The forearc is characterized by increasing intensity of reflections towards greater depth, and their sudden breakdown at ca. 80 km depth and in ca. 130 km distance away from the coast line. Above the sudden reflectivity loss and further towards the east, a prominent bright-spot is observed between 20-25 km depth. At depth greater than 80 km, subduction-related earthquakes occur with 20 km offset below the subducting plate.

Petrological processes appear to be imaged in 80-100 km depth, among them are pressure- and temperature-dependent phase transitions, release of water and migration of melts and fluids.

The active reflection seismic survey revealed a ca. 5 km thick, continuous band of reflections dips from the coast line below the continent and marks the subducting Nazca Plate down to a depth of 80 km.