Servicio Geologico Colombiano

Manizales, Colombia

Servicio Geologico Colombiano

Manizales, Colombia
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Inguaggiato S.,Italian National Institute of Geophysics and Volcanology | Londono J.M.,Servicio Geologico Colombiano | Chacon Z.,Servicio Geologico Colombiano | Liotta M.,Italian National Institute of Geophysics and Volcanology | And 2 more authors.
Chemical Geology | Year: 2016

Cerro Machín volcano in Colombia recently (2009-2013) exhibited new seismic activity. A geochemical characterization of emitted fluids was carried out based on the chemical and isotopic compositions of fumaroles and thermal springs discharged in this volcanic area with the aim of improving the volcano monitoring program.The isotopic composition of fumaroles located in the upper part of the dome was characterized by depleted δD and δ18O relative to the meteoric recharge fluids, which is due to a separation of the liquid phase in the lower part of the dome. A clear magmatic He signature was found in the fumaroles, with an increased magmatic contribution observed in the discharged fluids during 2011-2013 corroborating the increase in recorded seismic activity. Coupling the geochemical and seismic information has highlighted a clear awakening of Cerro Machín volcanic activity, indicating that this volcano is still active deserve an improvement of volcanic monitoring activity by the scientific community. © 2016 Elsevier B.V.

The amount of sulphur dioxide (SO2) emitted in 2008 during the ascent and extrusion of a lava dome in Galeras volcano was estimated and the behavior of emissions was compared with other parameters such as earthquakes associated with fluid motion and volcanic deformation. The flux of SO2 is the parameter that begins to show the rise of the 2008 lava dome, the other parameters reflect similar behavior but with time lags. Using a wind speed average value of 5 m/s, was estimated that 334.947 tons of SO2 were emitted into the atmosphere, equivalent to 2,2% of the global total annual volcanic emissions and 15,9% of the annual emissions of the South America subduction zone volcanoes.

Agency: European Commission | Branch: H2020 | Program: CSA | Phase: SC5-16-2016-2017 | Award Amount: 1.54M | Year: 2016

The project Towards a World Forum on Raw Materials (FORAM) will develop and set up an EU-based platform of international experts and stakeholders that will advance the idea of a World Forum on Raw Materials (WFRM) and enhance the international cooperation on raw material policies and investments. The global use of mineral resources has drastically increased and supply chains have become ever more complex. A number of global initiatives and organizations have been contributing to knowledge and information transfer, including the EC, UNEP International Resource Panel, the World Resources Forum, the World Material Forum, the OECD and others. It is widely felt that improved international resource transparency and governance would be beneficial for all, since it would lead to stability, predictability, resource-efficiency and hence a better foundation for competitiveness on a sustainable basis. The FORAM project will contribute to consolidate the efforts towards a more joint and coherent approach towards raw materials policies and investments worldwide, by closely working with the relevant stakeholders in industry, European and international organisations, governments, academia and civil society. Synergies with relevant EU Member States initiatives will be explored and fostered. The project will in particular seek to engage the participation of G20 Member countries and other countries active in the mining and other raw materials sectors, so that experiences will be shared and understanding of all aspects of trade in raw materials will be increased. By implementing this project an EU-based platform of international key experts and stakeholders is created, related to the entire raw materials value chain. This platform will work together on making the current complex maze of existing raw material related initiatives more effective. As such, the FORAM project will be the largest collaborative effort for raw materials strategy cooperation on a global level so far.

Torres-Corredor R.A.,Servicio Geologico Colombiano | Ponce-Villarreal P.,Servicio Geologico Colombiano | Gomez-Martinez D.M.,Servicio Geologico Colombiano
Boletin de Geologia | Year: 2017

The main focus of this research is a method for assessing the physical vulnerability of building roofs due to overloading of ashfall by eruptions of Galeras volcano. In order to know the possible affectation of roofs and buildings, damage relationships are established for types of roofs based on their typology, distances between supports and state. The vulnerability assessment allows estimating the likely degree of damage of the roof and building. The methodology starts from characterizing the hazard to establish the intensity pattern to analyze the resistance of the exposed element, which for ash, is the load transferred by a thickness accumulated on the roof. Additionally, an inventory of exposed elements was made, defining type of roofs, materials, geometric configuration and state, as well as of the building, which allow to categorize in roof types. Then the resistance is analyzed in order to determine the maximum stress that leads to failure, evaluating also, the impact on the entire building. The probability of damage is estimated using a cumulative distribution function, taking into account the variance of the boundary stress due to factors such as material heterogeneities, element dimensions, constructive effects or ash load distribution according to the wind path, roof style, as well as the moisture present in the ash. The vulnerability assessment in Galeras zone, shows that although light and moderate roofs are more vulnerable to ash loads, the effect of overall damage to the building is less, as opposed to heavy roofs and slabs. This study formulates considerations in the design of building roofs located in adjacent areas to active volcanoes, which could be the basis for the creation of a standard for design and construction of overload ash-resistant roofs.

