Pavol Zahorec

Pavol Zahorec
Slovak Academy of Sciences | SAV · Department of Gravimetry and Geodynamics

PhD

About

36
Publications
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156
Citations

Publications

Publications (36)
Article
In this study we have investigated the question as to whether highly accurate microgravimetric measurements on the side of a pyramid could also map the recently discovered “muon chamber” in the Great Pyramid of Giza in Egypt. Exploiting the technical capabilities of modern gravimeters, we performed three-dimensional model calculations with realisti...
Article
A quantum device uses ultracold atoms to sense gravitational changes that can detect a tunnel under a city street. Here, scientists discuss the advance from the viewpoints of quantum sensing and geophysics. Two views on quantum sensing in geophysics.
Article
Full-text available
We analyse spatiotemporal gravity changes observed on the Ischia island (Italy) accompanying the destructive earthquake of time-lapse gravity changes observed at 18 benchmarks of the Ischia gravimetric network are first corrected for the gravitational effect of the surface deformation using the deformation-induced topographic effect (DITE) correcti...
Article
Full-text available
We analyse spatiotemporal gravity changes observed on the Ischia island (Italy) accompanying the destructive earthquake of 21 August 2017. The 29 May 2016 to 22 September 2017 time-lapse gravity changes observed at 18 benchmarks of the Ischia gravimetric network are �rst corrected for the gravitational e�ect of the surface deforma- tion using the d...
Article
Full-text available
Gravitational effect of surface deformation is in 4D microgravimetry treated as the deformation-induced topographic effect (DITE). The DITE field is computed using Newtonian volumetric integration which requires high resolution digital elevation model (DEM) and vertical displacement field in areal form. If only elevation changes on benchmarks of th...
Article
Full-text available
The AlpArray Gravity Research Group (AAGRG), as part of the European AlpArray program, focuses on the compilation of a homogeneous surface-based gravity data set across the Alpine area. In 2017 10 European countries in the Alpine realm agreed to contribute with gravity data for a new compilation of the Alpine gravity field in an area spanning from...
Article
In volcano gravimetry, when analyzing residual spatiotemporal (time-lapse) gravity changes, the accurate deformation-induced topographic effect (DITE) should be used to account for the gravitational effect of surface deformation. Numerical realization of DITE requires the deformation field available in grid form. We compute the accurate DITE correc...
Preprint
Full-text available
The AlpArray Gravity Research Group (AAGRG), as part of the European AlpArray program, focuses on the compilation of a homogeneous surface-based gravity dataset across the Alpine area. From this data set, Bouguer- and Free Air anomalies are calculated and presented here. In 2016/17 ten European countries in the Alpine realm have agreed to contribut...
Article
Examples of the application of microgravity mehtod for the detection of potentially hazardous (empty) underground cavities caused by the collapse of coal mines are presented. Within these areas some alteration by previous remediation activity had occurred. This was not documented earlier and, therefore, such alteration was often unknown prior to th...
Article
Full-text available
Some geophysical or geodynamic applications require the use of true vertical gradient of gravity (VGG). This demand may be associated with reductions of or corrections to observed gravity or its spatiotemporal changes. In the absence of in situ measured VGG values, the constant value of the theoretical (normal) free air gradient (FAG) is commonly u...
Article
Detailed and precise measurement of the Earth's gravity field (microgravity method) can be effectively used for the detection and quantification of subsurface voids and/or cavities. There exist a variety of successful applications of the microgravity method in near surface geophysics, namely in geotechnical, environmental and archaeological prospec...
Article
Full-text available
We investigate the origin and implications of deformation-induced gravitational effects in interpretation of spatiotemporal gravity changes. We review the traditional approaches to handling the attraction of subsurface and surface deformations. These effects are relevant when inferring magmatic processes in volcano geodetic studies. We focus on the...
Article
Full-text available
Results from a detailed gravity survey realized along the planned highway tunnel in the karstic area of Slovak Karst in the eastern Slovakia are presented. Detailed gravity profiles crossed an area of rugged topography, therefore the terrain corrections played a crucial role in the gravity data processing. The airborne laser scanning technique (LiD...
Article
Full-text available
Predicted values of the vertical gradient of gravity (VGG) on benchmarks of Etna's monitoring system, based on calculation of the topographic contribution to the theoretical free-air gradient, are compared with VGG values observed in situ. The verification campaign indicated that improvements are required when predicting the VGGs at such networks....
Article
Full-text available
We present a simple and straightforward method for estimating the mean density of topographic masses based on underground gravity measurements along with topography modelling. Two examples under different conditions are given, the first coming from a railway tunnel passing through a Mesozoic karst area and the second from an active coal mine situat...
Chapter
When discussing the various aspects of the Bouguer anomaly calculation in the past we came across numerous discrepancies in its definition expressed either in textbooks (sometimes even including modern texts) or in not less than 10 important articles and discussions which have been published within the last 25 years. Therefore we continued in inves...
Chapter
Compilation of the Slovak gravimetric database with the actual amount of about 320,000 observation points is presented. Gravity data were collected during more than 50 years, which yields a very heterogeneous dataset, with large variations in the station coverage and processing methods. The regional gravimetric database (more than 212,000 points) w...
Chapter
The new software solution Toposk was developed in order to recalculate the terrain corrections of the unified gravity database of the Slovak Republic. The program is designed primarily for the calculation of the gravitational effect of the topographic masses, and the terrain corrections are then derived from these effects. The program application i...
