GROUNDWATER AND ENVIRONMENT

Geophysical techniques have demonstrated their potential to provide valuable information for hydrogeological and environmental studies. In particular the geoelectrical methods, such as electrical resistivity tomography (ERT) and Spectral Induced Polarization (SIP), have emerged as suitable techniques to permit site characterization with enhanced spatio-temproal resolution.
The Geophysics group is currently  involved in international, and multidiscipline, collaborations aiming at the application of the ERT and SIP techniques at the field scale for hydrogeological characterization (e.g., patterns of the hydraulic conductivity), assessment of contaminated sites (e.g., geometry of contaminant plumes), and the monitoring of biogeochemical processes accompanying remediation of groundwater pollutants (e.g., bioremediation and nano-particles injections).

Figure: Visualization of the electrical properties of the subsurface at the Department of Energy’s Integrated Field Research Challenge (IRFC) Rifle. Electrical Resistivity data were collected to characterize the hydrogeological properties at the floodplain scale with high spatial resolution, aiming at the delineation of aquifer geometry, heterogeneities and preferential flow paths.

Characterization of contaminated sites
Ongoing work in our group investigates the application of the Spectral Induced Polarization (SIP), Time-Domain Induced Polarization (TDIP), Ground Penetrating Radar (GPR) and low-induction number Electromagnetic methods. We aim at developing a robust non-invasive methodology for the in-situ characterization of contaminated sites. In particular, our results demonstrate that the Spectral induced Polarization (SIP) imaging method may permit the discrimination of source-zone and the plume of contaminants in case of aquifers affected by organic pollutants. Innovative research lead by Adrián Flores Orozco and Matthias Bücker targets the application of electrical imaging methods for the delineation of changes in pore-space geometry due to geochemical changes in groundwater composition or aquifer sediments.  Further research investigates the development of acquisition techniques for urban areas, characterized by high rates of anthropogenic noise.

Figure: Spectral Induced Polarization (SIP) measurements collected in the grounds of an industrial area (indicated by the gray line in the Figure top-left), characterize by high concentrations of organic contaminants (top-left). The SIP response (top right) revealed a flat spectra and a low polarization effect in areas characterized by high contaminant-concentrations and the occurrence of free-phase. The imaging results revealed significant spatial variations in the polarization effect, most likely due to variations in the pore-space due to the occurrence of free-phase contaminants (Figure bottom),. Further details can be found in Flores Orozco et al., 2012.

Collaborations with:
Prof. Dr. Thilo Hofmann, head of the Department of Environmental Geosciences at the Vienna-University.Prof. Dr. Andreas Kemna, head of the Applied Geophysics group at the University of Bonn.

Monitoring of biogeochemical processes along remediation of contaminated sites
The application of geophysical geoelectrical methods appear as a suitable alternative for the monitoring of processes accompanying the remediation of contaminated sites, as they permit to obtain continuous data (spatial and temporal) about the properties of the subsurface. Hence, geophysical monitoring (e.g., Flores Orozco et al., 2011) may permit to delineate contaminant attenuation and biogeochemical changes induced in the aquifer along remediation.

Current research led by Dr. Adrián Flores Orozco investigates the application of the spectral induced polarization (SIP) imaging method to monitor the injection of metallic particles at the field scale. The injection of nanoparticles for site remediation has become a key research topic in environmental sciences due to the fast degradation of pollutants reported in several studies, and because the remediation can be performed in locations not accessible to other methods. 
Investigations perform by our group aims at developing a geophysical monitoring method, which could provide in real-time information about changes in the pore space geometry and geochemical parameters, as required to improve the efficiency of the available remediation techniques. To achieve this, we work on the improvement of current methodologies for the collection and processing of field-scale monitoring datasets.

Figure: Spectral Induced Polarization (SIP) measurements collected in the grounds of an industrial area (indicated by the gray line in the Figure top-left), characterize by high concentrations of organic contaminants (top-left). The SIP response (top right) revealed a flat spectra and a low polarization effect in areas characterized by high contaminant-concentrations and the occurrence of free-phase. The imaging results revealed significant spatial variations in the polarization effect, most likely due to variations in the pore-space due to the occurrence of free-phase contaminants (Figure bottom),. Further details can be found in Flores Orozco et al., 2012.

