Integrated Perspective of the Present–Day Stress and Strain Regime in Colombia from Analysis of Earthquake Focal Mechanisms and Geodetic Data

Abstract

Focal mechanism analysis is a powerful tool for analyzing the geodynamic context of broad and complex regions, such as northwestern South America. In this zone, a complex tectonic convergence occurs among the Caribbean, Nazca, and South American Plates. The orientations of the maximum horizontal shortening and the values of the brittle strain/stress regime (k' ratio) are obtained based on the analysis of 617 centroid–moment tensors reported from 1976 to 2017 in the Global Centroid–Moment–Tensor Project. These results are complemented with an analysis of GPS velocities, which can be used to determine the surficial deformation and to compare it with the crustal deformation to define the stress field in Colombia, and to formulate a seismotectonic model. This model is characterized by the slow southeastwards displacement of the Caribbean Plate, the convergence of the Andean, Coiba, and Panamá Blocks in northwestern Colombia, and the westwards convergence of the Nazca Plate below the South American overriding Plate. The strain/stress regime maps also show different tectonic environments and large–scale geological heterogeneities.