Reference : An estimate of the influence of loading effects on tectonic velocities in the Pyrenees
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Earth sciences & physical geography
An estimate of the influence of loading effects on tectonic velocities in the Pyrenees
Ferenc, Marcell [> >]
Nicolas, Joelle [> >]
van Dam, Tonie mailto [University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Engineering Research Unit >]
Polidori, Laurent [> >]
Rigo, Alexis [> >]
Vernant, Philippe [> >]
Studia Geophysica and Geodaetica
Springer Netherlands
Yes (verified by ORBilu)
[en] GPS ; loading effects ; Pyrenees
[en] Surface displacements due to temporal changes in environmental mass redistributions
are observable in the coordinate time series of many Global Navigation Satellite System
(GNSS) sites. In this study, we investigated the effect of loading on estimates of tectonic
velocity computed from campaign-style GNSS observations. The study region is in the
Pyrenees mountain range between France and Spain (ResPyr campaigns). In this area,
seismic activity is continuous and moderate and the expected amplitude of the horizontal
tectonic velocity is less than 0.5 mm/yr. In order to determine the velocity, 4 sparse GNSS
campaigns were carried out from 1995 to 2010. Considering this small rate of
deformation, loading phenomena can contribute a non-negligible artifact to the velocity
computation that could affect our geodynamical interpretation. In this investigation, we
specifically considered the atmospheric, hydrological, and non-tidal ocean loading
phenomena. The computed loading deformations for this region show the horizontal
displacements are dominated by the non-tidal ocean loading (maximum 4 mm for the
North and 3.1 mm for the East components); the main vertical contributions are due to the
atmospheric and continental water storage loading (maximum 14.3 for the atmosphere
and 8.1 mm for the hydrology, respectively). We have found that the dominant loading
effect on the horizontal velocity is the non-tidal ocean loading (mean of 0.11 mm/yr),
whereas the vertical component is dominated by the hydrological loading (mean of
0.21 mm/yr). Since the study area is in a mountainous region, we also analyzed the
difference between the atmospheric and the topography dependent atmospheric loading
models at our GNSS campaign sites. We did not find any significant difference between
the two atmospheric loading models in terms of horizontal velocity. Finally, we performed
simulations to identify the optimum timing and frequency of future GNSS campaigns in
this area that would minimize the loading effects on tectonic velocity estimates.

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