[J05-4] Crustal dynamics: Multidisciplinary approach to seismogenesis IV

[J05-4-01] GPS VELOCITY FIELD IN THE NORTHWESTERN CORNER OF SOUTH AMERICA

^○Hector Mora-Paez¹, James Kellogg², Jeff Freymueller³, Dave Mencin⁴, Rui Fernandes da Silva⁵, Leonardo Cardona-Piedrahita¹, Sindy Lizarazo¹, Leidy Giraldo¹, Fredy Diaz-Mila¹ (1.Colombian Geological Survey, Space Geodesy Research Group, Bogota, Colombia, 2.University of South Carolina, Columbia SC, USA, 3.University of Alaska, Fairbanks, USA, 4.University of Colorado, Boulder, USA, 5.University of Interior Beira, Portugal)

invited

Global Positioning System (GPS) data from southern Central America and northwestern South America collected at GPS permanent stations during the last ten years reveal wide plate margin deformation along a 1400 km length of the North Andes. Associated with the oblique subduction of the Nazca plate at the Colombia-Ecuador trench is the “escape" of the North Andes block (NAB). This work presents and discusses a new horizontal velocity field for northwestern South America derived from CORS (Continuously Operating Reference Stations) GPS observations of geodetic networks located in Colombia, Panama and Ecuador. In Colombia, the GeoRed network is a dedicated GNSS network for geodynamic studies installed by the Colombian Geological Survey through the Space Geodesy Research Group that currently consists of 100 stations. In this work, we use data from GeoRed permanent stations with a minimum of 2.5 years of observations. Using GPS velocity vectors for 53 permanent stations, we have estimated a new regional geodetic velocity field. We used an updated model for the present-day angular velocity of the South American plate (SEGAL model) based on a much denser network of CORS velocity solutions (Fernandes et al., in prep.). We combined our velocity field with the published results of Nocquet et al. (2014), to provide a more complete picture of velocities across the entire North Andes block. Nocquet et al. (2014) used a large number of sites in Ecuador, with only a few sites in Colombia, so the two data sets are highly complementary. They defined the stable South American plate using a different set of sites than used in the SEGAL model, so we used the four overlapping sites between the two data sets, all located in northern Ecuador or southern Colombia, to compute the offset between the two South America frames. We then estimate the motion of the North Andes block using a subset of these sites, and investigate tectonic motions relative to the North Andes block.