GNSS Constraints to Active Tectonic Deformations of the South American Continental Margin in Ecuador

Abstract

GNSS observations constitute the main tool to reveal Earth’s crustal deformations in order to improve the identification of geological hazards. The Ecuadorian Andes were formed by Nazca Plate subduction below the Pacific margin of the South American Plate. Active tectonic-related deformation continues to present, and it is constrained by 135 GPS stations of the RENAGE and REGME deployed by the IGM in Ecuador (1995.4–2011.0). They show a regional ENE displacement, increasing towards the N, of the deformed North Andean Sliver in respect to the South American Plate and Inca Sliver relatively stable areas. The heterogeneous displacements towards the NNE of the North Andean Sliver are interpreted as consequences of the coupling of the Carnegie Ridge in the subduction zone. The Dolores–Guayaquil megashear constitutes its southeastern boundary and includes the dextral to normal transfer Pallatanga fault, that develops the Guayaquil Gulf. This fault extends northeastward along the central part of the Cordillera Real, in relay with the reverse dextral Cosanga–Chingual fault and finally followed by the reverse dextral Sub-Andean fault zone. While the Ecuadorian margin and Andes is affected by ENE–WSW shortening, the easternmost Manabí Basin located in between the Cordillera Costanera and the Cordillera Occidental of the Andes, underwent moderate ENE–WSW extension and constitutes an active fore-arc basin of the Nazca plate subduction. The integration of the GPS and seismic data evidences that highest rates of deformation and the highest tectonic hazards in Ecuador are linked: to the subduction zone located in the coastal area; to the Pallatanga transfer fault; and to the Eastern Andes Sub-Andean faults.

Tectono‐Stratigraphic Insights on the Dynamics of a Complex Subduction Zone, Northern Peruvian Forearc

“…Further northeast, projection of the Northwest Peruvian transpressional system coincides with the deep and active Puná‐Pallatanga fault analyzed by Tamay et al. (2021) (upper right side of Figure 12c). Earthquake focal mechanisms determined its dextral strike‐slip behavior from the Gulf of Guayaquil to the southern Western Cordillera (Ecuadorian Northern Andes).…”

“…Therefore, we interpret the ridges as minor shear zones. Further northeast, projection of the Northwest Peruvian transpressional system coincides with the deep and active Puná-Pallatanga fault analyzed by Tamay et al (2021) (upper right side of Figure 12c). Earthquake focal mechanisms determined its dextral strike-slip behavior from the Gulf of Guayaquil to the southern (c) Interpreted present-day configuration of oceanic microplates, formed since Farallon Plate split, which pushed the Talara Segment of the Nazca Plate, producing the Nazca Sliver.…”

Present-Day Crustal Velocity Field in Ecuador from cGPS Position Time Series

“…Here, earthquakes originate at different depths and with high magnitudes that can cause major catastrophes, such as the earthquake that occurred in Ecuador on 16 April 2016 in Pedernales, a province of Manabí, which generated impacts throughout the Ecuadorian territory. The South American Plate in turn is divided into two blocks—to the north, the Norandino block (BNA), and to the south, the South American plate proper (SOAM) [ 3 , 11 , 12 ]. Studies maintain that there is no well-defined guideline that divides these blocks [ 13 ]; however, it can be modeled with a Benioff plane in the coastal region, Santa Elena peninsula, with a structural dip between 4° and 5°, at a depth between 40 and 70 km, and a sudden change in the Andean region with a tilted plane between 17° and 28° [ 9 , 10 ].…”

An Evaluation of Radon in Drinking Water Supplies in Major Cities of the Province of Chimborazo, Central Andes of Ecuador

“…The Chimborazo province is located in the northern Andes of South America, along a mountain range which includes the Western Cordillera, the Inter-Andean Depression, and Eastern Cordillera [38][39][40]. The local geology is varied in age, lithology, types of deposits, and geological environments of formation, due to the geodynamic evolution of the active continental margin [41][42][43][44][45]. The rock formations range from a late Cretaceous accretion of an allochthonous oceanic terrane towards the more stable South American craton, between the long orogenic evolution that have shaped the local Andes.…”