U.S.-Costa Rica Dissertation Research: Operation of Seismic Array at Cerro Mercedes, Costa Rica

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0437181 LevinThis Americas Program award will help to support the major part of the PhD thesis of Alissa Henza, under the supervision of Dr. Vadim Levin of Rutgers University and in collaboration with a team of scientists from the Instituto Costarricense de Electricidad, headed by Dr. Guillermo Alvarado of that institute and also at the University of Costa Rica. The researchers intend to study processes at work on the Earth's mantle zone that exert control over plate tectonics, volcanic arcs, and strongly influence the accretion of continents. Among numerous volcanoes of Costa Rica only one, called Cerro Mercedes, is known to have produced lavas that carry within them inclusions of rock from beneath the crust. Finds of such mantle nodules, or xenoliths, are unusual in areas of active volcanism associated with subduction. A discovery of mantle nodules at Cerro Mercedes suggests special conditions at this site. The researchers intend to deploy a small array of portable broadband seismic sensors in the immediate vicinity of the locality where xenoliths were found, for the duration of 15 months. Primary aims of the study based on the data collected by this cooperative effort will be: a) Are xenoliths derived from the overriding plate or from the supraslab mantle wedge? and b) Are there depth regions characterized by coherent rock fabric; do xenoliths come from one of them? The seismological observatory campaign will be carried out in an area proximate to Arenal and Miravalles volcanoes that are major sources of volcanic hazards in Costa Rica. Thus, in addition to the scientific interest and the student training, the project's broader impacts will extend to volcanic risk assessment and hazard mitigation by involving Costa Rican researchers whose primary tasks and expertise reside in those areas.