Kobayashi D.,Pennsylvania State University | Kobayashi D.,University of Idaho | Lafemina P.,Pennsylvania State University | Geirsson H.,Pennsylvania State University | And 4 more authors.
Geochemistry, Geophysics, Geosystems | Year: 2014

Subduction of the Cocos plate and collision of the Cocos Ridge have profound effects on the kinematics of the western Caribbean, including crustal shortening, segmentation of the overriding plate, and tectonic escape of the Central American fore arc (CAFA). Tectonic models of the Panama Region (PR) have ranged from a rigid block to a deforming plate boundary zone. Recent expansion of GPS networks in Panama, Costa Rica, and Colombia makes it possible to constrain the kinematics of the PR. We present an improved kinematic block model for the western Caribbean, using this improved GPS network to test a suite of tectonic models describing the kinematics of this region. The best fit model predicts an Euler vector for the counterclockwise rotation of the CAFA relative to the Caribbean plate at 89.10W, 7.74N, 1.193 Ma-1, which is expressed as northwest-directed relative block rates of 11.3 ± 1.0-16.5 ± 1.1 mm a-1 from northern Costa Rica to Guatemala. This model also predicts high coupling along the Nicoya and Osa segments of the Middle American subduction zone. Our models demonstrate that the PR acts as a single tectonic block, the Panama block, with a predicted Euler vector of 107.65W, 26.50N, 0.133 Ma-1. This rotation manifests as northeast migration of the Panama block at rates of 6.9 ± 4.0-7.8 ± 4.8 mm a -1 from southern Costa Rica to eastern Panama. We interpret this motion as tectonic escape from Cocos Ridge collision, redirected by collision with the North Andes block, which migrates to the northwest at 12.2 ± 1.2 mm a-1. Key Points Collision of the Cocos Ridge is responsible for the upper plate kinematics The Panama Region acts as a single tectonic block, migrating northeast Interseismic coupling is high along the Nicoya and Osa segments of the trench © 2014. American Geophysical Union. All Rights Reserved.

Prieto G.A.,Massachusetts Institute of Technology | Florez M.,Massachusetts Institute of Technology | Barrett S.A.,Stanford University | Beroza G.C.,Stanford University | And 3 more authors.
Geophysical Research Letters | Year: 2013

Intermediate-depth earthquakes occur at depths where temperatures and pressures exceed those at which brittle failure is expected. There are two leading candidates for the physical mechanism behind these earthquakes: dehydration embrittlement and self-localizing thermal shear runaway. A complete energy budget for a range of earthquake sizes can help constrain whether either of these mechanisms might play a role in intermediate-depth earthquake rupture. The combination of high stress drop and low radiation efficiency that we observe for Mw 4-5 earthquakes in the Bucaramanga Nest implies a temperature increase of 600-1000°C for a centimeter-scale layer during earthquake failure. This suggests that substantial shear heating, and possibly partial melting, occurs during intermediate-depth earthquake failure. Our observations support thermal shear runaway as the mechanism for intermediate-depth earthquakes, which would help explain differences in their behavior compared to shallow earthquakes. Key Points Evidence for thermal shear runaway mechanism for intermediate-depth earthquakes Stress drop scaling and low radiation efficiencies observed for Mw 3.5-5.2 Fracture energies larger than for shallow earthquakes with similar slip ©2013. American Geophysical Union. All Rights Reserved.

Chiarabba C.,Italian National Institute of Geophysics and Volcanology | De Gori P.,Italian National Institute of Geophysics and Volcanology | Faccenna C.,Third University of Rome | Speranza F.,Italian National Institute of Geophysics and Volcanology | And 3 more authors.
Geochemistry, Geophysics, Geosystems | Year: 2016

Seismicity at the northern terminus of the Nazca subduction is diffused over a wide area containing the puzzling seismic feature known as the Bucaramanga nest. We relocate about 5000 earthquakes recorded by the Colombian national seismic network and produce the first 3-D velocity model of the area to define the geometry of the lithosphere subducting below the Colombian Andes. We found lateral velocity heterogeneities and an abrupt offset of the Wadati-Benioff zone at 5°N indicating that the Nazca plate is segmented by an E-W slab tear, that separates a steeper Nazca segment to the south from a flat subduction to the north. The flat Nazca slab extends eastward for about 400 km, before dip increases to 50° beneath the Eastern Cordillera, where it yields the Bucaramanga nest. We explain this puzzling locus of intermediate-depth seismicity located beneath the Eastern Cordillera of Colombia as due to a massive dehydration and eclogitization of a thickened oceanic crust. We relate the flat subducting geometry to the entrance at the trench at ca. 10 Ma of a thick - buoyant oceanic crust, likely a volcanic ridge, producing a high coupling with the overriding plate. Sub-horizontal plate subduction is consistent with the abrupt disappearance of volcanism in the Andes of South America at latitudes > 5°N. © 2015. American Geophysical Union. All Rights Reserved.

