Since its creation in 1998, the Argentine Continuous Satellite Monitoring Network (Red Argentina de Monitoreo Satelital Continuo [RAMSAC]) has grown to include more than 100 continuously operating Global Navigation Satellite Systems (GNSS) stations in Argentina. RAMSAC Receiver Independent Exchange Format (RINEX) data and their derived positioning products (e.g., Networked Transport of RTCM via Internet Protocol [NTRIP] streams and time series) have been used in more than 20 peer-reviewed publications studying the inter-, co-, and postseismic geodynamic evolution of the subduction interface between the South America and Nazca plates. Most of this research has focused on the deformation associated with the near-field megathrust earthquake cycle. Nevertheless, many authors have begun to include in their analyses far-field GNSS observations, which in general do not follow the elastic/viscoelastic deformation predicted by current models. We review the contribution of RAMSAC to scientific knowledge of earthquake elastic deformation and associated phenomena. We also describe the future plans for RAMSAC and the societal impact beyond geodetic and geophysical science.

The vertical reference frames for Argentina and Brazil present discrepancies due to their different datums and realizations. Thus, since 2008, we have started a series of activities with the aim of unifying the Argentine and Brazilian national vertical networks (NVNs). To achieve this goal, we have connected the two NVNs at three border points by using the geodetic levelling approach. Additionally, the gravity field approach was also applied, based on a suitable representation of the geoid by considering the Earth Gravitational Model (EGM2008) in its full resolution. In this regard, 1266 co-located Global Positioning System (GPS) and levelling benchmarks regularly distributed over Argentina (612) and Brazil (654) were considered. The geodetic levelling approach shows an offset value of 54 cm, which implies that the Argentine vertical reference frame is above that of the Brazilian vertical reference frame. However, the result of the gravimetric approach shows an offset of 57 cm, which implies a difference of approximately 3 cm between both methods. Hence, since Brazil and Argentina represent a significant part of South America, the solution to the datum problem between both countries could point towards a common vertical reference frame for the Atlantic side.

The recent improvements in satellite tracking data processing, the availability of new surface gravity data sets, and the availability of a new mean sea surface height model from altimetry processing gave rise to the generation of several new global gravity field models. However, to know their potentiality for using in practical situations, we understood that it was necessary their applications in a limited regions. This paper we compare recent geopotential models with gravimetric data over leveling points of Argentinean National Geografhical Institute (ANGI) vertical network in Santiago del Estero region, northwestern Argentine. We have highlighted the most important information, we have established the future expectations to continue with such applications. Results of comparisons are presented.

Temporary deformation in great earthquake cycles and permanent shear deformation associated with oblique plate convergence both provide critical clues for understanding geodynamics and earthquake hazard at subduction zones. In the region affected by the Mw 9.5 great Chile earthquake of 1960, we have obtained GPS observations that provide information on both types of deformation. Our velocity solutions for the first time span the entire latitudinal range of the 1960 earthquake. The new observations revealed a pattern of opposing (roughly arc‐normal) motion of coastal and inland sites, consistent with what was reported earlier for the northern part of this region. This finding supports the model of prolonged postseismic deformation as a result of viscoelastic stress relaxation in the mantle. The new observations also provide the first geodetic evidence for the dextral motion of an intravolcanic arc fault system and the consequent northward translation of a forearc sliver. The sliver motion can be modeled using a rate of 6.5 mm/a, accommodating about 75% of the margin‐parallel component of Nazca–South America relative plate motion, with the rate diminishing to the north. Furthermore, the new GPS observations show a southward decrease in margin‐normal velocities of the coastal area. We prefer explaining the southward decrease in terms of changes in the width or frictional properties of the megathrust seismogenic zone. Because of the much younger age of the subducting plate and warmer thermal regime in the south, the currently locked portion of the plate interface may be narrower. Using a three‐dimensional viscoelastic finite element model of postseismic and interseismic deformation following the 1960 earthquake, we demonstrate that this explanation, although not unique, is consistent with the GPS observations to the first order.

GPS crustal velocity data from the Scotia and South Sandwich plates, transform azimuths, spreading data, and an updated earthquake slip vector catalog provide the first Scotia and South Sandwich plate Euler vector estimates not dependent on closure as the GPS data tie them to the global plate circuit. Neither the GPS data, which sample limited portions of the plates, nor the geologic data, which are not tied to the global spreading circuit, are sufficient individually to define the Euler vectors. As Scotia plate GPS measurements do not sample the stable plate interior, plate boundary deformation field modeling is necessary for Euler vector estimation. Our South America‐Antarctic and Scotia‐South Sandwich Euler pole estimates agree with previous estimates from either GPS or geologic data. Our South America‐Scotia Euler vector, however, is significantly different and near the South America‐Antarctic Euler vector producing an approximately coaxial motion of Scotia between South America and Antarctica.

