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Geofísica Internacional
Revista Activa *
ISSN: 0016-7169
Ciencias de la Tierra
Universidad Nacional Autónoma de México

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Redalyc 3.0 versión beta.
La versión estable de Redalyc 3.0 se libera en febrero de 2017. En la actualidad, se muestran los resultados de la marcación de artículos científicos mediante la herramienta gratuita Marcalyc, liberada en su primera versión el 1ro de septiembre de 2016 y que está pensada como un elemento central en la construcción y consolidación de un modelo de AA sustentable para Iberoamérica.
en: We relocated 52 events of 2.5 ≤ Mc ≤ 3.6 from a seismic sequence of over 250 events that occurred during July-December 2012 southwest of the Linares area, northeastern Mexico. To examine this swarm four seismic stations were installed in the region and operated during different time periods from September to December. Relocation of the swarm showed that the earthquake hypocentral depths were at 8 (±5) km, and the time residuals had values ≤ 0.38 s. The fault plane solutions were generated for individual earthquakes and through the use of the composite mechanism technique. The focal mechanism solutions show pure reverse faulting; the SW dipping NNW – SSE trending nodal plane is the inferred fault plane (strike ~150 ° , dip ~50 ° and rake ~67 °), which reveals that maximum horizontal stress (S Hmax > S hmin > S v ) predominates in the area>>>
Carmen M. Gómez-Arredondo
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Juan C. Montalvo-Arrieta
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Arturo Iglesias-Mendoza
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Victor H. Espindola-Castro
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en: This paper presents the results of the investigation of a supergene manganese occurrence in the southeast of Brazil, using the Induced Polarization geophysical method. This study aims to characterize the surface and subsurface morphology of one of these occurrences, named São Roque, based on the contrast of the electrical properties of the ore and the host rocks. The ore, which is composed mainly of manganese oxides and hydroxides and subordinated graphite, occurs in the form of small discontinuous lenses hosted by quartzites and schists of the Itapira Group. The geophysical survey consisted on 10 lines of Induced Polarization Tomography using a Wenner-Schlumberger array, with an along- line electrode separation of 10 m for all lines. The IP data were modeled through commercial inversion software to generate 2D section models of chargeability. In order to create a 3D visualization model of chargeability, the 2D inversion models were then combined and interpolated in order to create a 3D visualization model. The 3D model revealed two independent ore bodies in both surface and subsurface, characterized for high chargeability (up to 20mV/V), instead of a single elongated orebody as suggested by the lateritic surface in the field. In addition, the model showed that the orebodies are elongated perpendicular to the area main structural trend and the regional alignment of the lateritic occurrences, which can bring new ideas in terms of local exploration strategies for manganese in this context.>>>
Leandro B. Vieira
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César A. Moreira
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Ariane R. P. Côrtes
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George L. Luvizotto
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en: This paper makes a comparative analysis between the Dipole-dipole, Wenner and Schlumberger arrays through electric resistivity tomography (ERT), about the sensitivity and resolution in the spatial characterization of infiltrating pollutants in septic tank and cone of depression in supply well, both contained in unconfined aquifer. Data acquisition consisted of electrical resistivity rea- dings using five parallel lines with 105m long, electrode spacing and lines of 5m. The data from each line were subjected to 2D inversion and then interpolated to generate 3D blocks, which were extracted from a fixed resistivity isosurface (620 W .m), which enabled the modeling of volumes related to the flow structures. The results for the Dipole-dipole array allowed the modeling of the cylindrical structure associated to the supply well, and an isosurface deformation associated to the septic tank, but did not allow the modeling of the plume. The data for the Schlumberger array cannot allow for the cone recognition, but resulted in a drop shape model, associated to the septic tank and similar to a contamination plume. The Wenner array resulted in a model with structu- re in elongated keel format associated to the cone of depression, and another that is similar to the drop shape model, also associated to the septic tank. The comparative analysis shows that the Dipole-dipole array is recommended in works of modeling vertically integrated three- dimensional structures of high resistivity in the saturated zone. The Wenner and Schlumberger arrays are recommended for modeling vertically integrated three-dimensional structures of low resistivity in unsaturated zone, with emphasis on the Schlumberger array.>>>
César Augusto Moreira
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Cesar Augusto
Universidade Estadual Paulista Júlio de Mesquita Filho
en: We studied the seismic response of broadband stations located around the Gulf of California, Mexico, using the horizontal to vertical component spectral ratio method (HVSR). We analyzed 92 earthquakes recor-ded by the NARS-Baja and RESBAN networks, operated by CICESE. The database consists of events recorded between 2002 and 2006, with magnitudes ranging from 3.2 to 6.6. We rotated the records to find radial and transversal ground-motion components and we calculated Fourier spectra of S -wave windows recorded for the three ground-motion components. Then, we calculated HVSR for the individual components and the average of both horizontal components for every event. We analyze records from 20 stations located on sites with different geologic characteristics and we find azimuthal dependence on six of them that have amplification factors varying from 1.5 to up to 13 times at narrow back- azimuth ranges. We also find that sites with significant amplification factors (above three) show increasing.>>>
Lenin Ávila-Barrientos
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Raúl R. Castro
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en: In this paper, we analyze the time delay between the occurrence of the minima in the geomagnetic Dst, SYM-H indices and the horizontal magnetic component (H) measured in the Teoloyucan Magnetic Observatory (TEO) of Mexico. This difference was calculated in Universal Time for 15 geomagnetic storms (Dst≤-100nT) occurred during the descending phase of solar cycle 23. We found that, when the TEO was at the dayside, dawn and dusk, the time difference was negative, indicating that the minimum appeared first in the Dst, SYM-H reported by Kyoto, and afterwards in the H reported by TEO. On the other hand, when the TEO was close to midnight the difference was positive, indicating that the minimum occurred first at TEO and afterwards in Dst. We noticed that 14 out of 15 geomagnetic storms followed this behavior, except the most intense one of the sample. For the rest of the storms, it seems that the cause of the delay is not the intensity of the magnetic field at minimum but the intensity of the current systems present during the storm occurrences.>>>
Julia Lénica Martínez-Bretón
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Blanca Mendoza Ortega
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Esteban Hernández-Quintero
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