Fracto-emissions as seismic precursors: The case-study of "san Pietro-Prato Nuovo" gypsum mine

Three different forms of energy (Acoustic Emission AE, Electro-Magnetic Emission EME, and Neutron Emission NE), induced by unstable local phenomena at the different scale, might be used as earthquake precursors for environmental protection against seismicity. At the tectonic scale and during the early stages of an earthquake, cracking is a multi-scale phenomenon, as well as the frequencies of pressure waves are spread over a broad spectrum, from TeraHertz at the nanoscale up to the simple Hertz at the kilometre scale, which is the typical and most likely frequency of seismic oscillations. So far, no reliable method has been developed yet for the successful application of earthquake prediction. Since July 1st, 2013, a dedicated in-situ monitoring at the "San Pietro-Prato Nuovo" gypsum mine located in Murisengo (Alessandria, Northern Italy) has started. The novelty of this experimental investigation consists in the simultaneous acquisition of the three forms of fracto-emission (AE, EME, and NE) and in their temporal correlation with the incoming seismic event by means of an appropriate multi-modal statistical analysis. From the comparison between the different diagrams, it is evident the strong correlation between acoustic, electromagnetic, neutron peaks and the seismic swarms occurring in the surrounding areas, and how the three fracto-emissions tend to anticipate the next seismic event with an evident and chronologically ordered shifting. Therefore, they should be considered as precursors of the next major earthquake rather than aftershocks of the previous one, on the basis of the statistical signal processing and of the different temporal distances.