Responses of Radon Anomaly Prior to Earthquake: A Short Review

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 7, Issue 2, February 2017)

86

Responses of Radon Anomaly Prior to Earthquake: A Short

Review

Pranab Hazra

1

, Moumita Banerjee

2

, Shreya Chatterjee

3

1,2,3

Department of Electronics and Communication Engineering, Narula Institute of Technology, Kolkata-700109, India

Abstract— Prediction of earthquake which is known as earthquake precursors has been started many years ago using different geophysical process. ELF-VLF-ULF signals have an important role for predicting earthquakes but now some

geochemical process also introduced as earthquake

precursors. Radon (222Rn) is the main geochemical

phenomena which has contribution to the process of earthquake generation. Prediction of earthquake with respect to location, magnitude and time is still difficult. The

radioactive gas (222Rn) generation from the transformation of

(226Ra)in the decay of(238U).Radon gas monitoring is relatively

inexpensive and its change can be monitored with short-term changes in radon concentration in the earth. Emanation of

Radon depends of (226Ra)content and the size of mineral grain

size. Due to some deformation in earth’s crust the stress and strain developed which leads to changes in radioactive gas emission.

From earth crust there is an emanation of radon (222Rn)

which creates radon anomalies during pre-seismic period. Emanation of radon gas is the result of ion-molecular reaction (pulinets 2004). The emitted gas helps to form ground plasma. The plasma formed by bunching the ions which are generated due to attachment of water.

In the pre-seismic time numbers of gases like CO2 and

other gases are released and generates the air motion near the ground surface. So the ions losses their stability and this intensive air motion breaks the plasma and generates the huge

number of ions ). The vertical electric

field anomaly is generated by charge separation processes which tells that the lithosphere-atmosphere-ionosphere coupling process is acts as an indicator for predicting the seismic activity.

The lithosphere-atmosphere-ionosphere coupling process has been reported in this paper. Present research focuses on

three main areas: the physical mechanism, main

phenomenological features of ionospheric variations

associated with earthquakes (Pulinets 2004), and their statistical properties permitting use of them in practical applications (Omori et al., 2007).

According to the non-stationary frenkel model of the generator in respect of created spikes nature of the local electric field with time scale of 1-100min, are suggested the cause of an aerosol cloud, velocity increase of ionisation and also upward air flow near seismic fracture region. Increases of ionization intensity of the atmosphere should be observed before an earthquake (Liperovsky et al., 2008).

Keywords—Earthquake, Radon, Thermal Anomalies, Humidity,LAI Coupling, ELF-VLF-ULF.

I. INTRODUCTION

This document is template. We ask that authors follow some simple guidelines. In essence, we ask you to make Some parameters are required for the prediction of earthquakes in present status of science. As well as for past decades the prediction is improved by measuring certain rare gases and prediction will much batter by measuring the geochemical and geophysical parameters (Kumar et al., 2012). Radon is one of the rare radio-active gases which should be taken into consideration for prediction. Before the occurrence of large earthquake changes in subsurface radon concentration have been observed so radon is act as an indicator for earthquake prediction (Hartmann and Levy, 2005; Italiano et al., 2008; Walia et al., 2009). The radon emission from the litosphere is due to the movement of tectonic plates and also on compaction, porosity and fractural faults(Choubey et al., 1997; Walia et al., 2005a). Ionospheric variation of ELF and VLF signals have an important role related to seismic event prediction so researchers are attracted towards the ionospheric perturbations (Hayakawa et al., 2004; Pulinets and Boyarchuk, 2004). The radio-active gas appearing at the surface from the fractural portion of lithosphere starts to ionize the particles which affects the ELF and VLF signals and relate to seismo-ionospheric disturbances which are treated by considering the interaction among the lithosphere, atmosphere and the ionosphere, i.e., the LAI coupling (Hayakawa et al.,2004; Kamogawa, 2006).

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International Journal of Emerging Technology and Advanced Engineering

87 It was investigated by numbers of workers like

(Trakhtengertz, 1989, 1992, 1994; Sorokin and

Jashtshenko, 2000).Radioactive dust greatly increase the atmospheric electric field before the strong earthquakes in fractural regions. The emission of good amounts of the metallic aerosols like-Zn,Pb,Ni,Rn occurred in the near-earth atmosphere through the faulty region.

II. PLATE MOVEMENT

In most of the cases earthquakes happen in a region of 'The Ring of Fire’. The only reason behind this is many of Earth's tectonic plates come together here. The plates are moving and pulling together in stuck condition. Suddenly it happens that one plate subducting beneath the other (Fig. 1) or pulling becomes too much so that the plates suddenly break free from each other and the tension send through the ground in all directions resulting earthquakes.

Fig.-1 Structure of plates during earthquake

As Nepal is at the junction of the Indian and Eurasian plates it is very sensitive to earthquake. Due to the collision plate the Himalayas were created millions of years ago, still Indian plate moving and push the mountains a few millimeters higher every year.

