Application of Geological Techniques to Identify Earthquakes Affecting Archaeological Sites: The Example of the 2011 Lorca Earthquake (SE Spain)

[EN] The main uncertainty when studying the destruction horizon of an archaeological site or a heritage building is to know which trigger mechanism generated these deformations. This is the case of archaeoseismology, which needs to have a method to be able to discriminate whether the ruin of a given site was caused by simple abandonment or by an earthquake. The structural geology discipline studies, among other aspects, the deformations in rocks in relation to the intrinsic properties (fabric and mineralogy) and the tectonic parameters. This technique has demonstrated its utility to identify deformations of seismic origin by measuring the orientation and clustering the deformation to find spatial patterns of ground shaking and building response. The passage of the seismic waves from an earthquake depends on the seismic source and the epicentral location, and the so-called seismic ray arrives to the archaeological site with a trending which is measurable. The 2011 Lorca earthquake (Mw 5.2, SE of Spain) was a good example of the application of this novel methodology to determine the pattern of deformation affecting the buildings. During this earthquake, a lot of relevant and ancient buildings were affected by the seismic ray, giving a good opportunity for calibrating the spatial patterns of building deformation with the seismological parameters and geological features of the seismic source. Several Earthquake Archaeological Effects (EAEs) were mapped and compared with the orientation obtained from a seismic accelerometer of the Spanish National Seismic Monitoring Network, located in the city hall (in the historic downtown of Lorca). The ground-shaking movement, obtained from the application of this novel technique is NW-SE trending, and it agrees with the main orientation obtained from the seismic accelerometer.This work is supported by the Spanish research project MINECO-FEDER PID2021-123510OB-I00 (QTECTSPAIN).Peer reviewe