Person: Muñoz Martín, Alfonso
Loading...
First Name
Alfonso
Last Name
Muñoz Martín
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
Department
Geodinámica, Estratigrafía y Paleontología
Area
Geodinámica Interna
Identifiers
23 results
Search Results
Now showing 1 - 10 of 23
Item Controles tectónicos y estructurales de la incisión fluvial en el centro-oeste de la Cuenca del Duero, NO de Iberia(Geogaceta, 2007) Antón López, Loreto; Muñoz Martín, AlfonsoThe present work approaches incision rates quantification of Duero River in the central- west par t of Iberia and implications of tectonics in the evolution and change of drainage patterns. For this aim we calculate incision rates from the two main geomorphological surfaces defined in the area. Comparing fluvial incision rates and fracture pattern a strong structural control is shown; either in the orientation of drainage network, either in the incision rates distribution. Drainage pattern shows two main orientations, NW-SE following the hercinian structure of the area and NE-SW to N-S matching with the main fracture sets (Duero, Almendra, Almeida-Valderaduey faults, as example). Fluvial incision is mostly controlled by the great faults and faults systems NE-SW to N-S oriented.Item Relationship between the fractal dimension anisotropy of the spatial faults distribution and the paleostress fields on a Variscan granitic massif (Central Spain): the F-parameter(Journal of Structural Geology, 2005) Pérez López, Raúl; Paredes, Carlos; Muñoz Martín, AlfonsoThe spatial distribution of faults is usually described as a fractal set characterised by the fractal dimension. In this work, we have filtered fault patterns interpreted from digital elevation models, aerial photographs and field maps, by using structural geological parameters of the stress ellipsoid (stress tensor direction and stress ratio R0) and age of deformation. From these filtered structural maps, we have obtained the fractal dimension associated with the fracture patterns developed during Permo-Triassic and Alpine tectonic events on a Variscan granitic massif located in the Spanish Central System. Oriented fractal dimensions were calculated on several transects crossing the fault-filtered maps. The fractal dimension (D), calculated by 1-D box-counting, describes an ellipse on a polar plot with the short axis as the minimum value (DHmin) and the long axis as the maximum value (DHmax) of the fractal dimensions measured. From these analyses, we have defined the F-parameter as a function of the maximum value, minimum value and vertical value of fractal dimension (Dz), FZ(DzKDHmin)/(DHmaxK DHmin). Finally we have established, from a local scale analysis, a perpendicular relationship between the principal axes of the ellipse of the fractal spatial anisotropy of fractures and the principal axes of the stress tensor (sHmax, sHmin and sz) that generates this dynamic pattern of fractures. Furthermore, the F-parameter and the stress ratio R0 are equivalents and, applied in this area, both show a triaxial extension.Item Geomagnetic secular variation of Bransfield Strait (Western Antarctica) from analysis of marine crossover data(Geophysical journal international, 2005) Catalán, Manuel; Agudo, Luis Miguel; Muñoz Martín, AlfonsoTracking the secular variation of the geomagnetic field in the past is severely limited in some cases by factors relating to the remoteness of the sites. This is maximal in the Antarctic where the remote location and severe climate lead to logistic limitations that make it difficult to keep a continuous record of magnetic field variations. From the magnetic information available from historical marine expeditions, it is possible to infer this time-varying component from the comparison of readings at crossovers. This study focuses on this technique, discusses the impact of the different error sources and proposes a simple mathematical procedure to infer average secular variation rates. The result is validated by comparing it with local data from the Arctowski and Livingston magnetic observatories, sited in the area. Additionally, using a high-quality data set from a local area in the neighbourhood of Deception Island, we have detected a systematic distribution in its secular variation. This dichotomy has been interpreted in terms of a volcano-magnetic signal. This fact and the nature of its principal mechanisms are analysed and discussed.Item Análisis de Mapas de Anomalías Gravimétricas en el Borde NE de la Placa Caribe(2006) Granja Bruña, José Luis; Carbo Gorosabel, Andrés; Muñoz Martín, AlfonsoAlong the Eastern Greater Antilles (Hispaniola and Puerto Rico area) takes place the interaction between the Caribbean and North-American plates. This interaction produced inside a broad band of deformation with a complex and active tectonics. Here, many tectonic models have been proposed: strain partitioning, microplates tectonics, oblique subduction, opposing subducted slabs, crust arching, and tear fault in the downgoing plate. Except the seismological data that provide a general idea about the disposition of the lithospherics plates in depth, the most of models has been proposed from geodetic data (GPS), geological surface data (onland and onsea) and refection seismic data, so the models are constrained only in the superficial