Electromagnetic Emission as Failure Precursor Phenomenon for Seismic Activity Monitoring

The electromagnetic (EM) signals detected during failure of brittle materials are analogous to the anomalous radiation of geoelectromagnetic waves observed before major earthquakes, reinforcing the idea that the EM effect can be applied as a forecasting tool for seismic events. Moreover, it has been argued (Widom-Swain-Srivastava) that the elastic energy released by micro-crack production eventually yields to forming macroscopic fractures, whose mechanical vibrations are converted into electromagnetic oscillations over a wide range of frequencies, from few Hz to MHz, and even up to microwaves. This excited state of the matter could be a precursor of subsequent resonance phenomena of nuclei able to produce neutron bursts in the presence of stress-drops or sudden catastrophic fractures. As a matter of fact, neutron emissions (NE) measured at seismic areas exceed the usual neutron background up to three orders of magnitude in correspondence to rather appreciable earthquakes. In this work the Authors measure the EM pulses generated during micro-cracking of rock specimens by a dedicated loop antenna sensitive up to MHz. Taking into account the relationship between EM, NE and seismic activity, it will be possible to set up a sort of alarm system that could be at the base of a warning network.