Papers by Carlos Alberto Vargas Jimenez
Geologia Colombiana, Aug 14, 2012
La región del "Eje Cafetero Colombiano" ha sido estudiada en términos de atenuación de ondas Coda... more La región del "Eje Cafetero Colombiano" ha sido estudiada en términos de atenuación de ondas Coda mediante la aplicación de los modelos de retro dispersión (SIBS)-Single Back Scattering (AKI & CHOUET 1975), Dispersion Isotropa Simple (SIS)-Single Isotropic Scattering (SATO 1977), y el modelo de múltiple dispersión basado en el Análisis por Ventanas Múltiples de Intervalo de Tiempo (MLTWA)-Multiple Lapse Time Window Analysis (HOSHIBA et al. 1991), en busca de establecer relaciones empíricas de dependencia de la Atenuación con la frecuencia para Qc-1 y Qt-1 , así como determinar los aportes de atenuación por absorción intrínseca y dispersiva. Para el efecto fueron utilizados alrededor de 300 sismogramas relacionados con 52 eventos registrados en 14 estaciones sismológicas: la mayor parte de estos eventos correspondieron a sismos de la crisis del Terremoto de Armenia (Mw = 6.2. 25/01/99). La aplicación de las dos primeras técnicas permitió establecer leyes de dependencia de la Atenuación con la frecuencia Qc-1 (f) = (0.018±0.001) f (1.04 ± 0.01) (SBS) Y Qc-1 (f) = (0.038±0.002) f (0.81 ± 0.01) (SIS). Así mismo, gracias a la distribución de estaciones y focos sísmicos, la regionalización de Qc evidencio contrastes importantes de atenuación con marcada influencia del Complejo Volcánico Ruiz-Tolima. Por su parte, los resultados hallados mediante la utilización de la tercera técnica (MLTWA) permiten interpretar procesos relacionados con la actividad tectónica del área que dificultan la discriminación de la atenuación, tanto intrínseca como dispersiva. Las leyes de dependencia entre la Atenuación y la frecuencia halladas para absorción intrínseca Qi-1 (f) = (0.004±0.001) f (0.81 ± 0.01) y para atenuación dispersiva Qs-1 (f) = (0.003±0.001) f (1.50 ± 0.01) sugieren un alto control estructural en la zona.
Earth Sciences Research Journal, 2014
The present research work examines three aspects of great importance for the future supply of oil... more The present research work examines three aspects of great importance for the future supply of oil and gas in Colombia. 1) The geographic and stratigraphic distribution of hydrocarbon resources for use in estimations of the contribution of different field sizes to the total supply of oil and gas in Colombia. 2) The current state of the hydrocarbon reserves in Colombia and factors that influence their increase or decrease; statistical tools are used to calculate the volume of hydrocarbons that may be found in the future. 3) The observed decline of hydrocarbon production in Colombia, which is used to estimate the amount of resources that may be extracted in the future once peak production has been reached. Based on these three aspects, we constructed different scenarios to forecast the potential production of oil and gas in Colombia. In addition, we calculated the amount of hydrocarbon reserves in these scenarios. ResumenEl presente trabajo resume tres aspectos considerados de gran imp...
Start from analysis of LANDSAT images with field check in several places toward north of the Sier... more Start from analysis of LANDSAT images with field check in several places toward north of the Sierra Nevada de Santa Marta and the La Guajira peninsula we found active tectonics evidences. In same manner the Colombian seismological network called as Red Sismológica Nacional de Colombia (RSNC), and the Global Seismological Network (NEIC) had been registered for this Colombian region a periodic shallow seismicity. The RSNC had registered shallow seismicity with 3.0
Cuadernos de Geografía: Revista Colombiana de Geografía, 2015
En este trabajo se pasa a mostrar como un gran sismo originado en el Sistema de Fallas de la Fall... more En este trabajo se pasa a mostrar como un gran sismo originado en el Sistema de Fallas de la Falla Frontal de la Cordillera Oriental (SFFFCO) puede producir grandes daños y pérdidas de vida tanto en el área metropolitana de Bogotá, como en el resto de la Sabana de Bogotá. El grado de la vulnerabilidad de Bogotá D.C. frente a un sismo cercano originado en el Piedemonte Llanero con una distancia inferior a 250 Km con una magnitud > 7.0, es muy alto teniendo presente que sus suelos de origen lagunar se ubican hacía el occidente y noroccidente, zonas que durante las dos últimas décadas se ha ido expansionado el área metropolitana.
