New criteria to define a susceptibility map in central Italy of DSGSD phenomena

Most of the DSGSD studied cases in Italy shows evidences related to a main activity in the Pliocene-Pleistocene age, characterized by an abrupt isostatic uplift. Actually, only during high seismic events, some DSGSD show evidences of reactivations. In this context, the central Apennines, as the results of a very complex geologic and geomorphologic history, show high values of relief energy, making possible a widespread natural hazard related to DSGSD. Moreover the presence of DSGSD in central Apennines is well known in literature since ‘80s even if several lacking areas are present also in physiographic regions with typical triggering morphologic and geologic conditions. In order to better characterize topography affected by DSGSD in the central Apennine, SRTM data combined with Spectral Mixing Analysis (SMA) of the Landsat ETM+ are used. The SMA uses a linear mixture model to provide a physical basis for a more detailed representation of land surface reflectance as mixture of endmembers. The topographic algorithm employed to derive these insights is not intended for use in site-specific analyses of DSGSD potential but instead identify slopes whose morphology is indicative of deep seated phenomena. The topographic DSGSD signature is determined by different topographic parameters such as slope, relief, aspect and curvature which can be used as a DSGSD index degree. To characterize important physical properties of the aforesaid signature was used the linear mixing model between the dark surface endmember and both the substrate and vegetation endmembers. That model highlights the extent to which shadowing and nonreflective surfaces, combined with illuminated substrate and vegetation at subpixel scale, can modulate spectrally mixed ETM+ reflectances in a ridge topography within the DSGSD signature. The final results indicate that when incorporated with optical SMA of the Landsat ETM+, the SRTM analysis should improve the capacity for mapping and identifying DSGSD in specific landscapes. The preliminary key results of this research are: 1) the identification of areas potentially affected by DSGSD still not detected, 2) the division of central Apennines in areas with an increasing DSGSD degree value, 3) the correlation of the identified areas with geologic and geomorphometric parameters characteristic of the phenomena.