Chapter
Vertical reference system in the Slovak Republic is realized by the first and second order of the National levelling network with the normal heights according to Molodenski. The reference heights are still calculated by the traditional method using the components of gravity correction. Nowadays we are preparing a new realization of the height syste...
Article
Full-text available
The paper deals with the revision and enrichment of the present gravimetric database of the Slovak Republic. The output of this process is a new version of the complete Bouguer anomaly (CBA) field on our territory. Thanks to the taking into account of more accurate terrain corrections, this field has significantly higher quality and higher resoluti...
Article
Full-text available
We present a detailed calculation of the topographic contribution to the vertical gradient of gravity (VGG) based on high-resolution digital elevation model (DEM) and new developed software (Toposk) for the purpose of predicting the actual VGGs in the field. The calculations presented here were performed for the Central Volcanic Complex (CVC) of Te...
Article
Full-text available
The vertical reference system in the Slovak Republic is realized by the National Levelling Network (NLN). The normal heights according to Molodensky have been introduced as reference heights in the NLN in 1957. Since then, the gravity correction, which is necessary to determine the reference heights in the NLN, has been obtained by an interpolation...
Conference Paper
Recent deep seismic studies support the existing isostatic systems only to a limited extent and, in some areas, considerable disagreements have been pointed at. This implies that we should attempt to replace the classic isostatic corrections by quantities calculated from a-priori information which should be as independent of the gravity data themse...
Conference Paper
Downward continuation of potential fields is an important tool in their interpretation - depths of shallowest important sources can be determined by means of stable downward continuation algorithms. In this contribution we analyse the properties of one from these algorithms (based on Tikhonov's regularization approach) from the scope of two most im...
Article
Full-text available
We review here the gravitational effects on the temporal (time-lapse) gravity changes induced by the surface deformation (vertical displacements). We focus on two terms, one induced by the displacement of the benchmark (gravity station) in the ambient gravity field, and the other imposed by the attraction of the masses within the topographic deform...
Article
It is well known that the vertical gradient of gravity measured on the Earth’s surface depends strongly on nearby topographical shapes. We simply inverted the problem and posed the question whether a zero vertical gradient can be observed using relative gravity meters and the classical tower method of measurement in appropriate terrain conditions....
Article
Full-text available
The discrepancy between real heights of gravity points and the elevation model has a significant impact on the terrain corrections calculation especially within the inner zone. The concept of interpolated heights of calculation points used instead of measured ones within the specified inner zone can considerably decrease the resulting errors. The c...
Conference Paper
The microgravity method has developed to be an important complementary method in non-invasive archaeological prospection in urban areas and buildings interiors, mainly in the area of cavity (crypts, tombs, cellars) detection. Thanks to the state of the art instrumentation low amplitude anomalies can be acquired and interpreted. In data processing t...
Conference Paper
Importance of precise vertical gradient of gravity (VGG) determination by means of relative gravity measurements is mainly connected with absolute gravity measurements and setting of global and local gravity reference networks. The gravitational effect of the topography and near building structures and their contribution on the vertical gradient of...
Article
Full-text available
The estimation of errors in calculated terrain corrections in the Tatra Mountains In general, calculation of terrain corrections can be a substantial source of errors in evaluating Bouguer anomalies, especially in rugged mountainous areas like the Tatra Mountains where we also get the largest values of the terrain corrections as such. It is then na...
Article
During the last four years some new geophysical results were obtained within the frame of the international project "Structural - geological conditions of Western Carpathians in border areas of northern Slovakia and their interpretation by means of geophysical measurements". The project was funded and supported by the Ministry of Environment of the...
Article
Full-text available
Results from microgravity survey for old crypts detection in the former church of St. Catherine are presented. Importance of selected steps in data acquisition and processing are discussed - mainly the problem of introduction of correct terrain corrections. The main part of the interpretation of the received residual Bouguer anomaly was the gravity...

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Projects

Projects (2)
Project
Detection of cavities and shallow burried structures of interest in archeological prospection and identification of geohazards
Project
Temporal gravity changes, such as those observed in restless volcanic areas, accompanied by surface deformations (vertical displacements) are coupled with the gravitational effect of the surface deformation. To interpret subsurface mass/density changes associated with volcanic signals the observed gravity changes must be stripped of the effect induced by surface deformations. The deformation induced topo effect (DITE) has two components: The Free Air Effect (FAE) which is due to the vertical displacement of the gravity benchmark in the static ambient field, and the Topographic Deformation Effect (TDE) due to the post-deformation surficial topo-deformation shell attraction. We review various approximations of DITE and FAE that have been in use in the past and present, such as those based on theoretical FAG, BUG, BCFAG, static Bouguer correction, etc. We revisit the controversial issue of using the normal vs the true (observed) vertical gradient of gravity (VGG). Using numerical simulations and in-situ verifications we show the size and spatial behaviour of the individual terms and step by step draw conclusions about the DITE and its applicability to volcano gravimetric monitoring and interpretation.