**2. Tectonic setting**

Gathering of geologic, tectonic, seismologic and geodetic data through the last decades has led to a better understanding of the Caribbean plate, its margins and adjacent regions, progressively bringing in more complexity to the once drawn "drawer-like" Caribbean plate model [17]. In fact, the Caribbean plate borders are actually "plate boundary zones", PBZ, in the sense of [18], "wide deformation zones" in the sense of [19], particularly transpressional along the southern Caribbean PBZ, or "wide plate margins" in the sense of [10]. These margins amalgamate tectonic blocks of diverse size, composition, origin and geometry (**Figure 1**), somehow surrounding the Caribbean Sea, cored by the Caribbean Large Igneous Province (CLIP) or plateau.

Caribbean plate. Stable GPS stations inside the Caribbean, such as on San Andrés

*Tectonic frame. Tectonic blocks: PB (Panama B.), CB (Chocó B.), NAB (North Andean B.),TMB (Triangular Maracaibo B.), BB (Bonaire B.). Other features: CAVA (Central America Volcanic Arc); CCRDB (Central Costa Rica Deformed Belt), EPGFZ (Enriquillo-Plantain Garden Fault Zone), LAS (Leeward Antilles Subduction), MP (Mona Passage), MPFS (Motagua-Polochic Fault System), NHDB (North Hispaniola*

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

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

(Venezuela), will provide a reliable answer as to the relative motion between the Caribbean and surrounding plates. In addition, longer time span comparisons between these internal sites to the plate should confirm any internal deformation or

Besides, strain partitioning at different scales is common to the four Caribbean plate PBZs (**Figure 1**). In Central America, a coastal sliver, bounded by the Central America trench on the southwest and the active Central America volcanic arc (CAVA) on the northeast, escapes to the north-west (NW), taking advantage of the weakening of the continental crust by the CAVA volcanic activity [21–24]. A similar situation is reported in the northern Lesser Antilles arc, where the forearc in this region, limited by the active arc on the west-southwest (WSW) and the Atlantic trench on the north-northeast (ENE), moves northward with respect to the arc [25, 26]. Along the northern Caribbean PBZ, the northernmost sliver of the Hispaniola Island, bounded by North Hispaniola and Septentrional faults on the north and south respectively, displaces west faster than most of the island. In the southern Caribbean PBZ, the Bonaire block as well as the block containing the Caribbean nappes overriden onto South America along northern Venezuela (outcropping in the Coastal and Interior ranges), accommodate shortening while slipping dextrally along the large west–east (W-E) trending Oca-Ancón, San Sebastián and El Pilar

and Providencia islands and Serranilla Cay (Colombia), and Aves Island

fragmentation of the Caribbean plate itself, as proposed by [13].

*Deformed Belt), NLAF (Northern Lesser Antilles Forearc). Modified from [13].*

fault system (**Figure 1**).

**145**

**Figure 1.**

The recognition of such tectonic blocks started first along the southern Caribbean margin and northwestern South America corner, because being poorly defined by a disperse infrequent and moderate-in-magnitude (instrumental) seismicity, as well as by a poor surface/sea-bottom expression of the active tectonic features in comparison with the other Caribbean PBZs (**Figure 2**).

The study of this very complex but subtly expressed southern PBZ was enhanced by the fact that a large portion of the features are on land (**Figure 1**). Conversely, the northern Caribbean plate boundary became a natural laboratory for numerous space geodesy studies due to its apparent structural simplicity, although the first of all GPS studies worldwide, GPS CASA (Central And South America) Project was carried out in the complex southern Caribbean PBZ between 1988 and 1998 [10, 20]. Not as expected, GPS networks have not fully resolved the posed kinematic questions along this northern Caribbean PBZ, since the networks are mostly installed in rather small islands that are within the plate margin themselves that also resulted to be a complex PBZ with several active features lying offshore (**Figure 3**). As a matter of fact, the larger islands, such as Jamaica and Hispaniola, exist as a proof of such PBZ compressional or transpressional processes. A similar situation happens along the eastern border of the Caribbean plate, where the Atlantic plate subducts beneath an arc of active volcanic islands sitting on the

