Thomas Günther

Thomas Günther
Leibniz Institute for Applied Geophysics | LIAG · Geoelectrics and Electromagnetics

Dr. rer. nat. (PhD)
Developing modelling & inversion routines in the context of hydrogeophysical characterization and monitoring

About

218
Publications
97,111
Reads
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Introduction
I am a senior researcher at Leibniz Institute of Applied Geophysics (LIAG) in Hannover, Germany. I am researching in the field of numerical algorithms and inversion of mainly electrical & electromagnetic data. I am particularly interested in joint inversion and time-lapse methods. Applications are in the fields of hydrogeophysics and environmental/engineering geophysics. Current projects include ERT, MRT and CSEM methods, and involve development of software with the aim of reproducible science.
Additional affiliations
April 2014 - September 2014
University of Leipzig
Position
  • Inverse Problems in Applied Geophysics
April 2010 - September 2010
Leibniz Universität Hannover
Position
  • Practical course Applied Geophysics
April 2008 - July 2008
Goethe-Universität Frankfurt am Main
Position
  • Inverse problems in Applied Geophysics
Education
August 2000 - December 2004
University of Mining Technology
Field of study
  • Geophysics
September 1994 - August 2000
University of Mining and Technology
Field of study
  • Geophysics

Publications

Publications (218)
Article
Full-text available
Abandoned mining waste dumps may become potential resources for mineral reuse. For evaluating such structures, their spatial extension, the mineral content and predominating grain size needs to be determined. Amongst geophysical prospection methods, induced polarization (IP) is particularly suited since ore minerals show significant polarization ch...
Article
Full-text available
The application of surface nuclear magnetic resonance (NMR) measurements, although proven to be valuable for various hydrogeological issues, is in practice often limited to single 1D surveys because measurement progress is slow. First, large stacking rates are necessary to overcome the low signal-to-noise ratio and, second, time and effort are requ...
Article
Electrical resistivity tomography (ERT) is a widespread technique used for geological and hydrological subsurface characterization. The three-dimensional application is limited to small scales due to the enormous effort required by field surveys. Long electrode (LE) ERT using steel-cased boreholes can overcome small-scale limitations and has rece...
Article
Full-text available
Besides floodplains, hillslopes are basic units that mainly control water movement and flow pathways within catchments of subdued mountain ranges. The structure of their shallow subsurface affects water balance, e. g. infiltration, retention, and runoff. Nevertheless, there is still a gap in the knowledge of the hydrological dynamics on hillslopes,...
Article
Full-text available
In order to do hydraulic modelling for simulating the salt-/fresh water dynamics, the parameters porosity, salinity and hydraulic conductivity are needed. We present a methodology retrieve them by the joint analysis of magnetic resonance (MRS) and and vertical electric (VES) soundings. Both data sets are jointly inverted for resistivity, water cont...
Preprint
The subsurface dissolution of soluble rocks, also called subrosion, can affect areas over a long period of time and pose a severe hazard. We show the benefits of a combined approach using P-wave- and SH-wave reflection seismics, electrical resistivity tomography, transient electromagnetics, and gravimetry for a better understanding of the subrosion...
Article
Full-text available
Historical slag dumps are of increasing interest due to economic, environmental or archaeological reasons. Geophysical investigations can help accessing the potential reuse of slag material to recover metallic raw material or the estimation of the hazard potential of the buried slag material due to dissolution occurrence. In our study, we have inve...
Conference Paper
Coaxial transmission line technique is widely used to deduce broadband dielectric spectra from measured scattering parameters. The inversion algorithm in frequently used proprietary software to determine electromagnetic properties of materials remains unknown as part of a commercial closed code. Against this background, we combine a forward operato...
Article
Full-text available
Soil characterization in coastal areas is essential for strategic coastal engineering implementation and for understanding the paleo-environmental conditions. However, the severe soil salinization in these regions, limited the geophysical measurements to shallow depths and conventional drilling is time-consuming and cumbersome. Here, we integrate r...
