**6.2 India**

154 Earthquake Research and Analysis – Statistical Studies, Observations and Planning

The first evidence of radon in groundwater as precursor of earthquakes was observed in Tashkent (*Ulomov, 1967*). The author observed that the radon concentration in a spring near

As already cited, studies performed by *Hatuda (Hatuda 1953),* at an active fault zone evidenced anomalous radon concentration before the strong earthquake (M=8) of Tonankai. Radon anomalies were recorded before the Nagano Prefecture earthquake (M= 6.8) on September 14, 1984 (*Hirotaka et al., 1988*). The authors observed a gradual increase in radon counts three months before the quake and a remarkable increase two weeks before

For about twenty years an extensive network of groundwater radon monitoring has been operated mainly by the University of Tokyo and the Geological Survey of Japan for the purpose of earthquake prediction in eastern Japan. In figure 1. a significant example of radon anomaly is reported (*Igarashi et al., 1995)*. The authors performed radon concentration analysis in a well 17 m deep from November 1993 to March 1995 and observed stable radon concentration of 20 Bq/l at the end of 1993. The radon concentration started to increase gradually from October 1994 reaching 60 Bq/l on November 1994, three times that in the same period one year before. Furthermore, a sudden increase of radon concentration, recorded on 7 January was followed by a sudden decrease on 10 January, 7 days before an earthquake of magnitude 7.2. After the earthquake, the radon concentration returned to the pre-October 1994 levels. The main result of this example is that it is possible to observe strange behavior before an anomaly. This, for instance, as in this case, must be preceded by a continuous increasing in the background level till its manifestation. Naturally it depends

Fig. 1. Radon concentration data at the well in the southern part of Nishinomiya city, Japan

Afterward many studies have been performed about radon anomalies and earthquakes. In the following some examples are reported on ground radon monitoring in the most

Tashkent increased constantly before the M=5.2 earthquake on April 15, 1966.

seismic regions in the world.

on the geodynamical evolution of the area

[From . *Igarashi et al., 1995*]

**6.1 Japan** 

the shock.

In Bhatsadam, Maharashtra, India, major earthquakes occurred during August 1983 - July 1984. In that region radon concentration was measured by *Rastogi et al.(1986).* They found an increase in radon concentration during March–April 1984 when seismicity was high enough. Precursory phenomena of radon in earthquake sequence were observed by *Rastogi et al. (1987)* and by other groups at the Osmansagar reservoir, Hederabad, India during January– February, 1982 (*Rastogi et al.,1987*). An earthquake with a magnitude of 3.5 occurred on January 14, 1982 with subsequent seismic events. There was an increase of radon concentration in soil gas during February due to those high seismic activities.

*Singh et al. (1991)* performed a daily radon monitoring in soil-gas in Amritsar from 1984 to 1987. They recorded radon anomalies before different earthquakes: June 1988 (M=6.8); April, 26, 1986 (M=5.7); July 1986 (M=3.8); Kangra earthquake March 1987 (M=7) and May 1987 (M= 5).

*Virk and Singh (1994)* carried out daily measurements of radon in soil-gas and groundwater at Palampur since 1989 and radon anomaly was recorded simultaneously in both soil- gas and groundwater. Weekly integrated data also showed abnormal radon behaviour during first week of October, 1991 at different recording stations. These recorded anomalies were correlated with an earthquake of magnitude 6.5 occurred in Uttarakashi area in October 1991.

### **6.3 Syria**

*Al-Hilal et al. (1998)* recorded groundwater radon data for two years, during 1993 and 1994 at monthly intervals, from two selected monitoring sites of the northern extension of the Dead Sea Fault System. The results showed that measured radon concentrations fluctuate around the mean value, showing some variations with peak values, about two or three times the mean value, preceding some seismic events. It is possible to consider those anomalies related to changes in crustal strain and thereby to indicate a probable relation with the local seismicity. Nevertheless, the authors conclude that this does not necessarily means that it is possible to relate univocally these radon peaks to seismic event occurrence, but rather, it may indicate the possibility of using groundwater radon variations as a useful tool.

#### **6.4 Turkey**

In soil radon gas was monitored by *Friedmann et al. (1988)* in a network of ve monitoring sites along 200 km at the North Anatolian Fault Zone, Bolu. They observed an increase in radon concentration during the strong earthquake (M=5.7) on July 5, 1983. In order to search some relation between earthquakes and radon concentration variations, more recently *Inceoz et al (2006)* performed a radon investigation at the North and East Anatolian fault system. They found that radon anomaly was quite signicant in particular over the fault line but not away from this line.

