Anna Martí
University of Barcelona
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Surveys in Geophysics | 2014
Anna Martí
The study of electrical anisotropy in the Earth, defined as the electrical conductivity varying with orientation, has experienced important advances in the last years regarding the investigation of its origins, how to identify and model it, and how it can be related to other parameters, such as seismic and mechanical anisotropy. This paper provides a theoretical background and a review of the current state of the art of electrical anisotropy using electromagnetic methods in the frequency domain, focusing mainly on magnetotellurics. The aspects that will be considered are the modelling of the electromagnetic fields with anisotropic structures, the analysis of their responses to identify these structures, and how to properly use these responses in inversion and interpretation. Also, an update on the most recent case studies involving anisotropy is provided.
Journal of the Geological Society | 2013
María Ortuño; Anna Martí; Carles Martín-Closas; Gonzalo Jiménez-Moreno; Edoardo Martinetto; Pere Santanach
The nature, structure and extent of a palaeo-basin sedimentary infill exposed in the Aran valley (Central Pyrenees) was studied by combining stratigraphical and biostratigraphical analyses and an audio-magnetotelluric survey. The basin developed on top of a pre-existing peneplain and was formed by the North Maladeta Fault activity. The fluvio-palustrine sequence filling the basin was at least 100 m thick. Specimens of the taxon Hippuris cf. parvicarpa Nikitin were identified for the first time in a European palaeoflora. The palynological and carpological analyses allowed us to (1) constrain the age of the basin infill as Vallesian (11.1–8.7 Ma), (2) characterize the vegetation of the belt surrounding the basin as a mainly temperate to warm-temperate assemblage, and (3) estimate the palaeoaltitude of the site at between 700 and 1000 m, which leads to an altitude change of 900–1200 m for the North Maladeta Fault downthrown block and 1640–1640 m for the upthrown block. These data allowed us to estimate the regional uplift of the area at between 0.08 and 0.19 mm a−1. The different exhumation values obtained by other researchers for sites located at both sides of the North Maladeta Fault are in agreement with its activity as a normal fault since the Late Miocene. Supplementary materials Details of the data acquisition, processing and modelling for the Porèra profile are available at www.geolsoc.org.uk/SUP18551.
Geochemistry Geophysics Geosystems | 2015
Xavier Garcia; H. Seillé; James R. Elsenbeck; Rob L. Evans; Marion Jegen; Sebastian Hölz; Juanjo Ledo; Andrea Lovatini; Anna Martí; Alejandro Marcuello; Pilar Queralt; Carlo Ungarelli; César R. Ranero
We present results of marine MT acquisition in the Alboran sea that also incorporates previously acquired land MT from southern Spain into our analysis. The marine data show complex MT response functions with strong distortion due to seafloor topography and the coastline, but inclusion of high resolution topography and bathymetry and a seismically defined sediment unit into a 3D inversion model has allowed us to image the structure in the underlying mantle. The resulting resistivity model is broadly consistent with a geodynamic scenario that includes subduction of an eastward trending plate beneath Gibraltar, which plunges nearly vertically beneath the Alboran. Our model contains three primary features of interest: a resistive body beneath the central Alboran, which extends to a depth of ~150 km. At this depth, the mantle resistivity decreases to values of ~100 Ohm-m, slightly higher than those seen in typical asthenosphere at the same depth. This transition suggests a change in slab properties with depth, perhaps reflecting a change in the nature of the seafloor subducted in the past. Two conductive features in our model suggest the presence of fluids released by the subducting slab or a small amount of partial melt in the upper mantle (or both). Of these, the one in the center of the Alboran basin, in the uppermost-mantle (20-30km depth) beneath Neogene volcanics and west of the termination of the Nekkor Fault, is consistent with geochemical models, which infer highly thinned lithosphere and shallow melting in order to explain the petrology of seafloor volcanics.
Geophysical Journal International | 2002
Juanjo Ledo; Pilar Queralt; Anna Martí; Alan G. Jones
Tectonophysics | 2008
María Ortuño; Pilar Queralt; Anna Martí; Juanjo Ledo; E. Masana; Hector Perea; Pere Santanach
Geophysical Journal International | 2005
Anna Martí; Pilar Queralt; Alan G. Jones; Juanjo Ledo
Geophysical Journal International | 2004
Anna Martí; Pilar Queralt; E. Roca
Terra Nova | 2011
Oriol Rosell; Anna Martí; Alex Marcuello; Juanjo Ledo; Pilar Queralt; E. Roca; Joan Campanyà
Physics of the Earth and Planetary Interiors | 2010
Anna Martí; Pilar Queralt; Juanjo Ledo; Colin Farquharson
Surveys in Geophysics | 2011
Ester Falgàs; Juanjo Ledo; Beatriz Benjumea; Pilar Queralt; Alex Marcuello; Teresa Teixidó; Anna Martí