The Geodesy Subcommitee of the National Commitee of IUGG created the working group "Geopotential Origin" in December 2000 in order to coordinate the national activities, establish and set down a new Vertical Reference System and to interact with Group III of SIRGAS (Geocentric Reference System for the Americas) Project.For that, all the activities were organised in four items. This contribution describes the main results obtained in each of them as well as future tasks for the near future:Tide Gauges: The origin of the Argentine Vertical Reference System, defined by means of tide gauge records, is affected by the sea surface topography at the gauge locations. A project to observe and model the sea level variations using both, tide gauges and satellite altimetry, is being carried out since 1998. Four permanently observing GPS stations have already been installed close to gauges along the Argentine Atlantic coast and integrated in the International GPS Tide Gauge (TIGA) Monitoring Project.Geopotential Numbers: All first order levelling network unadjusted height differences were migrated to digital media and merged with the benchmark positions and gravity values. The resulting database consists of 16,000 level differences distributed along about 3,170 lines. Gravity values are missing for 20 percent of the benchmarks. The data set is currently being checked for consistency.Linking of Altimetric Networks from Neighbour Countries: During 2002 the first link between the altimetric networks of Chile and Argentina was done. The result was a difference of 22 cm, the higher value corresponding to Argentine levelling lines. The border point, where the levelling lines of both countries are connected, is Puesto Monte Aymond, near Estrecho de Magallanes in the south extreme of South America. The corresponding activities in order to make two or three new comparisons along the 5,000 km long borderline between these countries are being coordinated.Recently, the determination of a natural water surface (Fagnano Lake) was used like an equipotential surface to connect the altimetric networks of Chile and Argentina where the classical spirit levelling is not accessible due to the lack of roads.Compensation of Height and Gravity Networks: Adjustment of the national gravity and altimetric networks and their linking with the nets of neighbouring countries are in progress, including both new absolute and relative gravity determinations, which are necessary for the adjustment and optimisation processes.

We present GPS measurements of the crustal velocity field in the southern Central Andes between the Santa Cruz corner and the Malargue fold and thrust belt, and model this interseismic velocity field as the combination of an ephemeral, elastic signal associated with locking of the main plate boundary, and a steady and non-reversing component of displacement associated with localized backarc convergence and growth of the mountain belt. We find that this second component, i.e. the ongoing and permanent displacement of the forearc and the high Andes relative to the craton, can be modeled very well as a steady clockwise rotation of an Andean microplate about a pole located in southern Argentina. Near the Malargue Basin, this microplate (or block) is moving nearly parallel to the strike of the orogen, transporting material towards the bend in the central Andes. Farther north, in the southern limb of the Central Andes, the motion of this same crustal block is directed nearly perpendicular to the strike of the mountain belt. Our results suggest that permanent deformation rates in the backarc range from a maximum of ~ 6-7 mm/yr in the Bolivian Subandes to less than ~ 3 mm/yr in the Argentine Precordillera and Malargue fold and thrust belt. It is likely that most active backarc deformation is accruing in a narrow zone (~ 50 km wide) associated with the backarc boundary (usually defined as the thrust front) though at this stage it is impossible to distinguish whether specific backarc structures are actively accruing strain.

We present GPS measurements of the crustal velocity field in the southern Central Andes between the Santa Cruz corner and the Malargüe fold and thrust belt, and model this interseismic velocity field as the combination of an ephemeral, elastic signal associated with locking of the main plate boundary, and a steady and non-reversing component of displacement associated with localized backarc convergence and growth of the mountain belt. We find that this second component, i.e. the ongoing and permanent displacement of the forearc and the high Andes relative to the craton, can be modeled very well as a steady clockwise rotation of an Andean microplate about a pole located in sou- thern Argentina. Near the Malargüe Basin, this microplate (or block) is moving nearly parallel to the strike of the orogen, transporting mate- rial towards the bend in the central Andes. Farther north, in the southern limb of the Central Andes, the motion of this same crustal block is directed nearly perpendicular to the strike of the mountain belt. Our results suggest that permanent deformation rates in the backarc range from a maximum of ~ 6-7 mm/yr in the Bolivian Subandes to less than ~ 3 mm/yr in the Argentine Precordillera and Malargue fold and thrust belt. It is likely that most active backarc deformation is accruing in a narrow zone (~ 50 km wide) associated with the backarc boun- dary (usually defined as the thrust front) though at this stage it is impossible to distinguish whether specific backarc structures are actively accruing strain.

