The flat to normal subduction transition study to obtain the Nazca plate morphology using high resolution seismicity data from the Nazca plate in Central Chile

摘要

Data from 45 seismological stations mostly temporary were used to obtain an accurate data set of intraslab seismicity of the Nazca subducted plate between 33 degrees S and 35 degrees S. The interest zone located in the transition section where the Nazca plate changes from flat slab north of similar to 33 degrees to normal slab south of that latitude. In addition, the study region is located where the active volcanic arc appears. From a set of earthquakes which were relocated using a grid-search multiple events algorithm we obtained the plate geometry from latitudes of 33 degrees S to 34.5 degrees S and from 60 km to 120 km in depth. The obtained morphology shows notable similarity in its structure to Maipo Orocline revealing some possible strong connection between the overriding plate and the subducting plate. We suggest that the subducted plate at the trench has been deformed in its shape consistently with the Maipo Orocline pattern and its deformation is observed below the interface zone. Our results are consistent with van Keken et al., 2011 models, and based on this the seismicity located between 70 and 120 km is probably related with dehydration processes rather than mechanical processes. From our precise earthquake locations we observed a complete lack of intraslab seismicity below 120 km depth. This valuable finding can be used to better constrain thermal models for the subduction region of Central Chile. (C) 2015 Elsevier B.V, All rights reserved.