Department of Gravimetry and Geodynamics

Web page of the Department of Earth Science Institute SAS

Research

Earth Crust and Lithosphere

Research devoted to the structure and properties of the Earth Crust and Lithosphere is based on forward density modeling and integrated modeling of gravity anomalies, geoidal undulations, topographic heights and surface heat flow, on 2D transects or in 3D, making use of all possible geophysical and gelogical constraints such as interpretations of reflection and refraction seismics, geothermics, geomorphology, existing tectonic and geological interpretations. We focus on the Carpatho-Pannonian region.

Inversion Methodology

Research devoted to development of and innovations in methods for solving the gravimetric inverse problem. A so called „Harmonic Inversion Method" has been developed at our department. We were involved in developing the so called „Truncation Filtering Methodology" based on a sequence of systematically varying the truncation parameter in the Stokes convolution integral for the computation of the geoid from gravity anomalies. We participate in enhancing the applicability of a novice and very verstaile inversion methodology, consisting of several steps: removal of a regional trend defined as a 2D harmonic function, vertical separation of signal of sources by triple harmonic continuation procedure, approximation of multiple sources by line segments, non-linear inversion based on local corrections producing contrast contact structural surfaces (interfaces) and/or homogenous 3D star-convex anomalous sources.

Geothermics

Research primarily devoted to modelling of the temperature field of the Western Carpathian's lithosphere and surrounding tectonic units. Development of suitable modeling approaches and numerical procedures for the interpretation of geothermal data in complex geological structures influenced by relatively young tectonic events i.e. solution of both direct and inverse geothermal problems in steady state or transient regime.  Prospection of deep geothermal energy sources in Slovakia by means of geothermic methods. 

Geodynamics

Research devoted to the study of earth tides and crustal deformations, monitoring and interpretation of extensometric measurements. Special attention is paid to the aperiodic component of the extensometric data with implications to slow tectonic crustal deformations, and to the derivation of rheological properties of the earth crust. We deal also with interpretation of surface deformations and gravity changes observed in active or awakening volcanic areas.

Microgravimetry

Research devoted to interpretation of detailed microgravity surveys with applications in archaeological investigations or geohazards, aiming at detection of shallow cavities such as crypts, hidden rooms and bunkers at historical or cultural sites, or abandoned mine-workings at urban sites. Microgravimetry is combined with georadar wherever possible. Detailed topographic correction, so called building correction, for the effect of building walls and other architectural features is calculated using an in-house program Polygrav that utilizes 3D

The implementation of geophysical methods in the monitoring of built heritage offers a valuable,   non-destructive insight into the internal structure. We have shown that 2D geophysical images or quantitative interpretations in form of 3D models can be easily incorporated into virtual databases of documented built heritage contributing to the understanding of its historical development also by the public and non-experts. Such multidisciplinary approach to sense the present and past of our historic monuments contributes significantly to their documentation for future generations.

 

Researchers from the Earth Science Institute went to Tenerife in June 2016 to carry out volcano-gravimetric field work. The objective of the observation campaign was to measure in-situ vertical gradients of gravity (VGGs) for the sake of verifying the numerically predicted (modelled) extreme values of the VGG. The crew comprised Peter Vajda and Pavol Zahorec of the Department of Gravimetry and Geodynamics of our institute, as well as Juraj Papčo of the Department of Geodesy of the Slovak Technical University in Bratislava. The campaign span one week (20–28 June, 2016). This field work campaign was conducted successfully and the acquired data seem promising.

 

Microgravity surveys for cavity detection conducted in the interior of buildings require high accuracy during data acquisition and modern processing procedures. We have developed a new method for the calculation of building effects, where geodetic measurements and photogrammetric software PhotoModeler are used. The advantages of the new approach are demonstrated on a small Slovak church, where two crypts were detected using microgravity and GPR methods in summer 2009. We have shown that close-range photogrammetry methods offer a possibility to improve the microgravity data processing.

The ruins of the St. Catherine's monastery complex are an important example of Slovak cultural heritage. An integrated geophysical approach to detect and characterize subsurface archaeological features has been applied in the nave of the former church. The combination of microgravimetry and GPR is shown to be a very effective tool for such mapping. Results from 36 GPR profiles were visualized in the form of horizontal time-slices and vertical time-sections. Several gravity anomalies were found in the residual Bouguer anomaly map. Semi-automated interpretation techniques including the Euler deconvolution and harmonic inversion were used to investigate the depth and shape of anomalous sources.

 

Radwan A. H. A. 1, Issawy E. A. 1, Dérerová J. 2, Bielik M. 2,3, Kohút I. 2

1National Research Institute of Astronomy and Geophysics

2Geophysical Institute of the Slovak Academy of Sciences

3Department of Applied and Environmental Geophysics, Faculty of Natural Sciences, Comenius University3

Introduction

The Red Sea is considered to be a typical example of a newly formed ocean, therefore, a great number of studies discuss its evolution and development especially in relationship to continental rifting, initiation of sea floor spreading and plate tectonics. We focused on the 2D integrated geophysical modelling with a goal to calculate an original model of the lithospheric structure and lithosphere thickness along Profile 1 (Fig. 1) in the Red Sea region. To know lithospheric structure and thickness is important for geodynamical reconstruction of the area.

Fig. 1. Surface geological map for the region of study (from EgyptianGeological Survey, 1994) with location of studied profile.

Measurable temporal changes of gravity and deformations of earth's surface are indicators of dynamic processes inside the earth, such as those associated with movements of magma preceding volcanic eruptions. The observation, analysis and interpretation of surface gravity changes and vertical displacements of the topographic surface contribute to understanding the physics of magma reservoirs and the processes associated with volcanic activity.

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