**3. Regional and national geodetic networks**

In the study area, it is observed that the number of installed cGPS stations has gradually increased, some of them as part of global networks as well as international networks as a benefic consequence of catastrophic natural events, and others that correspond to different countries to meet the needs of geospatial information and definition of national reference frames in some countries, as well as to carry out studies with various purposes such as tectonic, volcanic, subsidence, among others. cGPS stations established in North America, Central America and the Caribbean are described by [44]. For this paper, a survey of the cGPS stations currently in operation is made, including those of some national networks, which allows establishing that there are about 307 stations with data availability; the location of these stations is displayed in **Figure 3**. Twelve of the stations are part of the International GNSS Service (IGS) global network, installed in 10 countries, three of them in Ecuador.

On January 12, 2010, a magnitude 7.0 earthquake struck Haiti, causing more than 316,000 people dead or missing, 300,000 injured and more than 1.3 million homeless [45]. Due to this disaster, with the purpose of advancing in the knowledge of the geodynamics of the Caribbean plate and strengthening national and regional capacities for the hazards identification and risk mitigation of geophysical and meteorological origin, the National Science Foundation (NSF) of USA sponsored the establishment of the Continuously Operating Caribbean GPS Observational Network (COCONet) project, operated by UNAVCO, conceived as the appropriate strategy to complement existing national geodetic networks [46]. The COCONet network reached a number of 135 stations, incorporating stations owned by several national networks. **Figure 3** shows the location of 54 of these stations corresponding to 22 countries. We have only used these stations in order to have a wide spatial

## *GNSS Networks for Geodynamics in the Caribbean, Northwestern South America, and Central… DOI: http://dx.doi.org/10.5772/intechopen.97215*

coverage, and because some stations have experienced problems in their operation, limiting the continuous availability of data.

In Colombia, the Geological Survey began in 2007 the development of GeoRED, a research and development project based on space geodesy technology that relied on a multifaceted approach to cataloging and defining the geodynamics of northwestern South America [47]. GeoRED is a Spanish acronym for *Geodesia: Red de Estudios de Deformación*. The general purpose of the GeoRED Project is to improve the technical, scientific and operational capabilities in Colombia for analysis, interpretation and policy formulation regarding phenomena related to crustal deformation in Colombia, using GNSS satellite technology. The GNSS GeoRED project is being executed under the operations framework of the Space Geodesy Research Group-SGRG of the Geohazards Directorate [48]. The current cGPS network has 153 stations installed as December 2020. Among these stations, 117 are GeoRED stations, 5 GNSS stations as part of the COCONet Project, and the Bogotá IGS GNSS station. Under a collaborative partnership with local Colombian institutions, thirteen stations have been installed with the Geographical Institute under a joint initiative named GNSS Colombia; eight with the Sugar Cane Research Institute (CENICAÑA); seven with the Bogota City Water Supply Company; and two stations installed with the Universidad Nacional and the Universidad Distrital, respectively. These stations have been fixed to the ground, following mainly UNAVCO's directions for the installation of permanent stations for the study of crustal deformation. Additionally, the Geological Survey of Colombia –GSC- has deployed another geodetic network composed of 70 permanent stations installed in three volcanic regions for the surveillance of the active volcanoes of the country, where the monitoring is carried out from three volcanological and seismological observatories.

In Ecuador, The Geophysical Institute of the National Polytechnical School of Quito began installing in 2006 a network of GPS stations on the edifices of the most active volcanoes in the country. At the end of 2008, it started to implement a country-wide CGPS network of 70 stations [49]. At present, RENGEO (Spanish acronym for *Red Nacional de Geodesia*) is a geodetic network composed of 85 permanent stations, of which 30 are located in potentially active volcanoes [50]. The GPS receivers acquire data at different data tracking intervals, of 15 seconds and 1 second for volcanoes, and 30 seconds, 1 second and 0.2 seconds for tectonic studies, which are transmitted to the Monitoring Center in Quito through different ways such as radio links, internet, microwaves and satellite system. After the occurrence of the 2016 Pedernales earthquake, in order to improve the capacity of monitoring and generation of early warning information, especially due to tsunami hazards, a geodetic cGPS network in the province of Esmeraldas was implemented in real time. The data from this network are integrated with the seismic data to improve the rapid determination of the magnitudes and better characterize the source of the rupture.

The deployment of the GPS geodetic network in Costa Rica has been the result of actions carried out by institutions such as the OVSICORI, Spanish acronym for *Observatorio Vulcanológico y Sismológico de Costa Rica* (Volcanological and Seismological Observatory of Costa Rica), an institute that belongs to the Universidad Nacional, in coordination with foreign entities and researchers (UNAVCO, universities of South Florida, Central Washington, Georgia Tech, among others), as well as the contribution of National real estate institution. For geodynamic purposes, by the end of 2009, 19 cGPS stations had been established in the Nicoya Peninsula [51]. At present, the geodetic network of Costa Rica is composed of 55 cGPS stations [52].

