The MUSICA Seismic Deployment: Illuminating subduction complexities at the northern end of the South American Cordillera

The northern end of the South American convergent margin is influenced by the interplay between the Nazca, South American, and Caribbean plates. The relatively recently (Miocene) accretion of the Panama arc along the western margin of northernmost South America adds further uncertainty to an already complex tectonic region. Of note is the offset in the Wadati Benioff Zone (WBZ) at ~5.5° N, often referred to as the “Caldas Tear”. The shallowest (50-60 km depth) reach of the northern WBZ lies over 400 km from the nearest plate boundary, an observation that requires one or more subducting slabs to be horizontally emplaced (a.k.a. “flat slab”). But which plate (or plates) comprises this northern WBZ? We know that both the Caribbean and Nazca plates are subducting, but the spatial extent of each plate and their resultant interactions remain unclear. To address these (and many other questions) about this complex region, we installed a temporary array of 66 broadband seismometers straddling the Caldas Tear north-to-south and extending across both WBZs east-to-west as part of the NSF-funded Modeling, Uplift, Seismology, and Igneous geochemistry in the Colombian Andes (MUSICA) project. This deployment was installed in phases from July 2022 to July 2023. The full array was in place from July 2023 until June 2025. Preliminary results of our novel dataset indicate the presence of complex crustal and slab structures, as well as indications of the mantle’s response to the multiple downgoing slabs. Here we present information about our deployment (including the use of direct burial seismometers and Carnegie Quick-Deploy Boxes), as well as early insights from preliminary results.