© Dr. V.F. OSTAPENKO, Prof. V.A. KRASNOPEROV

(ALMATY, KAZAKHSTAN)

Institut of Seismology and Faculty of Engineering Suleyman Demirel University – Almaty - Kazakhstan.

Contact:

• Vitaly Ostapenko – OstVF@mail.ru,

• Vladimir Krasnoperov –krasva@km.ru, vkras@academician.samal.kz

Since 1996 we are carrying out continuous observations of the natural neutron flux (NF) magnitude in a drift near Almaty (Kazakhstan) at a height of 1600 meters above sea level. A year later similar works have been started on the surface in the same region. Measurements are conducted with data accumulation during a one-hour period.

It is found that sometimes the NF magnitude rises sharply within the one-hour interval in comparison with an ordinary one. Statistical distribution of dispersions of the NF magnitude is close to normal, however a quantity of dispersions from the average value, exceeding the latter more than by triple mean square error, is twice higher of theoretically expected value from Gauss distribution. Such magnitudes we consider as anomaly. Obviously there is a certain natural factor which causes such anomalies.

As is well known the natural neutron flux consists of three components. Firstly, neutrons are formed as a result of interaction of cosmic radiation with atomic kernels of substance of atmosphere and the earth's crust. Secondly, free neutrons segregate during spontaneous fission of uranium kernels. At last neutrons can be generated during nuclear reactions when alpha-particles of natural radionuclides have been interacted with atomic kernels of light elements which are a part of atmosphere and the earth's crust.

Therefore a changing of the NF magnitude can be caused either by variations of intensity of cosmic radiation or by alteration of concentration of uranium and other radioelements emitting alpha-particles in the space adjacent to the place of position of a neutron detector.

Comparison of measurement results showed that anomalous increase of the NF magnitude could not be explained by an additional inflow of radon, which is the most mobile radioelement in the nature. The fact is that in the drift, which is tightly closed with doors, there is no ventilation of the air so in case of additional inflow of radon NF anomalies had to be observed during the time substantially exceeding the one hour interval as long as a half-value period amounts 3.8 days.

Contents of other radioelements in the ambient the neutron detector space is practically stable. Thus, a cause of changing of NF magnitude most likely is variations of cosmic radiation and in particular variations of m -mesons relating to the hard component thereof as since only these particles are able to penetrate the drift though tens meters of rock. Besides, the evaluation shows that in our conditions in the drift the neutron component formed under cosmic radiation comes to about 90% of the total registered underground NF.

On analysis of measurement results it was determined a certain connection between the NF magnitude and seismic occurrences. Periods of increase of frequency of anomalies usually agree with periods of increase of seismic activity (see Fig. 1-3).

Figure 1. Comparison of moments of NF anomalies onset with earthquakes.

1 cond.unit.- earthquakes of energetic classes K ³ 10, 0.75 cond.unit.- anomalies of the surface NF, 0.5 cond.unit.- anomalies of the underground NF.

Figure 2. Smoothed curves of timing of moments of anomalies onset of the underground NF (1) and earthquakes of energetic classes ʳ 10 (2).

Figure 3. The same as Fig.2 but for the year 1999

Anomalous high values of the NF magnitude registered within the one hour interval are accompanied as a rule by subsequent earthquakes of energetic classes K ³ 10, epicenters of which are located within the range of 450 km from the place of the NF registration. Fig. 4 below illustrates such an occurrence.

Figure 4. A fragment of temporal series of the underground NF. 1 and 2 are the moments of earthquakes of energetic classes 12.2 è 12.7, epicenters of which are located at the distance of 120 km and 335 km from the place of measurement respectively.

Anomalies take place from 1 hour to 10 days prior to earthquakes but mainly (up to 70% of cases) the time interval is not more than 4 days. It is also indicated a tendency of growth of the anomaly magnitude in accordance with the growth of the energetic class of the subsequent earthquake (Fig. 5).

Figure 5. Amplitude dependence between anomalies of the underground NF and the energetic class of earthquakes.

All the mentioned above is not in contradiction with the data published in literature. Thus in the work of Armenian researchers [1] it is stated that 30 minutes prior to the earthquake in Spitak there has been registered the 100% increase of the hard component of cosmic radiation in stratosphere over Erevan. In another work [2] it is distinguished a linear dependence between intensity of cosmic radiation registered by neutron monitors and the total energy-release caused by earthquakes all over the terrestrial globe. It is also indicated [3] that at Baksanskaya neutrino observatory there were registered short-term (not more than 15 minutes) bursts of high energy m -mesons due to bursts of solar material into interplanetary space during solar flares.

A character of connection between the NF and earthquakes is still not clear. It is proposed that the NF anomalies caused by variations of cosmic radiation intensity under action of fluxes of solar material, which is burst into interplanetary space (solar wind) during solar flares. Energy of the solar wind transferred to Earth puts into action a trigger mechanism of the process of initiation of earthquakes at those places where conditions have already been prepared for them.

During the period of observations within the range of 450 km from the place of location of the neutron detector is has been registered 44 earthquakes of classes from 12 to 12.9 and 18 earthquakes of classes K ³ 13. All the earthquakes of the second group had been anticipated by NF anomalies. Only 5 earthquakes in the first group took place without preliminary anomalies (see Table 1).

Table 1

As a consequence of all the stated above is a deduction that NF anomalies can be used as substantial additional information for classical geophysical methods of short-term earthquake forecast.

REFERENCES:

1. Asatryan G.A., Asatryan Gr.A., Babayan V.H., Stozhkov Yu.I., Oganyan G.Zh. //Proc. AS USSR, Ser. Phys. 1991. V. 55, No.10, P. 1979-1981.

2. Sobolev G.A., Shestopalov I.P., Kharin E.P. Geoeffective solar flares and seismic activity of the Earth. // Physics of the Earth. 1998. No.7, P. 85-90.

3. Karpov S.N., Miroshnichenko L.I., Vashenyuk E.V. // Proc. RAS. Ser. Phys. 1997. V. 61, No.7, P. 1466-1469.

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