Also the Aksehir fault zone was investigated, by *Baykara and Dogru (2006)* and *Yalim et al. (2007),* trough radon measurements in well water. Although the observed radon levels could be related to several seismic activity that at the fault region occurred with high magnitude, the authors did not infer correlation between seismic activity and radon concentration.

Radon concentration in thermal water was investigated by *Erees et al. (2006,2007)* at two thermal springs at the Denizli basin site and signicant radon anomalies were observed before earthquakes with magnitude between 3.8 and 4.8.

Radon as Earthquake Precursor 157

It was observed that, as well as the radon raises the earthquake daily rate and strain release

A radon anomaly was recorded before the November 3rd event (M= 3.5), with epicentral zone close (less than 1 km) to the *Vena* Station (NE station), also associated to evident soil

Fig. 3. Radon concentration (black line), daily earthquakes rate (black column bar) and strain

More recently a systematic radon investigation was extended to fault systems, in particular the Pernicana fault, one of the more active etnean fault, was chosen as first monitoring area. In particular, two different horizontal profiles, orthogonally to the main fault plane, were investigated. The first one was located at 1400m asl, the second one at 1370m asl (*Giammanco et al, 2009*). Each profile consisted of ten measurement points where CO2 efflux values were also measured. Concentrations of 222Rn were obtained by means of three different methodologies: passive, spot and continuous. The pattern of soil 222Rn values measured in the two profiles is clearly similar: higher values were generally recorded on the up thrown side of the fault and the lowest values occurred generally close to the main fault plane. Differently to radon, higher CO2 emissions were recorded on the fault plane. This behavior can be justified by the in-soil gas transport mechanism. In particular, along the main fault plane, advective transport of deep gases (CO2, Rn) occurs because of the high ground fracturation and permeability. Near the surface, dilution of radon by CO2 prevails, thus

This kind of investigations is useful to study the dynamics of the faults and the possible

From many years a lot of efforts have been done in order to improve in-situ radon data monitoring and analysis, technical methodologies and mathematical modeling, with the aim to reinforce the link between ground radon concentration anomalies and geodynamical

release (grey histogram) measured in the period between 1st September 2002 and 30th

raise, correspondently at the eruption beginning.

November 2002 (Vena station).[*Immè et al., 2005*]

producing lower radon values.

earthquake mechanisms.

**7. Conclusion** 

fractures.

#### **6.5 Italy**

In the last ten years systematic studies on Radon as precursor of geophysical events have been carried out on Mt. Etna since 2001 ( *Immè et al, 2005; Immè et al. 2006a, Immè et al, 2006b; La Delfa et al. 2007; La Delfa et al., 2088; Morelli et al. 2006, Morelli et al., 2011*). In particular two sites were investigated among the cropping up structural discontinuities, which lie along the NE-SW direction through the volcano. One site (*Biancavilla*) is in the SW flank, while the other one (*Vena*) is in the NE flank (circles in fig.2). Continuous monitoring was performed by using active systems with time resolution of 10 min. Capillary probes inserted into the soil at one meter depth, allowed to reduce influence from the meteorological parameters that were measured too.

Fig. 2. Mt. Etna map– Circles indicate the sites where devices for continuous in soil gas Radon monitoring were positioned

Several studies conducted in tectonic areas evidenced relation to earthquakes of magnitude bigger than 3 (*Igarashi et al., 1995; Virk et al., 1994, Al-Hilal et al., 1998*). The etnean area is characterized by a big number of earthquakes, up to about thousands per day before an eruptive period (*Benina et al,1984; Patanè et al, 1995*), but with low magnitude (< 3) and rarely they exceed magnitude 4. Moreover Mt. Etna has a very complex structure, due to the occurrence of both tectonic and volcanic phenomena. Major results have been obtained respect to a possible link between radon concentration and volcanic activity. Nevertheless, some relations were also observed with seismic events as reported by *Immè et. al, 2005*, the data are referred to the period 2001-2002. Radon concentration values started to increase the 27th of October 2002, reached the maximum the 1st of November 2002 and the minimum the 3rd of November 2002. During this period several earthquakes of magnitude higher than 3 occurred, some of them reached values up to M= 4.5 (29/10/02 time 09:02:00 epicentral area of *Santa Venerina*).

