Acoustic emission and released seismic energy

Abstract

Abstract. Intense crises of crustal stress appear to cross large regions, and to precede by several months the eventual occurrence of some strong earthquake within them. The phenomenon is not linear, and the stress control reflects some wide scale-size rather than local effects. The stress propagation through the crust can be effectively monitored by means of acoustic emission (AE) techniques (ultrasounds). The correlation is here investigated between crustal stress crises and the total release of seismic energy within some space domain around the AE recording site. Some clear inferences can be envisaged, although a significant diagnosis of the state of the crust within a given region ought to request arrays of simultaneously operated AE recorders. Some case histories are described dealing with the Italian peninsula and with the Cephallonia Island.

Acoustic emission monitoring of medieval towers considered as sensitive earthquake receptors

“…In effect, an AE paroxysm, i.e. a large and almost abrupt increase of the AE signal, was observed ∼400 km far from the epicentral area several months before the eventual occurrence of the Assisi earthquake (Gregori and Paparo, 2004;Gregori et al, 2005). The progressively lower frequency (from ∼200 kHz to ∼25 kHz) of detected AE as time elapsed appeared consistent with the expectation that high-frequency AE, i.e.…”

“…In many physics problems -e.g., when studying test specimen failure in a laboratory, the modalities of collapse of a civil structure, the natural seismic activity of a volcano or the localisation of the epicentral volume of an earthquake -the modalities of a structural collapse are generally analysed after the event. This technique can be used instead to identify the premonitory signals that precede a catastrophic event, as, in most cases, these warning signs can be captured well in advance (Zapperi et al, 1997;Gregori and Paparo, 2004;Gregori et al, 2005).…”

"Storms of crustal stress" and AE earthquake precursors

“…The details of the following algorithms already appeared in several papers Gregori et al, , 2005Gregori et al, , 2007Paparo et al, 2001Paparo et al, , 2002Paparo et al, , 2006Poscolieri et al, 2006aPoscolieri et al, , 2006b. Hence, only some highlights are given here.…”

“…the planetary scale propagation of the loading tide stress (see Sect. 1.2; Gregori et al, 2005Gregori et al, , 2007Paparo et al, 2006;Poscolieri et al, 2006aPoscolieri et al, , 2006b). 328 G. P. Gregori et al: "Storms of crustal stress" and AE earthquake precursors In contrast, the LF AE -compared to HF AE -appear much more affected by regional or local tectonics.…”

Signal frequency distribution and natural-time analyses from acoustic emission monitoring of an arched structure in the Castle of Racconigi

“…In this framework, over the recent years there has been an increasing interest in AE monitoring related to environmental phenomena. Several case histories in the Italian territory and previous studies support the hypothesis that increased AE activity may be a signature of crustal stresses redistribution in a large zone during the preparation of a seismic event (Gregori and Paparo, 2004;Gregori et al, 2005;Carpinteri et al, 2007;Niccolini et al, 2011). According to previous research studies performed by Dobrovolsky et al (1979), it can be assumed that the preparation zone is a circle with its center at the epicenter of the impending earthquake.…”