GLORIA

GEOMAR Library Ocean Research Information Access

feed icon rss

Ihre E-Mail wurde erfolgreich gesendet. Bitte prüfen Sie Ihren Maileingang.

Leider ist ein Fehler beim E-Mail-Versand aufgetreten. Bitte versuchen Sie es erneut.

Vorgang fortführen?

Exportieren
  • 1
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Science Ltd
    Geophysical prospecting 50 (2002), S. 0 
    ISSN: 1365-2478
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Physik
    Notizen: A new filtering technique for single-fold wide-angle reflection/refraction seismic data is presented. The technique is based on the wavelet decomposition of a set of adjacent traces followed by coherence analysis. The filtering procedure consists of three steps. In the first, a wavelet decomposition of traces into different detail levels is performed. In the second, the coherence attributes for each level are evaluated by calculating cross-correlation functions of detail portions contained in a space–time moving window. Finally, the filtered traces are obtained as a weighted reconstruction of the trace details. Each weight is obtained from the coherence-attributes distribution estimated in a proper interval. A sequence of tests is then conducted in order to select possible optimum or unsuitable wavelet bases. The efficiency of the filter proposed was assessed by calculating some properly designed parameters in order to compare it with other standard de-noising techniques. The proposed method produced a clear signal enhancement in high-density wide-angle seismic data, thus proving that it is a useful processing tool for a reliable correlation of seismic phases.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Pure and applied geophysics 157 (2000), S. 1463-1491 
    ISSN: 1420-9136
    Schlagwort(e): Key Words: Threshold, denoising, filtering, wavelet, multiresolution, potential field.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract —Gravity and magnetic signals are usually affected by noise, which is in turn related either to the geological heterogeneity of the shallow structures or to the measurement and data processing procedures. Along the map, the signal is represented by field anomalies which overlap with the noise in a variable and complicated way. Classical filtering techniques such as the Fourier (band-pass) filtering or the wavelet “cycle-spinning” method denoise the data only in a global sense and are therefore inaccurate when the frequency content of the signal is no longer uniform. We propose instead a localized denoising of such data, based on localized filtering techniques using the wavelet transform. The localized denoising filtering is based on a “soft thresholding” rule and is characterized by a local thresholding parameter (LTP). An adaptive tuning of the LTP parameter allows enhancement of the high frequencies of the signal and is effective to remove the noise as much as possible. The method is confronted using two different kinds of wavelets, namely the biorthogonal and the multiscale shiftable transforms and is applied to the noisy vertical derivative of the gravity field of Sicily. The technique proves to be superior to classical methods and may be similarly applied to any manner of geophysical data.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 3
    Publikationsdatum: 2017-04-04
    Beschreibung: An analysis of the field scaling power spectrum yields useful information about the source distribution, but it is uncertain whether deterministic, random, fractal or mixed approaches have to be used for the interpretation. To this end, the scaling properties of potential field spectra are analysed for a number of different source models of geological interest. Besides the models of Naidu (purely random sources) and Spector and Grant (gross block statistical ensembles) we consider other types of density and magnetization distributions with spectral exponents in the fractal range, such as a single homogeneous body with a random white source distribution. Spectral slopes in the fractal range are obtained. We also study the effects of important natural sources, such as salt domes and sedimentary basins, representing them with simple Gaussians or combinations of Gaussian signals. The same spectral slopes as for gravity signals generated by 3-D fractal source distributions are found for them. Hence the power law decay of the field is not a characteristic only of fractal source models. If a 3-D fractal source distribution is assumed a priori, a way of verifying the goodness of the model is to examine the whitened field at source level. The probability that the whitened field derives from a random white population is estimated for synthetic and real anomalies by applying the usual statistical tests.
    Beschreibung: Published
    Beschreibung: 311-323
    Beschreibung: JCR Journal
    Beschreibung: reserved
    Schlagwort(e): fractals ; potential field ; spectral analysis ; 04. Solid Earth::04.02. Exploration geophysics::04.02.04. Magnetic and electrical methods ; 05. General::05.01. Computational geophysics::05.01.03. Inverse methods ; 05. General::05.05. Mathematical geophysics::05.05.99. General or miscellaneous
