Continuous GPS measurements across the Western Alps, 1996–1998

SUMMARY Global Positioning System (GPS) data are analysed from three permanent sites, two in the Western Alps (Grasse, France, and Zimmerwald, Switzerland) and the third in the Po Basin (Torino, Italy), for the 2.5-year period from 1 January 1996 to 1 July 1998. An analysis of the stochastic properties of the position time series reveals a significant amount of spatially and temporally correlated noise, which best fits a model combining white noise and flicker noise. The coloured noise is drastically reduced by spatially filtering the time series, suggesting that it is not due to site-specific eVects such as monument motion, but rather to noise sources common to the three sites, such as reference frame, satellite orbit or Earth orientation errors. We find velocity uncertainties (95 per cent confidence interval) of 2.7 mm yr’1 at GRAS, 2.3 mm yr’1 at ZIMM, and 2.9 mm yr’1 at TORI. The residual velocity in the Eurasian reference frame is statistically greater than zero at ZIMM only, with 2.4±2.3 mm yr’1 of motion in a NW direction. These uncertainties place an upper bound on the expected deformation in the Western Alps. Velocities relative to stable Eurasia do not exceed 3m m yr’1, corresponding to a maximum strain rate of 0.03 mstrain yr’1 over the GRAS‐TORI‐ZIMM triangle.

[1]  P. Molnar,et al.  Constraints on the deep structure and dynamic processes beneath the Alps and adjacent regions from an analysis of gravity anomalies , 1989 .

[2]  John Langbein,et al.  Correlated errors in geodetic time series: Implications for time‐dependent deformation , 1997 .

[3]  Present-day deformation of the French northwestern Alps/southern Jura mountains: comparison between historical triangulations , 1994 .

[4]  James L. Davis,et al.  Geodesy by radio interferometry: The application of Kalman Filtering to the analysis of very long baseline interferometry data , 1990 .

[5]  Guy Ouillon,et al.  The instrumental seismicity of the western Alps: spatio–temporal patterns analysed with the wavelet transform , 1998 .

[6]  M. Kasser,et al.  Global Positioning System Network monitors the western Alps , 1995 .

[7]  G. J. Mets,et al.  Crustal deformations in the Mediterranean Area computed from SLR and GPS observations , 1996 .

[8]  H. Philip.  Plio-Quaternary evolution of the stress field in Mediterranean zones of subduction and collision , 1987 .

[9]  F. Jouanne,et al.  Present-day deformation of the Dauphine Alpine and Subalpine massifs (SE France) , 1996 .

[10]  M. Cushing,et al.  Atlas of macroseismic maps for French earthquakes with their principal characteristics , 1994 .

[11]  Richard G. Gordon,et al.  Current plate motions , 1990 .

[12]  Thierry Camelbeeck,et al.  Geological and geophysical evidence for large palaeo-earthquakes with surface faulting in the Roer Graben (northwest Europe) , 1998 .

[13]  Jeffrey T. Freymueller,et al.  Global Plate Velocities from the Global Positioning System , 1997 .

[14]  Yehuda Bock,et al.  Southern California permanent GPS geodetic array: Error analysis of daily position estimates and site velocities , 1997 .

[15]  Richard G. Gordon,et al.  Effect of recent revisions to the geomagnetic reversal time scale on estimates of current plate motions , 1994 .

[16]  D. Agnew,et al.  Monument motion and measurements of crustal velocities , 1995 .

[17]  Yehuda Bock,et al.  Southern California permanent GPS geodetic array: Spatial filtering of daily positions for estimating coseismic and postseismic displacements induced by the 1992 Landers earthquake , 1997 .

[18]  K. Feigl,et al.  GEODETIC MEASUREMENT OF TECTONIC DEFORMATION IN THE SOUTHERN ALPS AND PROVENCE, FRANCE, 1947-1994 , 1998 .

[19]  J. Levrat,et al.  Laboratory convection experiments: Effect of lateral cooling and generation of instabilities in the horizontal boundary layers , 1981 .

[20]  David E. Smith,et al.  Horizontal crustal motion in the central and eastern Mediterranean inferred from satellite laser ranging measurements , 1994 .

[21]  Richard G. Gordon,et al.  No-net-rotation model of current plate velocities incorporating plate motion model NUVEL-1 , 1991 .

[22]  R. Lacassin,et al.  The Basel 1356 earthquake: which fault produced it? , 1994 .

[23]  W. Reilly,et al.  Crustal strain in Switzerland 1870–1970 , 1990 .