Earth Sciences …, 2005
... Page 10. 108 Carlos A. Vargas, Andreas Kammer, Mireya Valdes, Carlos E. Rodríguez Alexander C... more ... Page 10. 108 Carlos A. Vargas, Andreas Kammer, Mireya Valdes, Carlos E. Rodríguez Alexander Caneva, Jhon J. Sánchez, Eliana Arias, Carlos A. Cortes, Héctor Mora REFERENCES ... Bogotá. Cepeda, H., Méndez, R., Murcia, LA Núñez, A. & Monsalve, ML, 1995. ...
Nevado del Ruiz volcano (NRV), Columbia, is one of the most dangerous volcanoes in the world and ... more Nevado del Ruiz volcano (NRV), Columbia, is one of the most dangerous volcanoes in the world and caused the death of 25,000 people in 1985. Using a new algorithm for repeated tomography, we have found a prominent seismic anomaly with high values of the Vp/Vs ratio at depths of 2–5 km below the surface, which is associated with a shallow magma reservoir. The amplitude and shape of this anomaly changed during the current phase of unrest which began in 2010. We interpret these changes as due to the ascent of gas bubbles through magma and to degassing of the reservoir. In 2011–2014, most of this gas escaped through permeable roof rocks, feeding surface fumarole activity and leading to a gradual decrease of the Vp/Vs ratio in the reservoir. This trend was reversed in 2015–2016 due to replenishment of the reservoir by a new batch of volatile-rich magma likely to sustain further volcanic activity. It is argued that the recurring " breathing " of the shallow reservoir is the main ...
Cuadernos De Geografia Revista Colombiana De Geografia, Oct 5, 2012
El posible escenario de un sismo de magnitud ≥ 6,5 para la ciudad de Villavicencio (Colombia) O p... more El posible escenario de un sismo de magnitud ≥ 6,5 para la ciudad de Villavicencio (Colombia) O possível cenário de um terremoto de magnitude ≥ 6,5 para a cidade de Villavicencio (Colômbia) The Possible Scenario of an Earthquake with a Magnitude ≥ 6,5 in Villavicencio (Colombia)
Boletin de la Sociedad …, 2009
Selected P wave arrival time data of 518 events (mainly aftershocks) of the 25 January 1999 Armen... more Selected P wave arrival time data of 518 events (mainly aftershocks) of the 25 January 1999 Armenia Earthquake (Mw=6.2, Colombia), recorded by 23 temporary seismic stations during February, 1999 to July, 2001, have been inverted simultaneously for both hypocenter locations and three-dimensional Vp structure. The surface geology of this area suggests a complex disposition of tectonic flakes composed by diverse rocks and crossed by the Romeral Fault System (RFS). However, there is a good correlation between high-velocity zones and old oceanic rocks affected by plutonic rocks. Metamorphic belts that wrap these rocks are well correlated with low-velocity zones. The disposition of tectonic flakes in depth is solved with a flower structure where the Cordoba fault slipped in a contact between high-and low-density rocks during the Armenia earthquake. The low-velocity zones would correspond to the older rocks that constitute the nucleus of the Central range. We infer that the source volume of the Armenia earthquake sequence lies within 75.64º-75.72º W, 4.38º-4.52ºN and a depth of 5-21 km; the source volume is approximately 2 200 km3. Most of the well-located aftershocks occurred above the hypocenter of Armenia earthquake.
Vertical-component, short period seismograms from 435 well located volcano-tectonic earthquakes a... more Vertical-component, short period seismograms from 435 well located volcano-tectonic earthquakes are used to estimate S-wave attenuation in the Galeras volcanic complex (south western Colombia) using coda waves. The coda magnitudes (M c) of the events are less than 2. Event depths are less than 10 km and hypocentral distances up to 16 km. are on the same order as the usual values for the Earth's crust.