In the last ten years systematic studies on Radon as precursor of geophysical events have been carried out on Mt. Etna since 2001 ( *Immè et al, 2005; Immè et al. 2006a, Immè et al, 2006b; La Delfa et al. 2007; La Delfa et al., 2088; Morelli et al. 2006, Morelli et al., 2011*). In particular two sites were investigated among the cropping up structural discontinuities, which lie along the NE-SW direction through the volcano. One site (*Biancavilla*) is in the SW flank, while the other one (*Vena*) is in the NE flank (circles in fig.2). Continuous monitoring was performed by using active systems with time resolution of 10 min. Capillary probes inserted into the soil at one meter depth, allowed to reduce influence from the meteorological parameters

Fig. 2. Mt. Etna map– Circles indicate the sites where devices for continuous in soil gas

Several studies conducted in tectonic areas evidenced relation to earthquakes of magnitude bigger than 3 (*Igarashi et al., 1995; Virk et al., 1994, Al-Hilal et al., 1998*). The etnean area is characterized by a big number of earthquakes, up to about thousands per day before an eruptive period (*Benina et al,1984; Patanè et al, 1995*), but with low magnitude (< 3) and rarely they exceed magnitude 4. Moreover Mt. Etna has a very complex structure, due to the occurrence of both tectonic and volcanic phenomena. Major results have been obtained respect to a possible link between radon concentration and volcanic activity. Nevertheless, some relations were also observed with seismic events as reported by *Immè et. al, 2005*, the data are referred to the period 2001-2002. Radon concentration values started to increase the 27th of October 2002, reached the maximum the 1st of November 2002 and the minimum the 3rd of November 2002. During this period several earthquakes of magnitude higher than 3 occurred, some of them reached values up to M= 4.5 (29/10/02 time 09:02:00 epicentral area

**6.5 Italy** 

that were measured too.

Radon monitoring were positioned

of *Santa Venerina*).

It was observed that, as well as the radon raises the earthquake daily rate and strain release raise, correspondently at the eruption beginning.

A radon anomaly was recorded before the November 3rd event (M= 3.5), with epicentral zone close (less than 1 km) to the *Vena* Station (NE station), also associated to evident soil fractures.

Fig. 3. Radon concentration (black line), daily earthquakes rate (black column bar) and strain release (grey histogram) measured in the period between 1st September 2002 and 30th November 2002 (Vena station).[*Immè et al., 2005*]

More recently a systematic radon investigation was extended to fault systems, in particular the Pernicana fault, one of the more active etnean fault, was chosen as first monitoring area. In particular, two different horizontal profiles, orthogonally to the main fault plane, were investigated. The first one was located at 1400m asl, the second one at 1370m asl (*Giammanco et al, 2009*). Each profile consisted of ten measurement points where CO2 efflux values were also measured. Concentrations of 222Rn were obtained by means of three different methodologies: passive, spot and continuous. The pattern of soil 222Rn values measured in the two profiles is clearly similar: higher values were generally recorded on the up thrown side of the fault and the lowest values occurred generally close to the main fault plane. Differently to radon, higher CO2 emissions were recorded on the fault plane. This behavior can be justified by the in-soil gas transport mechanism. In particular, along the main fault plane, advective transport of deep gases (CO2, Rn) occurs because of the high ground fracturation and permeability. Near the surface, dilution of radon by CO2 prevails, thus producing lower radon values.

This kind of investigations is useful to study the dynamics of the faults and the possible earthquake mechanisms.

#### **7. Conclusion**

From many years a lot of efforts have been done in order to improve in-situ radon data monitoring and analysis, technical methodologies and mathematical modeling, with the aim to reinforce the link between ground radon concentration anomalies and geodynamical

Radon as Earthquake Precursor 159

Gauthier, P-J. and Condomines, M. (1999). 210Pb - 226Ra radioactive disequilibria in recent lavas

Giammanco, S., Immè, G., Mangano, G., Morelli, D., Neri, M. (2009). Comparison between

Hauksson, E., Goddard J.G (1981). Radon earthquake precursor studies in Iceland. *J.* 

Hatuda, Z. (1953). Radon content and its change in soil air near the ground surface. *Memoirs* 

Hirotaka, U., Moriuchi, H., Takemura, Y., Tsuchida, H., Fujii, I., Nakamura, M. (1988).

