INTEGRATION OF GNSS-GPS NETWORKS (cGPS) FOR OBTAINING STRESS AND STRAIN MODELS FOR THE SPINA REGION (SOUTH OF THE IBERIAN PENINSULA AND NORTH AFRICA)

Nowadays, both, the number of observations and the accuracy of satellite-based geodesic measurements, like GNSS, have increased. Therefore, GNSS provides more data as displacement values and velocities. This paper demonstrates that GNSS data analysis is a powerful tool to study geodynamic processes.

In this study, the analyzed GNSS data correspond to continuously recorded GPS (CGPS) stations, what we call the SPINA network. These stations are located in a region called Ibero-Maghrebian which includes the southern areas of the Iberian Peninsula and northern Africa.

The CGPS stations are included in the following organizations: RENEP (National Network of Permanent Stations), RAP (Andalusian Positioning Network), the Murcia Region CGPS Networks, ERVA (Valencian Reference Stations Network), IGN (National Geographic Institute) and the network TOPOIBERIA. The velocity was obtained in two steps: (1) preprocessing position time-series data of daily GPS measurements and (2) applying a combined model using the weighted least-squares method.

The prior knowledge of the crustal strain rate tensor provides a description of geodynamic processes such as the fault strain accumulation.

Based on the distribution of the GNSS stations, several grid sizes were tested to identify the best resolution. A Python script was used to compute the full two-dimensional velocity gradient tensor by means of inverting the GNSS velocities. The tensorial analysis provides different aspects of deformation, such as the maximum shear strain rate, including its direction, and the dilatation strain rate. These parameters can be used to characterize the mechanism of the current deformation.

Based on the computations from the GNSS-data model of components of horizontal deformations, the rates of both principal, values and axes, of the Earth’s crust deformation were found. Deformations measured in the Ibero-Maghrebian region with GPS could be interpreted in terms of either elastic loading or ductile deformation.