A local seismic network, over a five-year period, recorded about 450 earthquakes in western Argentina. In this region, the geodynamics is controlled by the subduction of the Nazca plate beneath the South American lithosphere, which is characterised here by a sub-horizontal path before reassuming its downward descent.As accurate earthquake locations are of primary importance when studying the seismicity of a given area, events recorded by the local seismic network enable in-depth investigations intoseismo-tectonic patterns, allowing to improve the earthquake source characterization andknowledge on the ongoing seismo-tectonics of the region. To this end, we performed a simultaneous 1-D inversion of both the velocity structure and the hypocentre location. Theminimum 1-D model obtained is complemented by station corrections which lead to a first insight into the deeper 3-D structure. In addition, stability tests were performed to verify therobustness of our earthquake location results. They reveal a fairly stable hypocentredetermination, demonstrating that the locations obtained by the inversion process are not systematically biased.The results show that Sierra Pie de Palo is characterised by a crustal seismogenic structure, dipping west and extending from its eastern boundary to about 30 km of depth. The study alsoprovided new constraints on the geometry of the subducted slab. We noted a greatconcentration of shallower seismicity compared to that of the surrounding areas of the Wadati-Benioff zone, at the expected position of the Juan Fernandez Ridge (JFR). Our hypocentres indicate that JFR certainly influences the subduction style along its strike, leading to theformation of a bend in the slab geometry.

Seismotectonic features from accurate hypocentre locations in southern central Andes (western Argentina)

IMPOSA, Sebastiano;
2012-01-01

Abstract

A local seismic network, over a five-year period, recorded about 450 earthquakes in western Argentina. In this region, the geodynamics is controlled by the subduction of the Nazca plate beneath the South American lithosphere, which is characterised here by a sub-horizontal path before reassuming its downward descent.As accurate earthquake locations are of primary importance when studying the seismicity of a given area, events recorded by the local seismic network enable in-depth investigations intoseismo-tectonic patterns, allowing to improve the earthquake source characterization andknowledge on the ongoing seismo-tectonics of the region. To this end, we performed a simultaneous 1-D inversion of both the velocity structure and the hypocentre location. Theminimum 1-D model obtained is complemented by station corrections which lead to a first insight into the deeper 3-D structure. In addition, stability tests were performed to verify therobustness of our earthquake location results. They reveal a fairly stable hypocentredetermination, demonstrating that the locations obtained by the inversion process are not systematically biased.The results show that Sierra Pie de Palo is characterised by a crustal seismogenic structure, dipping west and extending from its eastern boundary to about 30 km of depth. The study alsoprovided new constraints on the geometry of the subducted slab. We noted a greatconcentration of shallower seismicity compared to that of the surrounding areas of the Wadati-Benioff zone, at the expected position of the Juan Fernandez Ridge (JFR). Our hypocentres indicate that JFR certainly influences the subduction style along its strike, leading to theformation of a bend in the slab geometry.
2012
Minimum 1-D velocity model; high precision earthquake location; flat-slab subduction
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.11769/754
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