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

#### **Figure 1.**

results obtained from the geodetic networks, initially composed of field stations of data gathering under episodic campaigns type, and later by continuously operating reference stations (cGPS). Several authors have pointed out the extensive applications of space geodesy for scientific purposes, e.g. [14–16], among others. In the study area, despite the restrictions due to the limited coverage of the national GNSS/GPS networks, its impact is already being observed in studies of the Earth dynamics. The data from the stations have allowed the generation of high precision products such as geodetic time series, velocity fields and estimation of tectonic plate motion rates, seismic cycle analysis, estimation of the magnitude and spatial variability of the plate coupling, among other aspects. In addition to tectonic studies, its use has been extended to the volcano deformation monitoring in several countries (Colombia, Costa Rica, Ecuador, Nicaragua), subsidence studies; the use of data for ionosphere and troposphere studies as well as its inclusion, still in its initial state, in tsunami warning systems. Progress has also been made in the conception of multiparameter stations, based on the joint installation in the same site of diverse equipment such as geodetic, seismological, strong motion and meteorological instruments, among others. It is also important to note that there is a good data

*Geodetic Sciences - Theory, Applications and Recent Developments*

availability, although not from all stations due to particular restrictions, that allows its use for various scientific purposes. However, in some cases, through agreements

Gathering of geologic, tectonic, seismologic and geodetic data through the last decades has led to a better understanding of the Caribbean plate, its margins and adjacent regions, progressively bringing in more complexity to the once drawn "drawer-like" Caribbean plate model [17]. In fact, the Caribbean plate borders are actually "plate boundary zones", PBZ, in the sense of [18], "wide deformation zones" in the sense of [19], particularly transpressional along the southern Caribbean PBZ, or "wide plate margins" in the sense of [10]. These margins amalgamate tectonic blocks of diverse size, composition, origin and geometry (**Figure 1**), somehow surrounding the Caribbean Sea, cored by the Caribbean Large

The recognition of such tectonic blocks started first along the southern Caribbean margin and northwestern South America corner, because being poorly defined by a disperse infrequent and moderate-in-magnitude (instrumental) seismicity, as well as by a poor surface/sea-bottom expression of the active tectonic

The study of this very complex but subtly expressed southern PBZ was enhanced by the fact that a large portion of the features are on land (**Figure 1**). Conversely, the northern Caribbean plate boundary became a natural laboratory for numerous space geodesy studies due to its apparent structural simplicity, although the first of all GPS studies worldwide, GPS CASA (Central And South America) Project was carried out in the complex southern Caribbean PBZ between 1988 and 1998 [10, 20]. Not as expected, GPS networks have not fully resolved the posed kinematic questions along this northern Caribbean PBZ, since the networks are mostly installed in rather small islands that are within the plate margin themselves that also resulted to be a complex PBZ with several active features lying offshore (**Figure 3**). As a matter of fact, the larger islands, such as Jamaica and Hispaniola, exist as a proof of such PBZ compressional or transpressional processes. A similar situation happens along the eastern border of the Caribbean plate, where the Atlantic plate subducts beneath an arc of active volcanic islands sitting on the

features in comparison with the other Caribbean PBZs (**Figure 2**).

or by formal request of data to national institutions, these can be obtained.

**2. Tectonic setting**

**144**

Igneous Province (CLIP) or plateau.

*Tectonic frame. Tectonic blocks: PB (Panama B.), CB (Chocó B.), NAB (North Andean B.),TMB (Triangular Maracaibo B.), BB (Bonaire B.). Other features: CAVA (Central America Volcanic Arc); CCRDB (Central Costa Rica Deformed Belt), EPGFZ (Enriquillo-Plantain Garden Fault Zone), LAS (Leeward Antilles Subduction), MP (Mona Passage), MPFS (Motagua-Polochic Fault System), NHDB (North Hispaniola Deformed Belt), NLAF (Northern Lesser Antilles Forearc). Modified from [13].*

Caribbean plate. Stable GPS stations inside the Caribbean, such as on San Andrés and Providencia islands and Serranilla Cay (Colombia), and Aves Island (Venezuela), will provide a reliable answer as to the relative motion between the Caribbean and surrounding plates. In addition, longer time span comparisons between these internal sites to the plate should confirm any internal deformation or fragmentation of the Caribbean plate itself, as proposed by [13].

