The TUCAN Broadband Seismic Experiment: Imaging the Central America Subduction Factory
The TUCAN Broadband Seismic Experiment: Imaging the Central America Subduction Factory
Credit:
G. A. Abers, L. Auger, E. Syracuse, G. Reyes • Boston University; K. M. Fischer, C. Rychert, D. Abt, A. Walker • Brown University; J. M. Protti, V. G. Salas • OVSICORI, Costa Rica; W. Strauch, P. Perez • INETER, Nicaragua/IRIS Consortium
Description
The TUCAN broadband experiment in Costa Rica and Nicaragua. Yellow circles show TUCAN broadband stations, July 2004 – March 2006. Other seismic stations in the region include permanent broadband (open triangles), short-period (black triangles) and the 1999 SEIZE PASSCAL experiment (gray circles). Red triangles show the active arc front, and thin blue lines show 50 km contours to Wadati-Benioff zone. Here, the 20-25 Ma Cocos plate subducts beneath the Caribbean, producing earthquakes to a depth of 300 km.
The “Subduction Factory” processes the solids and volatiles entering oceanic trenches and produces volcanic arcs, deep earthquakes, and long-term modifications to the deep earth. Central America exhibits some of the global extremes in the factory operation: in the Nicaragua volcanic arc, fluxes of geochemical tracers associated with subducting sediment are among the highest on the planet, while in the adjacent Costa Rica arc, many of the same tracers are weak to absent. For this reason, the MARGINS Program has selected Central America as one of two focus areas for its Subduction Factory initiative. In advancing understanding of the Subduction Factory, seismic imaging of the downgoing plate, mantle wedge and upper-plate crust form a primary data set for understanding the cycling of volatiles and production of melt. To accomplish this, we deployed in July-August of 2004 the TUCAN seismic array (Tomography and other things Under Costa Rica And Nicaragua) of 48 broadband PASSCAL seismographs, operating until early 2006. The array includes two dense transects across the arc at 10 km spacing, in both Costa Rica and in Nicaragua, accompanied by distributed stations sampling arc and backarc along strike over 450 km. From the array data, we have begun applying a wide variety of imaging strategies to constrain structure from both teleseismic signals and signals from earthquakes within the downgoing slab. Overall, the data recovery and quality has been outstanding, with recovery of 90-95%. Analysis of these data and integration with parallel geochemical studies of arc lavas appear sufficient to characterize subduction here as well as any place on the planet.
Geoffrey A. Abers, Laura Auger, Ellen Syracuse, Gustavo Reyes • Boston University; Karen M. Fischer, Catherine Rychert, David Abt, Alexis Walker • Brown University; J. Marino Protti, Victor Gonzalez Salas • OVSICORI, Costa Rica; Wilfried Strauch, Pedro Perez • INETER, Nicaragua
Photographer / Contributor: G. A. Abers, L. Auger, E. Syracuse, G. Reyes • Boston University; K. M. Fischer, C. Rychert, D. Abt, A. Walker • Brown University; J. M. Protti, V. G. Salas • OVSICORI, Costa Rica; W. Strauch, P. Perez • INETER, Nicaragua
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