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A 20 year-long GNSS solution across South-America with focus in Chile

Abstract:

Over the last 3 decades, GPS measurements have been instrumental in quantifying tectonic plates current motion and deformation. Complex patterns of deformation along the plate boundaries revealed heterogeneous coupling on the plates interface and imaged seismic segments at different stages of their seismic cycle. Along the South-American trench in Chile, where large earthquakes occur frequently, continuous GPS observations (cGPS) captured both the long-term plate motion and the transient deformations associated with the seismic cycle. Over the years, a network of hundreds of cGPS stations has been deployed all across the South-American continent by many different institutions for many different sorts of purposes ranging from geographic reference to tsunami early warning. We report here on the processing of 20 years (2000-2020) worth of data over a selection of cGPS stations, devoted to the quantification and analysis of the deformation along the Chilean subduction zone between 18 S and 40 S. We use all available data near the trench in Chile and a less dense network inside the continent where the gradient of deformation is lesser. Our database, named SOAM_GNSS_solENS, provides time series of precise daily station position, obtained from double difference (DD) processing and expressed in the International Terrestrial Reference Frame 2014 (ITRF14). These time series allow to quantify, with sub-millimetric precision, any kind of ongoing deformation process, either from tectonic origin such as interseismic deformation, co-and post-seismic displacements associated with earthquakes, transient deformation associated to seismic swarms and/or a-seismic slow-slip events, or of other origin such as hydrological loading (for ex., the Amazonian basin load) or any other type of loading affecting the surface of the Earth (tides, atmosphere, etc.). We also provide a database of coseismic displacements associated with close to 60 earthquakes of Mw larger than 6.5 that occurred over the last 20 years within the observation area. All time series are directly accessible through a deposit and we plan to make them available through a web interface that will allow any user to perform elementary operations like estimating offsets, detecting outliers, detrending, filtering and stacking. That database will evolve with time, aggregating more data. In the future, we also plan to complement that database with a rapid solution in quasi real time processed in Precise Point Positioning (PPP), and with hourly atmospheric delays associated with water vapor content of the lower layer of the atmosphere.