Besides, strain partitioning at different scales is common to the four Caribbean plate PBZs (**Figure 1**). In Central America, a coastal sliver, bounded by the Central America trench on the southwest and the active Central America volcanic arc (CAVA) on the northeast, escapes to the north-west (NW), taking advantage of the weakening of the continental crust by the CAVA volcanic activity [21–24]. A similar situation is reported in the northern Lesser Antilles arc, where the forearc in this region, limited by the active arc on the west-southwest (WSW) and the Atlantic trench on the north-northeast (ENE), moves northward with respect to the arc [25, 26]. Along the northern Caribbean PBZ, the northernmost sliver of the Hispaniola Island, bounded by North Hispaniola and Septentrional faults on the north and south respectively, displaces west faster than most of the island. In the southern Caribbean PBZ, the Bonaire block as well as the block containing the Caribbean nappes overriden onto South America along northern Venezuela (outcropping in the Coastal and Interior ranges), accommodate shortening while slipping dextrally along the large west–east (W-E) trending Oca-Ancón, San Sebastián and El Pilar fault system (**Figure 1**).

#### **Figure 2.**

*Seismicity. Earthquake epicenters larger than 3 of magnitude recorded in the study area by the National Earthquake Information Center (NEIC) of the USGS and the National Seismic Network operated by the Geological Survey of Colombia for the period of time 2000–2020.*

(e.g., [12, 36]), with a tectonic paroxysm in the Pliocene (last 5–3 Ma, [21]), when most of the Eastern Cordillera of Colombia [37] and Mérida Andes of Venezuela [12] have actually started elevating to their present heights. A significant fraction of the time delay for the effective coupling (suturing) of the Chocó block against South America, besides the obliquity between the confronting plates, may be explained by the low rigidity exhibited by the Panamá arc at the latitudes of Panamá, which is intensely deformed internally by oroclinal bending and NW-SE trending en-echelon left-lateral faulting (e.g. [13, 24, 38]). The effective collision/ accretion of the Chocó block drives the extrusion of NAB (in the sense of [3]), which in the sense of [39] already comprises several NE-escaping blocks, such as Chocó, Maracaibo and Bonaire and others; NAB for this author was already an amalgamation of tectonic blocks. The subduction along which Caribbean plateau floor disappeared into the mantle and drove this indentation-extrusion process, is today partly fossilized between the Chocó block and South America, in association with or running near to the Romeral fault system. This collision has surface expression down to latitude 4°N in Colombia, up to an ENE-WSW-trending alignment of surface tectonic features running across the three Colombian chains at the latitude of Santa Fé de Bogotá, such as Garrapatas, Río Verde and Ibagué faults, and the change of structural style of the front of the Llanos foothills of the Eastern Cordillera, where a dominant dextral strike-slip style on the south (e.g. Algeciras fault) shifts to a much more compressional style on the north (e.g. Guaicáramo, Cusiana and Yopal faults. [39]). Also, the latter author underlines that the Eastern Cordillera becomes much wider across, north of this imaginary line. [40] proposes a broken indenter model for the Panamá-Chocó arc, in which the Chocó arc has been recently accreted to the NAB, resulting in a rapid decrease in shortening in the Eastern Cordillera. At depth,

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

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

*cGPS stations located on the study zone. Table 1 lists the cGPS stations by country.*

**Figure 3.**

**147**

In addition, block indentation and extrusion, and occasional induced oceanic subduction processes at the opposite side of indenters, are also present and rather common to the Caribbean PBZs. Indentation (collision) by submarine relieves or ridges (e.g. Carnegie and Cocos), as engine of tectonic block escape, has been invoked along the Pacific border of South America against the Nazca plate, as for the Pacific coastal sliver of Central America extending between Costa Rica and Guatemala, respectively. In other cases, such strain partitioning has been attributed to the oblique convergence of the subducting plate beneath the overriding one, such as along the northern sector of the Lesser Antilles arc and northernmost block of Hispaniola Island. So has the Ecuadorian-Colombian trench at the southern tip of the North Andes Block –NAB- [27], in the sense of [3]. However, the best regional example of indentation-extrusion is the collision and latter northward-prograding suturing of the Chocó block (originally a constitutive piece of the Cenozoic Panamá arc) against the north–south trending western coast of South America. Some authors as early as early 90's, e.g. [28–30], propose that such collision and diachronic suturing process induces the NNE-directed tectonic escape of a large portion of northwestern South America, extending from the Guayaquil Gulf-Tumbes basin –GGTB- in SW Ecuador to the Dutch Leeward Antilles (Aruba, Bonaire, Curaçao islands lying north of Venezuela, in the southern Caribbean), and incorporating most of Ecuador territory, the 3 main mountain chains (Western, Central and Eastern) of Colombia and all western mountainous Venezuela. This escape takes place along a major plate boundary named as the Eastern Frontal Fault System –EFFS- by [3]. Much precision has been gathered through the years as to the geometry of that NAB southeastern boundary (e.g., [31–35], among many others). This tectonic escape is probably young in age, starting in the late Miocene

