H.S. Virk

Radon anomalies in soil-gas and groundwater as earthquake precursor phenomena

Abstract Earthquake-related changes in soil-gas and groundwater radon have been detected at a sensitive observation site in the Kangra valley, Himachal Pradesh, India, using both instantaneous and time-integrated techniques. The recording station at Palampur in the Kangra valley is located near the main boundary fault of the Himalayas. Eleven earthquake-related anomalies have been recorded since August, 1989 in both the soil-gas and in the groundwater simultaneously. In order to differentiate the real signal from noise, the effect of meteorological variables (soil and air temperature, rainfall, pressure, humidity and wind velocity) on radon emanation was also studied. Most of the radon anomalies are found to be correlated with earthquakes rather than to changes in meteorological conditions.

Helium/radon precursory anomalies of Chamoli earthquake, Garhwal Himalaya, India

Abstract In the Garhwal Himalaya, the Bhagirthi and Alaknanda valleys were rocked respectively by two major earthquakes; the Uttarkashi earthquake of magnitude m b =6.5, M s = 7.0 on 20 October, 1991 and the Chamoli earthquake of m b =6.8, M s =6.5 on 29 March 1999, during this decade only. Both these seismic events are associated with ongoing deformation along the main central thrust (MCT) of the Himalayas. The helium and radon anomalies on 24 and 27 March 1999, respectively, were recorded at Palampur which is about 393 km from the Chamoli earthquake epicentre. A helium/radon ratio anomaly was recorded on 20 March, 9 days before the Chamoli earthquake. The precursory nature of radon and helium anomalies is a strong indicator of the physical basis of earthquake prediction and a preliminary test for the proposed conceptual helium/radon ratio model.

Physical and chemical changes induced by 70 MeV carbon ions in polyvinylidene difluoride (PVDF) polymer

Abstract Physical and chemical changes induced by 70 MeV carbon ions ( 12 C 5+ ) have been investigated in bulk polyvinylidene fluoride (PVDF) polymer. The induced changes have been studied with respect to their optical, chemical and structural response using UV-visible, FTIR and XRD techniques. The ion fluences ranging from 2.5×1011 to 9×10 13 ions cm −2 have been used to study the irradiation effects. It has been observed that at the fluence of 9×10 13 ions cm −2 the PVDF sample became brittle and practically it was not possible to handle it for any further measurements. The recorded UV-visible spectra show that the optical absorption increases with increasing fluence, indicating maximum absorption at 200 nm. An interesting feature of UV-visible spectra is that dips change into peaks and vice versa with increase of fluence. In the FTIR spectra, development of new peaks at 1714 and 3692 cm −1 along with disappearance of peaks at 2363 and 3025 cm −1 and shifting of peak at 2984–2974 cm−1 have been observed due to high energy irradiation, indicating the chemical changes induced by 12 C 5+ . The diffraction pattern of PVDF indicates that this polymer is semi-crystalline in nature; a large decrease in the diffraction intensity indicates decrease in crystallinity. Increase in crystallite size has also been observed due to heavy ion irradiation.

Physical and chemical response of 70 MeV carbon ion irradiated Kapton-H polymer

Abstract Physical and chemical response of 70 MeV carbon ion irradiated Kapton-H polymer has been studied by using UV-visible, FTIR and XRD techniques. The ion fluences ranging from 9.3×10 11 to 9×10 13 ions cm −2 have been used. Recorded UV-visible spectra clearly show a decrease in absorption initially with fluence, but for the higher fluences it shows a recovery characteristic. A decrease in band-gap energy of 0.07 eV was observed. The FTIR analysis indicated the high resistance to radiation induced degradation of polymer. The diffraction pattern of Kapton-H indicates that this polymer is semi-crystalline in its nature. In case of irradiated one, there was an average increase of crystallite size by 20%, but diffuse pattern indicates that there was a decrease in crystallinity, which may be attributed to the formation of complex structure induced by the cross-linking of the polymeric chains.

Exhalation rate study of radon/thoron in some building materials

Abstract Indoor radon/thoron have been recognised as one of the health hazards for mankind. Common building materials used for construction of houses, which are considered as major sources of these gases in indoor environment, have been studied for exhalation rate of radon/thoron. ‘Can’ technique using plastic track detector LR-115 type-II has been used for measurement. Exhalation rates for radon and thoron have been found to be varying from a minimum value of 0.024 and 29.4 Bq m −2 h −1 for cement plastered brick to a maximum value of 0.16 and 692.2 Bq m −2 h −1 for unfired brick, respectively. Exhalation rate for thoron has been found to be several times higher than that for radon. Measured exhalation rates for thoron indicate significant presence of thoron in indoor environment which is also supported by indoor measurements of thoron and its progeny.

