Goce derived vertical gravity gradient delineates great earthquake rupture zones along the chilean margin

ALVAREZ ORLANDO; SILVINA NACIF; GIMENEZ MARIO; FOLGUERA ANDRES; BRAITENBERG CARLA

TECTONOPHYSICS

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2014 vol. 622 p. 198 - 215

0040-1951

In the south Central Andes region, the Nazca oceanic plate that subducts beneath the South American plate is characterized by a rough topography derived from different oceanic features that collide against the continental margin. These features determine an important segmentation of both the margin and of the interplate zone. The Chilean subduction margin has been characterized by megathrust earthquakes affecting the plate interface with large rupture areas reaching hundreds of kilometers parallel to the trench. The occurrence of these phenomena has been linked, among other causes, to the subduction of sediments that fill the trench and their spatial relation to the relatively prominent oceanic features. We calculated the topography corrected vertical gravity gradient from GOCE satellite data and from EGM2008 model in order to delineate mass heterogeneities related to density variations along the south-central Chile subduction zone. Obtained results show a spatial relation between the subduction of the Nazca oceanic highs and associated along-strike segmentation of the vertical gravity gradients over the interplate zone. We compared our results with the different rupture areas and found a good correspondence with the ellipses for the main earthquakes such as the Valdivia-1960 and Maule-2010 ones. Then, we compared vertical gravity gradients with slip distribution obtained from different models, finding that they are actually correlated with high slip over negative vertical