Absolute gravity and GPS measurements in Chile : preliminary results
Abstract
High precision gravity combined with GPS geodesy offers increasing potentialities for the study of time variations of the earth gravity field and crustal deformations related with geodynamic, tectonic or volcanic processes. The continental margin of Chile, resulting from the subduction of Nazca and Antarctic plates under the South American plate, belongs to the most active zones in the world where such processes can be observed. During summer 2002, we carried out a first experience of simultaneous absolute gravity and GPS measurements in north and central Chile with the aim to set up a repetition network of precise reference stations. The objectives are : (i) to attempt an estimation of the present-day vertical crustal motions along the andean margin ; (ii) to better constraints the vertical displacements associated with large earthquakes ; (iii) to establish precise calibration lines for relative gravity meters. The measurements have been performed with the FG5 absolute gravity meter (n°206). The sites were selected to ensure precise and safe data acquisition and mid to long-term stability of the stations. Special care was attempted to get measurements on existing sites where other geodetic/gravity observations are available (permanent GPS, DORIS, VLBI, SLR absolute or superconducting gravity). For other sites, differential GPS observations have been realized simultaneously with the gravity measurements. Scintrex CG-3M relative gravity measurements have been taken for earth-tide recording and vertical gravity gradient determinations. A total number of 11 absolute gravity stations have been established in north and central/south Chile. A preliminary processing, confirms that an accuracy of 1 to 3 µGal is achieved for these absolute gravity networks. We present here the first results of this survey and discuss their implications for future monitoring of gravity changes along the south-american plate boundary.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA....13049B