Parameter sensitivity maps of surface geoelectric arrays I. Linear arrays

Szalai, S.; Szarka, László

doi:10.1556/ageod.43.2008.4.4

Cited by 33 publications

(16 citation statements)

References 19 publications

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“…These investigations also verified that the PS map is suitable -amongst many other possibilities (Szalai and Szarka, 2008b) -for estimating the related DD. The larger the PS map maximal value the larger is the DD.…”

Section: Tablesupporting

confidence: 64%

Multiplication of the depth of detectability using γ11n arrays

Szalai¹,

Lemperger²,

Metwaly³

et al. 2014

Journal of Applied Geophysics

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The depth from which one can get information has always been a crucial parameter in the geophysical exploration. This paper deals with the depth of detectability (DD) of 2D electric resistivity tomography configurations. DD is the maximal depth from which a given model body is detectable in the presence of a given noise level. Based on previous DD calculations for conventional electrode arrays it is shown in this paper that there is a nearly linear relation between the maximum value of their parameter-sensitivity (PS) maps and their DD values. Studying the PS maps of other arrays, as well, we found that many of them have higher PS max values than those of the conventional arrays. These so-called γ 11n arrays are therefore expected to have larger DD values, too. The performed DD-calculations have confirmed this expectation. γ 11n arrays are linear geoelectric arrays where γ refers to the CPCP order of the current (C) and potential (P) electrodes whilst the subscript numbers refer to the distance of the neighbouring electrodes. In case of the studied prism and dyke models the γ 11n arrays -if n is larger or equal to 2 -consistently produced higher DD-values than the best conventional arrays. The DD value of these arrays can be even 2-3 times larger than that of the best conventional array value. Such an increase in the DD value is especially useful if the available place for measurements is limited, e.g. due to infrastructural conditions. Anomalies in large depth, for example, which are not seen by traditionally used arrays, may become detectable using γ 11n arrays as it was verified also by numerical studies. These arrays require moreover less measurement than most conventional arrays resulting in shorter measuring time.

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Section: Tablesupporting

confidence: 64%

Multiplication of the depth of detectability using γ11n arrays

Szalai¹,

Lemperger²,

Metwaly³

et al. 2014

Journal of Applied Geophysics

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show abstract

“…). Practically all known arrays have been analyzed in terms of signal contribution sections or maps (Szalai and Szarka a, b). These maps help to understand the formation of resistivity anomalies prior to any numerical or physical modelling, and are useful tools for survey design and qualitative data interpretation.…”

Section: Introductionmentioning

confidence: 99%

Alternative theory for signal contribution sections and depth of investigation characteristics in electrical prospecting

Gómez‐Treviño

Flores

2015

Geophysical Prospecting

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We present an alternative to Roy's theorem for direct current regimes with the aim of validating the theoretical basis of signal contribution sections in electrical prospecting. Roy's theorem establishes that the electrical potential at a point can be expressed as an integral over all space of the electric field weighted by the gradient of inverse distance. The integrand is interpreted to represent elementary contributions to the potential that can be analyzed to compare different electrode arrays. Signal contribution sections and depth of investigation characteristics can be beautifully illustrated with important practical applications. However, the electric potential, being the solution of a boundary value problem, cannot be uniquely decomposed into elementary contributions. There is no guarantee for the integrand of a given integral to be meaningful in all situations. In the case of Roy's theorem, the concept has been severely criticized by respected scholars who challenged the scientific legitimacy of his approach. If we are going to keep the concept of elementary contributions alive, we need to go beyond Roy's theorem. In this paper, we develop an alternative theorem and show that it merges with the concept of sensitivity, which is unique and mathematically sound, and is also open to physical validation. This prevents any possible contradictions in the future and, equally important, eliminates the dichotomy between sensitivity and elementary contributions.

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“…On the other hand, we can also give another meaning of parameter λ: velocity response of rocks may be different to the same amount of change in rock pressure, or in other words, the pressure sensitivity of measured velocity is different. The parameter sensitivity functions are extensively used in the seismic (Dobróka 1987(Dobróka , 1988, the geoelectric (Gyulai 1989), electromagnetic (Szalai and Szarka 2008) and well-logging (Dobróka and Szabó 2011) literature. We introduce the (logarithmic) stress sensitivity of the u = v max − v velocity as…”

Section: The Pressure Dependent Acoustic Velocity Modelmentioning

confidence: 99%

The pressure dependence of acoustic velocity and quality factor — New petrophysical models

Dobróka

Molnar

2012

Acta Geodaetica et Geophysica Hungarica

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In this study we introduce new rock physical models which describe the pressure dependence of seismic velocity and quality factor. The models are based on the idea (accepted in the literature) that microcracks in rocks are opened and closed under the change of pressure. The models were applied to acoustic P wave velocity data measured on core samples originated from oil-drilling wells (27 samples) and also seismic velocity and quality factor data sets published in international literature. During the measurements the pulse transmission and the spectral ratio techniques were used. Measurements were carried out at various incremental pressures and parameters of the models were determined by linearized inversion methods. The calculated data matched accurately with measured data proving that the new rock physical models apply well in practice.

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Parameter sensitivity maps of surface geoelectric arrays I. Linear arrays

Cited by 33 publications

References 19 publications

Multiplication of the depth of detectability using γ11n arrays

Multiplication of the depth of detectability using γ11n arrays

Alternative theory for signal contribution sections and depth of investigation characteristics in electrical prospecting

The pressure dependence of acoustic velocity and quality factor — New petrophysical models

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