Monitoring of Gamma Radiation Prior to Earthquakes in a Study of Lithosphere-Atmosphere-Ionosphere Coupling in Northern Tien Shan

Round 1

Reviewer 1 Report

In this paper, the authors believe that radon and other radioactive substances in the seismogenic region will increase before the earthquake, which will lead to the abnormal variation of Gamma rays. The effect of ionosphere disturbance triggered by the growth of radioactivity in the near-earth atmosphere was confirmed. The Lithosphere-Atmosphere-Ionosphere Coupling is well discussed. But the paper also seems to needs minor modification before publication. The following are my little suggestions that the authors may consider.

1.The results show that the Gamma ray flux changes abnormally during the 2-8 days before the earthquake, but there is no abnormal variation in the Gamma ray flux during the co-earthquake and post-earthquake stages. This phenomenon is different from some observations, such as “Soil gas distribution in the main coseismic surface rupture zone of the 1980, Ms = 6.9, Irpinia earthquake (southern Italy)”, Ciotoli et al., 2014. Ciotoli et al. believe abnormal increasement of radioactive substances can last until the post-earthquake. The authors should try to explain why.

2.Figure 2 in this paper shows the background changes of the surface and underground Borehole gamma ray fluxes, but does not show the background changes of the acoustic signal, temperature, and Doppler shift in the absence of an earthquake.

3.Why not merge Figure 8 into Figure 6 and arrange the Borehole gamma-ray flux, surface gamma-ray flux, acoustic signal, temperature, and Doppler shift in order?

4.Why does the February 2020 earthquake in Table 1 still have an anomaly beyond the Dobrovolsky radius, while the January 2020 earthquake does not. Please clarify it.

Author Response

In this paper, the authors believe that radon and other radioactive substances in the seismogenic region will increase before the earthquake, which will lead to the abnormal variation of Gamma rays. The effect of ionosphere disturbance triggered by the growth of radioactivity in the near-earth atmosphere was confirmed. The Lithosphere-Atmosphere-Ionosphere Coupling is well discussed. But the paper also seems to needs minor modification before publication. The following are my little suggestions that the authorsmay consider.

1.The results show that the Gamma ray flux changes abnormally during the 2-8 days before the earthquake, but there is no abnormal variation in the Gamma ray flux during the co-earthquake and post-earthquake stages. This phenomenon is different from some observations, such as “Soil gas distribution in the main coseismic surface rupture zone of the 1980, Ms = 6.9, Irpinia earthquake (southern Italy)”, Ciotoli et al., 2014. Ciotoli et al. believe abnormal increasement of radioactive substances can last until the post-earthquake. The authors should try to explain why.

++++ ANSWER
Much thanks for the useful references.

In fact, the gamma background remained still disturbed a few days after the December 30, 2017 earthquake which is considered in detail in the article. Though an excess of gamma ray intensity can be traced up to 2-3 days after the earthquake immediately over the counting rate record of soft gamma rays (as in the upper panel of Figure 5), this effect revealed itself best in the dynamic power spectrum of the variation of gamma intensity. For this purpose a description of the corresponding operation procedure was now included into Experimental Data section, and its result is presented in the newly added Figure 8. In this plot it is quite evident the disturbance of the gamma radiation background both at the co- and post-earthquake time.

As for the more distant earthquakes listed in Table 1, in the cases of the August 31, 2018 M5.0, and, especially, of the January 19, 2020 M6.2 earthquakes the flux of gamma rays remained suppressed (5-10)days since the main shock, and during some days after the February 15, 2020 M5.6 earthquake there was observed a tendency to an enhanced intensity of the radiation flux (see Figures3 and 4).

This text fragment was included into Discussion section.

2.Figure 2 in this paper shows the background changes of the surface and underground Borehole gamma ray fluxes, but does not show the background changes of the acoustic signal, temperature, and Doppler shift in the absence of an earthquake.

