Introduction
Recently, several technological improvements have been implemented in hardware and software applied to Global Positioning System (GPS) technology. Modern receivers can be easily operated from remote sites and directly connected to the Internet. In particular, practically all of the standard modern instruments for permanent GPS stations available for the commercial user are provided with ftp and web servers and can be connected directly to the Internet with the aid of mobile phone technology, and in this way, they can be remotely operated. Facilities for real-time monitoring and positioning with GPS techniques are thus freely available to the user. Modern receivers can be operated by means of user-friendly, object-oriented utilities that are implemented as graphic user interfaces. Static and kinematic positioning applications are widely used to determine the positioning of aircraft in the sky or cars on roads. In Italy, more than 600 permanent GPS stations, which are available for different purposes, are relatively uniformly distributed throughout the territory.
Several continuous GPS (CGPS) station networks are operated by different public and private organizations to provide services to the user, such as correction of kinematic ambiguity and determination of real-time positioning of cars and aircraft. Furthermore, these networks can be used for real-time monitoring of environmental phenomena, including crustal deformation; geodynamic phenomena, such as the subsidence or uplift of the Apennines or Alps chains due to post-glacial rebound; or volcanic activity. High-rate, real-time kinematic applications are useful for computations of coseismic crustal movement and the consequent characterization of seismogenetic structures.
In this work, we begin by describing the methodology applied for the computation of CGPS data solutions that are used to estimate stable high-quality velocity fields from approximately 383 permanent stations that are densely distributed throughout the Italian Peninsula; GPS data are processed for the time span between January 2008 and December 2012. We process the data following a distributed-session multi-step procedure to achieve the task of computing dense velocity fields as well as the strain-rate pattern of the total network. Moreover, the results of the computation of the strain-rate magnitude pattern are presented based on the method developed by Hackl et al. [1] and references therein, which interpolates the horizontal components of the velocity fields by means of the spline in tension technique [2], and then, we calculate the velocity gradient using Generic Mapping Tools (GMT) version 4.5.13 [3]. The strain pattern shows interesting similarities with the map of seismic hazard for the Italian Peninsula, published on the web as “Mappa di pericolosità sismica del territorio nazionale” [4].
Finally, a comparison with the historical seismicity that occurred in the Italian Peninsula during the last 1000 years is presented, showing good analogies with the strain-rate pattern derived from geodetic data.
IntroductionRecently, several technological improvements have been implemented in hardware and software applied to Global Positioning System (GPS) technology. Modern receivers can be easily operated from remote sites and directly connected to the Internet. In particular, practically all of the standard modern instruments for permanent GPS stations available for the commercial user are provided with ftp and web servers and can be connected directly to the Internet with the aid of mobile phone technology, and in this way, they can be remotely operated. Facilities for real-time monitoring and positioning with GPS techniques are thus freely available to the user. Modern receivers can be operated by means of user-friendly, object-oriented utilities that are implemented as graphic user interfaces. Static and kinematic positioning applications are widely used to determine the positioning of aircraft in the sky or cars on roads. In Italy, more than 600 permanent GPS stations, which are available for different purposes, are relatively uniformly distributed throughout the territory.Several continuous GPS (CGPS) station networks are operated by different public and private organizations to provide services to the user, such as correction of kinematic ambiguity and determination of real-time positioning of cars and aircraft. Furthermore, these networks can be used for real-time monitoring of environmental phenomena, including crustal deformation; geodynamic phenomena, such as the subsidence or uplift of the Apennines or Alps chains due to post-glacial rebound; or volcanic activity. High-rate, real-time kinematic applications are useful for computations of coseismic crustal movement and the consequent characterization of seismogenetic structures.In this work, we begin by describing the methodology applied for the computation of CGPS data solutions that are used to estimate stable high-quality velocity fields from approximately 383 permanent stations that are densely distributed throughout the Italian Peninsula; GPS data are processed for the time span between January 2008 and December 2012. We process the data following a distributed-session multi-step procedure to achieve the task of computing dense velocity fields as well as the strain-rate pattern of the total network. Moreover, the results of the computation of the strain-rate magnitude pattern are presented based on the method developed by Hackl et al. [1] and references therein, which interpolates the horizontal components of the velocity fields by means of the spline in tension technique [2], and then, we calculate the velocity gradient using Generic Mapping Tools (GMT) version 4.5.13 [3]. The strain pattern shows interesting similarities with the map of seismic hazard for the Italian Peninsula, published on the web as “Mappa di pericolosità sismica del territorio nazionale” [4].Finally, a comparison with the historical seismicity that occurred in the Italian Peninsula during the last 1000 years is presented, showing good analogies with the strain-rate pattern derived from geodetic data.
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