The present-day tectonic regimes of the Colombian Andes and the role of slab geometry in intraplate seismicity

Understanding the present-day crustal stress field is fundamental to comprehending active deformation in complex intraplate settings. This is especially true in the Colombian North Andean Block (C-NAB), where the Nazca, Caribbean, and South American plates interact. Our main goals of this study are: (1) to improve our understanding of seismotectonics of the C-NAB, (2) to test the hypothesis that slab geometry controls intraplate stresses, and (3) to evaluate the coherence between crustal stresses and strain field data obtained from GPS data. We show that south of the slab tear that separates the Nazca Plate from a northern plate (Caribbean Plate? Coiba Microplate?), a maximum horizontal compression (SHmax) trending N83°E is associated with a regional strike-slip faulting regime. In this region, the SHmax responds to the oblique subduction of the Nazca Plate, thus favoring the northeastern escape of the C-NAB. Oppositely, north of the slab tear, clockwise rotation in the SHmax to an NW–SE direction (N111°E) is associated with a regional thrust-faulting tectonic regime. Overall, the correspondence between SHmax and subducting slabs underscores relations between plate geometry, plate motion, and intraplate stresses. Finally, significant angular differences between the SHmax and horizontal shortening obtained from GPS displacements are important north of the slab tear and the western forearc region. We hypothesize that north of the slab tear, strain accumulation is enhanced due to the coupling between the upper plate and flat-slab subduction, causing clockwise rigid body rotation of the C-NAB.