crust. In this survey, an analysis of anomaly gravity maps is presented. Those maps have been realized from the gravity data acquired during the PRICO (1997) and GEOPRICO-DO (2005) marine geophysical surveys, on-land data and satellite gravity data. In the maps analysis we emphasize the extreme values of Bouguer gravity anomaly (-400 mGals) located in the oceanic crust of the North American plate and the maximum free air gravity anomaly of the Earth (-350 mGals) located in the Puerto Rico Trench. This analysis, integrated with geomagnetic, seismologic and deep seismic sounding data is the way to approach the study of deep crust and to can elaborate lithosphere models constrained in depth.Item Alboran basin, Southern Spain. Part II: Neogene tectonic implications for the orogenic float model(Marine and Petroleum Geology, 2008) Gómez Ballesteros, María; Rivera, Jesus; Muñoz, Araceli; Muñoz Martín, Alfonso; Acosta, Juan; Carbo Gorosabel, Andrés; Uchupi, E.We infer that the Alboran Basin, the first western Mediterranean Basin found after crossing Gibraltar, is an orogenic float underlained by a de´ collement system, a multi-layered ductile shear extending from 10km to between 30 and 40km below sea level. This float was formed as consequence of the collision of the African–Eurasian plates in the Oligocene–late Miocene. Synchronous with this compression the float experienced basin wide crustal thinning and subsidence about 25 m/year ago by subcrustal processes. Since latest Miocene the float has undergone compression due to the continuous convergence of Eurasia and Africa. The faults created as a result of this compression are dominated by a conjugate system of northeast trending left-lateral and northwest right-lateral strike–slip faults. This deformation is taking place under a simple shear mechanism. Associated with the northwest and northeast lateral faults are zones of compression trending west and east of north extending from the base of the basin’s north upper slope to the Alboran Ridge. The initial morphology of the Alboran Ridge on the southern side of the Alboran Basin was due to the construction of a volcanic edifice at the northeast end of the ridge and igneous activity along northeast trending fractures southwest of the edifice. At the northeast end of the Alboran Ridge motion along a right-lateral fault cutting across the ridge led to sediment collapse and the creation of a prominent embayment on the ridge’s northwest flank. Deformation is more subdued in the western than in the eastern part of the Alboran Basin, a tectonic style due either to differences in sediment rheology or that the accommodation of the convergence of Africa and Iberia is more diffused and attenuated in the west than in the east.Item Cinturón Deformado de Los Muertos (Noreste de la Placa Caribe): Análisis Morfotectónico y Procesos Activos.(2006) Granja Bruña, José Luis; Carbo Gorosabel, Andrés; Muñoz Martín, Alfonso; Gómez Ballesteros, MaríaThe Muertos Deformed Belt (MDB) is a tectonic feature located within the Northeastern Caribbean Plate Boundary Zone. This deformed belt is occupying a broad band of active compression regime with an east-west trend along the south of Hispaniola and Puerto Rico islands. In our survey area, the deformed belt is limited to the south by the Muertos Trough (>5500 m depth), where the Venezuelan Basin oceanic crust is being underthrusted beneath western Puerto Rico and eastern Hispaniola areas. Here, we present the morphotectonic interpretation from the multibeam systematic survey in Muertos Deformed Belt area (from GEOPRICO-DO marine geophysical survey (2005)) and the relationship with seismicity and kinematic data (GPS). Active deformation features have been widely found in the area from bathymetry model and Chirp sub-bottom seismic profiles (TOPAS). These features include: folded and faulted recent sediments (Holocene), submarine landslides scars associated with faults (tsunamogenic potential) and submarine canyons deflected by fault traces. All these features are well preserved and show a little erosion. Future works will integrate potential field data and deep seismic data, which will allow us to elaborate complete tectonic models for this active and complex plate boundary.Item Comparación entre las técnicas AEOS, Re-Mi y PS-logging aplicadas en un terreno de estructura profunda conocida(Geotemas, 2008) García Mayordomo, Julián; Pérez Santisteban, Itziar; Pantín, V.; Muñoz Martín, Alfonso; Carbo Gorosabel, AndrésEn este estudio se contrastan los resultados que ofrecen dos técnicas de uso habitual en el Laboratorio de Geotecnia del CEDEX, el AEOS y el PS-logging, con los de una técnica relativamente novedosa, el Re-Mi (o sísmica pasiva). Para ello se emplean los resultados obtenidos por las tres técnicas en un emplazamiento común de estructura profunda conocida: un tramo de terraplén ferroviario recién construido. La técnica más precisa en la identificación de las diferentes partes de la estructura de tierras (terraplén, cimiento y contacto con el terreno natural) es el PS-logging, seguido por el AEOS y Re-Mi. Los valores de Vs promedio proporcionados por cada técnica presentan importantes diferencias, obteniéndose los más altos con el PS-logging, seguido por AEOS y Re-Mi. La desviación de los valores Vs promedio obtenidos