Collaborations with:
Prof. Dr. Thilo Hofmann, head of the Department of Environmental Geosciences at the Vienna-University.
Prof. Dr. Andreas Kemna, head of the Applied Geophysics group at the University of Bonn.

INFRASTRUCTURE and ENERGY

Geophysical methods are well established for subsurface investigations of planned infrastructure or energy projects like highways, railways, tunnels or water / wind power plants. They provide a high resolution image of the subsurface until some hundreds of meters. The knowledge about the underground such as the thickness of overlaying material, depth of hard rock, faulting zones within the rock, groundwater situation or the existence of cavities at the construction site is essential, especially in Austria with its difficult terrains and underground conditions.
In recent years the requirements regarding resolution and applications in the different terrains have increased a lot. Together with the company Pöyry-Infra GmbH we focus on new applications and methods in the different geophysical fields.

The following projects are just some examples of what was done and developed within this research group.

  • In Tirol a new water tunnel was planned beneath an existing active landslide. A 3D-seismic survey was carried out to investigate the depth and structure of it. The new tunnel now is beneath this zone.
  •  Another project was the detection of cavities along a new railway tunnel with a specific combination of seismic, electric and gravimetric measurements.
  • The use of surface waves lead to a new method to investigate the safety of dams.
  • The actual project focus is the prediction of fault zones during tunneling with seismic methods (TSWD).
Figure: Expansion of an existing water power station in the Alps. Conducted geophysical methods on the surface and in the tunnel supported these projects in the planning phase and also during construction. Potential risks for the tunneling, like fault zones could be determined in advance and therefore leaded to a save and efficient realization of this tunnel.
Figure: Resulting reflection wavefield of TSWD; high amplitudesindicates a fault zone. The prediction distance is until 100 m ahead of the TBM.

ACTIVE TECTONICS

Within the frame of the international projects CELEBRATION 2000, ALP 2002, and ALPASS the Research Group Geophysics took part, partly as pricipal investigator, in the exploration of the Earth’s crust and upper mantle since about 2000. Reviews of the outcome of these considerable efforts are provided e.g., by Brückl (2011) and Brückl and Hammerl (2014) verlinkt. The most relevant publications of members of the Research Group Geophysics to this topic can be found in the reference list below. The analysis of the structure of the Moho discontinuity and the upper mantle led to the development of a plate tectonic model of the Eastern Alps valid for the time since the collision between Adria and Europe and the close of the Penninic Ocean (e.g., Brückl & Hammerl, 2014).

Figure: Plate tectonic model of the evolution of the Eastern Alps since Oligocene. Details in Brückl & Hammerl, 2014.

Monitoring of actual tectonic processes supplies the data, from which we are able to decide if the current kinematics proposed by the plate tectonic model shown above is still valid, or if the general deformation regime changes during very recent times. The projekt ALPAACT (Seismological and geodetic monitoring of ALpine-PAnnonian ACtive Tectonics) was a first step into this direction. The efforts started with ALPAACT will be continued within the frame of the Sparkling Science project SCHOOLS & QUAKES. This project started on 1st October 2014. The seismological research aspects of SCHOOLS & QUAKES are pursued by a cooperation with the seismological service of the ZAMG (Zentralanstalt für Meteorologie  und Geodynamik). The geodetic component of the project is provided by the Research Group Advanced Geodesy of our department. The following animation intends to visualize the monitoring efforts within SCHOOLS & QUAKES.

The main research goals within „Active Tectonics“ are:
•    Precisely locate hypocenters to delineate seismically active faults.
•    Determine focal mechanisms to reveal stress regime.
•    Reduce earthquake detection limit to improve the Gutenberg-Richter statistics.
•    Establish long term and continuous GPS / GNSS-time series to reveal plate tectonic kinematics.
•    Quantify slip deficits and seismic inactive deformations.
•    Constrain MCE (maximum credible eathquake).
For the near future we will keep at the Mürz Valley and Vienna Basin fault system as the main target area.