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Accurate hypocentre determination in the seismogenic zone of the subducting Nazca Plate in northern Chile using a combined on-/offshore network

Husen, S. ; Kissling, E. ; Flueh, E. ; Asch, G.

In: Geophysical Journal International, 1999, vol. 138, no. 3, p. 687-701

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    Titre
    • Accurate hypocentre determination in the seismogenic zone of the subducting Nazca Plate in northern Chile using a combined on-/offshore network
    Auteur
    • Husen, S.. GEOMAR Research Center for Marine Sciences of the Christian Albrechts University, Wischhofstrasse 1-3, D 24148 Kiel, Germany. E-mail:shusen@geomar.de
    • Kissling, E.. Institute of Geophysics, ETH-Hönggerberg, Zurich, Switzerland
    • Flueh, E.. GEOMAR Research Center for Marine Sciences of the Christian Albrechts University, Wischhofstrasse 1-3, D 24148 Kiel, Germany. E-mail:shusen@geomar.de
    • Asch, G.. GeoForschungsZentrum (GFZ), Department 4, Potsdam, Germany
    Type de document
    • Postprint
    Identifiant OAI-PMH
    • oai:doc.rero.ch:290588
    Summary
    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; Mw= 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