Three-dimensional inversion of magnetotelluric data from the Central Andean continental margin

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• 作者：Christine Kühn ; Jonas Küster ; Heinrich Brasse
• 关键词：Magnetotellurics ; 3 ; D inversion ; Subduction zones ; Central Andes
• 刊名：Earth, Planets and Space
• 出版年：2014
• 出版时间：December 2014
• 年：2014
• 卷：66
• 期：1
• 全文大小：3320KB
• 参考文献：Allmendinger RW, Gonzalez G: Neogene to Quaternary tectonics of the Coastal Cordillera, Northern Chile. Tectonophysics 2010, 495:93-10. 10.1016/j.tecto.2009.04.019CrossRef
  Baker MCW, Francis PW: Upper Cenozoic volcanism in the Central Andes - Ages and Volumes. Earth Planet Sci Lett 1978,41(2):175-87. 10.1016/0012-821X(78)90008-0CrossRef
  Beike J: Studien zur anisotropen Leitf?higkeitsverteilung und ein Versuch zur Erkl?rung magnetotellurischer übertragungsfunktionen in der Küstenkordillere Nordchiles, diploma thesis, Inst. für Geol. Wiss., Freie Universit?t Berlin; 2001.
  Bloch W, Kummerow J, Salazar P, Wigger P, Shapiro SA: High-resolution image of the North Chilean subduction zone: seismicity, reflectivity and fluids. Geophys J Int 2014,197(3):1744-749. doi:10.1093/gji/ggu084 10.1093/gji/ggu084CrossRef
  Br?ndlein D: Geo-electromagnetic monitoring of the Andean Subduction Zone in Northern Chile. Dissertation, Freie Universit?t Berlin; 2013.
  Brasse H, Lezaeta P, Rath V, Schwalenberg K, Soyer W, Haak V: The Bolivian Altiplano conductivity anomaly. J Geophys Res 107(B5):EPM 4-–EPM 2002, 4-4. doi:10.1029/2001JB000391
  Brasse H, Eydam D: Electrical conductivity beneath the Bolivian Orocline and its relation to subduction processes at the South American continental margin. J Geophys Res 2008, 113:B07109. doi:10.1029/2007JB005142
  Brasse H, Kapinos G, Li Y, Mütschard L, Soyer W, Eydam D: Structural electrical anisotropy in the crust at the South-Central Chilean continental margin as inferred from geomagnetic transfer functions. Phys Earth Planet Inter. 2009,173(1-):7-6.CrossRef
  Brasse H: Electromagnetic images of the South and Central American subduction zones. In The Earth’s magnetic interior, IAGA Special Sopron Book Series. Edited by: Petrovsky E, Herrero-Bervera E, Harinarayana T, Ivers D. Berlin: Springer; 2011:43-1.CrossRef
  Breitkreuz C: Das Pal?ozoikum in den Kordilleren Nordchiles (21°-25°S). Geotektonische Forschungen 1986, 70:1-8.
  Budach I, Brasse H, Díaz D: Crustal-scale electrical conductivity anomaly beneath inflating Lazufre volcanic complex. Central Andes J S Am Earth Sci 2013, 42:144-49. doi:10.1016j.jsames2012.11.002CrossRef
  Caldwell TG, Bibby HM, Brown C: The magnetotelluric phase tensor. Geophys J Int 2004, 158:457-69. 10.1111/j.1365-246X.2004.02281.xCrossRef
  Chong Díaz G, Mendoza M, García-Veigas J, Pueyo JJ, Turner P: Evolution and geothermal signatures in a Neogene forearc evaporitic basin: the Salar Grande (Central Andes of Chile). Palaeograph Palaeoclimatol Palaeoecol 1999, 151:39-4. 10.1016/S0031-0182(99)00014-0CrossRef
  Comeau MJ, Unsworth MJ, Ticona F: Magnetotelluric images of magma distribution beneath Volcan Uturuncu, Bolivia. In IAVCEI Scientific Assembly. Japan: Kagoshima; 2013. 20-4 July 2013
  Constable CS, Parker RL, Constable GC: Occam’s inversion: a practical algorithm for generating smooth models from electromagnetic sounding data. Geophysics 1987, 52:289-00. 10.1190/1.1442303CrossRef
  De Silva SL: Altiplano-Puna volcanic complex of the central Andes. Geology 1989, 17:1102-106. 10.1130/0091-7613(1989)017<1102:APVCOT>2.3.CO;2CrossRef
  Del Potro R, Diez M, Blundy JD, Gottsmann JH, Camacho AG: Diapiric ascent of silicic magma beneath the Bolivian Altiplano. Geophys Res Lett 2013,40(10):2044-048. 10.1002/grl.50493CrossRef
  Díaz D, Brasse H, Ticona F: Conductivity distribution beneath Lascar volcano (Northern Chile) and the Puna, inferred from magnetotelluric data. J Volc Geotherm Res 217-18 2012, 21-9. doi:10.1016/j.jvolgeores.2011.12.007
  Echternacht F, Tauber S, Eisel M, Brasse H, Schwarz G, Haak V: Electromagnetic study of the active continental margin in Northern Chile. Phys Earth Planet Inter 1997, 102:69-7. 10.1016/S0031-9201(96)03261-XCrossRef
  Egbert GD, Kelbert A: Computational recipes for electromagnetic inverse problems. Geophys J Int 2012, 189:251-67. 10.1111/j.1365-246X.2011.05347.xCrossRef
  Egbert GD: Comments on ’Concerning dispersion relations for the magnetotelluric impedance tensor-by. E. Yee and K. V. Paulson. Geophys J 1990, 102:1-.
  Ege H: Exhumations- und Hebungsgeschichte der zentralen Anden in Südbolivien (21°S) durch Spaltspur-Thermochronologie an Apartit. Dissertation, Freie Universit?t Berlin; 2004.
  Elger K: Analysis of deformation and tectonic history of the Southern Altiplano Plateau (Bolivia) and their importance for plateau formation. Dissertation, Freie Universit?t Berlin; 2003.
  Eydam D: Magnetotellurisches Abbild von Fluid- und Schmelzprozessen in Kruste und Mantel der zentralen Anden. Diploma, Freie Universit?t Berlin; 2008.
  Galindo JC: Anisotropic modelling of magnetotelluric data in North Chile. BSc. thesis, Freie Universit?t Berlin; 2010.
  Gonzalez-Ferran O: Volcanes de Chile, Inst. Geográfico Militar. Santiago de Chile 1994, 640.
  Heit B, Koulakov I, Asch G, Yuan X, Kind R, Alcocer-Rodriguez I, Tawackoli S, Wilke H: More constraints to determ
• 作者单位：Christine Kühn (5)
  Jonas Küster (5)
  Heinrich Brasse (5)
  
