High-resolution coherency functionals for improving the velocity analysis of ground-penetrating radar data

We aim at verifying whether the use of high-resolution coherency functionals could improve the signal-to-noise ratio (S/N) of Ground-Penetrating Radar data by introducing a variable and precisely picked velocity field in the migration process. After carrying out tests on synthetic data to schematically simulate the problem, assessing the types of functionals most suitable for GPR data analysis, we estimated a varying velocity field relative to a real dataset. This dataset was acquired in an archaeological area where an excavation after a GPR survey made it possible to define the position, type, and composition of the detected targets. Two functionals, the Complex Matched Coherency Measure and the Complex Matched Analysis, turned out to be effective in computing coherency maps characterized by high-resolution and strong noise rejection, where velocity picking can be done with high precision. By using the 2D velocity field thus obtained, migration algorithms performed better than in the case of constant or 1D velocity field, with satisfactory collapsing of the diffracted events and moving of the reflected energy in the correct position. The varying velocity field was estimated on different lines and used to migrate all the GPR profiles composing the survey covering the entire archaeological area. The time slices built with the migrated profiles resulted in a higher S/N than those obtained from non-migrated or migrated at constant velocity GPR profiles. The improvements are inherent to the resolution, continuity, and energy content of linear reflective areas. On the basis of our experience, we can state that the use of high-resolution coherency functionals leads to migrated GPR profiles with a high-grade of hyperbolas focusing. These profiles favor better imaging of the targets of interest, thereby allowing for a more reliable interpretation

SH-wave seismic reflection at a landslide (Patigno, NW Italy) integrated with P-wave

The aim of this paper is to present the acquisition and processing up to the depth migrated section of an SH-wave reflection seismic profile. This experience is conducted on a deep-seated gravitational slope deformation located in the Northern Apennines in Italy. The SH-wave depth-migrated image in the investigated area provides a detailed description of the small reactivation slip surfaces delineating minor landslides at shallow depths, which are responsible for the major damages observed. These results are integrated with a recently acquired P-wave seismic reflection profile investigating the same slope and delineating the highly deformed layer at depth, liable for the deep-seated gravitational slope deformation. The combined use of P-waves and SH-waves allows to gain a deeper knowledge of the landslide internal setting that is necessary to mitigate the risk associated with the mass movement

SH-wave reflection seismic survey at the Patigno landslide: integration with a previously acquired P-wave seismic profile

Seismic investigation on landslide is hampered by several factors that could prevent the use of the reflection seismic method to characterize the subsurface architecture (Jongmans and Garambois, 2007). Moreover, acquisition and processing of reflection seismic data are more time consuming compared with other geophysical techniques such as refraction seismic and electrical resistivity tomography (ERT), leading inevitably to higher costs. Notwithstanding these difficulties, recently some attempts to delineate the deep slip surface of large landslides have been carried out using P-wave reflection seismic surveys (Apuani et al., 2012; Stucchi and Mazzotti, 2009; Stucchi et al., 2014;). P-wave reflection seismic method is effective in imaging the slip surface at a depth sufficiently greater than the seismic wavelength, whereas, for very shallow horizons, it suffers from the limited resolution that can be obtained by the use of compressional waves. In this regards, SH-waves can be used to overcome this limitation (Deidda and Balia, 2001; Guy, 2006; Pugin et al., 2006,), but they require a specifically-designed energy source for waves generation, geophones measuring horizontal components of particles motion and an accurate choice of acquisition parameters. On the contrary, due to attenuation, the depth of investigation for SHwaves can be lower than for P-waves (Pugin et al., 2006). Therefore the geological understanding of a mass movement can take advantage of a combined use of both these geophysical methodologies. This is the case of the Patigno landslide, a great landslide located in the upper basin of Magra River, in the Northern Appennines, Italy (Fig.1), where a P-wave study carried out in the last years (Stucchi et al., 2014) was able to image the deepest discontinuity of the landslide body at around 40-50 m depth, but no description of the shallower layers can be inferred. Because these surface layers are the slip surfaces of quick reactivation movements of the landslide, an SH high-resolution reflection seismic survey was planned along the previous P-wave profile (Fig.1). This new survey associated to the P-wave investigation allows a more robust description of the landslide body, from the deepest discontinuity up to the very shallow portions of the landslide. This work describes the planning, acquisition and processing of the SH reflection seismic survey, and also gives a possible combined interpretation of both P and SH seismic images