Igarashi, G., Saeki, S., Takahata, N., Sumikawa, K., Tasaka, S., Sasaki, Y., Takahashi, M.,

Imamura, G. (1947). Report on the observed variation of the Tochiomata hot spring immediately before the Nagano earthquake of july 15, 1947*, Kagaku*, 11, 16-17 Immè, G., La Delfa, S., Lo Nigro, S., Morelli D., Patanè, G. (2005). Gas Radon emission related to geodynamic activity of Mt. Etna. *Annals of Geophysics*, 48 N.1, 65-7. Immè, G., La Delfa, S., Lo Nigro, S. , Morelli D., Patanè, G. (2006a) Soil Radon concentration

Immè, G., La Delfa, S., Lo Nigro, S., Morelli D., and Patanè, G. (2006b). Soil Radon

Inceoz, M., Baykara, O., Aksoy, E., Dogru, M. (2006). Measurements of soil gas radon in

La Delfa, S., Immè, G., Lo Nigro, S., Morelli, D., Patanè, G., Vizzini, F. (2007) Radon

La Delfa, S., Agostino, I., Morelli, D., Patanè, G. (2008). Soil Radon concentration and

Martinelli, G. (1992). Fluidodynamical and chemical features of radon 222 related to total

Morelli, D., Immè, G., La Delfa, S. , Lo Nigro, S., Patanè, G. (2006). Evidence of soil Radon as tracer of magma uprising at Mt. Etna. *Radiation Measurements* Vol. 41, 721-725

King, C.Y. (1978). Radon emanation on San Andreas Fault. *Nature*, Vol. 271, 576-519.

*Advisory Group Meeting held in Vienna, 9-12 September 1991*, 48-62.

*of the College of Science*, University of Kyoto, Series B 20, 285–306.

*Geophys. Res.* , Vol.86, No. B8, 7037-7054

Merapi volcanoes. *Earth and Planetary Science Letter,* Vol. 172, 111-126.

9410.

1–2, 147–152.

624-629.

Vol. 42, 1404-1408

*Science* Vol. 269, 60-61.

*Measurements* Vol.41, 241-245.

in Turkey*. Radiation Measurements* 41 (3), 349–353.

*Radiation Measurements* 43 1299- 1304.

and radon degassing: inferences on the magma chamber dynamics at Stromboli and

different methodologies for detecting Radon in soil along an active fault: the case of the Pernicana fault system, Mt. Etna(Italy). *Applied radiation and Isotopes* 67, 178 -185. Hauksson, E. (1981). Radon content of groundwater as an earthquake precursor: evaluation

of worldwide data and physical basis. *Journal of geophysical research,* Vol. 86, 9397-

Anomalously high radon discharge from the Atotsugawa fault prior to the western Nagano Prefecture earthquake (m 6.8) of September 14, 1984. *Tectonophysics* 152 No

Sano ,Y. (1995). Ground-water radon anomaly before the Kobe earthquake in Japan

and volcanic activity of Mt. Etna before and after the 2002 eruption. *Radiation* 

monitoring in NE flank of Mt. Etna (Sicily), *Applied Radiation and Isotopes,* Vol.64,

active fault systems: a case study along the North and East Anatolian fault systems

measurements in the SE and NE flank of Mt. Etna (Italy). *Radiation Measurements*,

effective stress variation at Mt Etna (Sicily) in the period January 2003-April 2005

gases: implications on earthquakes prediction topics. IAEA-TECDOC-726 Isotopic and geochemical precursors of earthquakes and volcanic eruptions *Proceedings of an* 

events. Measurements of radon gas in soil and in ground water have been carried out all over the world and the results seem to indicate the radon as a good indicator of crustal activity such as earthquakes. However, the current literature describing the possible correlation between radon levels and earthquake activity uses such qualifying and caution words as possible, apparent, limited, could, sometimes, may be, and so on.

It is clear that in some cases there are precursor changes in radon levels, but that the causal relationship or mechanism relating these to earthquake activity is not yet well understood. Thus, even if some results seem to suggest that geodynamical events could influence radon concentrations, however, because of the complexity of its transport mechanism, the correlation needs more investigations in order to clearly and firmly established it.

Further contributions can be obtained from more extended continuous data recording, in particular near active faults, and from the comparison with other earthquake precursors.

#### **8. References**


events. Measurements of radon gas in soil and in ground water have been carried out all over the world and the results seem to indicate the radon as a good indicator of crustal activity such as earthquakes. However, the current literature describing the possible correlation between radon levels and earthquake activity uses such qualifying and caution

It is clear that in some cases there are precursor changes in radon levels, but that the causal relationship or mechanism relating these to earthquake activity is not yet well understood. Thus, even if some results seem to suggest that geodynamical events could influence radon concentrations, however, because of the complexity of its transport mechanism, the

Further contributions can be obtained from more extended continuous data recording, in particular near active faults, and from the comparison with other earthquake precursors.

