GNGTS 2014 - Atti del 33° Convegno Nazionale

GNGTS 2014 S essione 3.2 153 Moho doubling in correspondence with the zero-Bouguer anomaly where Tuscan Moho overlaps the Adriatic one for 30 km. The Moho depth below Apennine Chain is approximately 32 km. Piana Agostinetti et al. (2002) do not show a doubling of Moho and do not give information about the thickness and velocity of the upper and lover crust. They estimated the depth of the crust below Apennine Chain of about 35-38 km. Mele and Sandvol (2003) consider a doubling of Moho beneath the Val Tiberina and the partial overlapping between the shallow Tuscan Moho and the deeper Adriatic Moho. They also consider a deep crustal root beneath Apenninic Chain to a depth of 49±3 km. Density data. We decided to calculate density values of lithologic units, considering density, ρ, as function of seismic P waves velocities, V P . In particular we used the polynomial regression (Brocher, 2005) that fits the Nafe-Drake empirical curve (Ludwig et al. , 1970), where V p is in m/s. ρ(g/cm 3 )= 1.6612V P -0.4721V 2 P +0.0671V 3 P -0.0043V 4 P +0.000106 V 5 P We choose V P for the lithologic units on the base of the literature for the studied area. In particular for the sedimentary cover we used Amato et al. , (1994) and Mirabella et al. (2011). As regard of V P velocities for the crust and the mantle we take in to account the detailed velocity Tab. 1 - Densities values used in this study calculated follow the emipirical relation of considering density, ρ, as function of seismic P waves velocities, VP, (Brocher, 2005). Lithologic Unit References P waves velocity Calculated density This model V P (m/s) ρ (g/cm 3 ) ρ (g/cm 3 ) Plio-Pleistocene Units Mirabella et al. , 2011 2000 1.91 1.91 Amato et al., 1994 2750-2900 2.16-2.20 2.18 Ligurids Units Amato et al. , 1994 3900 2.38 2.38 Tuscan-Umbrian turbidites Mirabella et al. , 2011 4000-4300 2.39-2.43 2.41 Carbonates Units Mirabella et al. , 2011 5600 2.64 2.64 Evaporites Units Mirabella et al. , 2011 6100 2.74 2.74 Basement s.l. Mirabella et al. , 2011 5100 2.55 2.55 Upper crust Ponziani et al. , 1995 6000-6300 2.72-2.78 2.75 Tuscan lower crust Ponziani et al. , 1995 6300-6700 2.78-2.88 2.83 Adriatic lower crust Ponziani et al. , 1995 6500-6700 2.83-2.88 2.85 Tuscan Mantle Ponziani et al. , 1995 7800 3.22 3.22 Adriatic Mantle Ponziani et al. , 1995 7900-8000 3.26-3.29 3.27 Fig. 2 – Intermediate sector (see trace in Fig. 1) which extends fromM. Amiata toAdriatic coast. This figure shows the original data points of Bouguer gravity anomaly and the gravity signal of the main tectonic structures of the studied area.