++++ ANSWER
Presently, Figure 9 with the plots of the mentioned signals in the pre-earthquake time and corresponding text notices were added to Experimental Data section. 

3.Why not merge Figure 8 into Figure 6 and arrange the Borehole gamma-ray flux, surface gamma-ray flux, acoustic signal, temperature, and Doppler shift in order?

++++ ANSWER
Figure 8 (which is presently Figure 6) is drawn in a much larger time scale than former Figure 6 (presently it is Figure 5). This was intentionally made to stress the internal thin structure of the gamma ray outburst which precedes the earthquake.

4.Why does the February 2020 earthquake in Table 1 still have an anomaly beyond the Dobrovolsky radius, while the January 2020 earthquake does not. Please clarify it.

++++ ANSWER
Much thanks for this remark. There was a misprint in the last row of Table 1. Presently it is corrected, and all the earthquake events listed there occur within their Dobrovolsky zone.

Submission Date
20 September 2022
Date of this review
28 Sep 2022 10:18:46

Reviewer 2 Report

Dear editor

The paper presents an analysis of  Gamma Radiation Prior to Earthquakes at a Study of Lithosphere-Atmosphere-Ionosphere Coupling in Northern Tien Shan. The paper is well written, uses original data and I find it interesting and of possible interest to the involved community. I believe that it might eventually be suitable for publication once the points mentioned in my detailed comments below are properly addressed.

1. The author needs to clarify the cause of characteristic bay-like depressions in the time series of gamma radiation intensity, both in subsoil layers and in the atmosphere.

2. About what is the reason for the difference in the timing of The gamma radiation and sound waves and temperature changes before the M4.2 earthquake in 2017

3. Usually, the  Doppler shift is due to atmospheric fluctuations caused by seismic surface wave vibrations, which propagate to the ionosphere and thus cause a traveling ionospheric disturbance. The authors need to clarify what is the physical mechanism by which surface ionizing radiation causes electric field changes and thus ionospheric Doppler shifts?

Author Response

Dear editor

The paper presents an analysis of  Gamma Radiation Prior to Earthquakes at a Study of Lithosphere-Atmosphere-Ionosphere Coupling in Northern Tien Shan. The paper is well written, uses original data and I find it interesting and of possible interest to the involved community. I believe that it might eventually be suitable for publication once the points mentioned in my detailed comments below are properly addressed.

1. The author needs to clarify the cause of characteristic bay-like depressions in the time series of gamma radiation intensity, both in subsoil layers and in the atmosphere.

++++ ANSWER
A paragraph was added to Discussion section which contains explanation of possible physical reasons of the bay-like depression effect from the viewpoint of specific condition of radon exhalation in the compression tectonic zone of Northern Tien Shan.

2. About what is the reason for the difference in the timing of The gamma radiation and sound waves and temperature changes before the M4.2 earthquake in 2017

++++ ANSWER
Seemingly, this can be interpreted as delayed exhalation of an excessive amount of radon through the micro-cracks which have opened, with accompaniment of enhanced geoacoustic emission, at the preceding stage of seismic activity. The delay between the beginning of the sequence of detected acoustic signals and the rise of gamma radiation reflects the time which was necessary for the radioactive gases to penetrate from the depth of the earth's crust into the subsoil lithosphere layers.

This explanation was added to Discussion section.

3. Usually, the  Doppler shift is due to atmospheric fluctuations caused by seismic surface wave vibrations, which propagate to the ionosphere and thus cause a traveling ionospheric disturbance. The authors need to clarify what is the physical mechanism by which surface ionizing radiation causes electric field changes and thus ionospheric Doppler shifts?

++++ ANSWER
Into Discussion section it was included a review of the two physical mechanisms responsible for propagation of seismogenic disturbances over the chain of lithosphere-atmosphere-ionosphere connections, namely the acoustic mechanism of infrasonic waves and propagation by the intermediary electric currents and fields.

Submission Date
20 September 2022
Date of this review
29 Sep 2022 03:30:18