Abstract
A net of mainly reversed seismic refraction profiles has been measured in the years 1987 and 1989 in northern Chile, northern Argentina and southern Bolivia to investigate the crustal structure beneath the Andes from the coastal range to the Andean foreland. Regular blasts of the Chuquicamata copper mine, sea shots in the Pacific Ocean and land shots in Chile, Argentina and Bolivia were used as energy sources. One- and two-dimensional model calculations were applied to the data. Strong west-east as well as north-south variations in the crustal structure are observed which allow one to distinguish mainly three different crustal blocks.
The forearc block (Coastal Cordillera to Precordillera) increases in thickness from 40 km at the coast to 70 km under the Precordillera. A discontinuity between 20 km (west) and 35 km (east) depth is interpreted as the base of the Jurassic crust. The Moho of the oceanic crust is proven at 40 km depth under the Coastal Cordillera. The depth range from 20–30 (west) to 35–70 km (east) characterized by alternation of high and low velocities is interpreted as a mixture of continental crustal and mantle material and Nazca plate derivates. The average velocities of 6.6 km/s beneath the Coastal Cordillera to 6.2 km/s (Precordillera) suggest a rigid behaviour for this forearc block.
For the Western Cordillera and the western Altipiano the data indicate a strong, vertically structured, about 70-km-thick crust. Only at the southern W-E profile are clear signals observed from the lower crust and uppermost mantle. At the other related profiles signals from this depth range are missing. These data indicate a weakened crust with, in part, strongly reduced velocities, also suggesting partially melted zones. The backarc crust (eastern part of the Altipiano, the Eastern Cordillera and the Subandean Ranges) shows a rigid behaviour. Here, continental crust is overthrusted over its foreland. The data evidence the base of the crust in a rather shallow position at 25–30 km depth beneath the Eastern Cordillera. The underlying upper and middle crusts are characterized by a low velocity zone. Total crustal thickness decreases from 70 km under the Altipiano to 40 km at the Andean foreland, already representing shield conditions.
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References
Asch G, Blümecke T, Buness H (1992) An application of evolutionary strategy on geophysical modelling. Subm to Geophys J Int
Baldzuhn S (1992) Tiefenseismische Untersuchungen in der Ostkordillere und im Subandin Südboliviens. Dipl Thesis, Freie Universität Berlin, FB Geowiss
Barton PJ (1986) The relationship between seismic velocity and density in the continental crust — a useful constraint? Geophys J R Astr Soc 87: 195–208
Chinn DS, Isacks BL, Barazangi M (1980) High-frequency seismic wave propagation in western South America along the continental margin, in the Nazca plate and across the Altipiano. Geophys J R Astr Soc 60: 209–244
Fisher RL, Raitt RW (1962) Topography and structure of the Peru-Chile trench. Deep Sea Res 9: 423–443
Gerver M, Markushevich V (1966) Determination of a seismic wave velocity from the travel-time curve. Geophys J R Astr Soc 11: 165–173
Giese P (1976a) General remarks on travel time data and principles of correlation. In: Giese P, Prodehl C, Stein A (eds) Explosion seismology in Central Europe, data and results. Springer, Berlin Heidelberg New York, pp 130–136
Giese P (1976b) Depth calculation. In: Giese P, Prodehl C, Stein A (eds) Explosion seismology in Central Europe, data and results. Springer, Berlin Heidelberg New York, pp 146–161
Giese P, Schütte K-G (1980) Resultados das medidas de sísmica de refraçao a leste da Serra do Espinhaçao, M.G., Brasil. In: Nuevos Resultados de la Investigación Geocientífica Alemana en Latinoamerica. EH Forschungsgemeinschaft y el Inst de la Colab Científica, Tübingen, pp 44–50
Götze H-J, Schmidt S, Strunk S (1988) Central Andean gravity field and its relation to crustal structures. In: Bahlburg H, Breitkreuz C, Giese P (eds) The Southern Central Andes. Lecture Notes in Earth Sciences 17. Springer, Berlin Heidelberg New York, pp 199–208
Haak V, Giese P (1986) Subduction induced petrological processes inferred from magnetotelluric, seismological and seismic observations in N-Chile and S-Bolivia. Beri Geowiss Abh (A) 66: 231–246
Heinsohn W-D (1990) Krustenseismische Untersuchungen in der Küstenkordillere Nordchiles und Aufbau und Realisierung einer automatischen Registrier-Apparatur. Dipl Thesis, Freie Universität Berlin, FB Geowiss, 58 pp
Isacks BL (1988) Uplift of the central Andean plateau and bending of the Bolivian orocline. J Geophys Res 93: 3211–3231
Ludwig WJ, Nafe JE, Drake CL (1970) Seismic refraction. In: Maxwell AE (ed) The sea 4, Wiley, New York, pp 53–84
Meissner R (1986) The continental crust. Academic Press, Orlando USA,426pp
Ocola LC, Meyer RP (1972) Crustal low-velocity zones under the Peru-Bolivia Altipiano. Geophys J R Astr Soc 30: 199–209
Ocola LC, Meyer RP (1973) Crustal structure from the Pacific Basin to the Brazilian Shield between 12° and 30° south latitude. Geol Soc Am Bull 84: 3387–3404
Ocola LC, Meyer RP, Aldrich LT (1971) Gross crustal structure under Peru-Bolivia Altipiano. Earthquake Notes XLII, 3–4: 33–48
Reutter K-J, Giese P, Götze H-J, Scheuber E, Schwab K, Schwarz G, Wigger P (1988) Structures and crustal development of the Central Andes between 21° and 25°S. In: Bahlburg H, Breitkreuz C, Giese P (eds) The southern Central Andes. Lecture Notes in Earth Sciences 17. Springer, Berlin Heidelberg New York, pp 231–261
Reutter K-J, Heinsohn W-D, Scheuber E, Wigger P (1991) Crustal structure of the Coastal Cordillera near Antofagasta, northern Chile. VI. Congr Geol Chil, Vina del Mar, Actas. SERNAGEOMIN Santiago, pp 862–866.
