Earthquake-Rotated Objects (EROs) induced by the 2016 M w 6.0 Amatrice (Central Italy) earthquake: the contribution from site and source effects

The 2016 August 24th, M w 6.0 Amatrice (Central Italy) normal faulting earthquake produced a remarkable number of Earthquake-Rotated Objects (EROs) that affected chimneys, as well as pillars and capitals on gates and walls. In this paper we present the EROs dataset, and perform some qualitative analyses to evaluate if specific geological and seismological features such as intensity, epicentral distance, potential amplification of the seismic shaking at the site, heterogeneities of the rupture on the fault and directivity effects, and peak ground accelerations, favoured the distribution of EROs observed after the earthquake. A first important outcome is that the distribution of the EROs of Amatrice 2016 mimics the general pattern of damage, and that EROs occurrence should be regarded as a diagnostic element of intensity degrees lower than those presently established by formalized scales. We also find that site factors, namely the surface geology and the local amplification, are the most significant contributors to the EROs occurrence. In addition, we find that the position respect to the fault can enhance the occurrence of local rotations. The distinctive features characterizing the 2016 EROs dataset resemble and substantiate the most important findings produced by previous studies carried out following the 2009 L’Aquila and 2012 Emilia seismic sequences, and allow to calibrate the empirical relations on the EROs distribution presented in the world Catalog of Earthquake-Rotated Objects.