Accurate hypocentre determination in the seismogenic zone of the subducting Nazca Plate in northern Chile using a combined on-/offshore network |
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Authors: | S. Husen,E. Kissling,E. Flueh,& G. Asch |
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Affiliation: | GEOMAR Research Center for Marine Sciences of the Christian Albrechts University, Wischhofstrasse 1–3, D 24148 Kiel, Germany. E-mail:;, Institute of Geophysics, ETH-Hönggerberg, Zurich, Switzerland,;GeoForschungsZentrum (GFZ), Department 4, Potsdam, Germany |
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Abstract: | The coupled plate interface of subduction zones—commonly called the seismogenic zone—has been recognized as the origin of fatal earthquakes. A subset of the after-shock series of the great Antofagasta thrust-type event (1995 July 30; M w = 8.0) has been used to study the extent of the seismogenic zone in northern Chile. To achieve reliable and precise hypocentre locations we applied the concept of the minimum 1-D model, which incorporates iterative simultaneous inversion of velocity and hypocentre parameters. The minimum 1-D model is complemented by station corrections which are influenced by near-surface velocity heterogeneity and by the individual station elevations. By relocating mine blasts, which were not included in the inversion, we obtain absolute location errors of 1 km in epicentre and 2 km in focal depth. A study of the resolution parameters ALE and DSPR documents the importance of offshore stations on location accuracy for offshore events. Based on precisely determined hypo-centres we calculate a depth of 46 km for the lower limit of the seismogenic zone, which is in good agreement with previous studies for this area. For the upper limit we found a depth of 20 km. Our results of an aseismic zone between the upper limit of the seismogenic zone and the surface correlates with a detachment zone proposed by other studies; the results are also in agreement with thermal studies for the Antofagasta forearc region. |
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Keywords: | aftershocks earthquake location seismic tomography subduction. |
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