Jan Vozar

Earth Science Institute of the Slovak Academy of Sciences, Bratislava, Slovakia · Division of Geophysics

Dobrá Voda village is located in the Malé Karpaty Mts. (Brezovské Karpaty) and is well known for its increased seismic activity. For a better understanding of the processes preceding earthquakes, this area has been studied using several methods. One of them is magnetotellurics. Magnetotellurics provides an image of the distribution of electrical co...

We present the crustal-scale geophysical model based on the magnetotelluric method focused on 3-D model¬ling of the seismic 2T profile crossing the major Western Carpathian tectonic units in central Slovakia. The results of the 3-D modelling show substantial improvement in previous 2-D models of deep crustal structure in central Slovakia, mainly of...

2D integrated modelling approach was applied to determine the lithospheric structure along transect HT-1 located in the Carpathian-Pannonian Basin–European platform region. Our approach combines simultaneous interpretation of surface heat flow, topography, gravity and geoid data. All available geophysical and geological data were used to create an...

We present modelling of the geophysical data from the Newcastle area, west of Dublin, Ireland within the framework of the IRETHERM project. IRETHERM's overarching objective was to facilitate a more thorough strategic understanding of Ireland's geothermal energy potential through integrated modelling of new and existing geophysical, geochemical and...

The contact zone between the Outer and Inner Western Carpathians was investigated. The combination of different geophysical modeling (mainly magnetotelluric, gravimetric, and seismic) brings a new perspective to the understanding of deep crustal structures of this contact zone. The Klippen Belt is surface representation of this contact zone. Accord...

The paper presents the interpretation of magnetotelluric measurements along the SW–NE profile near Stará Ľubovňa (Northern Slovakia). The profile passes through the Outer Carpathian Flysch Belt, Klippen Belt and ends in the Inner Western Carpathians Paleogene NW from Ružbachy horst structure. The interpretation of the older measurements from profil...

As a consequence of measuring time variations of the electric and the magnetic field, which are related to current flow and charge distribution, magnetotelluric (MT) data in two dimensional (2-D) and three dimensional (3-D) environments are not only sensitive to the geoelectrical structures below the measuring points but also to any lateral anomali...

Kilbrook spring is a thermal spring in east-central Ireland. The temperatures in the spring are the highest recorded for any thermal spring in Ireland (maximum of 25 °C). The temperature is elevated with respect to average Irish groundwater temperatures (9.5–10.5 °C), and represents a geothermal energy potential, which is currently under evaluation...

A hydrogeological conceptual model of the sources, circulation pathways and temporal variations of two low-enthalpy thermal springs is derived from a multidisciplinary approach. The springs are situated in the Carboniferous limestones of the Dublin Basin, in east-central Ireland. Kilbrook spring (Co. Kildare) has the highest recorded temperatures f...

We present an update on geophysical investigations, as part of the IRETHERM project, to explore the geothermal energy prospectivity of the Galway granite batholith. Magnetotelluric data show that the electrical resistor associated with the Galway granite extends to a maximum depth of 12 – 12.5 km. Gravity data are incorporated to further examine th...

Crustal flow is an important tectonic process active in continent-continent collisions and which may be significant in the development of convergent plate boundaries. In this study, the results from multidimensional electrical conductivity modeling have been combined with laboratory studies of the rheology of partially molten rocks to characterize...

The work presented here is part of the IRETHERM project, an investigation into the deep geothermal energy potential of radiothermal granites, sedimentary basins and warm springs in low-enthalpy settings across Ireland. Within this framework, magnetotelluric (MT) data were acquired at 75 locations across the Caledonian calc-alkaline Galway granite i...

The Altyn Tagh Fault (ATF) is a left-lateral, strike-slip fault that forms the northern margin of the Tibetan Plateau and plays a significant role in accommodating the convergence between the colliding Indian and Eurasian plates. As a part of the fourth phase of the INDEPTH project, magnetotelluric (MT) data were collected across the central segmen...

As part of the IRETHERM geothermal project, magnetotelluric (MT) and audio-magnetotelluric (AMT) data were acquired at 75 locations across the Galway granite batholith and the surrounding metamorphic and sedimentary rocks. We present the results of 3-D inversions of these data, which reveal the electrical resistivity structure beneath Connemara....

As part of the IRETHERM geothermal project, magnetotelluric (MT) and audio-magnetotelluric (AMT) data were acquired at 75 locations in a grid across the Galway granite batholith, at 59 locations along two profiles across the Leinster granite and at 23 locations along a profile over the buried Kentstown granite in Meath. The ongoing investigations...

Project INDEPTH (InterNational DEep Profiling of Tibet and the Himalaya) is an interdisciplinary program designed to develop a better understanding of deep structures and mechanics of the Tibetan Plateau. As a component of magnetotelluric (MT) work in the 4th phase of the project, MT data were collected along a profile that crosses the eastern segm...