Probabilistic inversions of electrical resistivity tomography data with a machine learning-based forward operator

Casting a geophysical inverse problem into a Bayesian setting is often discouraged by the computational workload needed to run many forward modeling evaluations. Here we present probabilistic inversions of electrical resistivity tomography data in which the forward operator is replaced by a trained residual neural network that learns the non-linear mapping between the resistivity model and the apparent resistivity values. The use of this specific architecture can provide some advantages over standard convolutional networks as it mitigates the vanishing gradient problem that might affect deep networks. The modeling error introduced by the network approximation is properly taken into account and propagated onto the estimated model uncertainties. One crucial aspect of any machine learning application is the definition of an appropriate training set. We draw the models forming the training and validation sets from previously defined prior distributions, while a finite element code provides the associated datasets. We apply the approach to two probabilistic inversion frameworks: a Markov Chain Monte Carlo algorithm is applied to synthetic data, while an ensemble-based algorithm is employed for the field measurements. For both the synthetic and field tests, the outcomes of the proposed method are benchmarked against the predictions obtained when the finite element code constitutes the forward operator. Our experiments illustrate that the network can effectively approximate the forward mapping even when a relatively small training set is created. The proposed strategy provides a forward operator three that is orders of magnitude faster than the accurate but computationally expensive finite element code. Our approach also yields most likely solutions and uncertainty quantifications comparable to those estimated when the finite element modeling is employed. The presented method allows solving the Bayesian electrical resistivity tomography with a reasonable computational cost and limited hardware resources

Biodegradable All-Polymer Field-Effect Transistors Printed on Mater-Bi

The growing demand of disposable electronics raises serious concerns for the corresponding increase in the amount of electronic waste, with severe environmental impact. Organic and flexible electronics have been proposed long ago as a more sustainable and energy-efficient technological platform with respect to established ones. Yet, such technology is leading to a drastic increase of plastic waste if common approaches for flexible substrates are followed. In this scenario, biodegradable solutions can significantly limit the environmental impact, actively contributing to eliminate the waste streams (plastic or electronic) associated with disposal of devices. However, achieving suitably scalable processes to pattern mechanically robust organic electronics onto largely available biodegradable substrates is still an open challenge. In this work, all-organic and highly flexible field-effect transistors, inkjet printed onto the biodegradable and compostable commercial substrate Mater-Bi, are demonstrated. Because of the thermal instability of Mater-Bi, no annealing steps are applied, producing devices with limited carrier mobility, yet showing correct n-type behavior and robustness to bending and crumpling. The degradation behavior of the final system shows unaltered biodegradability level according to ISO 14851. These results represent a promising step toward sustainable flexible and large-area electronics, combining energy and materials efficient processes with largely available biodegradable substrates

Polifarmacia psiquiátrica en personas con esquizofrenia en un establecimiento público de salud mental en Lima

