Gravity derived depth to basement in Santiago Basin, Chile: implications for its geological evolution, hydrogeology, low enthalpy geothermal, soil characterization and geo-hazards

A recording of 1,115 gravimetric stations, the review of 368 wells, and the petrophysics measurements of 106 samples from representative outcrops have been used for a comprehensive geological/geophysical study of Santiago Basin. 2.5D and 3D gravimetric modeling, constrained by regional geology, soil...

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Autores principales: Yáñez,Gonzalo, Muñoz,Mauricio, Flores-Aqueveque,Valentina, Bosch,Andrés
Lenguaje:English
Publicado: Servicio Nacional de Geología y Minería (SERNAGEOMIN) 2015
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Acceso en línea:http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-71062015000200001
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spelling oai:scielo:S0718-710620150002000012015-06-26Gravity derived depth to basement in Santiago Basin, Chile: implications for its geological evolution, hydrogeology, low enthalpy geothermal, soil characterization and geo-hazardsYáñez,GonzaloMuñoz,MauricioFlores-Aqueveque,ValentinaBosch,Andrés Gravity Density Sedimentary basin Tectonics Geo-hazards Ground water Low enthalpy geothermal resources A recording of 1,115 gravimetric stations, the review of 368 wells, and the petrophysics measurements of 106 samples from representative outcrops have been used for a comprehensive geological/geophysical study of Santiago Basin. 2.5D and 3D gravimetric modeling, constrained by regional geology, soil and bedrock densities, edge-basin outcrops, depth (minimum) to basement from wells, and detailed modeling of heterogeneous bedrock and midcrustal blocks, provided a well-constrained depth to basement model. Model results indicate the presence of a relatively shallow basin with an average of 250 m depth, and three sub basins with depth in excess of 500 m, but comprising less than 30% of the basin surface. From erosion rates in central Chile we estimate a basin infill lasting between 10 to 20 Ma. Basement topography/geomorphology, undercover a structural pattern dominated by NE and NW-trending structures that can be traced out of the basin, westwards in the Coastal Cordillera and eastwards in the Main Cordillera, with second order relevance of NS structures in the eastern border of the basin. This observation, further supported by natural crustal seismicity and basement-derived-magnetic signatures, suggests that the basin origin is mainly controlled by inherited old structures oblique to the margin. Active seismicity along these traverse NE and NW structures suggest that permanent deformation, and associated seismic hazard in the basin is mostly concentrated along these structures. The dynamic response of soils, in terms of the natural resonance frequency, shows that the basement-to-sedimentary/ infilling-impedance-ratio is proportional to the amplitude of the resonance peak. On the other hand, the expected correlation between fundamental frequency and depth to basement is only partially supported by the empirical evidence. The difference between a greater gravimetric depth-to-basement compared to lesser seismic depth-to-basement, is attributed to changes in mechanical stiffness with depth compaction with minor effects in bulk density. Finally low enthalpy geothermal resources of the Santiago Basin is analyzed considering depth to bedrock, water table estimates and simple Darcy's-temperature coupled flow modeling. Results show that high groundwater temperature is restricted to deeper parts of southern sub-basin, which improves direct uses of geothermal energy for heating purposes.info:eu-repo/semantics/openAccessServicio Nacional de Geología y Minería (SERNAGEOMIN)Andean geology v.42 n.2 20152015-05-01text/htmlhttp://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-71062015000200001en10.5027/andgeoV42n2-a01
institution Scielo Chile
collection Scielo Chile
language English
topic Gravity
Density
Sedimentary basin
Tectonics
Geo-hazards
Ground water
Low enthalpy geothermal resources
spellingShingle Gravity
Density
Sedimentary basin
Tectonics
Geo-hazards
Ground water
Low enthalpy geothermal resources
Yáñez,Gonzalo
Muñoz,Mauricio
Flores-Aqueveque,Valentina
Bosch,Andrés
Gravity derived depth to basement in Santiago Basin, Chile: implications for its geological evolution, hydrogeology, low enthalpy geothermal, soil characterization and geo-hazards
description A recording of 1,115 gravimetric stations, the review of 368 wells, and the petrophysics measurements of 106 samples from representative outcrops have been used for a comprehensive geological/geophysical study of Santiago Basin. 2.5D and 3D gravimetric modeling, constrained by regional geology, soil and bedrock densities, edge-basin outcrops, depth (minimum) to basement from wells, and detailed modeling of heterogeneous bedrock and midcrustal blocks, provided a well-constrained depth to basement model. Model results indicate the presence of a relatively shallow basin with an average of 250 m depth, and three sub basins with depth in excess of 500 m, but comprising less than 30% of the basin surface. From erosion rates in central Chile we estimate a basin infill lasting between 10 to 20 Ma. Basement topography/geomorphology, undercover a structural pattern dominated by NE and NW-trending structures that can be traced out of the basin, westwards in the Coastal Cordillera and eastwards in the Main Cordillera, with second order relevance of NS structures in the eastern border of the basin. This observation, further supported by natural crustal seismicity and basement-derived-magnetic signatures, suggests that the basin origin is mainly controlled by inherited old structures oblique to the margin. Active seismicity along these traverse NE and NW structures suggest that permanent deformation, and associated seismic hazard in the basin is mostly concentrated along these structures. The dynamic response of soils, in terms of the natural resonance frequency, shows that the basement-to-sedimentary/ infilling-impedance-ratio is proportional to the amplitude of the resonance peak. On the other hand, the expected correlation between fundamental frequency and depth to basement is only partially supported by the empirical evidence. The difference between a greater gravimetric depth-to-basement compared to lesser seismic depth-to-basement, is attributed to changes in mechanical stiffness with depth compaction with minor effects in bulk density. Finally low enthalpy geothermal resources of the Santiago Basin is analyzed considering depth to bedrock, water table estimates and simple Darcy's-temperature coupled flow modeling. Results show that high groundwater temperature is restricted to deeper parts of southern sub-basin, which improves direct uses of geothermal energy for heating purposes.
author Yáñez,Gonzalo
Muñoz,Mauricio
Flores-Aqueveque,Valentina
Bosch,Andrés
author_facet Yáñez,Gonzalo
Muñoz,Mauricio
Flores-Aqueveque,Valentina
Bosch,Andrés
author_sort Yáñez,Gonzalo
title Gravity derived depth to basement in Santiago Basin, Chile: implications for its geological evolution, hydrogeology, low enthalpy geothermal, soil characterization and geo-hazards
title_short Gravity derived depth to basement in Santiago Basin, Chile: implications for its geological evolution, hydrogeology, low enthalpy geothermal, soil characterization and geo-hazards
title_full Gravity derived depth to basement in Santiago Basin, Chile: implications for its geological evolution, hydrogeology, low enthalpy geothermal, soil characterization and geo-hazards
title_fullStr Gravity derived depth to basement in Santiago Basin, Chile: implications for its geological evolution, hydrogeology, low enthalpy geothermal, soil characterization and geo-hazards
title_full_unstemmed Gravity derived depth to basement in Santiago Basin, Chile: implications for its geological evolution, hydrogeology, low enthalpy geothermal, soil characterization and geo-hazards
title_sort gravity derived depth to basement in santiago basin, chile: implications for its geological evolution, hydrogeology, low enthalpy geothermal, soil characterization and geo-hazards
publisher Servicio Nacional de Geología y Minería (SERNAGEOMIN)
publishDate 2015
url http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-71062015000200001
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