1st EAGE/GRSG Remote Sensing Workshop

A first airborne transient electromagnetic survey was flown in Antarctica in December 2011 with the SkyTEM system. This transient airborne EM system has been optimized in Denmark for almost ten years and was specially designed for ground water mapping. The SkyTEM tool is ideal for mapping conductive targets, and the transient AEM method provides a better understanding of the saline ground water system for microbiology, paleoclimate studies, or geothermal potential. In this study we present preliminary results from our field survey which resulted in more than 1000 km of flight lines. The spatial sampling was 20 m along the lines providing more than 30 000 sounding locations. To handle this large amount of data, the software Aarhus Workbench was developed to make spatially constrained inversions which provide a quasi-3D view of the underground. The inversion results of the Fryxell Basin are presented here, the Taylor Valley demonstrating the promising capabilities of the geophysical method to map permafrost and the saline ground water systems.

Geological geophysics essentially refers to any geophysical map that is based on, or classified according to, existing geological knowledge. Here the geological classification of UK bedrock conductivity, derived from 5 airborne EM surveys conducted over 10 years is assessed. At a scale of 1:625k the UK digital bedrock geological lexicon comprises just 86 lithological classifications. The lowest common AEM frequency of 3 kHz is found to provide an 87% coverage (by area) of the UK lithologies. The geological classification is then extended to provide a new and complete 1:625k UK map of the near-surface bedrock conductivitity. Geological classifications inherently address grain size and clay/silt content of rock and these parameters also underpin theoretical descriptions of the materials electrical properties. When AEM conductivity data are examined on the basis of geological classification, they are found to be information rich. The challenge remains to successfully relate the bulk geophysical property variations to potentially more revealing lithological and physical characteristics.

SqueeSAR™ interferometry, the latest evolution of PSInSAR™ technology, is one of today’s most advanced technologies for ground deformation analysis and monitoring. It exploits long temporal series of satellite radar data, acquired over the same area of interest at different times, to identify “natural radar targets”, that return stable radar reflections over time back to the satellite, where very precise displacement information can be retrieved. Thanks to its capability in detecting millimetre level displacements over long periods and large areas, SqueeSAR™ analysis can be considered complementary to conventional geological and geomorphological studies in landslide detection and monitoring, supporting also the effectiveness of landslide inventories at regional scale. The availability of surface displacement time series for all the radar targets identified also makes it possible to change the scale of analysis from regional to local, allowing in depth studies into the evolution of single instability phenomena, supporting the design of traditional monitoring networks and even verifying the efficiency of remedial works. In this paper, examples of integration of SqueeSAR™ data with other conventional geological and geomorphological studies at local and regional scale will be presented, pointing up the benefits offered by an integrated approach.

In the presented paper the PSInSAR data were used to analyse the small, long-period road deformations in Dabrowskie Basin area in Upper Silesia Mining Region (Poland). It is the area of intensive coal exploitation since XIX century. The seven coal mines are located in the basin. Only the one of them is the active mine. The others were closed in 1995-2004 period. The dense faults network with throws ranging from several dozens to over three hundred meters crosses the road network so they also can be the reason of subsidence. Based on PSInSAR data, the interpolation of average annual motion rates were performed for all studied region. The interpolation was done using kriging method. The analysis of PSInSAR data revealed that main roads in the Dabrowski Basin are located in the region with different values of average annual motion rates. The largest values of subsidence rates were revealed for part of road number 86 and part of Eastern GOP Ring Road. In both cases the average annual motion rates rapidly increase up to 20 mm/year and then also very fast decrease to 0 mm/year.

Ground-based remote sensing by Open path Fourier-transform infrared (OP-FTIR) spectrometry provides data for the identification and quantification of emissions over wide surface areas. Large-scale OP-FTIR spectroscopy measurements are carried out associated with point-scale chamber-based soil CO2 flux measurement at a natural CO2 degassing area in the context of the hierarchical approach. The application of ground-based remote sensing using passive OP-FTIR spectroscopy represents a rapid and non-invasive assessment method for detecting variations in atmospheric concentrations of target gases and for the spatial identification of sources of increased gas concentrations. The presentation introduces results of a feasibility study investigating various scenarios such as urban regions, agricultural landscapes and natural CO2 degassing areas. Some examples of how to successfully deploy passive open path FTIR spectroscopy to identify anomalous greenhouse gas concentrations along greater optical pathways are presented.