Broad depth range seismic imaging of the subducted Nazca Slab, North Chile S. Buske a, * , S. Lu ¨th a , H. Meyer b , R. Patzig a , C. Reichert b , S. Shapiro a , P. Wigger a , M. Yoon a a Institut fu ¨r Geologische Wissenschaften, Fachrichtung Geophysik, Freie Universita ¨t Berlin, Malteserstr. 74-100 (Haus D), D-12249 Berlin, Germany b Bundesanstalt fu ¨r Geowissenschaften und Rohstoffe, Stilleweg 2, D-30655 Hannover, Germany Received 28 September 2001; accepted 7 March 2002 Abstract In this paper, we present a compilation of modern seismic and seismological methods applied to image the subduction process in North Chile, South America. We use data from active and passive seismic experiments that were acquired within the framework of the German Collaborative Research Center SFB267 ‘Deformation Processes in the Andes’. The investigation area is located between 20j and 25jS and extends from the trench down to 100 km depth. In the depth range between the sea bottom and 15 km, we process an offshore seismic reflection profile using a recently developed velocity-model-independent stacking procedure. We find that the upper part of the subducting oceanic lithosphere in this depth range is characterized by a horst-and- graben structure. This structure supports an approximately 3 km thick coupling zone between the plates. In the depth range between 15 and 45 km, we analyse the spatial distribution of aftershocks of the Antofagasta earthquake (1995). The aftershock hypocenters are concentrated in an approximately 3 km thick layer. Finally, in the depth range between 45 and 100 km, we apply Kirchhoff prestack depth migration to the onshore ANCORP profile. A double reflection zone is observed between 45 and 60 km depth, which may represent the upper and lower boundary of the subducted oceanic crust. Over the whole range down to more than 80 – 90 km depth, we obtain an image of the subducting slab. At that depth, the hypocenters of local earthquakes deviate significantly in the direction perpendicular to the slab face from the reflective parts of the slab. Consequently, our results yield a complete seismic image of the downgoing plate and the associated seismic coupling zone. D 2002 Published by Elsevier Science B.V. Keywords: Deep seismic reflection; Crustal seismology; Subduction; Imaging 1. Introduction The Andean mountain belt is the result of sub- duction of the oceanic Nazca Plate below the South American continent. During the last two decades, various seismic reflection and refraction profiles have been acquired in the central Andes within the frame- work of the German Collaborative Research Center SFB267 ‘Deformation Processes in the Andes’ (Wig- ger, 1988; Wigger et al., 1994; Schmitz et al., 1999). These profiles lead to a detailed seismic image in this area and they have been used to complement the 0040-1951/02/$ - see front matter D 2002 Published by Elsevier Science B.V. PII:S0040-1951(02)00117-8 * Corresponding author. Tel.: +49-30-83870580; fax: +49-30- 83870729. E-mail address: buske@geophysik.fu-berlin.de (S. Buske). www.elsevier.com/locate/tecto Tectonophysics 350 (2002) 273– 282