MONITORING OF RADON AND AIR IONIZATION IN A SEISMIC … · romanian reports in physics 69, 709...

Romanian Reports in Physics 69, 709 (2017)

MONITORING OF RADON AND AIR IONIZATION

IN A SEISMIC AREA

VICTORIN-EMILIAN TOADER1, IREN-ADELINA MOLDOVAN1, ALEXANDRU

MARMUREANU1, PUSHAN KR DUTTA2, RALUCA PARTHENIU 1, EDUARD NASTASE1

1 National Institute for Earth Physics, P.O.Box MG-2, RO 077125, Magurele, Romania,

E-mails: [email protected]; [email protected]; [email protected] 2 Erasmus Post-Doctoral, Mechatronics University of Oradea,

E-mails: [email protected]; [email protected]; [email protected]

Received September 10, 2016

Abstract. Our multidisciplinary network (AeroSolSys) located in Vrancea

(Curvature Carpathian Mountains) includes radon concentration monitoring in five

stations. We focus on lithosphere and near surface low atmosphere phenomena using

real-time information about seismicity, + / – ions, clouds, solar radiation, temperature

(air, ground), humidity, atmospheric pressure, wind speed and direction, telluric

currents, variations of the local magnetic field, infrasound, variations of the

atmospheric electrostatic field, variations in the earth crust with inclinometers,

electromagnetic activity, CO2 concentration, ULF radio wave propagation, seismo-

acoustic emission, animal behavior. The main purpose is to inform the authorities

about risk situation and update hazard scenarios. The radon concentration monitoring

is continuously with 1 hour or 3 hours sample rate in locations near to faults in an

active seismic zone characterized by intermediate depth earthquakes. Trigger

algorithms include standard deviation, mean and derivative methods. We correlate

radon concentration measurements with humidity, temperature and atmospheric

pressure from the same equipment. In few stations we have meteorological

information, too. Sometime the radon concentration has very high variations (maxim

4 535 Bq/m3 from 106 Bq/m3) in short time (1–2 days) without being accompanied by

an important earthquake. Generally the cause is the high humidity that could be

generated by tectonic stress. Correlation with seismicity needs information from

minimum 6 month in our case. For 10 605 hours, 618 earthquakes with maxim

magnitude 4.9 R, we have got radon average 38 Bq/m3 and exposure 408 111 Bqh/m3

in one station. In two cases we have correlation between seismicity and radon

concentration. In other one we recorded high variation because the location was in an

area with multiple faults and a river. Radon can be a seismic precursor but only in a

multidisciplinary network. A pair of ions counters (positive and negative) work

together in few stations. The anomalies for short or long period of time should be

correlated with local environment factors (e.g. humidity).

Key words: radon anomalies, multidisciplinary monitoring, precursor phenomena,

air ionization monitoring, radon monitoring, earthquake cumulative

energy, cross-correlation.

mailto:[email protected]

mailto:[email protected]

Article no. 709 Victorin-Emilian Toader et al. 2

1. INTRODUCTION

Many applications detect events from real world that involve monitoring for

long time period. AeroSolSys network is one of them specialized in a

multidisciplinary monitoring of an active area located in Vrancea (Fig. 1) [1],

geological described in [2] and [3]. The specificity of this area is the seismicity at

depths greater than 80 km (Fig. 1 and Fig. 4) with effects at long distances.

Monitoring of gas emissions and particularly of radon aim effects on population

(lung cancer) [4–8], and the possibility of providing seismicity forecasts and reduce

risk situation and update hazard scenarios [2, 3, 9–15]. Radon (222

Rn) is a gas with

origin in radium (226

Ra) and 238

U decay chain in Earth’s crust and short half-life of

3.82 days. Its presence in air or water depends from many factors. Koike et al. [17]

demonstrate that radon is correlated with tectonic stress in faults that has like effect

the crustal deformation (micro cracks occurrence). This encourages the release of

radon from the soil surface together with air pressure, temperature, humidity,

rainfall, groundwater, and wind. AeroSolSys project measures radon in correlation

with meteorological factors, air ionization, CO2, electromagnetic field, acoustic

effects of fracturing described in this paper. Zoran et al. [2, 3] correlate the radon

concentration with seismicity in Vrancea area using CR-39 and LR-115 nuclear

track detectors in 3 location. We use a continuous monitoring (sample time 1 or

3 hours) in 5 station presented in Fig. 1. The equipment includes a barometric

pressure, temperature and humidity sensors. An on-line analysis of CO2, CH4, H2,

N2, H2S, O2, He and Ar was made in the Tekke Hamam geothermal field located

along the Eastern end of the Büyük Menderes Graben in Western Anatolia, Turkey

with a mass spectrometer [18]. We measure only the CO2 in one station but the

geochemical monitoring is a future project. Radon and CO2 are seismic precursors

and could find together in the same location. Many authors studied the radon

concentration anomalies caused by tectonic stress, earthquakes and hydro

meteorological effects. We have the possibility to make such analysis, too.