The Nepal Earthquake (M 7.8) on April 25, 2015 happened due to slip on the segment of the Main Himalayan Thrust (MHT), the segment of the Himalaya displaced by (4.8 ± 1.2) meter south-westward over the India plate (Mitra et al., 2015). In this earthquake the Himalayas are pushed by the Indian plate as it pushes against the Eurasian plate as shown in Fig.-2.

Fig.2Subduction of India plate below the Eurasian Plate

Fig.3- Subduction of India plate beneath Sunda and Eurasian Plate

Due to reverse faulting at an intermediate depth of india plate and sunda trench the myanmar earthquake occurred on april 13,2016.The india plate moves towords the northeast of sunda trench with a velocity of 44-49 mm/yr.

III. MEASURING PROCESS OF RADON

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International Journal of Emerging Technology and Advanced Engineering

88 Fine powder of samples are placed in cylindrical cans having dimensions and the alpha sensitive LR-115 are fixed at the bottom of the lid so that the sensitive side of the detector faced the sample(Kumar et al., 2015).

IV. RADON EFFECTS ON ATMOSPHERIC PARAMETERS

A. Anomalous Electric Field Effects in the Ionosphere Anomaly observed in the ionosphere when a vertical electric field generated due to radon emissions and propagate through E-region of the ionosphere (Liperovsky et al. 2000). The shape of the irregularity within the ionosphere is determined by the shape of the area generating the electric field. An erratic E-layer will be formed in the ionosphere over the area of earthquake preparation where the anomalous electric field is directed down to the ground surface. This has been tested experimentally by Ondoh and Hayakawa (1999) and theoretically considered by Kim et al. (1994) as well.

In the F-region two main effects should be noted. In the area of maximal conductivity due to Joule heating acoustic gravity waves will be generated giving rise to the small-scale density irregularities within the ionosphere (Hegai et al. 1997). The electron density oscillations at different levels of ionosphere are supported by radio-physical techniques and optical monitoring of the ionosphere, it was also supported by the experimental data (Chmyrev et al.1997).

B. Effects in the Magnetosphere

In magnetosphere there was also irregularities along the geomagnetic field lines which creates field associated ducts (Kim and Hegai 1997; Sorokin et al. 2000;McCormick et al. 2002). As a result the levels of VLF emission within the magnetic tubes along the areas of anomalous electric field generation (Shklyar and Nagano 1998).The shape of the modified area at magnetospheric heights will not be exactly the same as that on the earth surface due to plasma drift

processes, but elongated in the zonal direction

proportionally at approximately 1:3 for the meridional and longitudinal sizes of the modified volume of the magnetosphere (Larkina et al. 1989; Kim and Hegai 1997). As a result of the cyclotron interaction of VLF emissions with radiation belt particles their stimulated precipitation starts.

The precipitating particles associated with earthquake preparation were also registered on many satellites (Galper et al. 1995).

C. Effects in D-region of the Ionosphere

As a final point the complex chain of processes in the atmosphere, ionosphere, and magnetosphere results in precipitating particles producing ionization of the lower ionosphere. Due to the ionization electron density increases in the D-region of the ionosphere and the ionosphere height goes down (Kim et al. 2002). This lowering changes the condition of radio wave propagation in different frequency bands from VLF up to VHF. Anomalous effects of radio waves propagation before strong earthquakes have been registered experimentally (Gufeld et al. 1992, Biagi et al. 2001, Kushida and Kushidhha 2002).

V. EFFECTSOFTHETHERMALANOMALIESAND

LATENTHEAT

Thermal anomalies have a greater impact on the atmosphere a few days before the earthquake. The changes due to the thermal anomalies can be observed not only the surface temperature, but also other atmospheric parameters, for example, humidity (Tronin 2002). A change in one of these parameters immediately leads to a change in the others. Another important parameter is latent heat which is closely related with water content in the air and processes of water evaporation. In the earthquake preparation zone the anomalous surface latent heat increase takes place within a time interval several days before a strong earthquake. There exists a strong effect of the strong electric field action on water evaporation properties in the earthquake preparation zone.

Now we can conclude that to change the

thermodynamics of the lower atmospheric layers at least two processes are essentially required. They are the action of the ionization source and strong electric fields, and that these processes are the most probable sources of observed thermal and surface latent heat flux anomalies before strong earthquakes.

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89

Fig 4 Temperature (solid line) and Humidity (Dashed line)variation for Michoacan earthquake M8.1 Sept. 19, 1985.

Soil moisture, rainfall, temperature, barometric pressure etc, are also the responsible meteorological parameters with seismic activities for radon anomalies. Then a controversy created for the reason of small earthquakes that is it caused for seismic activities or for the changes that happened in the atmosphere.

