Decollement depth of Active thrust faults in Italy

Based on available geological and geophysical data, the depth of the basal thrust decollement for compressional areas of Italy is collected. The proposed dataset is useful to a large scientific and risk-management audience (e.g., input for numerical modelling of regional studies, or providing the maximum depth of brittle crust useful to constraints maximum expected magnitudes for the study region). The dataset is presented as a long table (2019-028_Petricca_Table1.txt) in tab-separated text format. The table contains three columns indicating 1) the longitude, 2) the latitude and 3) the depth (in km) values of the maximum thrust faulting depth. Obtained depths range between 1 and 17 km. Conceptual model for the definition of the active thrust decollement depths (see Petricca et al., 2019): to define the basal decollement depth of active thrust faults are selected 75 published geological and seismic sections plus two maps of basal decollement (Table 1 in Petricca et al., 2019 for references). The study domain is gridded with nodes every 10x10 km. At each node coinciding with a seismic or geological section, the punctual value of the basal decollement depth with respect to the sea level is assigned. For the Calabrian Arc and part of Sicily, we used values picked from depth maps. Depth values at empty nodes are assigned by interpolation criteria using the minimum curvature method (Briggs, 1974), generalized by Smith and Wessel (1990) including the tension factor (i.e., the smoothing grade - 0.5 in this case). Further, the trend of the obtained isodepth contours is recalibrated following the composite sources (i.e. the maximum depth of seismogenic sources given in the DISS database - see Basili et al., 2008). Depth correction is obtained adding/subtracting the topography/bathymetry elevation/depth at nodes using values interpolated from ETOPO1 Global Relief Model. Due to the fact that the brittle-ductile transition (BDT) depth is possibly and locally shallower than the basal thrust depth (zbt), further correction is necessary. For this purpose, the BDT depths from Petricca et al. (2015) is compared with the basal thrust depths zbt from this study to select at each node of the computation grid the shallower value. The majority of the studied areas show a basal thrust depth (zmax) shallower than the BDT. An exception occurs offshore in the southern Tyrrhenian Sea, Sicily, where the BDT depth (10-12 km) is considerably shallower than the basal thrust depth (zmax<30 km). Limited portions of the northern Apennines and the part of the Calabrian arc close to the coast show comparable depths between the basal thrust (zmax) and BDT (i.e., 14-17 km).