Publication Date:
2017-04-04
Description:
A particular synergy among GPS and SAR techniques, to improve the precision of the
current ground deformation monitoring techniques, is investigated. The study of atmo-
spheric anomalies in the GPS EM waves propagation is useful to extrapolate information
about the wet refractivity field. Because of its height and the quite variable weather
conditions, the estimation of Mount Etna atmospheric anomalies using GPS measure-
ments have noticeable importance to calibrate the SAR interferograms and to establish
the “effective” ground deformation of the volcanic edifice. In this study we presented
a method to obtain a 3D electromagnetic waves velocity tomography, starting from the
GPS output data analysis. Thanks to the agreement between the University of Catania
and the INGV-OE, the GPS data used in this work come from ”Etn@net” framework.
The GPS processing has been carried out by using the GAMIT software, by adopting
appropriate processing parameters. A new software was developed for deriving the tro-
pospheric tomography from the GPS data. The code was validated by using synthetic
tests which assume different structure of atmospheric anomalies and with random noise
about twice severe than the typical errors of the GPS. The results of the tests proved
that the tomography software is able to reconstruct the simulated anomalies faithfully.
The code was applied to study the structure of the atmosphere in an actual case: the
period of August 12, 2011 at 10.00 am. The results of the tomography indicate clearly
important features of the refractivity field of the studied day. In conclusion, the syn-
thetic tests and the application on actual data sets of the new software demonstrate that
it is able to reveal the tropospheric anomalies and thus it is an useful tool to improve
the results of the SAR interferometry. An indirect outcome of the use of the GPS for the atmospheric sounding on an active
volcanic area is that concerning the detection of volcanic products in the atmosphere.
Due to the Mt. Etna persistent activity occurred during the last two years, the capability
of GPS to detect the volcanic plume was investigated. The Etna volcano is particularly
suited for an in-depth investigation into the aptitude of GPS observations to detect
volcanic plumes, owing to both the high frequency of explosive episodes and also the
well-developed GPS network. Two different approaches were tested, in order to examine
the capability of the GPS network to detect volcanic plumes at Etna. The first approach
is applied on the signal strength of the GPS L2 carrier phase data, the second approach,
instead, is statistical, and analyzes the single difference post fit residual of elaboration
signals to assert the hypothesis that the plume affects the GPS data. The proposed
method has been tested for the September 4–5, 2007 activity of Mt. Etna. Results from
nineteen GPS permanent stations show that during this explosive activity, the GPS
residuals definitely include the contribution of the volcanic plume. In the future, data
derived from the GPS stations located on Etna’s flanks could be used to improve the
alerting system of volcanic ash, already operating at the Istituto Nazionale di Geofisica
e Vulcanologia, Osservatorio Etneo.
Description:
Università degli Studi di Catania
Description:
Published
Description:
3V. Dinamiche e scenari eruttivi
Description:
4V. Vulcani e ambiente
Description:
5IT. Osservazioni satellitari
Description:
restricted
Keywords:
Atmosphere
;
Etna
;
Tomography
;
01. Atmosphere::01.01. Atmosphere::01.01.01. Composition and Structure
;
01. Atmosphere::01.01. Atmosphere::01.01.07. Volcanic effects
;
01. Atmosphere::01.01. Atmosphere::01.01.08. Instruments and techniques
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
thesis
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