Importance of DEM's accuracy in the activity classification of faults: the case of a fault in the Gulf of Corinth, Greece

The current study presents the impact of DEM’s accuracy in the tectonic activity designation of an area. The classification of the activity of a fault, after the calculation of a variety of geomorphic indices, consist a common tool in tectonics. These indices provide relatively quick recognition of actively deformed areas that rely on the DEM accuracy used for the delineation and the quantification of the geomorphic attributes in the area. The present study considers the case of a known active fault in the Gulf of Corinth, Greece, that is featuring in six different DEMs, including digitations of conventional 1:5000 topographic maps, satellite imageries (SRTM 90, SRTM 30, ALOS, ASTER) and aerial photographs. The calculated indices are represented by the basin elongation Bs/Rf, the basin asymmetry Af, the valley width to valley height Vf and the stream length – gradient index SL. Based on the evaluation of the data and the assessment process different findings for each DEM are concluded. Thus, the means that are used in order to draw conclusions on an area’s tectonic activity can have different importance and outcome on the calculation of separate components of the indices. As technology advances rapidly, it is rather clear that much more accurate DEMs will be available in future. However, as these products are acquired rather slowly, ALOS products can be regarded as accurate DEM basis for the purposes of the tectonic geomorphology.