A new Global Positioning System (GPS)‐derived velocity field for the Andes mountains (26°–36°S) allows analysis of instantaneous partitioning between elastic and anelastic deformation at the orogen's opposing sides. Adding an “Andes” microplate to the traditional description of Nazca‐South America plate convergence provides the kinematic framework for nearly complete explanation of the observed velocity field. The results suggest the oceanic Nazca boundary is fully locked while the continental backarc boundary creeps continuously at ∼4.5 mm/yr. The excellent fit of model to data (1.7 mm/yr RMS velocity misfit), and the relative aseismicity of the upper crust in the interior Andean region in comparison with its boundaries, supports the notion that the mountains are not currently accruing significant permanent strains. Additionally, the model implies permanent deformation is not accumulating throughout the backarc contractional wedge, but rather that the deformation is accommodated only within a narrow deformational zone in the backarc.

Global Positioning System (GPS) measurements provide the first direct measurement of plate motion and crustal deformation across the Scotia‐South America transform plate boundary in Tierra del Fuego. This plate boundary accommodates a part of the overall motion between South America and Antarctica. The subaerial section of the plate boundary in Tierra del Fuego, about 160 km in length, is modeled as a two dimensional, strike‐slip plate boundary with east‐west strike. Along the Magallanes‐Fagnano fault system, the principal fault of this portion of the plate boundary, relative plate motion is left‐lateral strike‐slip on a vertical fault at 6.6 ± 1.3 mm/year based on an assumed locking depth of 15 km. The site velocities on the Scotia Plate side are faster than the relative velocity by an additional 1–2 mm/yr, suggesting there may be a wider region of diffuse left‐lateral deformation in southern Patagonia. The north‐south components of the velocities, however, do not support the existence of active, large‐scale transpression or transtension between the South America and Scotia plates along this section of the plate boundary.

The vertical reference system for Argentina was realized through a series of tide gauge observations collected in Mar del Plata in the year 1924. Within the forties, the reference mark on the tide gauge was connected by high precision geodetic leveling to a highly more stable mark in Tandil, located less than 200 km to the west. This point remains today to be the origin of the national height system. This reference frame was extended to the whole country by high precision geodetic leveling. The first order network was completed in 2001 by IGM. It consists of roughly 16,000 points distributed along several tens of thousands kilometers of high precision geodetic leveling lines. The need of heights referred to the sea level during the long period the establishment of the network took, forced IGM to compute and deliver preliminary heights by sequentially adjusting the leveling observations in rings from the network origin and outwards. Since 1997, SIRGAS Working Group III, vertical datum, works towards the establishment of a unified vertical reference frame for the American continent. This implies both the revision and unification of vertical reference realizations and their densifications. As regards the last item, GTIII has recommended to the participating countries to compute the geopotencial numbers corresponding to their high precision leveling networks whenever measured gravity information is available. As this is the case for Argentina, since March 2001, IGM and UNLP work together to produce a consistent set of geopotencial numbers for the national first order leveling network. This work describes the tasks already accomplished and shows the results obtained so far.

In 1993 a precise GPS network was established in the region of Tierra del Fuego. In 1998, a levelling line was measured with origin at Ushuaia tide gauge. Gravimetric measurements were also made to apply the orthometric correction.

The "first order" reference frame of Argentina is currently realized by about 130 points. Regional densifica- tions up to about 2000 points were made, covering the whole country. Different criteria were used for both, field and calculus procedures, giving as a result densifications of different accuracies and precessions. This paper presents a quantitative analysis that shows the convenience to unify all the existing networks, per- forming a rigorously re-computation. This task will establish a frame consistent in accuracy with SIRGAS and ITRF, but with variable precision, and will assign to each point of the frame a realistic estimation of pre- cision, necessary to qualify the networks in any system of geodetic standards.

The SIRGAS project (Sistema de Referencia Geocéntrico para las Américas) could be considered as one of the most ambitious initiatives that have been taken to practice within geodesy. Its success is both remarkable for the quality of the results obtained and for the large amount of institutions from most South American countries that took and keep taking part in the activities along with European and North American partners. This work summarizes the contributions made by Argentina to the SIRGAS project from its beginnings in 1993 to the present.

SIRGAS (Sistema de Referencia Geocéntrico para las Américas) is a joint project of South, Central and North American countries in cooperation with some international institutions for the establishment and maintenance of a geocentric reference frame for practical and scientific use. A unique reference frame for the American continent was established by two extremely successful geodetic observation campaigns, SIRGAS95 and SIRGAS2000. It provides the basis for the requirements of modern geodesy, and is one of the most important enterprises within geodetic science. At present, its goals aim at the complete integration of all American countries, the maintenance and processing of a continuously observing stations network in the continent, and the adoption of a unified vertical system (height datum). The general outlines for the future tasks are presented in this paper. 1 SIRGAS history, structure and present situation SIRGAS was established during an international meeting in Asunción, Paraguay, in October 1993 by representatives of most of the South American countries, the International Association of Geodesy (IAG), the Pan American Institute of Geography and History (PAIGH), and the National Imagery and Mapping Agency (NIMA), now National Geospatial- Intelligence Agency (NGA), as the "Sistema de Referencia Geocéntrico para América del Sur" (South American Geocentric Reference System) Project. The main objectives were