Evaluation of seismic risk in regional areas by AE monitoring of historical buildings

In this contribution a new method for evaluating seismic risk in regional areas based on Acoustic Emission (AE) technique is proposed. Most earthquakes have precursors, i.e. phenomena of changes in the Earth physical-chemical properties, that take place prior to an earthquake. Acoustic Emission in materials, and earthquakes in the Earth Crust, despite they take place on very different scales, are very similar phenomena, both are caused by a release of elastic energy from a source located in a medium. For the AE monitoring two important constructions of the Italian cultural heritage are considered: a Chapel of the “Sacred Mountain of Varallo” and the “Asinelli Tower” of Bologna. They were monitored during earthquakes sequences in the relative areas. By using the Grassberger-Procaccia algorithm a statistical method of analysis was developed that detects AEs as earthquake precursors or aftershocks. Under certain conditions it was observed that AEs precede earthquakes. These considerations reinforce the idea that the AE monitoring can be considered as an effective tool for earthquake risk evaluation.