Article
Electrical resistivity tomography has potential as a complementary long-term monitoring method in embankment dams; however, the 3D character of the geometry including the shape of the embankment, its internal zoned construction and the reservoir water make interpretation challenging. To tackle this problem, a qualified inversion model considering t...
Article
Full-text available
As one main objective in hydrogeophysics, we aim at describing hydraulic properties in the subsurface in at least two dimensions. However, due to the limited resolution and ambiguity of the individual methods, those images often remain blurry. We present a methodology to combine two measuring methods, magnetic resonance tomography (MRT) and electri...
Data
Data and scripts for the scientific journal article: Martin, T., Günther, T., Flores Orozco, A. & Dahlin, T. (2020): Evaluation of spectral induced polarization field measurements in time and frequency domain, J. Appl. Geophys., 180, 104141, doi:10.1016/j.jappgeo.2020.104141. The paper deals with the comparison of instruments for measuring induced...
Article
Full-text available
There is a cleardemand to increase detection depths in the context of raw materialexploration programs. Semi-airborne electromagnetic (semi-AEM) methodscan adress these demands by combining the advantages of powerful transmitters deployed on the ground with efficienthelicopter-borne mapping of the magnetic field response in the air.The penetration...
Article
Full-text available
Geophysical methods can characterize aquifer systems non-invasively and are particularly helpful to image the complex depositional structure of the subsurface.Among these, ground-penetrating radar (GPR) is an effective tool for detailed investigations of shallow subsurface geometry, but provides only limited information on hydraulic properties.Magn...
Article
Full-text available
In the framework of the Deep Electromagnetic Sounding for Mineral EXploration (DESMEX) project, we carried out multiple geophysical surveys from regional to local scales in a former mining area in the state of Thuringia, Germany. We prove the applicability of newly developed semi-airborne electromagnetic (EM) systems for mineral exploration by cros...
Article
Full-text available
A major problem for the freshwater supply of coastal regions is the intrusion of saltwater into aquifers. Due to extensive extraction of freshwater to suffice increasing drinking water demands and/or periods of reduced groundwater recharge, the equilibrium state may be disturbed. The result is an upconing or movement of the fresh‐saline groundwater...
Article
Full-text available
Spectral induced polarization (SIP) measurements have been demonstrated to correlate with important parameters in hydrogeological and environmental investigations. Although SIP measurements were often collected in the frequency domain (FDIP), recent developments have demonstrated the capabilities to solve for the frequency-dependence of the complex...
Article
We present an approach for the estimation of ore processing residue volumes in historical mine waste dumps by the use of different geophysical methods in combination with mineralogical investigations. The stamp mill dump in the Harz mountains, Germany was examined with the methods electrical resistivity tomography (ERT), ground penetrating radar (G...
Article
Full-text available
We present new evidence for neotectonic activity along the Harz Boundary Fault, a Cretaceous reverse fault that represents a key structure in northern Germany. For the fault analysis, we use a multimethod approach, integrating outcrop data, luminescene dating, shear wave seismics, electrical resistivity tomography (ERT) and numerical simulations. A...
Presentation
Full-text available
Hydrogeophysics is interdisciplinary by definition. As researchers strive to gain quantitative information on process-relevant subsurface parameters while integrating non-geophysical measurements, multi-physical geoscientific models are often developed that simulate the dynamic process and its geophysical response. Such endeavors are associated wit...
Article
S U M M A R Y Structural joint inversion of several data sets on an irregular mesh requires appropriate coupling operators. To date, joint inversion algorithms are primarily designed for the use on regular rectilinear grids and impose structural similarity in the direct neighbourhood of a cell only. We introduce a novel scheme for calculating cross...
Article
Full-text available
Nuclear-Magnetic Resonance (NMR) is a powerful tool for groundwater system imaging. Ongoing developments in surface NMR, e.g., multi channel devices, allow for investigations of increasingly complex subsurface structures. However, with growing complexity of the field cases, the availability of appropriate software to accomplish the in-depth data an...