Objetivos: El presente estudio busca identificar retrospectivamente la prevalencia de polifarmacia psiquiátrica en pacientes con el diagnóstico de esquizofrenia que reciben atención ambulatoria en el Instituto Nacional de Salud Mental “Honorio Delgado – Hideyo Noguchi” (Lima, Perú). Material y Métodos: Se revisaron 430 historias clínicas de pacientes con diagnóstico único de esquizofrenia, supuestamente estables clínicamente, atendidos en Consulta Externa de la Dirección de Adultos o en el Módulo de Intervención Breve del Instituto, durante el año 2016. Resultados: El 84,4% de la muestra recibió más de un psicofármaco, con un promedio de 3,0 psicofármacos por paciente; el 40,5% recibió más de un antipsicótico, con un promedio de 1,5 antipsicóticos por paciente; al 96,2% de los que recibían antipsicóticos de depósito, se agregó uno o más psicofármacos, y al 86,2%, uno o más antipsicóticos por vía oral. Como psicofármacos adicionales, el 50,9% tomaba una benzodiacepina, el 47,0% un anticolinérgico, el 24,4% un antidepresivo inhibidor de la recaptación de serotonina, y el 21,2%, por lo menos un estabilizador del ánimo. El número de psicofármacos en general y antipsicóticos en particular se asoció significativamente con hospitalizaciones previas, antecedente de terapia electroconvulsiva, uso de antipsicóticos de primera generación y uso de antipsicóticos de depósito. Conclusiones: Se encontró una elevada prevalencia de polifarmacia psiquiátrica en la población estudiada, lo que debe motivar la revisión de las guías de práctica clínica y la elaboración de normas que regulen el uso de psicofármacos

Seismic preprocessing and amplitude cross-calibration for a time-lapse amplitude study on seismic data from the Oseberg reservoir

The cross-calibration of different vintage data is an important prerequisite in attempting to determine the time-lapse seismic effects induced by hydrocarbon production in a reservoir. This paper reports the preprocessing and cross-calibration procedures adopted to modify the data of four seismic vintages (1982, 1989, 1992 and 1999) from the Oseberg field in the North Sea, for optimal conditions for a time-lapse seismic amplitude analysis. The final results, in terms of time-lapse variations, of acoustic impedance and of amplitude-versus-offset, are illustrated for selected data sets. The application of preprocessing to each individual vintage data set reduces the effects of the different acquisition and noise conditions, and leads to consistency in the amplitude response of the four vintages. This consistency facilitates the final amplitude cross-calibration that is carried out using, as reference, the Cretaceous horizon reflections above the Brent reservoir. Such cross-calibration can be considered as vintage-consistent residual amplitude correction. Acoustic impedance sections, intercept and gradie nt amplitude-versus-offset attributes and coherent amplitude-versus-offset estimates are computed on the final cross-calibrated data. The results, shown for three spatially coincident 2D lines selected from the 1982, 1989 and 1999 data sets, clearly indicate gas-cap expansion resulting from oil production. Such expansion is manifested as a decrease in acoustic impedance and a modification of the amplitude-versus-offset trends in the apical part of the reservoir

High-resolution coherency functionals for velocity analysis: an application for subbasalt seismic exploration

We tested the properties of three different coherency functionals for the velocity analysis of seismic data relative to subbasalt exploration. We evaluated the performance of the standard semblance algorithm and two high-resolution coherency functionals based on the use of analytic signals and of the covariance estimation along hyperbolic traveltime trajectories. Approximate knowledge of the wavelet was exploited to design appropriate filters that matched the primary reflections, thereby further improving the ability of the functionals to highlight the events of interest. The tests were carried out on two synthetic seismograms computed on models reproducing the geologic setting of basaltic intrusions and on common midpoint gathers from a 3D survey. Synthetic and field data had a very low signal-to-noise ratio, strong multiple contamination, and weak primary subbasalt signals. The results revealed that high-resolution coherency functionals were more suitable than semblance algorithms to detect primary signals and to distinguish them from multiples and other interfering events. This early discrimination between primaries and multiples could help to target specific signal enhancement and demultiple operations

Seismic hazard data for the new, Italian building code based on European standard

Prior to 2003 the Italian building code, established in 1974, was mostly based on working stress design. The zonation that guided its application was made up in 1981 using a semi-quantitative, mainly seismological approach; it was enforced in 1984 and left about 2/3 of the territory without seismic provisions. In 1998 a new zonation was proposed but never adopted. The 2002 Mw5.7 earthquake in Molise (Southern Italy) caused the collapse of a school and the death of 26 children. The school was built in an area where seismic provisions were not applied, although the zonation proposed in 1998 assigned it to the second zone. The earthquake triggered a process that led in a few months to a new set of seismic provision