We undertake a petrologically-driven approach to jointly model magnetotelluric (MT) and seismic surface wave dispersion (SW) data from central Tibet, constrained by topographic height. The approach derives realistic temperature and pressure distributions within the upper mantle and characterizes mineral assemblages of given bulk chemical compositio...

Electrical resistivity of the Earth’s crust is sensitive to a wide range of petrological and physical parameters, and it particularly clearly indicates crustal zones that have been tectonically or thermodynamically disturbed. A complex geological structure of the Alpine nappe system, remnants of older Hercynian units and Neogene block tectonics in...

In this paper, we use synthetic data sets from a profile to demonstrate the importance of aligning the 3-D mesh and data coordinate system with the dominant geo-electrical strike direction in 3-D inverse modelling. The resistivity model investigated consists of a regional, elongated 2-D conductive structure at 45° to the profile. We compare the res...

Magnetic map of Slovakia (Kubeš et al., 2008) shows distribution of rock complexes with higher magnetic properties. A basic division of magnetic anomalies according to geological provenance is as follows: • The first group contains well identifiable rock complexes situated mostly on the surface, or in the shallow depths, represented by Neogene volc...

The overall objective of the final phase of the INDEPTH (International Deep Profiling of Tibet and Himalaya) project has been to develop a better understanding of the structure and evolution of the northern margins of the Tibetan plateau, namely the Kunlun and Altyn Tagh faults. For the Kunlun Fault, both INDEPTH Phase III and new Phase IV magnetot...

Poster or oral presentation

IRETHERM (www.iretherm.ie) is an academic-government-industry, collaborative research project, funded by Science Foundation Ireland, with the overarching objective of developing a holistic understanding of Ireland's low-enthalpy geothermal energy potential through integrated modelling of new and existing geophysical and geological data. With the ex...

A hitherto unknown magnetic anomaly has been detected in the framework of assembling magnetic picture of the Slovakian territory. The impressive magnetic object was recognized in the northeasternmost part of Slovakia within the area which is created by sediments of the Flysch belt. This is certain rarity because the Flysch sequence is practically w...

A positive gravity anomaly was observed in the Flysch belt realm. Based on this fact and available geological knowledge we suppose that the source of gravity anomaly might be carbonate rocks lying perhaps in the footwall of Flysch sediments. The carbonates belong perhaps to the Penninic crust cover (a part of Klippen belt), or to lower structural s...

The weak lithosphere of the Tibetan plateau is surrounded by rigid crustal blocks(1) and the transition between these regimes plays a key role in the ongoing collision between India and Eurasia. Geophysical data(2-5) and magmatic evidence(6,7) support the notion that partial melt exists within the anomalously hot(7,8) crust of northern Tibet. The K...

Induced magnetic fields in the Earth arise due to two phenomena: induction generated by the time-variable exciting field and the motional induction caused by movement of the conductive planet in the outer magnetic fields. The comparison of both approaches on the spherical Earth has been analyzed in the present work for two sources in the ionosphere...

Scientists working under the auspices of the INDEPTH project (InterNational DEep Profiling of Tibet and the Himalaya) have undertaken a series of integrated geological and geophysical studies across the Tibetan Plateau since 1993. The final stage of INDEPTH study (INDEPTH-IV) is focused on the dynamics of the northern Tibetan Plateau. As part of th...

Determining the nature of the transition between weak Tibetan Plateau lithosphere and the surrounding rigid blocks is a key issue for understanding the ongoing India-Eurasia collision. The overall goal of Phase IV of the INDEPTH (International Deep Profiling of Tibet and Himalaya) project is to develop a better model of the structure and evolution...

Combined seismological and electromagnetic investigations of the lithosphere and underlying asthenosphere have the potential to yield superior inferences than using either one on its own. Central Tibet offers an excellent natural laboratory for testing such approaches, given the high quality seismological and magnetotelluric (MT) data available as...

Magnetotelluric measurements (MT) in the southeast (SE) part of MT–15 profile in the frame of CELEBRATION 2000 project identified a subhorizontal zone with higher conductivity in the depth of cca 2–6 km below the Tribeč Mts. surface. This zone is interpreted as a complex of metamorphic rocks under the tectonically overlaying granites. The original...

Scientists working under the auspices of the INDEPTH project (InterNational DEep Profiling of Tibet and the Himalaya) have undertaken a series of integrated geological and geophysical studies across the Tibetan Plateau since 1993. The final stage of INDEPTH study (INDEPTH-IV) is focused on the dynamics of the northern Tibetan Plateau. As part of th...

