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Published October 2010 | Published + Supplemental Material
Journal Article Open

Asperities and barriers on the seismogenic zone in North Chile: state-of-the-art after the 2007 Mw 7.7 Tocopilla earthquake inferred by GPS and InSAR data


The Mw 7.7 2007 November 14 earthquake had an epicentre located close to the city of Tocopilla, at the southern end of a known seismic gap in North Chile. Through modelling of Global Positioning System (GPS) and radar interferometry (InSAR) data, we show that this event ruptured the deeper part of the seismogenic interface (30–50 km) and did not reach the surface. The earthquake initiated at the hypocentre and was arrested ~150 km south, beneath the Mejillones Peninsula, an area already identified as an important structural barrier between two segments of the Peru–Chile subduction zone. Our preferred models for the Tocopilla main shock show slip concentrated in two main asperities, consistent with previous inversions of seismological data. Slip appears to have propagated towards relatively shallow depths at its southern extremity, under the Mejillones Peninsula. Our analysis of post-seismic deformation suggests that small but still significant post-seismic slip occurred within the first 10 d after the main shock, and that it was mostly concentrated at the southern end of the rupture. The post-seismic deformation occurring in this period represents ~12–19 per cent of the coseismic deformation, of which ~30–55 per cent has been released aseismically. Post-seismic slip appears to concentrate within regions that exhibit low coseismic slip, suggesting that the afterslip distribution during the first month of the post-seismic interval complements the coseismic slip. The 2007 Tocopilla earthquake released only ~2.5 per cent of the moment deficit accumulated on the interface during the past 130 yr and may be regarded as a possible precursor of a larger subduction earthquake rupturing partially or completely the 500-km-long North Chile seismic gap.

Additional Information

© 2010 The Authors. Geophysical Journal International © 2010 RAS. Accepted 2010 July 20. Received 2010 July 19; in original form 2009 December 18. We thankMatt Pritchard, an anonymous reviewer and EditorDuncan Agnew for thorough reviews that helped to improve the manuscript. This work was performed in the frame of the French/Chilean international collaboration (CNRS/CONICYT LIA 'Montessus de Ballore'). We thank the European Space Agency (ESA) for providing the ENVISAT images (project AO-720). This work was made possible thanks to the funding of the French National Research Agency (ANR-05-CATT-014, ANR-06-CATT-010-01), CNRS/INSU (funding of post-seismic task force), ARCUS project and BQR IPGP. The Caltech component of the GPS network was made possible by support from the Gordon and Betty Moore Foundation. MBP was partly supported by a grant of the Universidad Complutense de Madrid, CNRS and an Eiffel fellowship. DC was supported by an Ile-de- France Postdoctoral Fellowship and IPGP. GMT was used to create most of the figures (Wessel & Smith 1998). We thank C. Lasserre and R. Grandin for the linear inversion code. We thank S. Peyrat, P. Bernard, J.P. Vilotte, R. Madariaga, M. Sobiesiak, R. Lacassin, A. Coudurier Curveur and J.J. Martínez-Díaz for scientific discussion. This is IPGP contribution number 3032.

Attached Files

Published - BejarPizarro2010p11513Geophys_J_Int.pdf

Supplemental Material - GJI_4748_sm_Appendix_A.zip

Supplemental Material - GJI_4748_sm_Appendix_B.zip

Supplemental Material - GJI_4748_sm_Appendix_C.zip

Supplemental Material - GJI_4748_sm_Appendix_D.zip

Supplemental Material - GJI_4748_sm_Appendix_E.zip

Supplemental Material - GJI_4748_sm_Appendix_F.zip

Supplemental Material - GJI_4748_sm_Appendix_G.zip

Supplemental Material - GJI_4748_sm_Appendix_H.zip

Supplemental Material - GJI_4748_sm_Appendix_I.zip


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August 22, 2023
October 20, 2023