We have estimated the Curie Point Depth (CPD) using the average radial power spectrum in a tecton... more We have estimated the Curie Point Depth (CPD) using the average radial power spectrum in a tectonically complex area located in the SW Caribbean basin. Data analyzed came from the World Digital Magnetic Anomaly Map, and three methods have been used to compare results and evaluate uncertainties: Centroid, Spectral Peak, and Forward Modeling. Results show a match along the three methods, suggesting that the CPD values in the area ranging between 6 km and 50 km. The results share the following characteristics: A) High values (N 30 km) are in continental regions; B) There is a trend of maximum CPD values along the SW-NE direction, starting from the Central Cordillera in Colombia to the Maracaibo Lake in Venezuela; C) There is a maximum CPD at the Sierra Nevada de Santa Marta (Colombia) as well as between Costa Rica-Nicaragua and Nicaragua-Honduras borders. The lowest CPD values (b 20 km) are associated with the coastal regions and offshore. We also tested results by estimating the geothermal gradient and comparing measured observations of the study area. Our results suggest at least five thermal terrains in the SW Caribbean Basin: A) The area that is comprising the Venezuela Basin, the Beata Ridge and the Colombia Basin up to longitude parallel to the Providencia Throat. B) The area that includes zones to the north of the Cocos Ridge and Panam Basin up to the trench. C) The orogenic region of the northern Andes and including areas of the Santa Marta Massif. D) The continental sector that encompasses Nicaragua, northern Costa Rica and eastern of Honduras. E) Corresponds to areas of the northern Venezuela and Colombia, NW of Colombia, the Panamanian territory and the transition zones between the Upper and Lower Nicaragua Rise.
To investigate the subduction dynamics in northwestern South America, we measured SKS and slab-re... more To investigate the subduction dynamics in northwestern South America, we measured SKS and slab-related local S splitting at 38 seismic stations. Comparison between the delay times of both phases shows that most of the SKS splitting is due to entrained mantle flow beneath the subducting Nazca and Caribbean slabs. On the other hand, the fast polarizations of local S-waves are consistently aligned with regional faults, which implies the existence of a lithosphere-confined anisotropy in the overriding plate, and that the mantle wedge is not contributing significantly to the splitting. Also, we identified a clear change in SKS fast directions at the trace of the Caldas Tear (58N), which represents a variation in the subduction style. To the north of 58N, fast directions are consistently parallel to the flat subduction of the Caribbean plate-Panama arc beneath South America, while to the south fast polarizations are subparallel to the Nazca-South America subduction direction. A new change in the SKS splitting pattern is detected at 2.88N, which is related to another variation in the subduction geometry marked by the presence of a lithosphere-scale tearing structure, named here as Malpelo Tear; in this region, NE-SW-oriented SKS fast directions are consistent with the general dip direction of the underthrusting of the Carnegie Ridge beneath South America. Further inland, this NE-SW-trending mantle flow continues beneath the Eastern Cordillera of Colombia and Merida Andes of Venezuela. Finally, our results suggest that the subslab mantle flow in northwestern South America is strongly controlled by the presence of lithospheric tearing structures.
Seismic event characterization is often accomplished using algorithms based only on in... more Seismic event characterization is often accomplished using algorithms based only on information received at
seismological stations located closest to the particular event, while ignoring historical data received at those stations.
These historical data are stored and unseen at this stage. This characterization process can delay the emergency
response, costing valuable time in the mitigation of the adverse effects on the affected population. Seismological
stations have recorded data during many events that have been characterized by classical methods, and these data
can be used as previous “knowledge” to train such stations to recognize patterns. This knowledge can be used to
make faster characterizations using only one three-component broadband station by applying bio-inspired algorithms
or recently developed stochastic methods, such as kernel methods. We trained a Support Vector Machine (SVM)
algorithm with seismograph data recorded by INGEOMINAS’s National Seismological Network at a three-
component station located near Bogota, Colombia. As input model descriptors, we used the following: (1) the integral
of the Fourier transform/power spectrum for each component, divided into 7 windows of 2 seconds and beginning at
the P onset time, and (2) the ratio between the calculated logarithm of magnitude (Mb) and epicentral distance. We
used 986 events with magnitudes greater than 3 recorded from late 2003 to 2008.
The algorithm classifies events with magnitude-distance ratios (a measure of the severity of possible damage caused
by an earthquake) greater than a background value. This value can be used to estimate the magnitude based on a
known epicentral distance, which is calculated from the difference between P and S onset times. This rapid (< 20
seconds) magnitude estimate can be used for rapid response strategies.
The results obtained in this work confirm that many hypocentral parameters and a rapid location of a seismic event
can be obtained using a few seconds of signal registered at a single station. A cascade scheme of SVMs or other
appropriate algorithms can be used to completely classify an event in a very short time with acceptable accuracy
using data from only one station.