2. MONITORING NETWORK IN A SEISMIC AREA

We present a general structure of monitoring network in Fig. 1. The most

important is the position of stations from epicentral areas. Vrancea generates

important intermediate depth earthquakes in two main points: Nereju and Gura

Teghii. Panciu (PANC) is a reference station because is out from the subcrustale

seismic area.

The positions of the stations relative to the geological structure are presented

in Fig. 2. Each location is under the effect of a fault. This is important for aerosol,

ions, radio ULF wave propagation, radon and cloud monitoring. Every station

sends automatically information to NIEP center (National Institute for Earth

3 Monitoring of radon and air ionization in a seismic area Article no. 709

Physics from Romania) where a server saves, displays and makes a power

spectrum analysis in real time.

Fig. 1 – Multidisciplinary monitoring network in Vrancea area, Romania seismicity.

Fig. 2 – Monitoring network, main faults

(map by C. Dinu, V. Raileanu et al. CEEX 647/2005).


We made a geological investigation for every station (Fig. 3). The

particularity of Vrancea area is presented in Fig. 4.

Fig. 3 – Electrical tomography, Plostina site.

Fig. 4 – Vrancea hypocenter distribution.

Comparing Figs. 2 and 4 is not obvious a relationship between the

distribution of epicenters and faults at a depth of more than 80 km. Each station

position is on a fault but what we measure is an indirect effect of an activity at high

depth. Radon monitoring is indoor in air near the ground. In this case atmospheric

air currents can introduce errors. We use meteorological station to correct these

effects.


The equipment in each station is presented in Table 1. Every site has seismic

equipment.

Table 1

Configuration of monitoring stations

Station Location Equipment

BISR Bisoca Seismic speed-acceleration, acoustic, radio ULF, inclinometer, radon,

air temperature, pressure and humidity

LOPR Lopatari Acoustic, inclinometer, radon, air temperature, pressure and humidity

NEHR Nehoiu Seismic speed-acceleration, acoustic, ionization, meteorological station,

inclinometer, radon, air temperature, pressure and humidity

MLR Muntele Rosu Seismic speed-acceleration, acoustic, inclinometer, radon, air

temperature, pressure and humidity, magnetic field, X, Y, Z

COVR Covasna Seismic speed-acceleration, radio ULF

PLOR4 Plostina

Seismic speed-acceleration, acoustic, infrasound, meteorological

station, ionization, telluric field, air electrostatic field, inclinometer, air

-ground – borehole temperature

PLOR7 Plostina

Seismic speed-acceleration, radio ULF, video camera for clouds,

radiometer for solar direct and reflected monitoring (long and short

waves)

VRI Vrancioaia

Seismic speed-acceleration, air-ground acoustic, radio ULF, infrasound,

ionization, telluric field, solar radiation (pyranometer), ground

temperature, meteorological station, air electrostatic field, scalar

magnetic field, video for clouds, radon, air temperature, air pressure and

humidity

ODBI Odobesti

Seismic speed-acceleration, acoustic, radio, telluric field, borehole

temperature, meteorological station, radon, air temperature, pressure

and humidity

PANC Panciu Seismic speed-acceleration, radio ULF

Radon measurements in Odobesti station had variations which are not

correlated with seismic activity. It is hard to determinate the source of anomalies in

this case. For this reason the equipment were moved in MLR location. Fluid

pressure is important in micro fracturing process. Robert A. Meyers in Extreme


Environmental Events Complexity [19] said that “crustal fluids play an important

passive role in all brittle failure models by counteracting the rock matrix stress

acting on a fracture through pore pressure”. Stuart Crampin [20, 21] consider rock

deformation (micro cracks, fracturing process) a result of pore pressure like a

source of tectonic stress. BISR and LOPR locations are in area where the

groundwater determine landslides and the radon measurements could be affected.

