2. Methodological approach

2.2 Morphological approach

Data collection and analysis

In order to target morphological expressions of active faulting at the scale of the URG, a set of aerial photograph (1/30 000) has been studied. Every identified slope has been reported on a map and digitized in GIS application (Arcview/ESRI). To understand whether slopes were due to differences in geological properties, these morphological slopes (presumed scarps of active faults) were individually examined (geological maps at 1/50 000 BRGM).

Digital elevation model of the URG area has been extracted from the French Altimetric Database (Institut Géographique National). Several simple image processing techniques were performed on this DEM (shade derivation, slope derivation, drainage extraction) in order to identify topographic anomalies.

Six Spot multispectral images have also been analysed to identify discontinuities and slopes anomalies.

Results of all these interpretations are combined in a GIS wich allow comparison of these three layers of information at different scales (map).

Interpretation :

In the inner graben, "ried" borders and some clearly expressed slopes are good candidates for active tectonic expression at this stage of the study. Furthur research has been performed in the field in order to comfirm or not these preliminary results.

• Achenheim Mundolsheim Blaesheim scarp
• Pfaffenheim
• Wasselone scarp
• Ried borders, Merxheim, Blodelsheim
• Western border of the Mulhouse horst