A three-dimensional estimation of the Vp, Vs and Vp/Vs ratio structure at Galeras volcano was con... more A three-dimensional estimation of the Vp, Vs and Vp/Vs ratio structure at Galeras volcano was conducted by means of passive local earthquake tomography. 14,150 volcano-tectonic events recorded by 58 stations in the seismological network established for monitoring the volcanic activity by the Colombian Geological Survey –Pasto Volcano Observatory between the years 1989 and 2015, were inverted by using the LOTOS code. The seismic events are associated with shear-stress fractures in solid rock as a response to pressure induced by magma flow. Tomography resolution tests suggest a depth of imaging that yield 10 km from the summit of the main cra-
ter, illuminating a large portion of the volcanic structure and the interaction of tectonic features like the Buesaco and Silvia-Pijao faults. Full catalog tomographic inversion, that represents the stacked image of the volcanic structure or the most permanent features underneath the volcano, shows vertical structures aligned with seismicity beneath the main crater. We hypothesize that these structures correspond to a system of ducts or fractures through which magma and fluid phases flow up from deeper levels toward the top and related with the intersection of the surface traces of the Silvia-Pijao and Buesaco faults.
An earthquake relocation by seismic simultaneous inversion and double differences methods were do... more An earthquake relocation by seismic simultaneous inversion and double differences methods were done in the Colombian Llanos Foothills from 3º to 5ºN and from 73º to 75ºW. The data used in this work take account 483 earthquakes registered by The Colombia National Seismological Network (RSNC) between 1993 and 2012. For the events relocation the root mean square (RMS) was reduced and several earthquake clusters were identified. The new locations shows principally at southwestern zone are related with the Eastern Frontal Fault System with faults as the Servitá-Santa Maria fault and the Algeciras Fault. In addition this work shows a 3D velocity model indicating an anomaly in the wave behavior related mainly to the low velocity zone under the Eastern Cordillera and minimum variations in average velocity toward southeast zone related with the Amazon Craton. Finally in southwest region where located the faults shows a Vp high velocity anomaly.
Journal of Geophysical Research: Solid Earth, 2015
We used the receiver function technique to deduce crustal thickness beneath the northwestern Ande... more We used the receiver function technique to deduce crustal thickness beneath the northwestern Andean system, using data from the permanent seismic network of Colombia, combined with some of the IRIS and CTBTO stations in Colombia and Ecuador. The estimation of crustal thickness was made using the primary P to s conversion and crustal reverberations. The bulk crustal V P /V S ratio was constrained using a crustal thickness versus V P /V S stacking method, in addition to estimations using a time to depth conversion technique based on results of a modified Wadati diagram analysis. We observed a wide range of crustal thicknesses, including values around 17 km beneath the Malpelo Island on the Pacific Ocean, 20 to 30 km at the coastal Pacific and Caribbean plains of Colombia, 25 to 40 km beneath the eastern plains and foothills, 35 km beneath the Western Cordillera, 45 km at the Magdalena River intermountain valley, 52 to 58 km under the northern Central Cordillera, and reaching almost 60 km beneath some of the volcanoes of the Southern Cordilleran system of Colombia; crustal thickness can be slightly greater than 60 km beneath the plateau of the Eastern Cordillera. The values of V P /V S are particularly high for some of the stations on the volcanic centers, reaching values above 1.79, probably related to the addition of mafic materials to the lower crust, and in the plateau of the Eastern Cordillera near Bogota, where we speculate about the possibility of crustal seismic anisotropy associated with shear zones.
Geofísica internacional, 2007
Computers & Geosciences, 2003
We have developed a portable station with a low-frequency signal conditioning and acquisition sys... more We have developed a portable station with a low-frequency signal conditioning and acquisition system for seismic event recording. This station records events in different modes and transmits them in the cellular mobile telephone network via active pages. Setup of the station is done directly at the station or remotely via a TCP-IP connection to the site. The designed station has a 101 dB dynamic range and nine channels. Three are for the tri-axial array geophones. The other six are used for the acquisition of signals with less than 100 samples per second requirements (temperature, radiometry, inclinometers, battery monitoring, etc.). The station software allows detection of seismic events using a short-term/long-term coverage standard algorithm, as well as threshold detection, periodic capture and continuous channel capture. The conditioning and acquisition system was designed as an embedded command-driven system with its own real-time clock and storage memory. r
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Papers by Carlos Alberto Vargas Jimenez
seismological stations located closest to the particular event, while ignoring historical data received at those stations.
