Gravimetric modeling of the Nazca plate subduction geometry West of Ecuador

Abstract

The Ecuador and Andean Cordillera in South America are highly vulnerable to hazard-ous events. Despite this, the geometry of the subduction plate in Ecuador has rarely been studied using the gravimetric method, a remarkable tool used to understand geological structures. In this study, a gravimetric model of the subduction zone at the western boundary of Ecuador was created using the European-enhanced gravity model of the Earth and the seismic catalog of Ecuador. A workflow was enforced using terrain corrections, the radial power spectrum, and Euler deconvolution to determine the regional and residual gravimetric components and depth of the gravimetric sources. Seafloor morphological structures were then incorporated into the model construction, including the Carnegie Ridge, fracture of Grijalva, and other elements that split the Nazca and Farallon Plates. Additionally, existing faults in the continental plate were considered, mainly the Dolores-Guayaquil system fault that separates the North Andean and South American Blocks. The models were directly constructed from gravimetric anomalies and calibrated using seismic hypocenters. The root mean square error of the current models exhibited a small offset, indicating a good fit between the processed gravimetric data and the theoretical response of the constructed model. The results were described for two sections along latitudes 1°S and 3°S, indicating that the geometric variations in the subduction plate were caused by heterogeneous physiographic elements in the oceanic crust or by a prior subduction area of the Farallon Plate.