In Venezuela, [53] points out that there are currently six cGPS stations that are part of COCONet (**Figure 3**), and two stations of the VENCREEP project funded by

such a change of structural style roughly coincides with the Caldas tear, as described by [41]. In fact, it is not a plate tear but the confrontation of two different oceanic slabs [13]. On the north, the oceanic-plateau-affinity Caribbean plate sinks to the ESE, as a flat slab lying under the Triangular Maracaibo block and Mérida Andes and reaching depths of almost 700 km further east. This subducted piece of Caribbean plate was the one carrying the Panamá arc on its trailing edge and its consumption into the mantle conducted to the collision of the Panamá arc against South America. Meanwhile on the south, the Nazca plate which is a typical oceanic plate at these latitude, subducts under western South America. [42] propose that buoyant Caribbean crust has been amagmatically subducting under the North Andes for

*Geodetic Sciences - Theory, Applications and Recent Developments*

Finally, the Caribbean plate itself can be considered as a single unit, at least at

In the study area, it is observed that the number of installed cGPS stations has gradually increased, some of them as part of global networks as well as international networks as a benefic consequence of catastrophic natural events, and others that correspond to different countries to meet the needs of geospatial information and definition of national reference frames in some countries, as well as to carry out studies with various purposes such as tectonic, volcanic, subsidence, among others. cGPS stations established in North America, Central America and the Caribbean are described by [44]. For this paper, a survey of the cGPS stations currently in operation is made, including those of some national networks, which allows establishing that there are about 307 stations with data availability; the location of these stations is displayed in **Figure 3**. Twelve of the stations are part of the International GNSS Service (IGS) global network, installed in 10 countries, three of them in Ecuador. On January 12, 2010, a magnitude 7.0 earthquake struck Haiti, causing more than 316,000 people dead or missing, 300,000 injured and more than 1.3 million homeless [45]. Due to this disaster, with the purpose of advancing in the knowledge of the geodynamics of the Caribbean plate and strengthening national and regional capacities for the hazards identification and risk mitigation of geophysical and meteorological origin, the National Science Foundation (NSF) of USA sponsored the establishment of the Continuously Operating Caribbean GPS Observational Network (COCONet) project, operated by UNAVCO, conceived as the appropriate strategy to complement existing national geodetic networks [46]. The COCONet network reached a number of 135 stations, incorporating stations owned by several national networks. **Figure 3** shows the location of 54 of these stations corresponding to 22 countries. We have only used these stations in order to have a wide spatial

the current resolution level of the GPS results in the order of 2–3 mm/a [43]. However, the Hess escarpment is seismically active towards its southwestern end [13] and is moving left-laterally in that order of magnitude. In addition, this major submarine tectonic feature juxtaposes two very different Caribbean entities at naked eye. And it lies in the southern prolongation of an imaginary northeastsouthwest (NE–SW) striking line passing over the southern tip of the Bahamas platform, where transpression north of it is dominant, building up the Island of Hispaniola. This author proposes that such accident may have played a major role in the faster eastward migration of the Southern Caribbean, the one carrying the LIP or oceanic plateau, in the late and middle Miocene. This author further indicates that a modern reactivation could be starting in the recent geologic time, also with dominant sinistral and subordinate normal components, but this time related to the

push of the floating Cocos ridge when being subducted.

**3. Regional and national geodetic networks**

75 Ma.

**148**


#### **Table 1.**

*Number of cGPS stations discriminated by country in the study region and depicted in Figure 3.*

the French National Research Agency. Initial efforts by FUNVISIS since 2003 have focused on the installation of 2 local campaign networks (western and eastern Venezuela) of more than 70 benchmarks. These data is complementary for tectonic studies.

**Table 1** indicates the number of stations installed in each country that are part of the study area, which are represented in **Figure 3**. It is possible that there are additional stations in some countries, but we have considered that these stations will improve, in a short-term, the understanding of the geodynamics of the study region.

available to GeoRED under a cooperation agreement. Final orbits are used in the processing, which include satellite orbits of the GNSS constellations, satellite clock and Earth orientation parameters that are provided in the appropriate format for Gipsy-X by JPL-NASA as contribution to the International GNSS Service (IGS). For the estimation of the tropospheric delay of the GNSS signals, the numerical model known as the Vienna Mapping Function (VMF1) is used, which is an update of the previous model known as VMF [57]. The ocean loading corrections are obtained from the Onsala Space Observatory, and are applied to eliminate the land and ocean tides. The amplitudes and phases of the main oceanic tidal loading terms are estimated by applying the FES2014b model [58]. The processing includes ionospheric

*GNSS Networks for Geodynamics in the Caribbean, Northwestern South America, and Central…*

GIPSY-X/RTGx v 1.3 software uses the Precise Point Positioning (PPP) data processing strategy which is based on obtaining precise reference satellite orbit and

Site coordinates for each day are computed in the non-fiducial frame and transformed to the ITRF2014 frame using a 7-parameter Helmert transformation [59]. The ECEF coordinates have been transformed into topocentric coordinates, which allow daily changes in the coordinates to be expressed in terms of local displacements in the North, East and Up (NEU) components with respect to a

GPS time series have been generated using the HECTOR software v 1.7.2 [60] developed by SEGAL (Space & Earth Geodetic Analysis Laboratory), a center formed by the cooperation between the University of the Interior of Beira (UBI) and the Geophysical Institute Infante D. Luiz (IDL) from Portugal. HECTOR is a specialized software for the study of geodetic time series, which allows estimating

models generated regularly by the IGS.

*cGPS stations processed at GeoRED-GSC.*

*DOI: http://dx.doi.org/10.5772/intechopen.97215*

position in an initial epoch.

**151**

**Figure 4.**

clock products using the IGS GNSS global network.

In terms of instrumentation, **Figure 3** depicts that cGPS station distribution is rather homogenous throughout the Caribbean region and adjacent areas, except for 3 countries (Colombia, Costa Rica and Ecuador). Such homogeneity is a result from the COCONet project implementation, trying to reduce large gaps of data availabilty. Conversely, the concentration of stations in the 3 abovementioned countries responds to national policies, as already mentioned (Nicoya experiment in Costa Rica, post-Pedernales 2016 earthquake instrumentation in Ecuador and GeoRED project in Colombia).