In the radioactive transformation of radium some fraction of radon atoms created. Crack & faults are the mediums by which radon atoms are come out in the earth surface by the processes of diffusion and advection. The radon diffusion is described by Fick’s law. Mathematical equation of Fick’s Law

Where J is the “diffusion flux”, D is the “diffusion coefficient”, is the concentration of which the dimension is amount of substance per unit volume, x is position. Different media are responsible for gas diffusion from which porous media one of them. Diffusion is mainly done in capillaries and small-pored rocks. Radon come to the earth surface with a very low velocity which is ≤ 10 -3 cm/s. Diffusion coefficient is varied with the volume through which gas diffuses is reduced and the average path length between two point is increased. Carrier gases like- Co2, CH4 ,H2 and rare gases like- He, Rn become mixed up and formed a mixture gas which is called “geogas”. There is present two types of porous media by which this geogas is transported.

Gas flows through an interstitial or fissure space for dry, porous or fractured media and for saturated porous media gas can transported in three ways:- 1) By ground water, 2) By displacing water, 3) By forming a bubble flow.

When a changes become in the sallow soil levels due to meteorological parameters then deeper soil levels are effected more. We can get radon in the depth of 0.8m or deeper. From meteorological effects barometric pressure and radon concentration in soil gas is inversely related. Radon concentration increased when all environmental parameters are constant but the barometric pressure decreased. When pressure increased radon is diluted to the ground like pressure, temperature is also inversely related with radon concentration [Klusman & Jaaacks 1987]. Low air temperature as compared with soil temperature during winter months radon gas is promoted to an upward movement and convection of radon occurred but during summer months soil temperature when become low and compared with air temperature the flux is become upward and then the concentration of radon is observed. Soil moisture and rainfall in the soil controlled the activities of radon through the opening of cracks in the surface. For the barometric pressure of the radon, concentration of radon in soil occur higher gas flow. Radon anomalies are connected with earthquake. For this reason there is performed several measurements, experiments and model which are help in detecting the relation of radon anomalies with earthquake. Radon transportation is done by two ways-diffusion and advection which depends on porosity and permeability of soil. A change in the strain field occurred before the earthquake as a stress is build up in the earth surface. New cracks and pathways formed under the tectonic stress which leads the change in gas transport and volatiles are rise from the layers to the surface. Several mechanisms are proposed to explain the relationship between radon anomalies and earthquake. Radon anomalies can be studied in soil gas and thermal waters, thermal waters could be much more representative of the geological environment and could be more reactive to stress/strain changes acting at depth than soil gases. In figure continuous radon concentration recorded in soil gas. Straight lines represent the mean value and two standard deviations of radon concentration.

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International Journal of Emerging Technology and Advanced Engineering

90 VI. LTHOSPHERE-ATMOSPHERE-IONOSPHERE COUPLING

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DUE TO RADON ANOMALY

Fig 5: Processes involve for generating earthquake

During any large earthquake, there will be coupling between lithosphere–atmosphere and ionosphere through some probable channels, e.g., chemical channel, acoustic channel and electromagnetic (EM) channel. From chemical channel, there will be water elevation, gas emanation/radon emanation, changes in geophysical parameters which introduce chemical/conductivity changes in air resulting in a modification of the atmospheric electric field perturbing the plasma density in the ionosphere. Acoustic channel introduces excitation of atmospheric oscillations that propagate up to the ionosphere thereby modifying the ionosphere density. EM channel is supposed to introduce VLF emission, ionizations, electric charge redistribution above the surface of the earth by which anomalous electric

field would be generated producing large-scale

irregularities. Anomalous field propagates into the inner magnetosphere and interacts with energetic particles. These particles precipitate into the lower ionosphere initiating direct heating, liberation of exo-electrons, and/or ionization of the ionosphere by seismo-ELFVLF waves. These are detected as precursors of any large earthquake of large M-value [Hazra et al., 2014]. The preseismic lithosphere-atmosphere-ionosphere coupling has been intensively discussed (Kamogawa, M., (2006) preseismic Lithosphere-Atmosphere-Ionosphere Coupling, Eos, 87, 417 & 424.).

Fig 6 Lithosphere-Ionosphere-Atmosphere coupling mechanism (http://space.geocities.jp/SeismoSTAR/LAI-Coupling.html)

VII. CONCLUSION

Lithosphere-Ionosphere-Atmosphere is linked by the emitted radioactive gasses before the earthquake. This radioactive gas generates the electric fields near the earth surface which create anomalies in the earth ionosphere region. The ELF-VLF signals are affected by this electric field which helps to predict the seismic activity. Among the radioactive gasses radon is the most effective element for predicting earthquake but role of other radioactive gasses cannot be neglected. Continue radon measurement near to the earthquake region shows some relation with earthquake in some researches as well as fluid mechanism near the region of earthquake may also have contributions. It was demanded that radon flux generated few days before which makes air temperature to rise by releasing latent heat and humidity drops due to the condensation but it also demands a comparative study for several strong earthquakes.

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