The seismic sequence in Central Italy (August-November 2016). Acoustic Emission (AE) monitoring and analysis

The seismic sequence in Central Italy of August-November 2016 is a useful experiment in the natural laboratory suited to check the effectiveness of AE monitoring in order to diagnose the state of the crust that precedes an earthquake. The difference is shown between (i) a "once-in-a-while" earthquake, which is characterized by a main event - composed of one strong shock or at most of two shocks occurring during a reasonably short time delay (several hours or a few days) followed by aftershocks etc., and (ii) a sequence of destructive events of comparable magnitude that denotes a time-delayed release of potential energy. The Central Italy sequence is of the second kind, i.e. it is an intermediate case history, compared to the extreme occurrence which is non-destructive, i.e. a so-called "slow" or "silent" earthquake. In the case of a sequence of destructive events, a reasonable concern is therefore about whether the total amount of the stored potential energy has been fully released. The very different role and responsibility has to be very clearly distinguished between geologists, seismologists, statisticians, applied mathematicians, and geophysicists, in order to approach problems according to logical rigor. Seismologists - by means of a statistical approach (pattern recognition) and of some intricate related algorithms - afford to give some objective and reliable information suited to make a concrete planning for preventive intervention on the territory. In addition, from the geophysicist viewpoint, it has been envisaged that seismic catastrophes can be operatively managed in terms of a 4-level approach. The focus of the present study deals with levels 2 and 3. No precise prediction is however possible, and this holds either by this or by any other method. However, a sound, and understating approach can reduce fatalities, damages and sufferance. The ultimate purpose is to focus on reliable diagnostic information suited for a realistic appraisal of hazard and risk and also of its evolution in both space and time. However, also the geodynamic interpretation is to be considered. This item is discussed in a subsequent paper ("paper II") in terms of an objective, unconventional, physical and non-paradigmatic approach. In addition, a subsequent "paper III" is concerned the physical meaning and heuristic perspective of seismic (and volcanic) "transmigration", considered like a source of some indicative, and sometimes possibly significant, "hunch".