Actualización preliminar del Sistema Nacional de Referencia Espacial — SIRGAS-Ecuador, posterior al terremoto de Pedernales 7.8 Mw, 16 de abril de 2016

Abstract

The validity and maintenance of a National Geocentric Reference Framework, belonging to countries located in areas of tectonic, seismic, volcanic activity, is a difficult directly related to the level of deformation and stability of the official
coordinates. The horizontal and vertical components change from day to day due to the steady motion of the earth’s crust. However tectonic plates interaction leads to a high level of energy accumulation in the zone of convergence, where
accumulated stress are released when surpassing the resistance of the rocks, giving rise to large or great earthquakes. It is clear that the main losses in an irremediable way will always be the human lives and social catastrophes that
derive from these telluric events; however, as far as the National Georeference is concerned, there are high levels of local deformation, destruction of Geodesic infrastructure of both Passive Networks and Active Networks. Furthermore
irreversible changes determine a before and after in terms of official coordinates and Geographic/Cartographic inputs that were generated from the use of Official Geoinformation.
As in past decades, Ecuador has experienced several geophysical events that have caused serious distortions and local deformation of the Earth’s crust, mainly caused by the subduction process, seismic and volcanic activity, among
others. These effects are clearly reflected in the evaluation of the difference in coordinates and distances between the baseline control points, between the time before the Pre-seismic earthquake and the post-earthquake period. According to
the magnitude of the seismic event, the distortions and discontinuities can reach several centimeters and even meters.
Providing a technical-scientific solution that guarantees a National System of Space Reference consistent post-earthquake and adopt it officially at the national level, is vital to ensure the homogeneous relationship between what is
measured in the field and what is represented in mapping, cadastre and other official applications. The State of the Art of Ecuadorian Geodesy, is a National System of Space Reference Accurate and Exact. This paper first summarizes the concepts of transformation from national to continental and global reference frame accounting for the steady deformation. Using GPS data between 1994 and 2011, we evaluate the linear (constant velocity) part of time evoluting coordinates before the 2016 Pedernales earthquake. Finally, we evaluate the change of coordinates during and immediately after the Pedernales earthquake and present a preliminary solution for the new national reference frame.