These historical data are stored and unseen at this stage. This characterization process can delay the emergency
response, costing valuable time in the mitigation of the adverse effects on the affected population. Seismological
stations have recorded data during many events that have been characterized by classical methods, and these data
can be used as previous “knowledge” to train such stations to recognize patterns. This knowledge can be used to
make faster characterizations using only one three-component broadband station by applying bio-inspired algorithms
or recently developed stochastic methods, such as kernel methods. We trained a Support Vector Machine (SVM)
algorithm with seismograph data recorded by INGEOMINAS’s National Seismological Network at a three-
component station located near Bogota, Colombia. As input model descriptors, we used the following: (1) the integral
of the Fourier transform/power spectrum for each component, divided into 7 windows of 2 seconds and beginning at
the P onset time, and (2) the ratio between the calculated logarithm of magnitude (Mb) and epicentral distance. We
used 986 events with magnitudes greater than 3 recorded from late 2003 to 2008.
The algorithm classifies events with magnitude-distance ratios (a measure of the severity of possible damage caused
by an earthquake) greater than a background value. This value can be used to estimate the magnitude based on a
known epicentral distance, which is calculated from the difference between P and S onset times. This rapid (< 20
seconds) magnitude estimate can be used for rapid response strategies.
The results obtained in this work confirm that many hypocentral parameters and a rapid location of a seismic event
can be obtained using a few seconds of signal registered at a single station. A cascade scheme of SVMs or other
appropriate algorithms can be used to completely classify an event in a very short time with acceptable accuracy
using data from only one station.
ter, illuminating a large portion of the volcanic structure and the interaction of tectonic features like the Buesaco and Silvia-Pijao faults. Full catalog tomographic inversion, that represents the stacked image of the volcanic structure or the most permanent features underneath the volcano, shows vertical structures aligned with seismicity beneath the main crater. We hypothesize that these structures correspond to a system of ducts or fractures through which magma and fluid phases flow up from deeper levels toward the top and related with the intersection of the surface traces of the Silvia-Pijao and Buesaco faults.
seismological stations located closest to the particular event, while ignoring historical data received at those stations.
These historical data are stored and unseen at this stage. This characterization process can delay the emergency
response, costing valuable time in the mitigation of the adverse effects on the affected population. Seismological
stations have recorded data during many events that have been characterized by classical methods, and these data
can be used as previous “knowledge” to train such stations to recognize patterns. This knowledge can be used to
make faster characterizations using only one three-component broadband station by applying bio-inspired algorithms
or recently developed stochastic methods, such as kernel methods. We trained a Support Vector Machine (SVM)
algorithm with seismograph data recorded by INGEOMINAS’s National Seismological Network at a three-
component station located near Bogota, Colombia. As input model descriptors, we used the following: (1) the integral
of the Fourier transform/power spectrum for each component, divided into 7 windows of 2 seconds and beginning at
the P onset time, and (2) the ratio between the calculated logarithm of magnitude (Mb) and epicentral distance. We
used 986 events with magnitudes greater than 3 recorded from late 2003 to 2008.
The algorithm classifies events with magnitude-distance ratios (a measure of the severity of possible damage caused
by an earthquake) greater than a background value. This value can be used to estimate the magnitude based on a
known epicentral distance, which is calculated from the difference between P and S onset times. This rapid (< 20
seconds) magnitude estimate can be used for rapid response strategies.
The results obtained in this work confirm that many hypocentral parameters and a rapid location of a seismic event
can be obtained using a few seconds of signal registered at a single station. A cascade scheme of SVMs or other
appropriate algorithms can be used to completely classify an event in a very short time with acceptable accuracy
using data from only one station.
ter, illuminating a large portion of the volcanic structure and the interaction of tectonic features like the Buesaco and Silvia-Pijao faults. Full catalog tomographic inversion, that represents the stacked image of the volcanic structure or the most permanent features underneath the volcano, shows vertical structures aligned with seismicity beneath the main crater. We hypothesize that these structures correspond to a system of ducts or fractures through which magma and fluid phases flow up from deeper levels toward the top and related with the intersection of the surface traces of the Silvia-Pijao and Buesaco faults.