Relationships between radon anomalies and seismic parameters in N-W Himalaya, India

Abstract Radon data accumulated during 1992–1999 in the grid (30–34°N, 74–78°E) in N-W Himalaya have been anlaysed vis a vis seismic data recorded in the same area, supplied by Indian Meteorological Department (IMD) network. In general, there is a positive correlation between the total radon emission and the microseismicity in the area under investigation. The earthquake magnitude has moderate positive correlation with epicentral distance and low positive correlation with amplitude of radon precursory signal, whereas both show low negative correlation between them. Empirical scaling relations are proposed using the best fit straight line from the log-linear graphs between magnitude of the events and log of the product of amplitude of radon anomaly and epicentral distance. The error between the recorded and calculated magnitude is also taken into account. The error range is higher at lower epicentral distances and magnitudes, showing that the local geology and tectonics have predominant influence on radon signals.

Effects on insulators of swift-heavy-ion irradiation: ion-track technology

Polymers (CR-39, SR-86 and Makrofol-KG) and glasses (soda lime and barium phosphate) were irradiated using ions from the 15UD Pelletron at the NSC, New Delhi. The beam energy was fixed at 60 MeV and the fluence was varied in the range -. Irradiation effects were studied using UV-visible and IR spectroscopic techniques. For all the polymer targets there was an increase in absorption due to irradiation mainly in the shorter wavelength region. The change in chemical behaviour of bulk samples is studied by the etching technique. Annealing effects are observed in Makrofol-KG after 75 min heating at C. There is no appreciable change in the optical properties of glasses studied with ion doses in the range -. The morphology of heavy-ion latent tracks in insulators is revealed by atomic force microscopy. The applications of ion-track filters produced by swift heavy ions in thin polymer films are also discussed.

Helium=radon precursory signals of Chamoli Earthquake, India

The Bhagirthi and Alaknanda valleys of Garhwal Himalaya, were rocked, respectively, by two major earthquakes: the Uttarkashi earthquake of magnitude m b = 6.5, M s = 7.0 on October 20, 1991 and the Chamoli earthquake of m b = 6.8, M s = 6.5 on March 29, 1999, during this decade. Both these seismic events are associated with ongoing deformation along the main central thrust of the Himalayas. Helium and radon anomalies on March 24 and March 27, 1999, respectively, were recorded at Palampur which is about 393 km from the Chamoli earthquake epicentre. A He/Rn ratio anomaly was recorded on March 20, 9 days before the Chamoli earthquake. The precursory nature of radon and helium anomalies is a strong indicator of the physical basis of earthquake prediction and a preliminary test for the proposed conceptual He/Rn ratio model.

Radon, helium and uranium survey in some thermal springs located in NW Himalayas, India: mobilization by tectonic features or by geochemical barriers?

Radon, helium and uranium measurements have been carried out in hot water springs in the Parbati and Beas valleys of Himachal Himalaya. Most of these hot springs are known as famous pilgrimage centers. The activity of dissolved radon in the liquid phase is found to vary widely, by an order of magnitude, between 10 and 750 Bq L(-1), whereas, the dissolved helium content in these thermal springs varies between 10 and 100 ppm. The uranium contents are low and vary from <0.01 to 5 microg L(-1). The measured values of radon, helium and uranium are possibly controlled by structural geology, namely the presence of pervious fault systems, and by the lithology of the leached host rocks. Redox-potential geochemical barriers cause the mobilization of uranile ions in solution (UO2+); the most plausible hypothesis is when the conditions are oxidising, confirming the importance of physico-chemical conditions up to the supergenic environment, to control the fluid geochemistry of the U-He-222Rn system. Some evidence is available from both geothermometric considerations and geochemical data which will be reported elsewhere, whereas the present study is focused on U decay series-noble gas geochemistry. The first analysis of collected 3He/4He data is consistent with a crustal signature at the studied thermal springs.

Radon monitoring in groundwater of some areas of Himachal Pradesh and Punjab states, India

Radon measurements have been carried out in groundwater of Himachal Pradesh and Punjab states, India. Radon concentration values in potable water show a wide range of variation from source to source and from place to place. Generally, radon concentration values in thermal springs groundwater have been found to be higher than the values from other sources.