Al-Hilal, M., Sbeinati, M.R. and Darawcheh, R. (1998) Radon variation and

Anderson, O.L., and Grew, P.C. (1977) Stress corrosion theory of crack propagation with

Antsilevich, M.G. (1971). An attempt to forecast the moment of origin of recent tremors of

Barsukov, V.l., Varshal, G.M., Garanin, A.B., and Serebrennikov, V.S. (1984). Hydrochemical Precursors of Earthquakes. *Earthquake Prediction, UNESCO, Paris,*169-180. Baykara, O., Dogru, M. (2006). Measurements of radon and uranium concentration in water

Benina, A., Imposa, S., Gresta, S., Patanè, G. (1984). Studio macrosismico e strutturale di due

Dobrovolsky, I.P., Zubkov, S.I., Achkin, V.I. (1979). Estimation of the size of earthquakes

Erees, F.S., Yener, G., Salk, M., Ozbal, O. (2006). Measurements of radon content in soil gas and in the thermal waters in Western Turkey. *Radiation Measurements,* 41, 354–361. Erees, F.S., Aytas, S., Sac, M.M., Yener, G., Salk, M. (2007). Radon concentrations in thermal

Friedmann, H., Aric, K., Gutdeutsch, R., King, C.Y., Altay, C., Sav, H. (1988). Radon

Friedmann, H. (1991) Selected problems in Radon measurement for earthquake prediction

application to geophysics. *Rev. Geophys. Space Phys.,* Vol. 15, 77-104.

microearthquakes in western Syria. *Applied Radiation and Isotopes* Vol.49, Nos.1-2,

the Tashkent earthquake through observations of the variation of radon. *Izvestiâ* 

and soil samples from East Antolian active fault systems (Turkey). *Radiation* 

terremoti tettonici avvenuti sul versante meridionale dell'Etna, *Atti III convegno* 

waters related to seismic events along faults in the Denizli Basin, Western Turkey.

measurements for earthquake prediction along the North Anatolian Fault Zone: a

*Proceedings of the Second workshop on Radon Monitoring in Radioprotection, Environmental and/or Earth Science*, Furlan, G. and Tommasino, L. (Ed.) World

words as possible, apparent, limited, could, sometimes, may be, and so on.

**8. References** 

pp. 117-123

*Akademii nauk Uzbekskoj* SSR 188-200.

preparation zone. *Paleoph.,*Vol.117, 1025-1044.

progress report. *Tectonophysics* 152 (3–4), 209–214.

*Measurements* 41 (3), 362–367.

*annuale del GNGTS*; 931-946

*Radiation Measurements*, 42, 80–86.

Scientific.307-316.

correlation needs more investigations in order to clearly and firmly established it.


**8** 

Ming-Ching T. Kuo

*Taiwan* 

*National Cheng Kung University* 

**Application of Recurrent Radon** 

**Precursors for Forecasting Local Large and Moderate Earthquakes** 

Measurement of radon-222 in groundwater has been frequently used in earthquake prediction (Igarashi et al. 1995; Liu et al. 1985; Noguchi & Wakita 1977; Teng, 1980; Wakita et al. 1980; Kuo et al. 2006, 2010a, 2010b). According to a worldwide survey (Hauksson 1981; Toutain & Baubron 1999), more than 80 % of radon (Rn-222) anomalies associated with earthquakes show increases in radon concentration precursor to a rupture while a few anomalies manifested decreases in radon. The purpose of this chapter is to provide a practical guide of monitoring groundwater radon for the early warning of local disastrous earthquakes. In this chapter, methods of monitoring groundwater radon including procedures of sample collection and radon determination will be addressed. The following sections outline suitable geological conditions to consistently catch precursory declines in groundwater radon, in-situ radon volatilization mechanism for interpreting anomalous decreases in groundwater radon prior to earthquakes, and mathematical model for quantifying gas saturation developed in newly created cracks preceding an earthquake. Case studies are provided to illustrate the application of recurrent radon precursors for

Accurate sampling for radon measurements depends on appropriate monitoring wells. Because radon concentration in groundwater relates to emanation rates of geological layers, representative sampling must be from properly constructed wells. A submersible pump is commonly used in monitoring wells for groundwater sampling except artesian wells. Every sampling starts with flushing the stagnant water in the well and especially in the screen zone. Inadequate purging can be a major source of error, because the water sample is a mixture of stagnant water from the well bore, pore water from the filter gravel and groundwater influenced by the natural emanation rate of the aquifer. Fig. 1 shows the radon concentration in the well discharge during continuous sampling in a monitoring well. During the first period of flushing, the radon concentration of the water samples is practically zero and then increases rapidly to 529 pCi/L. The mean radon concentration measured for this monitoring well was 529 ± 19 pCi/L (eleven samples). A minimum of 3

well-bore volumes was purged before taking samples for radon measurements.

**1. Introduction** 

forecasting local large and moderate earthquakes.

**2. Sample collection radon determination** 

