Neural network interpretation of LWD data (ODP Leg 170) con¢rms complete sediment subduction at the Costa Rica convergent margin

The internal structure of a convergent plate boundary was the focus of ODP Leg 170 in 1996 at the subduction zone off Costa Rica. Although the structure of the subduction zone is rather well known from seismic surveys, prior to drilling of ODP Leg 170 it was a matter of discussion whether it is accretionary or non-accretionary. With a neural network approach, we confirm the evidence gained during drilling of Leg 170, that at least presently no lower-plate sediments are transferred to the upper plate by accretion. To supplement lithological information, Logging-WhileDrilling geophysical data have been included in this study and were interpreted in terms of lithology using a genetically trained artificial neural network. ß 2000 Elsevier Science B.V. All rights reserved.