Crustal mobility analysis in the proximal Andean broken foreland at 31°S: A geodetic and geophysical approach

Abstract

In this study, we delve into an in-depth analysis of crustal mobility within the broken foreland of theSouthern Central Andes, specifically focusing on the proximal area between 31°S and 32°S. This regionpresently stands as one of the most dynamically evolving and seismically active zones in the extensiveAndean retroarc area. To achieve our goal, we employed a multidisciplinary approach encompassing theanalysis of gravity data and GNSS measurements. Here, we discuss previous GNSS data and present newmeasurements collected from a high-precision geodetic network established along the proximal brokenforeland at 31°S latitude. To enhance our findings, we complemented this data with measurements oftemporal gravity variations, primarily of tectonic origin, and conducted geophysical modeling of basementstructures in the foreland area. Our geophysical model of the upper crust unveiled that deformation isclosely associated with basement structures marked by faulted blocks and transverse lineamentsidentified in previous surface studies. The GNSS data analysis revealed complex crustal mobility patternsthat are not easily explained. In general, the integrated analysis highlights varied responses observed invectors and gravitational changes across distinct crustal domains in the study area that seem to conformto the characteristics of a fragmented or broken foreland setting. This structural configuration allows, toa certain degree, independent movement of crustal blocks. However, it appears that a substantial portionof the fractured foreland exhibits a relatively cohesive behavior, serving as coherent domains thatfacilitate elastic deformation linked to the underlying deep structures beneath the EasternPrecordillera.Therefore, this study provides further insights into the crustal mobility of broken forelandsystems, where far-field tectonic stress interacts with complex basement block structures andintermontane sedimentary depocenters. These findings are of paramount significance in the context ofintraplate earthquakes in the Andean broken foreland near San Juan City.