Orozco-Alzate M.,National University of Colombia | Castro-Cabrera P.A.,National University of Colombia | Bicego M.,University of Verona | Londono-Bonilla J.M.,Servicio Geologico Colombiano
Computers and Geosciences | Year: 2015

Distinguishing among the different seismic volcanic patterns is still one of the most important and labor-intensive tasks for volcano monitoring. This task could be lightened and made free from subjective bias by using automatic classification techniques. In this context, a core but often overlooked issue is the choice of an appropriate representation of the data to be classified. Recently, it has been suggested that using a relative representation (i.e. proximities, namely dissimilarities on pairs of objects) instead of an absolute one (i.e. features, namely measurements on single objects) is advantageous to exploit the relational information contained in the dissimilarities to derive highly discriminant vector spaces, where any classifier can be used. According to that motivation, this paper investigates the suitability of a dynamic time warping (DTW) dissimilarity-based vector representation for the classification of seismic patterns. Results show the usefulness of such a representation in the seismic pattern classification scenario, including analyses of potential benefits from recent advances in the dissimilarity-based paradigm such as the proper selection of representation sets and the combination of different dissimilarity representations that might be available for the same data. © 2015 Elsevier Ltd.

The Arenisca de Chiquinquira can be divided and mapped into five contrasted lithological segments, which have been denominated from base to top as A, B, C, D and E. Segments A, C and E are predominantly sandy, whereas segments B and D are lutaceous. Sandy facies are composed of 81% of quartzarenites and 19% of sublithoarenites. These rocks accumulated into a progradating shallow marine, tide-dominated environment (subtidal zone and intertidal flat), under a lower flow hydraulic regime. Lutaceous facies represent a calm marine offshore bottom, which was affected by quick accumulations of sandy or mixed sediments (sandy clastic material and shell remains). These quick accumulations of sediments occurred as a result of sediment gravitaty flows related to storms (storm beds). Occasionally, the storms deposited massive flows of sand or mixed sediments in channels or traverse depressions to the coast over the intertidal flat. The measured thickness of the Arenisca de Chiquinquira is 780 m. Upper Albian is represented along the segments A and B, while segments C, D and E represent the Cenomanian. Differential tectonic subsidence related to NW-SE normal faulting took place during the early Cenomanian, which was concomitant with sedimentation of the lower part of the segment C.

This work is framed within a geothermal research project cofinanced by ISAGEN and COLCIENCIAS called "Modeling Subsurface Structure Resistive From Surveys Magnetotelluric In Geothermal Areas Of Colombia, Case Nevado Del Ruiz" In which through a cooperative agreement between the Universidad Autónoma de México (UNAM) the Servicio Geológico Colombiano (SGC) and the Centro Internacional de Física (CIF) has been acquired magnetotelluric information composed of 105 soundings located to west of the Nevado del Ruiz. This paper illustrates the application of a methodology for processing and modeling based on 58 soundings associated with five (5) profiles. The selection of the profiles was performed using criteria such as high density of stations, proximity to a well drilled in the area and the possibility of crossing some of the surface geological structures most relevant. In the data field processing, the SSMT2000 and MTEDITOR software were used, both from the Phoenix Geophysics House, which are programmed in the basic processing algorithms such as transformation to the frequency domain programmed, the cross spectra and auto spectra, and magnetotelluric transfer function; thus is possible to obtain as a first result the MT (magnetotelluric) soundings values e xpressed in apparent resistivities and phases for each frequency. For the modeling state we used the winGlink software from the Geosystem house. As a first approximation 1D inversion were made. The invariant curve of the impedance tensor with Bostick algorithm (Bostick Transform), with Occam algorithm and additionally with the model resistivities discrete layers were used. After an analysis of the dimensionality is passed to the 2D inversion. The procedure consisted of rotating the impedances tensor to the main axes (as a first approximation) for profiles oriented NW (MT 1 and MT 2) and SW (MT 3) and rotate the tensor in EW direction for profiles oriented NS (MT 4 and MT 5), selection made from regional strike directionality found. For the 2 models, two electromagnetic modes (TE and TM) simultaneously in the inversion process were used. Finally, electrical resistivity models were obtained along five magnetotelluric profiles where we can observe that 2D models are more accurated due to the high complexity of the area (as best approach to information present in soundings).

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