Preliminary Earthquake Locations From the Costa Rica Component of the TUCAN Network

The TUCAN (Tomography Under Costa Rica And Nicaragua) network is a multi-institutional and international project funded by the US National Science Foundation as part of the Subduction Factory Initiative of the MARGINS program. The project's objective is to tribute to the understanding of the local tectonic processes that cause extreme changes in the fluxes of geochemical tracers associated with subducting sediments from Nicaragua to Costa Rica. The observed variations hint that the subduction factory must be behaving differently at depth over short distances. The TUCAN network is a 48 station broadband seismic array composed of two dense (~10 km spacing) lines across the volcanic arcs in Nicaragua and Costa Rica and two other lines (~30 km spacing) parallel to the trench, one in the forearc, at the foothills of the volcanic arc, and the other along the back arc ~70 km from the arc. This network was designed and deployed this summer to collect, for 18 months, seismic data that will be analyzed in many different ways including precise earthquake locations, local velocity and attenuation tomography, receiver functions, anisotropy studies and local, regional and teleseismic wave phases analysis. We will present preliminary earthquake locations recorded at the Costa Rica component of the TUCAN network. The cross line in Costa Rica extends from where the seismogenic zone of large underthrust earthquakes occur along the Nicoya segment at depth of 30 km, to 40 km into the backarc from where the deepest portion (~150 km) of the seismic slab projects to the surface. This geometry combined with OVSICORI's permanent seismic network promises precise local earthquake locations.