Geodetic measurements at the northern border of the Adria plate

Abstract

This work describes measurements and results relevant to crustal movements at the northern border of the Adria plate. The measurements taken into consideration are subsurface observations made with extensometers and tiltmeters and episodic and continuous GPS (CGPS) observations. The subsurface measurements cover a remarkably long period of 34 years, while the episodic GPS campaigns have been performed over a time period of 7 years. The CGPS observations are available since July 1996, and 3.5 years of data have been considered in this work. The main characteristics of each different type of measurement are illustrated, and a first approach is made to compare the results. It is shown that environmental effects are present both in subsurface and surface measurements. Methods to interpret and remove these signals are also proposed. The correlation between crustal deformation and seismic events is investigated, and some examples are presented. The long-term observations are discussed with respect to a well-known model of plate motion. The subsurface crustal long-term observations reveal inversions in the direction of deformation with time scales of 10 or more years, providing important boundary conditions for future geodynamic models of the northern Adria plate. The results show that the comparison between subsurface deformation and CGPS measurements, if made over a sufficiently long period of time, in the order of 10 years, can give important contributions to the understanding of the geodynamical and physical mechanisms related to the earthquake occurrence in this area.