Article
The greenhouse-gas (GHG) balance of CH4 and N2O emissions and CO2 respiration in peatlands plays a key role in climate change. A GHG balance is mostly calculated from point measurements. In this study we propose and test a geophysical method of low frequency domain electromagnetic method (FDEM) as a proxy for forest-floor CO2 respiration and CH 4 e...
Article
Full-text available
The Cheb Basin, a region of ongoing swarm earthquake activity in the western Czech Republic, is characterized by intense carbon dioxide degassing along two known fault zones – the N–S-striking Počatky–Plesná fault zone (PPZ) and the NW–SE-striking Mariánské Lázně fault zone (MLF). The fluid pathways for the ascending CO2 of mantle origin are one of...
Data
Underlying data for the paper Nickschick, T., Flechsig, C., Mrlina, J., Oppermann, F., Löbig, F. & Günther, T. (2019): Large-scale electrical resistivity tomography in the Cheb Basin (Eger Rift) at an ICDP monitoring drill site to image fluid-related structures. Solid Earth. https://doi.org/10.5194/se-2019-38. The paper contains two types of data:...
Article
Full-text available
Quantitative estimation of pore fractions filled with liquid water, ice and air is crucial for a process-based understanding of permafrost and its hazard potential upon climate-induced degradation. Geophysical methods offer opportunities to image distributions of permafrost constituents in a non-invasive manner. We present a method to jointly estim...
Preprint
Full-text available
The Cheb Basin, a region of ongoing swarm earthquake activity in the western Czech Republic, is characterized by intense carbon dioxide degassing along two known fault zones – the N-S-striking Počatky-Plesná fault zone (PPZ) and the NW-SE-striking Mariánské Lázně fault zone (MLF). The fluid pathways for the ascending CO2 of mantle origin are subjec...
Article
Full-text available
We present the open-source toolbox custEM (customizable Electromagnetic Modeling) for the simulation of complex three-dimensional controlled-source electromagnetic (CSEM) problems. It is based on the open-source finite-element library FEniCS, which supports tetrahedral meshes, multiprocessing, higher order polynomials, and anisotropy. We use multip...
Article
Full-text available
Hydrological parameters like porosity, salinity, and hydraulic conductivity are key for understanding the subsurface. Hydrogeophysical investigations can lead to ambiguous results, particularly in the presence of clay and saltwater. A combination of magnetic resonance sounding (MRS) and vertical electrical sounding (VES) is known to provide insight...
Presentation
Full-text available
presentation of open-source toolbox custEM
Article
Transient electromagnetics (TEM) is a well-established method for mineral, groundwater, and geothermal exploration. Supercon- ducting quantum interference device (SQUID)-based magnetic- field receivers used for TEM have quantitative advantages and higher sensitivity compared with commonly used induction coils. Special applications are deep sounding...
Article
Full-text available
There is an increasing demand for trustworthy engineering geological conceptual models in urban areas due to an increasing trend in the underground infrastructure construction. Good‐quality site investigations can reduce the risk of encountering unexpected geological conditions during construction. Geoelectrical measurements can be used as a tool f...
Article
In the framework of earth-filled dykes characterization and monitoring, Electrical Resistivity Tomography (ERT) turns out to be a commonly used method. 2D sections are generally acquired along the dyke crest thus putting forward the question of 3D artefacts in the inversion process. This paper proposes a methodology based on 3D direct numerical sim...
Article
Irregular meshes allow to include complicated subsurface structures into geophysical modelling and inverse problems. The non-uniqueness of these inverse problems requires appropriate regularisation that can incorporate a priori information. However, defining regularisation operators for irregular discretisations is not trivial. Different schemes fo...
Article
Full-text available
We present a new versatile datalogger that can be used for a wide range of possible applications in geosciences. It is adjustable in signal strength and sampling frequency, battery saving and can remotely be controlled over a Global System for Mobile Communication (GSM) connection so that it saves running costs, particularly in monitoring experimen...