It is known that magnetic poles of the Earth is accelerated and is now being ≈ 50 km/year (Olsen & Mandea, 2007) while the geomagnetic pole (the dipole part), which is computed (fictitious) value, has much less velocity. It is believed that the magnetospheric outer ring currents are held by the dipole part of the Earth’s magnetic field. The low fre...

It is known that magnetic poles of the Earth is accelerated and is now being ≈ 50 km/year (Olsen & Mandea, 2007) while the geomagnetic pole (the dipole part), which is computed (fictitious) value, has much less velocity. It is believed that the magnetospheric outer ring currents are held by the dipole part of the Earth’s magnetic field. The low fre...

The on-going continent-continent collision between the Indian and Eurasian plates has created the spectacular topography of the Tibetan plateau. The tectonic processes that occurred during this collision process are still not fully understood and different tectonic models have been proposed. Horizontal motions are clearly important, as evidenced by...

We present analytical solution of the forward magnetometric problem for the oblate spheroid (rotational ellipsoid) as a causative body. The shorter semiaxis of the ellipsoid is supposed to be vertical to the surface of the earth. There is proved that the uniform inducing magnetic field B0 induces inside the spheroid also uniform magnetic field but...

Anomalies of geomagnetic field due to a vertical prolate rotational ellipsoid We present an exact analytical solution of the forward magnetometric problem for the perturbing body having the shape of the rotational prolate ellipsoid with the longer axis oriented vertically to the surface of the earth. The anomaly of Δ Z and Δ T is calculated for the...

Poster

Formulations that form the basis of experimental impedances in induction soundings result from the impedance boundary conditions or from the simplified theoretical models. The formulations are essentially different for the magnetotelluric and magnetovariation sounding methods. In order to increase reliability of mantle investigations, studies of th...

During the years 1995 and 1999, broadband (BBMT) and long period (LMT) magnetotelluric data were collected and interpreted for two profiles crossing the Banggong-Nujiang Suture, as a part of InterNational DEep Profiling of Tibet and the Himalaya project (INDEPTH). These profiles cross the Banggong-Nujiang suture, which separate Qiangtang and Lhasa...

During the INDEPTH (International Deep Profiling of Tibet and Himalaya) project Phase III surveys in 1999, broadband and long period magnetotelluric (MT) data were collected in Northern Tibet across the Kunlun Fault. The MT stations, placed along the northern part of the Lhasa to Golmud highway, defined the so-called 600-line profile extending from...

In the years 2001–2003, we accomplished the experimental phase of the project CEMES by collecting long-period magnetotelluric data at positions of eleven permanent geomagnetic observatories situated within few hundreds kilometers along the south-west margin of the East European Craton. Five teams were engaged in estimating independently the magneto...

This publication is a contribution to discussion on the geometry and petrography of the rock complex responsible for the Carpathian conductivity anomaly. We analysed arguments showing that this anomaly is caused by induction in the sedimentary basin, and make a critical review of various data to find out whether the good conductivity is connected w...

A spherical model of the Earth including a heterogeneous upper mantle and excited by the magnetic field of a magnetospheric ring current is constructed. The obtained synthetic data are used for testing a new approach to gradient geomagnetic sounding ensuring the immunity of the sought impedance to distortions caused by lateral heterogeneity of the...

Studying the Earth's deep conductivity structures, important for developing our understanding of the dynamics of the Earth, is complicated due to effects of the shallow conductive structures on the electromagnetic (EM) responses for periods larger than hours. The results of the deep EM soundings can be heavily distorted by the surface shell conduct...

A b s t r a c t We present a synthetic review of laboratory data, theoretical formulae and relevant geophysical/geological knowledge concerning the Western Carpathians which can be used for explanation of the Carpathian conductivity anomaly below the flysch zone. Implications in favour of the alternative with mineralized (sa-line) water in pores of...

Results of numerical calculations for the time-harmonic EM induction in two-layer Earth which contains a three dimensional (3-D) well conducting block in the first layer are presented. For these calculations, a method of vector integral equations is used. The parameters of the model are selected in order to approximate the gross-structural model of...

The paper presents exact formulae numerical modeling of D. C. geoelectric measurements near or inside of a spherical body. The calculations are based on well known spherical function series for the potential due to source electrode buried outside or inside of spherical body. These classical formulae are modified to the form which provides faster co...

Some new formulae connecting the Bessel functions of the first kind with spherical harmonics are presented. The utilization of these formulae is applied to the calculation of Fourier-Bessel integrals even for the double products of the Bessel functions.

In preparation for the Magnetotelluric (MT) Phase IV of the INDEPTH (International Deep Profiling of Tibet and Himalaya) project, focusing on the northern margins of the Tibetan plateau, MT data from the Phase III 600-line were re-analyzed and re-modelled. Previous inversions of the data from the 600-line used the MT TE-mode, TM-mode and vertical m...