In PLOR we have natural springs, too. COVR and NEHR are next to rivers.

3. EQUIPMENT, DATA STRUCTURE

Fig. 5 – Ions, radon, seismic equipment.

Fig. 6 – CO2, humidity, temperature equipment.


Fig. 7 – L1, L2 data levels.

Figure 5 is an example of multidisciplinary monitoring station (NEHR). The

tectonic stress produces a degassing process that generates CO2 (Fig. 6) and radon.

There are two levels of data processing: L1 direct information from sites and L2

data corrected and packed in 24 hours files (Fig. 7).

4. METHODS

Figure 8 presents a multidisciplinary analysis (radon, meteorological

information, CO2, humidity, temperature, magnetic field and NOAA satelitare data,

ions positive and negative, atmospheric electric field [9], telluric field, and

seismicity magnitude-depth). Before 3 earthquakes (4.4R, 4.1R, 4.2R) we have

radon variation but this is not enough. The emission of radon is affected by

pressure, temperature, and humidity. A high atmospheric pressure closes the rock's

micro fractures and reduces the exhalation of gases. In Fig. 8 we observe a raining

period. The number of positive ions is higher, there are spikes on electric field, and

CO2 oscillates. In Fig. 9 we have the radon evolution in Vrancea area correlated

with global seismic energy. The method used in this picture for detecting abnormal

variations is standard deviation (+/–2σ green lines, mean red line)

[10, 16]. For MLR, NEHR and LOPR we have recorded spikes. The cause could be

the environment conditions relative to stations position. The radon detector in MLR

is in an open tunnel with a high humidity that could bring the radon. The BISR is

affected by Casin–Bisoca fault (Fig. 2). Radon could be emitted in a near place and

brought by wind. We observe the daily and seasonal variation, too.

An earthquake has an energy E corresponding to its magnitude [22]. The

effect in a location is [18]

TEEi = Ei / di2, (1)

where d is the distance to hypocenter in km2, E – the energy in Erg = 1E18.


Cumulate the effects of all magnitudes in a period of time to a location gives

the total earthquake energy (TEE). In this case we expect that 4.9R earthquake,

15/03/29, with preparation zone 127.9 km (Dobrovolsky 1979) [10] to have the

maximum effect in LOPR (epicentral distance 18.7 km) but the TEE is higher in

VRI location. We consider the case from Table 2, for a seismic analysis (period

15/01/01–16/04/29, ML > 3.6R) calculating the preparation zone and epicentral

distances from monitoring stations. In Fig. 10 we have the TEE energy for location

where we monitor the radon. Figure 11 presents the analysis of seismicity

(magnitude, depth), global seismic energy, rupture and strain for ML > 3.6R.

Fig. 8 – Multidisciplinary analysis, AeroSolSys network.


Fig. 9 – Radon evolution in Vrancea area correlated with seismicity and seismic energy.


Fig. 10 – Total earthquake energy in radon monitoring locations.

Fig. 11 – Analysis of seismicity, energy, rupture and strain, ML > 3.6R.


Table 2

Seismic analysis, preparation zone and epicentral distances from monitoring stations, ML > 3.6R

Time M H Lon Lat Prep.

