Alvarado, G.E.

Dzierma, Yvonne

Flueh, Ernst R.

Mora, M. M.

Rabbel, Wolfgang

Thorwart, Martin

English

OceanRep

Geophysical Research Abstracts,Vol. 10, EGU2008-A-03480, 2008SRef-ID: 1607-7962/gra/EGU2008-A-03480EGU General Assembly 2008© Author(s) 2008A receiver function study of the southern Costa Ricansubduction zoneY. Dzierma (1), M. Thorwart (1), W. Rabbel (1), E. R. Flueh (1,2), G. E. Alvarado(3), M. M. Mora (4)(1) Sonderforschungsbereich 574 at Christian-Albrechts-Universität Kiel, Wischhofstr. 1-3,24148 Kiel, Germany, (2) IFM-GEOMAR, Wischhofstr. 1-3, 24148 Kiel, Germany , (3) Areade Amenazas y Auscultacion Sismica y Volcanica, ICE, Apdo. 10032-1000, Costa Rica, (4)Escuela Centroamericana de Geologia, Universidad de Costa Rica, San Jose, Costa Rica(ydzierma@geophysik.uni-kiel.de)The Central American subduction zone is particularly interesting due to its pro-nounced lateral variability. To explore the deeper structure of the subduction zone,a transect of broadband seismometres across the Talamanca Range (Southern CostaRica) was operated from spring 2005 to spring 2007. This region is characterized bythe subduction of the aseismic Cocos Ridge, which has been observed to dip at anangle of 18 deg down to depths of about 40 km. Based on this shallow angle, it wasspeculated that shallow underplating of the Cocos Ridge is responsible for the gap inactive volcanism and strong uplift in this region.We performed a standard receiver function analysis of 522 teleseismic earthquakes,yielding 1777 receiver functions. The Moho of the overriding plate is imaged around35 km depth, and an intracrustal discontinuity is observed at about 20 km depth, ingood comparison with previous active seismic studies. Below 40-50 km depth, how-ever, the receiver functions show a steeply dipping plane (60 deg), interpreted as thesubducting Cocos Plate, which reaches a depth of about 170 km. These results showfor the first time that the Cocos Ridge is subducting beneath southern Costa Rica at aconsiderably larger angle and to greater depths than previously thought, opening newquestions about the mechanism causing the gap in active volcanism and strong upliftin the Cordillera de Talamanca.

A Receiver Function Study of the Southern Costa Rican Subduction Zone, (2008)

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