por una técnica en particular, en comparación con las otras, es similar. Respecto a la técnica Re-Mi, cabe destacar que, si bien no se ha mostrado muy precisa en este estudio, presenta un alto grado de operatividad en cuanto a implantación, ejecución y procesado de datos.Item Morphotectonics of the central Muertos thrust belt and Muertos Trough (northeastern Caribbean)(Marine Geology, 2009) Granja Bruña, José Luis; Ten Brink, Uri S.; Carbo Gorosabel, Andrés; Muñoz Martín, Alfonso; Gómez Ballesteros, MaríaMultibeam bathymetry data acquired during the 2005 Spanish R/V Hespérides cruise and reprocessed multichannel seismic profiles provide the basis for the analysis of the morphology and deformation in the central Muertos Trough and Muertos thrust belt. The Muertos Trough is an elongated basin developed where the Venezuelan Basin crust is thrusted under the Muertos fold-and-thrust belt. Structural variations along the Muertos Trough are suggested to be a consequence of the overburden of the asymmetrical thrust belt and by the variable nature of the Venezuelan Basin crust along the margin. The insular slope can be divided into three east–west trending slope provinces with high lateral variability which correspond to different accretion stages: 1) The lower slope is composed of an active sequence of imbricate thrust slices and closed fold axes, which form short and narrow accretionary ridges and elongated slope basins; 2) The middle slope shows a less active imbricate structure resulting in lower superficial deformation and bigger slope basins; 3) The upper slope comprises the talus region and extended terraces burying an island arc basement and an inactive imbricate structure. The talus region is characterized by a dense drainage network that transports turbidite flows from the islands and their surrounding carbonate platform areas to the slope basins and sometimes to the trough. In the survey area the accommodation of the ongoing east–west differential motion between the Hispaniola and the Puerto Rico–Virgin Islands blocks takes place by means of diffuse deformation. The asymmetrical development of the thrust belt is not related to the geological conditions in the foreland, but rather may be caused by variations in the geometry and movement of the backstop. The map-view curves of the thrust belt and the symmetry of the recesses suggest a main north–south convergence along the Muertos margin. The western end of the Investigator Fault Zone comprises a broad band of active normal faults which result in high instability of the upper insular slope.Item Resultados y experiencias de aplicación del método de Refracción por Microtremor (Sísmica Pasiva) para la investigación geofísica de las nuevas líneas de metro en Madrid (España)(Geogaceta, 2006) Muñoz Martín, Alfonso; Carbo Gorosabel, AndrésGeophysical exploration with seismic methods in urban zones presents several disadvantages: the presence of numerous sources of seismic noise, the scanty penetration when the seismic source is a hammer and the disability to detect buried low-velocity beds. Recently (Louie, 2001) a new method of seismic investigation has been developed, which allows vertical modeling of Raleygh waves from spectral analysis (Vphase/frequency) using the seismic signal registered with conventional seismographs and geophones. This method allows to detect low-velocity buried beds of great interest in tunneling, and to reach depths below 50 meters. In this work we discuss the conditions of application and experiences obtained during the 2005 geophysical surveys carried out in Madrid before the excavation of the new subway tunnels.Item Upper crustal structure of Deception Island area (Bransfield Strait, Antarctica) from gravity and magnetic modelling(Antarctic Science, 2005) Muñoz Martín, Alfonso; Catalán Morollón, Manuel; Martín Dávila, José; Carbo Gorosabel, AndrésDeception Island is a young, active volcano located in the south-western part of Bransfield Strait, between the Antarctic Peninsula and the South Shetland archipelago. New gravity and magnetic data, from a marine geophysical cruise (DECVOL-99), were analysed. Forty-eight survey lines were processed and mapped around Deception Island to obtain Bouguer and magnetic anomaly maps. These maps show welldefined groups of gravity and magnetic anomalies, as well as their gradients. To constrain the upper crustal structure, we have performed 2+1/2D forward modelling on three profiles perpendicular to the main anomalies of the area, and taking into account previously published seismic information. From the gravity and magnetic models, two types of crust were identified. These were interpreted as continental crust (located north of Deception Island) and more basic crust (south of Deception Island). The transition between these crustal types is evident in the Bouguer anomaly map as a high gradient area trending NE–SW. Both magnetic and gravity data show a wide minimum at the eastern part of Deception Island, which suggests a very low bulk susceptibility and low density intrusive body. With historical recorded eruptions and thermal and fumarolic fields, we interpret this anomaly as a partially melted intrusive body. Its top has been estimated to be at 1.7 km depth using Euler deconvolution techniques.
- «
- 1 (current)
- 2
- 3
- »