Dear Mr. Alam,

the alpha-cup method or track-etch method strongly depends on the bedrock-soil relationship (tickness ratio etc.). Another parameter is the lithological situation underneath as to joint spacing, porosity and the overall-lithology. The pedological overburden is another part of the story, as it is the hydrology and water saturation. Therefore it does not make very much sense to provide you with a "general distance". It is an equation at the moment with too many unknown parameters. I know this from my time I spent with the U branch. Please also carefully deal with the expected source of U and Th in the parent rock and the U disequilibria.

I do not want to discourage you but it is wise to think of these limitations prior to collect data in the field with a unsuitable array or spacing of monitoring stations that supply data based on a doubtful basis.

Best regards

H.G.Dill

If you are limited to only two stations, you will only get a limited amount of information about the variability in radon fluxes from the soil. As Dr. Dill stated, any knowledge of the geology and uranium or thorium parents of the decay series responsible for the radon will help you understand the radiochemical environment.

Consider setting up your two monitoring sites with a spacing of one tenth of the distance that you need to study. Collect data for a period of about one tenth of your field data collection time. After the first collection (1/10 of your field data collection time) move the first station beyond the second site by the same distance that separated the stations one and two. After the second tenth of your field study, move the second station beyond the third station. After you repeat this process 9 times, you will have data for 10 sites and can assess the natural variability in the radon fluxes. This will allow you to decide on the long-term sites with a better understanding of the variability in the radon fluxes in your study area.

I hope that helps to get you started.

Best regards,

Ronald Miller

Dear colleagues,

I think you all know that seasonal changes, precipitation and the rate of evaportranspiration have also a strong say on the water saturation of the topstratum and the soil gas circulation. To say it in a few plain words. Two stations moving around in a certain test site over a rather long period of time is not the most suitable approach to be taken. I do not know what the study is aimed at. Whether it is for applied sciences or to write a paper, I consider this attempt not a reasonable one to achieve reliable data for whatever goal.

This is my personal opinion.

Nevertheless I wish you all the best in your overall studies.

Harald G. Dill

What is the most suitable distance between 2 continuous radon monitoring in soil gas sites?

Dear Aftab Alan,

I think it is very important to do frequent (or, better, continuous) radon monitoring in sites where gas emission from the soil occurs, with a capillary distribution of research centers on the territory, for a reason of  health prevention, but there can be economical problems in many country, so it is at least desirable that a frequent radon monitoring is undertaken in schools, hospitals and underground working places of every town, city, … and  it is right to do a continuous radon monitoring in every working place in mines, in tunnels and in caves…, independently from the distance between 2 continuous radon monitoring stations.

What is the most suitable distance between 2 continuous radon in soil gas monitoring stations?

This is an issue of research on seismic forecast: we must consider the seismic classification of different places and the different geological structures, for example if an area is rich in minerals with uranium, radon is indeed a very good seismic precursor, so a continuous radon monitoring can give important information about earthquakes forecast. We must always consider the whole seismic precursors in their synergic complexity , not only radon emission, for a forecast always more and more precise.

I can answer to your question, but let me tell you that we can individuate only a good and suitable distance between 2 continuous radon monitoring studies in research centers and not “the most suitable”, in relation to the seismic classification of diverse areas and in relation to the actual spatial and temporal earthquake forecast that the radon monitoring can give us. It is necessary to consider also the different geological structure in relation to the depth of the future earthquake and its magnitude, because the radon emission can change. It is also important to take into account the classification of earthquakes: tectonic earthquakes, earthquakes originated by volcanic activity and earthquakes originated by balances in underground caves.

So I can only answer you on the basis of my experimental researches that I conduct with my “Seismic Precursors Study Center” (SPSC, a no-profit association), whose operative centre is in Torre Pellice. I do not know what cat be “the most suitable distance between 2 continuous radon in soil gas monitoring stations” in other areas with a different geological structure and with a different seismic classification. We must always be prudent if we would like to give an ideal model of prevention and forecast planning.

So I can sum the following, based on my observations:

- increase in radon emission over mean values is significantly higher 2-3 days before earthquakes with magnitude M ≤ 1, with a distance from SPSC of the future epicentrum d ≤ 20 km;

- increase in radon emission over mean values is significantly higher 2-3 days before earthquakes with magnitude 1 < M ≤ 2, with a distance of SPSC from future epicentrum d ≤ 50 km;

- increase in radon emission over mean values is significantly higher 2-4 days before earthquakes with magnitude 2 < M ≤ 3, with a distance of SPSC from future epicentrum d ≤ 90 km;

- increase in radon emission over mean values is significantly higher 3-7 days before earthquakes with magnitude 3 < M ≤ 4, with a distance of SPSC from future epicentrum d ≤ 130 km;

- increase in radon emission over mean values is significantly higher 3-15 days before earthquakes with magnitude 4 < M ≤ 5, with a distance of SPSC from future epicentrum d ≤ 280 km.

So, considering an earthquake with a magnitude 2 < M ≤ 3, we can propose the following model for a forecast planning, about a good and suitable distance between 2 research centers undertaking a continuous radon monitoring: 180 km.

 In the attached image:

- the circle with radium of 90 km shows the area in which the future earthquake can occur with a magnitude 2< M≤ 3.

- the circle with radium of 20 km shows the area in which the future earthquake can occur with a magnitude M ≤ 1.

The future magnitude is deduced by the difference between the maximum and minimum of radon values in a temporal period Δt comprised between a rapid increasing and a rapid decreasing, in relation to means values.

This is valid if the differences between maximum and minimum radon values are only considered as relative values for every research center.

I would like to note that, for greater magnitudes, the radon emission rises too much and the radius of the area where a possible earthquake can occur is bigger. An integration of data from different research centers and the eventual discussion about radon anomalies give good information about the future earthquakes, under the point of view of the temporal and the spatial forecast, but this study is now at the beginning, we must experimentally prove.

I don’t know if this model of mine could be good for other regions of Italy or other countries, with a different seismic classification, but it is good for the Piedmont region, in Italy. It is necessary to share the same research.

Best regards

Giovanna de Liso

Thanks for your replies.I am installing instruments for continuous monitoring of radon in soil gas for earthquake studies.

Hi

I think according to dobrovky equation for precursor appearig, you can determine earthquake magnitude of studied region and by using dob. Eq. Estimate distance between 2 station of monitoring.