952011-01-01T00:00:00Z