Roeder D (1988) Andean-age structure of Eastern Cordillera (Province of La Paz, Bolivia). Tectonics 7 (1): 23–39
Rössling R (1989) Petrologie in einem tiefen Krustenstockwerk des jurassischen magmatischen Bogens in der nordchilenischen Küstenkordillere südlich von Antofagasta. Berl Geowiss Abh (A) 112, 73 pp
Schmitz M, Wigger P, Heinsohn W-D, Baldzuhn S, Rudioff A (1990) Data compilation from the Central Andes refraction seismic experiments of the research group “Mobility of Active Continental Margins” in the years 1982, 1984, 1987 and 1989. Open file report, Institute of Geophysical Sciences, Free University, Berlin
Schmitz M, Wigger P, Araneda M (1991) La estructura Preandina entre el Salar de Huasco y Chuquicamata mediante sismica de refracción. VI Congr Geol Chil, Vina del Mar, Actas,. SERNAGEOMIN Santiago, pp 882–886
Schwarz G, Haak V, Martinez E, Bannister J (1984) The electrical conductivity of the Andean crust in northern Chile and southern Bolivia as inferred from magnetotelluric measurements. J Geophys 55: 169–178
Schwarz G, Martínez E, Bannister J (1986) Untersuchungen zur elektrischen Leitfähigkeit in den Zentralen Anden. Berl Geowiss Abh (A) 66: 49–72
Sheffels B (1990) Lower bound on the amount of crustal shortening in the central Bolivian Andes. Geology 18: 812–815
Spence GD, Whittall KP, Clowes RM (1984) Practical synthetic seismograms for laterally varying media calculated by asymptotic ray theory. Bull Seismol Soc Am 74 (4): 1209–1223
Strunk S (1990) Analyse und Interpretation des Schwerefeldes des aktiven Kontinentalrandes der zentralen Anden (20°–26°S). Berl Geowiss Abh (B) 17: 135 pp
Tatel HE, Tuve MA (1958) Seismic studies in the Andes. Am Geophys Union Trans 39: 580–582
von Huene R, Lallemand S (1990) Tectonic erosion along the Japan and Peru convergent margins. Geol Soc Am Bull 102: 704–720
Wiechert E (1910) Bestimmung des Weges der Erdbebenwellen im Erdinnern: 1. Theoretisches. Phys Z 11: 294–304
Wigger P (1986) Krustenseismische Untersuchungen in Nord-Chile und Süd-Bolivien. Berl Geowiss Abh (A) 66: 31–48.
Wigger P (1988) Seismicity and crustal structure of the Central Andes. In: Bahlburg H, Breitkreuz C, Giese P (eds) The southern Central Andes. Lecture Notes in Earth Sciences 17. Springer, Berlin Heidelberg New York, pp 209–229
Wigger P, Araneda M, Röwer P (1988) Investigaciones sísmicas de refracciones en el norte de Chile. V Congr Geol Chil, Actas II, Santiago, F185–F202
Wigger P, Araneda M, Giese P, Heinsohn W-D, Röwer P, Schmitz M, Viramonte J (1991) The crustal structure along the Central Andean transect derived from seismic refraction investigations. In: Omarini R, Götze H-J (compilers) Global geoscience transect 6, Central Andean transect, Nazca Plate to Chaco Plains. ICL and AGU, Washington D.C.: pp 13–19.
Woollard GP (1960) Seismic crustal studies during the I.G.Y. Part II. Continental program. Am Geophys Union Trans 41: 351–355
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Wigger, P.J. et al. (1994). Variation in the Crustal Structure of the Southern Central Andes Deduced from Seismic Refraction Investigations. In: Reutter, KJ., Scheuber, E., Wigger, P.J. (eds) Tectonics of the Southern Central Andes. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-77353-2_2
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