Departament de Geodinàmica i Geofísica us convida a la conferència de la Sra. Zuzana Alasonati Tasarova, Kiel University, Institute for Geosciencies/ Dept. of Geophysics
Lloc: Sala de Juntes de la Facultat de Geologia a les 12.30h.

The Southern Andes differ significantly from the Central Andes with respect to topography and crustal structures and are from a geophysical point of view less known. In order to provide more insight into the along-strike segmentation of the Andean mountain belt, an integrated 3-D density model was developed for the area between latitudes 36 and 42°S. The model is based on geophysical and geological data acquired in the region over the past years and was constructed using IGMAS (Interactive Gravity and Magnetics Application System). In general, the gravity field of the South American margin is characterised by a relatively continuous positive anomaly along the coastline and the forearc region, and by negative anomalies along the trench and the volcanic arc. However, in the forearc region of the central part of the study area, corresponding to the region of the largest ever recorded earthquake (Valdivia, 1960), the trench-parallel positive anomaly is disrupted. In the density model, this observed negative forearc gravity anomaly is reproduced by greater depth to the slab beneath the forearc region. The depth to the slab is, however, dependent upon the density of the upper plate structures. Therefore, both the upper and lower plates, and their interaction have a significant impact on the subduction zone gravity field. Moreover, the geometry of the modelled structures showing a thicker forearc in the middle segment, together with other factors, implies a higher plate coupling underneath this anomalous segment of the southern part of the Chilean margin.