Zone

DE

MLR

DE

NEHR

DE

VRI

DE

LOPR

DE

BISR

Y/M/D R km Grd Grd km km km km km km

15/01/03 4.1 78.7 26.6848 45.7782 57.9 65.8 49.4 10.3 35.0 25.6

15/01/03 3.9 138.4 26.3674 45.4843 47.5 33.0 8.5 50.8 15.6 27.6

15/01/04 4.2 119.3 26.4225 45.5605 63.9 38.1 17.8 41.4 14.9 22.4

15/01/12 4.2 18.8 27.0448 45.542 63.9 85.9 59.8 43.6 37.8 91.4

15/01/14 4.2 145.9 26.3503 45.5501 63.9 32.3 14.3 45.7 19.0 28.0

15/01/24 4.7 88.4 26.5712 45.7123 104.9 54.6 38.3 20.9 26.5 21.2

15/01/28 4.1 128.7 26.4940 45.6405 57.9 45.9 28.3 30.9 19.4 19.7

15/02/21 4.1 141.3 26.5791 45.6883 57.9 54.0 36.5 22.8 23.8 18.6

15/02/27 4.2 129.6 26.6709 45.7250 63.9 62.2 44.1 16.2 29.0 19.9

15/03/13 3.9 118 26.5517 45.5698 47.5 48.1 25.5 35.6 10.7 12.5

15/03/16 4.8 114.1 26.4214 45.5821 115.8 38.5 19.8 39.5 16.6 22.8

15/03/29 4.9 141.6 26.4579 45.6231 127.9 42.6 25.2 34.1 18.7 21.3

15/06/09 4.1 140.3 26.3444 45.5497 57.9 31.9 14.1 46.0 19.4 28.4

15/06/26 3.9 133.5 26.3853 45.5046 47.5 34.4 11.1 48.1 14.7 25.7

15/07/05 4 132.9 26.6526 45.6957 52.4 59.6 40.8 19.8 25.5 17.0

15/07/13 4.1 146.1 26.5119 45.6529 57.9 47.7 30.2 29.0 20.4 19.3

15/07/15 4 141.3 26.6281 45.6949 52.4 57.8 39.4 20.5 25.0 17.5

15/07/15 3.9 133.9 26.6241 45.6126 47.5 54.6 32.9 29.2 16.0 9.8

15/09/21 3.9 125.9 26.3903 45.4951 47.5 34.8 10.6 48.8 14.1 25.6

15/09/29 4.1 121 26.7268 45.7228 57.9 66.0 47.0 15.9 30.2 19.5

15/10/07 4.5 129.7 26.8586 45.6574 86.0 73.5 50.8 25.3 30.4 16.8

15/11/05 4 132.1 26.3553 45.5018 52.4 32.0 9.5 49.7 16.9 28.1

15/11/29 4.4 125.6 26.6777 45.7178 77.9 62.4 43.9 16.9 28.4 19.0

15/12/16 4.1 140.2 26.5507 45.6515 57.9 50.4 31.9 27.5 19.8 16.9

15/12/18 4.2 142.9 26.5487 45.6533 63.9 50.4 32.0 27.4 20.0 17.1

16/01/07 4.1 117.3 26.293 45.5232 57.9 27.4 10.7 50.9 22.2 32.6

16/03/01 4 66.5 26.9874 45.8248 52.4 89.1 69.6 20.6 50.7 37.5

16/03/18 4 117.3 26.719 45.7294 52.4 65.8 47.0 15.2 30.7 20.2

16/03/20 3.9 148.7 26.4017 45.5978 47.5 37.5 20.7 39.1 19.0 24.6

16/04/29 3.9 146.1 26.4738 45.6162 47.5 43.5 25.2 34.0 17.5 19.9


5. CONCLUSIONS

A monitoring network involves a multidisciplinary activity that highlights

the interdependence of environmental factors (air, earth) and their balance under

normal conditions. Weather or seismic events represent the point of maximum

imbalance. Electromagnetic, radon, CO2, infrasound, seismoacoustic,

air ionization and solar radiation monitoring, in correlation with global and

local environmental factors (including seismic zones), is a new approach for

atmospheric study in our area. Radon is a precursor element but only in a

multidisciplinary network. The spikes are not followed by earthquakes in 3 cases.

The positions of monitoring stations are important to get useful results. The

variations of radon from Fig. 12 (LOPR) are very high.

Fig. 12 – Lopatari radon measurements, spikes.

There is a relation with seismicity but it is not possible to make a forecast

only from this information. Others studies in Vrancea with maxim 3 stations use

plastic film detectors CR-39 [2, 3]. In this case it is impossible to detect spikes and

to trigger in real time a precursor anomaly.

Outkin et al. in Radon monitoring as a possible indicator of events analysis

the concentration of radon in many station under compression or in stretch of an


array. The magnitude in our analysis period is low (maxim 4.9R) and we measure

the radon in indoor air.

The result of AeroSolSys project is the growth of the seismic alert service

through: perfecting risk evaluation, seismic forecast, informing the decision factors

regarding the impact minimization of natural disasters and the education of the

population. The main purpose is to detect events before they occur. The papers [23]

and [24] presents complex networks for multidisciplinary observations of pre-

earthquake signals with the same goal.

Acknowledgements. This work was supported by a grant of the Romanian National Authority

for Scientific Research, Programme for research – Space Technology and Advanced Research –

STAR, project number 84/2013, AeroSolSys.

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