Research
Research foci of the Geophysics Section at the University of Bonn comprise geophysical imaging methods, modeling of coupled flow and transport processes in porous and fractured media, and integration of process models and geophysical data through petrophysical models.
Applications in these fields are manifold and include soil / aquifer characterization, monitoring of subsurface flow, transport and biogeochemical processes, in the context of water management, contaminated site characterization / remediation, soil-root interactions, permafrost characterization, enhanced geothermal systems, mud volcanoes, and slope (in)stability.
Research projects
For more info on our research projects, please visit our site below:
Publications
A listing of our current publications can be found further down our page:
Research topics
Cryogeophysics
Thawing processes as a consequence of anthropogenic global warming alter the Earth's cryosphere and can potentially lead to various forms of landscape deformations, vegetation degradation, and slope instabilities in alpine regions.
A precise and physical representation of permafrost dynamics is important to improve multiple-scale earth system models and answer questions related to climate change impacts and natural hazards. In this regard, non-invasive geophysical methods often offer the only opportunity to image the spatiotemporal evolution of subsurface ice content and to monitor meltwater flow dynamics. Geoelectrical methods are particularly suited for permafrost monitoring, as the electrical medium properties are directly sensitive to the phase change between ice and unfrozen water. The section of Geophysics develops new monitoring approaches based on spectral induced polarization and electrical self-potential measurements particularly applied at the Schilthorn (Bernese Alps, Switzerland), where long-term records of other monitoring data (e.g. temperature, soil moisture, electrical resistivity tomography) are already available, in close collaboration with partners at the University of Fribourg (Prof. C. Hauck).
Biogeophysics
Biological processes are ubiquitous in nature and thus a fundamental part of most geophysical efforts. It is therefore important to assess any influence of these biological components on traditional research aspects such as structural or hydrogeophysical investigations.
More importantly, a huge number of biological processes has been found to exhibit characteristics that can be captured by geophysical equipment usually used to investigate inanimate parts of the subsurface.
Thus, biogeophysics comprises the chracterization and monitoring of biological processes, and their interaction, in the subsurface of the earth.
The section of Geophysics focuses on the characterization of crop root systems using electrical polarization measurements. These measurements have been shown to be sensitive not only on the structure, but also on the physiological activity and internal functions of root systems. This is remarkable as even today most root research is conducted by manual excavation of the `hidden-half'! We develop electrical methods both for the laboratory and the field scale that can not only image the distribution of roots in the subsurface, but also provide information about the temporal evolution and links to the internal dynamics.
Numerical Modeling
Physical and numerical modeling of complex mechanisms enable a deeper understanding of natural phenomena like earthquakes and landslides. The section of Geophysics focuses on the physical description of coupled hydro-electro-thermal and mechanical processes and develops its own numerical tools as well as contributes to cutting-edge open-source projects. Emphasize is set on a continuum-mechanical description of relevant processes. The numerical methods used are manifold, mainly based on a discretization with finite differences or finite elements. Our models are used for stability analysis as well as run-out modeling for landslides (e.g. www.avaflow.org); for reproduction of fluid-triggered seismicity on lab and tectonic scale; and for estimating heat transfer in partially saturated, fractured porous rock masses in volcanic, hydro-thermal or geothermal systems.
Geophysical imaging and monitoring
Geophysical imaging and monitoring refers to the application of geophysical methods to acquire and visualize information about the nature and structure of the earth. It is an important tool in various fields such as geology, environmental sciences and resource exploration.
Geophysical imaging involves taking measurements at or near the Earth's surface to obtain information about the underlying geological formations. Various techniques such as seismic, gravimetric, magnetic and electromagnetic methods are used for this purpose.
Seismic methods use sound waves to obtain information about the structure and composition of the earth. Gravimetry measures the acceleration of gravity to obtain information about the density distribution underground. Magnetic methods record variations in the Earth's magnetic field to obtain information about magnetic rocks and structures. Electromagnetic methods use electric and magnetic fields to obtain information about the electrical conductivity of the subsurface.
Monitoring refers to the continuous monitoring of geophysical parameters to record changes in the earth over time. This can help to understand natural processes such as earthquakes or volcanic activity and identify potential risks. It can also help to monitor human activities such as the extraction of mineral resources or the storage of carbon dioxide.
Geophysical imaging and monitoring are important tools to improve our understanding of the Earth and identify potential risks. They enable us to make informed decisions and better understand the impact of human activities on the environment.
PHENOROB: Robotics and Phenotyping for Sustainable Crop Production
Food, feed, fiber, and fuel: Crop farming plays an essential role for the future of humanity and our planet. The environmental footprint of agriculture needs to be reduced: less input of chemicals like herbicides and fertilizer and other limited resources like water or energy. Simultaneously, the decline in arable land and climate change pose additional constraints like drought, heat, and other extreme weather events.
Spectral electrical impedance tomography (sEIT) is used as in-situ tool for the structural and functional sensing of root systems in the field; data processing will be optimized and linked with established soil-root electrical relationships to monitor rooting and water uptake depth. The project is part of CP 3: THE SOIL-ROOT-ZONE, SP2: Structural and functional field root sensing using tomographic and endoscopic electrical impedance spectroscopy.
SPICE: Geophysics in alpine permafrost
The project “Improved ice quantification at alpine permafrost sites based on electrical and electromagnetic measurements of spectral induced polarization (SIP)” addresses the following research questions:
Can electrical and electromagnetic measurements of SIP be used to reliably quantify ice content changes in mountain permafrost regions?
