Abstract
Due to the prominent topography of Mt. Etna, the use of satellite geodetic techniques may significantly suffer from atmospheric heterogeneities. This problem mainly affects the DInSAR technique. To overcome these drawbacks the present study attempts to make headway in measuring and interpreting atmospheric anomalies. We used the GAMIT software to obtain the ZTD (Zenith Total Delay) values for the GPS sessions performed on 1996-97, during ERS-2 passes at Mt. Etna. GAMIT software also allows to characterize the statistical behaviour of the tropospheric effects, by using residuals for each station-satellite pair, and to locate the atmospheric anomalies, present mostly at low altitudes. The attempt at using these results to produce a tomography of radio waves velocity of the troposphere suggests that the number of GPS stations used to investigate atmosphere is a critical point in such a study. The three stations are too few to invert anomalies eventually existing in the lower atmosphere. This result is a good starting point for better direct future study to verify the applicability of this tomographic technique to a geodetic network with a higher number of stations, with the aim of characterizing the lower atmosphere of Mt. Etna for a more accurate monitoring of ground deformations.
Highlights
Monitoring of ground-deformations belongs to geophysical methodologies applied to the study of volcanic and seismogenetic areas for over a century
The removal or the reduction of this unwelcome effect on the interferogram is a critical point in the differential SAR interferometry (DInSAR) technique, because it could be confused with a deformation of volcanic edifice (Puglisi and Coltelli, 2001)
Ters at sea level which minimize the radio waves velocity values, consistently with the values recorded in the area of interest during 1996-1997, we find that the absolute value of difference between these values vmini and the smallest values of vi corresponding to each horizontal plane considered for tomographic analysis, is higher or equal to 4 times the sigma values σi
Summary
Monitoring of ground-deformations belongs to geophysical methodologies applied to the study of volcanic and seismogenetic areas for over a century Satellite based techniques, such as GPS (Global Positioning System) or differential SAR interferometry (DInSAR), are used to meas-. The removal or the reduction of this unwelcome effect on the interferogram is a critical point in the DInSAR technique, because it could be confused with a deformation of volcanic edifice (Puglisi and Coltelli, 2001) To overcome this problem, it is possible to calibrate interferograms using measurements carried out with GPS (Williams et al, 1998), if on the surveyed area a GPS geodetic network exists for ground-deformation monitoring
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