1,721,014 research outputs found
The use of 3-D and 2-D seismic tomography for assessing the physical integrity of building panels
No full textThis paper describes an application of 3-D seismic tomography for evaluating the inner structure of some building panels. The measurements were performed on two building panels that had been expressly constructed using the building techniques of the ancient Romans. The study was made to assist the design of restoration work on ancient Roman monuments, and walls in particular. The aim of the survey was to assess whether the seismic tomography technique could be used to determine the elastic properties of brick walls and how these might vary when the walls are subjected to different loads. Different loads were applied to both building panels and seismic tomographic images were obtained for each loading. By noting the changes in elastic properties, it was hoped to predict the onset of cracks or fractures. For the first wall, images were obtained for two load phases. On the second wall, the experiment was conducted for only one loading. The study showed that it was possible to identify the internal variations in seismic velocity caused by the applied loads and to predict the zones that were going to fracture. The inversion algorithm used was based on the LSQR method
The use of 3D and 2D seismic tomography for assessing the physical integrity of building panels.
No full textEvaluation of restoration results on the Antonino and Faustina temple in Rome through seismic transmission tomography: comparison of P-wave velocities before and after restoration
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Seismic refraction, isotropic and anisotropic seismic tomography on an ancient monument (Antonino and Faustina temple 141 A.D.)
No full textEvaluation of restoration results on the Antonino and Faustina Temple in Rome through seismic transmission tomography: Comparison of P-wave velocities before and after restoration
No full textTo evaluate the state of preservation of two columns of the Pronao of the Antonino and Faustina temple in the Roman forum (Rome, Italy - 141 A.D.), 2D seismic tomography was used. In this paper we describe the results of seismic transmission tomography before and after restoration, comparing sections of the two restored columns. The aim of this work was to test the validity of seismic tomography to guide the restorer during the restoration. We assessed the value of using this method to determine elastic properties in terms of P-wave velocity and, consequently, identify zones with little cracks and fractures, and detect improved dynamic characteristics after the restoration. Considering the dimensions nad shape of the studied objects, particular field and acquisition techniques were adopted. To obtain high-resolution tomograms, we used piezoelectric sensors with high cut-off frequency and short sampling intervals for the recorder unit; furthermore a particular recording technique was used to avoid reading errors (double trigger). The investigated sections are divided into cells, whose dimensions are calculated using Fresnel theory and a priori information. To invert the data we used the Least Square Inversion (LSI) method modified with variable damping factors, taking into account the mean slowness of the marble as constraint. The results of comparing P-wave velocities indicate that transmission tomography is able to detect differences in the elastic properties that occur before and after restoration. These results provide information to evaluate the degree of restoration needed, and to guide and help to improve the work of the restorer
Seismic refraction, isotropic anisotropic seismic tomography on an ancient monument (Antonino and Faustina temple AD 141)
No full textThis paper describes the results of using geophysical techniques to investigate three columns of the Pronaos of the Antonino and Faustina temple (AD 141) in Rome, Italy; the columns are of cipollino marble which shows alternate sequences of mica and calcite beds. We applied seismic refraction using traditional interpretation, and seismic transmission tomography. The comparison between the results of the refraction study and the 2D and 3D isotropic tomographic analyses suggested anisotropic characteristics for the marble, and this prompted us to perform a further tomographic experiment, taking into account these characteristics of the material. Assuming an elliptical model, the main directions of anisotropy were detected. Two velocity fields corresponding to the main directions of the anisotropy were measured and anomalies such as cracks and fractures were noted. The conjugate-gradient algorithm was used to invert the data. The results of the isotropic and anisotropic models were compared. The correlation between the methods highlighted the characteristics of the marble, i.e. anisotropy, depth of the weathering, fractures and small cracks. The results show that the material of the columns is in reasonable condition, with the exception of a surface area 6 cm to 15 cm deep that we estimate has been weathered for 2000 years, and that has been particularly affected by pollution in the last century
Quasi-2D hybrid joint inversion of seismic and geoelectric data
No full textMany joint inversion schemes use 1D forward modelling in the integrated interpretation of various geophysical data. In extending the joint inversion approach to the investigation of 2D structures, the discretization of the model parameters and the appropriate choice of the forward-modelling procedure play a very important role. In this paper, a hybrid seismic-geoelectric joint inversion method is proposed for the investigation of 2D near-surface geological structures. The electric and seismic models are coupled together through the use of common boundaries between the adjacent layers. Assuming a 2D model composed of homogeneous layers with curved boundaries, a fast ray-tracing algorithm is used for the calculation of refraction seismic traveltime data. In the geoelectric forward modelling, a locally 1D approximation is used. The boundary surfaces are written in the form of series expansion; the inversion algorithms are formulated for the expansion coefficients and the petrophysical parameters as unknowns. Two versions of the inversion method are proposed: in versions A and B, interval-wise constant functions and Chebyshev polynomials are, respectively, used as basis functions of the series expansion. The versions are tested by means of synthetic and in situ measured data. The tests show that both methods are stable and accurate
Rates of active compressional deformation in central Italy and Sicily: evaluation of the seismic budget
No full textHistorical and recent seismicity records and available source mechanisms in eastern-central Italy (Marche–Adriatic region), in mainland-southern Sicily and in the Tyrrhenian offshore of northern Sicily show com- parable deformation patterns. Seismotectonic consider- ations indicate that each of the three areas represents a broad seismogenic province of relatively homogeneous deformation. On the basis of the historical earthquake catalogue, the parameters of the Gutenberg–Richter dis- tribution have been calculated by means of a Monte Carlo simulation method. The average moment tensors have been computed from focal mechanism data and the strain rate and velocity tensors evaluated by means of Kostrov’s (in Izv Acad Sci USSR Phys Solid Earth 1:23–44, 1974) relation, which also considers the shape and size of the seismogenic volume. The uncertainties have been system- atically incorporated. The results show that the three seis- motectonic provinces are all undergoing shortening at seismic rates (*0.3 mm/year in the WSW–ENE direction in the eastern Marche–Adriatic region, *0.1 mm/year in the N–S direction in mainland-southern Sicily and *0.2 mm/year in the NW–SE direction in the Southern Tyrrhenian zone). The motion pattern in the Marche– Adriatic and in the Sicilian provinces suggests that these areas undergo active crust-scale deformation along reverse shear zones, in agreement with recent horizontal GPS motion model and other independent evidence.Published2T. Tettonica attivaJCR Journalrestricte
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