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
    Standort Signatur Einschränkungen Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 4
    Publikationsdatum: 2019-11-04
    Beschreibung: Fractal dimension is widely used to give a measure of variability and roughness of curves, signals, objects, sta- tistical distributions, and so on, We found that an often used method, the so-called triangular prism surface- area method, for estimating the tractal dimension of fractal surfaces possesses some intrinsic mistake., in appli- cation. This note describes the misintel"pretation and suggests the proper application, that we calI Revised Tri- angular Prism Method (RTPM). To show its feasibility we apply RTPM to some synthetic Euclidean and frac- tal surfaces of known dimension.
    Beschreibung: JCR Journal
    Beschreibung: open
    Schlagwort(e): Fractal dimension ; self-affinity ; self-similarity ; triangulation ; 05. General::05.06. Methods::05.06.99. General or miscellaneous
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
    Format: 3648043 bytes
    Format: application/pdf
    Standort Signatur Einschränkungen Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 5
    Publikationsdatum: 2019-11-04
    Beschreibung: In this work, some results of a GPR survey carried out in a 10000 m2 large archaeological site, located in Lecce (Italy) near to a necropolis dating from the Messapian to the Roman imperial age, are reported. After a preliminary survey, performed on the entire area along parallel 1 m spaced profiles using a 200 MHz and a 500 MHz antenna in single-fold continuous mode, some smaller areas were selected, where the survey was repeated decreasing the profile spacing down to 0.50 m for the lower frequency antenna and to 0.25 m for the higher one. For two selected zones (D and B) the processed data were visualized in 3D space not only by the standard time slice technique, but also by two recently proposed approaches, namely by iso-amplitude surfaces of the complex trace amplitude and by 3D projection of energy and envelope stacks. The immediacy in revealing the spatial positioning of highly reflecting bodies, such as the anomaly interpreted as an old refilled cistern in zone D, makes 3D visualization techniques very attractive in archaeological applications of GPR. Their sensitivity to the signal/noise ratio is, on the other hand, highlighted by the quite poor performance in zone B, where the only reliable result provided by all the techniques was the soil/bedrock reflection, whereas none of them could effectively enhance the visibility of weak dipping reflections noted on 2D sections and probably related to fractures or bedding planes in the calcarenitic basement. The performance of the various techniques in these two different situations allowed insights into their main advantages and drawbacks to be gained.
    Beschreibung: Published
    Beschreibung: JCR Journal
    Beschreibung: open
    Schlagwort(e): ground-penetrating radar ; archaeological investigations ; visualization techniques ; 05. General::05.09. Miscellaneous::05.09.99. General or miscellaneous
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
    Format: 936566 bytes
    Format: application/pdf
    Standort Signatur Einschränkungen Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 6
    Publikationsdatum: 2019-11-04
    Beschreibung: In this paper an example is given of an application of statistical techniques to the Bouguer anomalies analysis in order to design a simple crustal model using few a priori assumptions. All gravity measurements carried out in Sardinia have been collected and processed. The Bouguer anomalies have been calculated according to local density estimates. Spectral analysis of the Bouguer anomalies has been carried out along selected profiles in order to estimate the mean depth of the Moho discontinuity and that of an infracrustal discontinuity. The use of this technique inferred the presence of a discontinuity at a mean depth of ~ 28 km, interpreted as Moho and the likely presence of an infracrustal discontinuity at a mean depth of ~18 km, interpreted as the upper-lower crust transition. In order to roughly reconstruct the shape of these interfaces, 2D inversion techniques were applied to the large wavelength components of the Bouguer anomalies, relative to profiles oriented along the E-W direction, extracted from low-pass filtered Bouguer anomaly maps. The density model obtained is compatible with some velocity models achieved from the interpretation of the seismic refraction profiles carried out within the European Geotraverse project.
    Beschreibung: JCR Journal
    Beschreibung: open
    Schlagwort(e): gravity ; seismic ; spectral analysis ; filtering ; modelling ; 04. Solid Earth::04.02. Exploration geophysics::04.02.02. Gravity methods
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
    Format: 3456731 bytes
    Format: application/pdf
    Standort Signatur Einschränkungen Verfügbarkeit
    BibTip Andere fanden auch interessant ...
Schließen ⊗
Diese Webseite nutzt Cookies und das Analyse-Tool Matomo. Weitere Informationen finden Sie hier...