Constraints on the Structure of the Shallow Crust in Central Italy from Geophysical Log Data

Abstract

To better define the seismic velocities of the shallow crust in central Italy, in the area affected by the 1997 Colfiorito, 2009 L’Aquila and 2016–2018 Amatrice–Norcia seismic sequences, we selected all deep wells with available sonic logs from the Apennine belt to the related Adriatic foredeep. Sonic logs are among the most important in situ measurements of rock properties and provide a reliable image of physical conditions at depth. By analysing the wave train transit times, we inferred the P-wave velocity within depth intervals displaying homogeneous sonic log properties, and estimated the rock density by applying an empirical relationship between the sonic velocity and density in sedimentary rocks. We compared these results with the main litho-stratigraphic units in stratigraphic profiles of the wells. From the density estimates, we inferred the trends of the vertical stress magnitude in the belt, eastern front and foredeep geodynamic domains. This work is a contribution to better interpretation of physical conditions at depth and provides data that can be applied to define more complete seismological, gravity and magnetic models. We provide data uncertainties that must be considered to ensure proper use of data and to evaluate the spatial resolution of the models derived from those data.