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

**Figure 3.** *cGPS stations located on the study zone. Table 1 lists the cGPS stations by country.*

(e.g., [12, 36]), with a tectonic paroxysm in the Pliocene (last 5–3 Ma, [21]), when most of the Eastern Cordillera of Colombia [37] and Mérida Andes of Venezuela [12] have actually started elevating to their present heights. A significant fraction of the time delay for the effective coupling (suturing) of the Chocó block against South America, besides the obliquity between the confronting plates, may be explained by the low rigidity exhibited by the Panamá arc at the latitudes of Panamá, which is intensely deformed internally by oroclinal bending and NW-SE trending en-echelon left-lateral faulting (e.g. [13, 24, 38]). The effective collision/ accretion of the Chocó block drives the extrusion of NAB (in the sense of [3]), which in the sense of [39] already comprises several NE-escaping blocks, such as Chocó, Maracaibo and Bonaire and others; NAB for this author was already an amalgamation of tectonic blocks. The subduction along which Caribbean plateau floor disappeared into the mantle and drove this indentation-extrusion process, is today partly fossilized between the Chocó block and South America, in association with or running near to the Romeral fault system. This collision has surface expression down to latitude 4°N in Colombia, up to an ENE-WSW-trending alignment of surface tectonic features running across the three Colombian chains at the latitude of Santa Fé de Bogotá, such as Garrapatas, Río Verde and Ibagué faults, and the change of structural style of the front of the Llanos foothills of the Eastern Cordillera, where a dominant dextral strike-slip style on the south (e.g. Algeciras fault) shifts to a much more compressional style on the north (e.g. Guaicáramo, Cusiana and Yopal faults. [39]). Also, the latter author underlines that the Eastern Cordillera becomes much wider across, north of this imaginary line. [40] proposes a broken indenter model for the Panamá-Chocó arc, in which the Chocó arc has been recently accreted to the NAB, resulting in a rapid decrease in shortening in the Eastern Cordillera. At depth,

In addition, block indentation and extrusion, and occasional induced oceanic subduction processes at the opposite side of indenters, are also present and rather common to the Caribbean PBZs. Indentation (collision) by submarine relieves or ridges (e.g. Carnegie and Cocos), as engine of tectonic block escape, has been invoked along the Pacific border of South America against the Nazca plate, as for the Pacific coastal sliver of Central America extending between Costa Rica and Guatemala, respectively. In other cases, such strain partitioning has been attributed to the oblique convergence of the subducting plate beneath the overriding one, such as along the northern sector of the Lesser Antilles arc and northernmost block of Hispaniola Island. So has the Ecuadorian-Colombian trench at the southern tip of the North Andes Block –NAB- [27], in the sense of [3]. However, the best regional example of indentation-extrusion is the collision and latter northward-prograding suturing of the Chocó block (originally a constitutive piece of the Cenozoic Panamá arc) against the north–south trending western coast of South America. Some authors as early as early 90's, e.g. [28–30], propose that such collision and diachronic suturing process induces the NNE-directed tectonic escape of a large portion of northwestern South America, extending from the Guayaquil Gulf-Tumbes basin –GGTB- in SW Ecuador to the Dutch Leeward Antilles (Aruba, Bonaire, Curaçao islands lying north of Venezuela, in the southern Caribbean), and incorporating most of Ecuador territory, the 3 main mountain chains (Western, Central and Eastern) of Colombia and all western mountainous Venezuela. This escape takes place along a major plate boundary named as the Eastern Frontal Fault System –EFFS- by [3]. Much precision has been gathered through the years as to the geometry of that NAB southeastern boundary (e.g., [31–35], among many others).

*Seismicity. Earthquake epicenters larger than 3 of magnitude recorded in the study area by the National Earthquake Information Center (NEIC) of the USGS and the National Seismic Network operated by the*

*Geological Survey of Colombia for the period of time 2000–2020.*

*Geodetic Sciences - Theory, Applications and Recent Developments*

**Figure 2.**

**146**

This tectonic escape is probably young in age, starting in the late Miocene

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 75 Ma.

coverage, and because some stations have experienced problems in their operation,

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

the monitoring is carried out from three volcanological and seismological

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

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

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

limiting the continuous availability of data.

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

observatories.

source of the rupture.

**149**

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