Article
Full-text available
In the past few years, the focus on Alum shale hazards and the need for efficient mapping tools have increased in Norway. Alum shale is highly toxic and poses a substantial obstacle to infrastructure development such as tunnel projects. We present an evaluation of the ground-based electrical resistivity tomography, induced polarisation, and airborn...
Article
The inversion of geoelectric data is non-unique. Therefore, electric resistivity tomography (ERT) usually results in different subsurface models that fit observed apparent resistivity values equally well. To reduce the uncertainty, constraints on both geometry and resistivity of subsurface structure can be incorporated into the ERT inversion. In ou...
Poster
Full-text available
Many tasks in applied geosciences cannot be solved by a single measurement method and require the integration of geophysical, geotechnical and hydrological methods. In the emerging field of hydrogeophysics, researchers strive to gain quantitative information on process-relevant subsurface parameters by means of multi-physical models, which simulate...
Article
Full-text available
Identifying principles of water movement in the shallow subsurface is crucial for adequate process-based hydrological models. Hillslopes are the essential interface for water movement in catchments. The shallow subsurface on slopes typically consists of different layers with varying characteristics. The aim of this study was to draw conclusions abo...
Conference Paper
Full-text available
Solving joint inverse problems requires appropriate regularisation and coupling operators. In particular, when the inversion is performed on irregular meshes where cell sizes vary throughout the domain, the operators should be designed to be as independent of the discretisation as possible. We define regularisation operators for inversions on irreg...
Conference Paper
Full-text available
Magnetic resonance tomography using elongated transmitter and in-loop receiver arrays (MRTetra) is designed to efficiently image the groundwater in two-dimensional. However, due to resolution limitations and the volume effect, the structure and boundary features of the aquifer are ambiguous. We make use of the GPR reflection data to generate struct...
Article
Full-text available
Many tasks in applied geosciences cannot be solved by single measurements, but require the integration of geophysical, geotechnical and hydrological methods. Numerical simulation techniques are essential both for planning and interpretation, as well as for the process understanding of modern geophysical methods. These trends encourage open, simple,...
Article
Full-text available
We present a new versatile datalogger that can be used for a wide range of possible applications in geosciences. It is adjustable in signal strength and sampling frequency, battery-saving and can remotely be controlled over Global System for Mobile Communication (GSM) connection so that it saves running costs, particulaly in monitoring experiments....
Article
Full-text available
Tunnelling below water passages is a challenging task in terms of planning, pre-investigation and construction. Fracture zones in the underlying bedrock lead to low rock quality and thus reduced stability. For natural reasons they tend to be more frequent at water passages. Ground investigations that provide information of the subsurface are necess...
Article
Full-text available
We combined two completely different methods measuring the frequency-dependent electrical properties of moist porous materials in order to receive an extraordinary large frequency spectrum. In the low frequency (LF) range, complex electrical resistivity between 1 mHz and 45 kHz was measured for three different soils and sandstone, using the spectra...
Article
Electrical resistivity tomography (ERT) and refraction seismics are among the most frequently used geophysical methods for site-investigations and the combined results can be very helpful to fill in the gaps between the point measurements made by traditional geotechnical methods such as Cone Penetration Test (CPT), core-drilling and geophysical bor...
Conference Paper
Full-text available
When working with unstructured meshes for geophysical inversions, special attention should be paid to the design of the operators that are used for regularizing the inverse problem and coupling of different property models in joint inversions. Regularization constraints for inversions on unstructured meshes are often defined in a rather ad-hoc mann...
Article
Full-text available
Identifying principles of water movement in the shallow subsurface is crucial for adequate process-based hydrological models. Hillslopes are the essential interface for water movement in catchments. The shallow subsurface on slopes typically consist of different layers with varying characteristics. The aim of this study was to draw conclusion about...
Article
Full-text available
Excavation and piling works related to seafront development in Oslo’s historic harbour area need to mitigate the risk of damaging buried archaeological objects. In the Bjørvika harbour in Oslo, Norway, electrical resistivity tomography was performed to detect structures with potential archaeological value. A 2.5 dataset consisting of four equally s...