30 Jan 2021. Cumiana update; "Predictive Capability Of VLF/LF Emissions"; Part 4: Discussion, Pt B
6Second half of the Discussion portion of the research.
"Prediction Capabilities of VLF/LF Emission as the Main Precursor of Earthquake"
Wordpress link: (https://vertearbustosschumannresonanceharmonics.wordpress.com/prediction-capabilities-of-vlf-lf-emission-as-the-main-precursor-of-earthquake/)
M.K.Kachakhidze1 and N.K.Kachakhidze1
[1] {Saint Andrew the First-Called Georgian University}
At the final, third stage of the avalanche-like unstable model of fault formation the relatively big size faults use to unite into one - the main fault. This process, according to our model, in case of emission spectrum monitoring should correspond to gradual fall of frequencies in kHz, which according to the formula (1) refers to the increase of fault length in the focus.
Increase of crack length in focus refers to the increase of a magnitude of the incoming earthquake (Ulomov, 1993): 6
lgl =0.6M−2.5 (2)
In case of L’Aquila earthquake, due to the fact that on 4.04.2009 the main frequency kHz was already fixed in the electromagnetic emission spectrum, (Papadopoulos, G. A., et al., 2010), the main fault in the earthquake focus should have been of kilometer order already.
Of course, association of cracks into one fault, which at the final stage of earthquake preparation proceeds intensely, will use definite part of energy accumulated in the focus and therefore, will result in its decrease. In such situation a period settles before a large earthquake (which can last from several hours to even 2 days), when in the focus a fault is already formed, while earthquake has not occurred yet, since accumulated tectonic stress is not yet sufficient to overcome the limit of strength of geological environment. The system, which is waiting for further “portion” of tectonic stress, is in the so-called “stupor”, in the principle, the process of crack formation is not going on in it anymore, and respectively, electromagnetic emission would not take place.
Although, later, at the approach of critical value of tectonic stress, the balanced state in the system will be deranged and the earthquake will occur. This process is expressed correspondingly in the electromagnetic emission spectrum: some hours before the earthquake (up to 2 days) in the spectrum the emission intermittence is observed. Up to interruption of electromagnetic emission, by the use of final value of the main frequency of the spectrum (on the basis of the formula 1) we can determine, by a rather high accuracy, the length of expected fault of the future earthquake, that is, a magnitude of the incoming earthquake (Kachakhidze et al., 2011; Kachakhidze et al., 2012; Kachakhidze et al., 2013). We can expect renew of electromagnetic emission immediately before the earthquake.
In the period of electromagnetic emission monitoring the moment of interruption of emission spectrum is urgent for determination of time of occurrence of incoming earthquake, since at the final stage of earthquake preparation, very short time is needed to fill in the critical reserve of tectonic stress needed for main fault realization. It should be noted that this fact was experimentally proved for the case of L’Aquila earthquake. In this case this time lasted up to 1.5-2 days.
Often, in cases of rather large earthquakes we observe large foreshock too. The main shock can follow large foreshock rather swiftly. In this case, there is no reliable criterion, which can distinguish large foreshock from incoming earthquake. Example of this is L’Aquila earthquake, when it was considered that the incoming foreshock was the main shock.
This issue can be resolved by rather high accuracy on the basis of analogous model by EM emission monitoring. Namely, in case of M=5 earthquake, electromagnetic emission should equal to 95 kHz. 7
In this case fault length in the focus equals to approximately 3 km. (Kachakhidze et al., 2011; Kachakhidze et al., 2012). If after this earthquake electromagnetic emission still continues to exist and the frequency data still tend to decrease, it means that the process of fault formation in the focus of the earthquake is not completed yet and we have to wait for the main shock to occur.
Generally we should not expect stopping of electromagnetic emission after large earthquake but the frequency values in the spectrum must grow, which will refer to the fact that we should not expect the larger than the occurred earthquake but we have to wait for a series of aftershocks. This was well proved by the example of L’Aquila earthquake (Rozhnoi et al., 2009).
Since the processes of developing of foreshocks and aftershocks generally are connected with the fault formation process, it is clear that at this time too, VLF/LF electromagnetic emission will take place (Rozhnoi et al., 2009; Papadopoulos et al., 2010; Hayakawa et al., 2013). Analogous model on the basis of electromagnetic emission enable us to evaluate magnitude of each separate foreshock and aftershock.