  5. Freie Universit?t Berlin, Fachrichtung Geophysik, Malteserstr. 74-100, 12249, Berlin, Germany
  
• 刊物类别：Earth Sciences, general; Geology; Geophysics/Geodesy;
• 刊物主题：Earth Sciences, general; Geology; Geophysics/Geodesy;
• 出版者：Springer Berlin Heidelberg
• ISSN：1880-5981

文摘

Magnetotelluric data were collected in the late 1990s in the Central Andes of Chile and Bolivia, with the aim to delineate the electrical conductivity distribution in the subsurface and its relations to subduction processes. In previous studies, these data were interpreted based on 2-D models. The principal result was a vast conductivity zone beneath the Altiplano high plateau at mid and lower crustal depths and a much smaller, though significant conductor associated with the Precordillera Fault System. However, there are some significant 3-D effects in the investigation area, in particular near the coast and on the eastern Altiplano. The aim of this work is to give a reinterpretation based on new 3-D inversion of these data. The 3-D inversion not only provides a better fit to the data compared to 2-D results but furthermore allows to include sites with strong telluric distortion which were ignored in previous studies. We are now able to explain anomalous phases above 90° and induction arrows pointing subparallel to the coast as observed at several sites in the Coastal Cordillera. These strongly distorted data are caused by highly conductive near-surface structures that are partly connected to the Pacific Ocean, forcing currents to flow around the sites. The lower crust beneath the Coastal Cordillera resembles a poorly conductive, nearly homogeneous half-space and is electrically unremarkable. Besides, we can now image the Precordillera conductor as a continuous, elongated feature. The volcanic arc of the Western Cordillera is highly resistive with the exception of a few conductive spots which may be associated with certain individual volcanoes or geothermal resources, respectively. The Altiplano conductor is again the dominant electrical feature in the Central Andes, indicating widespread melting of the middle and lower back-arc crust. Keywords Magnetotellurics 3-D inversion Subduction zones Central Andes