Can the SIP response of partially frozen soils/rocks be predicted from a petrophysical model, and can the model be applied to real permafrost field cases?
To what extent does the new methodology represent an improvement over the standardly used electrical resistivity and refraction seismic tomography approach in mountain permafrost research?
E-TEST: Einstein Telescope EMR Site & Technology
The Einstein-Telescope (ET) is an advanced gravitational-wave observatory, currently in the planning stage. A possible target area is the Euregio Meuse-Rhine (EMR) border region between the Netherlands, Belgium and Germany. One objective of the E-TEST project is the (hydro)geological characterization of the target area, to find a suitable location for the construction of the ET. The Institute for Geosciences contributes to the implementation of the underground observatory and the development of the (hydro)geological model for the potential ET site by integrating hydrogeophysical imaging and monitoring methods which exploit electrical signatures of the earth. Geoelectric ERT and IP measurements are performed using a cross-borehole electrode setup, ensuring high resolution of rock formations at depth. Additional laboratory measurements and synthetic studies are carried out to adjust the measurement setup to the specific location of the observatory and to provide a basis for interpretation of the field results.
Completed projects
TR32 - TransRegional Collaborative Research Centre 32
FOR 1320 - Crop Sequence and Nutrient Acquisition from the Subsoil
iSoil - Interactions between soil related sciences
ModelPROBE - Model driven Soil Probing, Site Assessment and Evaluation
research interest
- Biogeophysics
- Cryogeophysics & Permafrost
- Hydrogeophysics
- Numerical Modeling
Research regions
- Spitzbergen/Svalbard
- Alps
- Spiekeroog
- Ahrtal
Research methods
- SIP
- IP
- Geoelektrics
- Georadar
- Magnetics
Hase, J.; Gurin, G.; Titov, K.; Kemna, A. (2023)
Conversion of Induced Polarization Data and Their Uncertainty from Time Domain to Frequency Domain Using Debye Decomposition. Minerals 2023, 13, 955. https://doi.org/10.3390/min13070955
Maximilian Weigand, Egon Zimmermann, Valentin Michels, Johan Alexander Huisman, and Andreas Kemna (2022)
Design and operation of a long-term monitoring system for spectral electrical impedance tomography (sEIT)
Geosci. Instrum. Method. Data Syst., 11, 413–433, 2022, https://doi.org/10.5194/gi-11-413-2022
Grifka, J.; Weigand, M.; Kemna, A.; Heinze, T. (2022)
Impact of an Uncertain Structural Constraint on Electrical Resistivity Tomography for Water Content Estimation in Landslides. Land 2022, 11, 1207. https://doi.org/10.3390/land11081207
Theresa Maierhofer, Christian Hauck, Christin Hilbich, Andreas Kemna, and Adrián Flores-Orozco (2022)
Spectral induced polarization imaging to investigate an ice-rich mountain permafrost site in Switzerland
The Cryosphere, 16, 1903–1925, 2022, https://doi.org/10.5194/tc-16-1903-2022
Thanushika Gunatilake, Thomas Heinze, Stephen A. Miller, Andreas Kemna (2021)
Hydraulically conductive fault zone responsible for monsoon triggered earthquakes in Talala, India,
Tectonophysics, Volume 820, 2021, 229117, ISSN 0040-1951, https://doi.org/10.1016/j.tecto.2021.229117
Moradi, S.; Heinze, T.; Budler, J.; Gunatilake, T.; Kemna, A.; Huisman, J.A. (2021)
Combining Site Characterization, Monitoring and Hydromechanical Modeling for Assessing Slope Stability. Land 2021, 10, 423. https://doi.org/10.3390/land10040423
Solomon Ehosioke, Frédéric Nguyen, Sathyanarayan Rao, Thomas Kremer, Edmundo Placencia-Gomez, Johan Alexander Huisman, Andreas Kemna, Mathieu Javaux, Sarah Garré (2020)
Sensing the electrical properties of roots: A review, https://doi.org/10.1002/vzj2.20082
Sascha Heinemann, Bastian Siegmann, Frank Thonfeld, Javier Muro, Christoph Jedmowski, Andreas Kemna, Thorsten Kraska, Onno Muller, Johannes Schultz, Thomas Udelhoven, Norman Wilke and Uwe Rascher (2020)
Land Surface Temperature Retrieval for Agricultural Areas Using a Novel UAV Platform Equipped with a Thermal Infrared and Multispectral Sensor
Remote Sens. 2020, 12(7), 1075; https://doi.org/10.3390/rs12071075
Sathyanarayan Rao, Nolwenn Lesparre, Adrián Flores-Orozco, Florian Wagner, Andreas Kemna & Mathieu Javaux (2020)
Imaging plant responses to water deficit using electrical resistivity tomography
Plant Soil (2020) 454:261–281; https://doi.org/10.1007/s11104-020-04653-7
Maximilian Weigand, Florian M. Wagner, Jonas K. Limbrock, Christin Hilbich, Christian Hauck, and Andreas Kemna (2020)
A monitoring system for spatiotemporal electrical self-potential measurements in cryospheric environments
Geosci. Instrum. Method. Data Syst., 9, 317–336, 2020, https://doi.org/10.5194/gi-9-317-2020
F. M. Wagner, C. Mollaret, A. Kemna, C. Hauck (2019)
Quantitative imaging of water, ice and air in permafrost systems through petrophysical joint inversion of seismic refraction and electrical resistivity data
Geophysical Journal International, Volume 219, Issue 3, December 2019, Pages 1866–1875, https://doi.org/10.1093/gji/ggz402