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  • Author or Editor: R. Savastru x
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Abstract  

Due to the subcrustal earthquakes located at the sharp bend of the Southeast Carpathians, Vrancea zone in Romania has a high potential seismic hazard in Europe. Among several seismic precursors, radon anomalies in air, ground, and groundwater in the epicentral areas can be associated with the strain stress changes that occurred before and after earthquakes. In order to support this theoretical view, the main aim of this paper was to investigate temporal variations of radon concentration levels in air near the ground and in ground air by the use of solid state nuclear track detectors CR-39 and LR-115 in relation with some seismic events at two seismic stations Vrancioaia and Plostina, located in Vrancea active region. This paper reports essentially the observation of radon concentration levels in the air near the ground at 1 m height for the earthquakes that occurred during the period of November 2010–October 2011 and moment magnitudes M w in the range of
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. The average radon concentration in air above the ground measured with CR-39 detectors recorded for 1 year period in Vrancea area was 1,094.58 ± 150.3 Bq/m3 and 10 days fluctuations were placed in the range of 129 ± 40 Bq/m3 and 5,888 ± 700 Bq/m3. Also have been reported measurements of in soil radon concentrations in drill holes at 0.5 m depths during period of March 1977–October 1980, just after 4 March 1977, M w 7.4 Vrancea earthquake. The knowledge of air–ground–gas 222Rn anomalies is very important for earthquake pre-signals assessment as well as for precisely location of geologic active faults.
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Abstract  

Atmospheric radon concentration was continuously monitored in Bucharest-Magurele area both near the ground at 1 m height as well as at 10 m height. This paper presents the results of radon in air near the ground concentrations obtained during the 1 July 2010 to 1 February 2012 period by use of solid state nuclear track detectors SSNTD CR-39. The mean atmospheric radon concentration near the ground at 1 m height was found to be 360.91 ± 66.49 Bq/m3, which was about more than an order of magnitude lower than average radon concentration in range of 44.92 ± 9.94 Bq/m3 recorded for period 1 August 2011 to 20 December 2011 at 10 m height by AlphaGUARD Radon monitor. The meteorological effects on the variation of atmospheric radon concentration were discussed. The analysis of spatio-temporal variations in time series radon concentration in air near the ground is a useful tool to study geo-dynamical processes associated with seismic activity in active Vrancea zone in Romania. Taking off the variations induced by external variables, such as temperature, barometric pressure, rainfall, and other meteorological parameters, can be assessed radon anomalies due to possible tectonic movements and also can be surveyed radioactivity background in relation with nuclear emergencies.

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Abstract  

South-Eastern part of Romania has a highest potential seismic risk in Europe due to the earthquake-prone Vrancea zone placed at conjunction of four tectonic blocks in the South-Eastern part of Carpathian Arc. This paper is an attempt to analyze the development of radon pre-earthquake anomaly in relation with moderate seismic events in Vrancea area through permanent monitoring with solid state nuclear track detectors CR-39 detectors. Radon in air above the ground was measured during 1 year period (November 2010–October 2011) in four selected test sites: Vrancioaia (VRI) and Plostina (PLOR) located in Vrancea zone, and Muntele Rosu-Cheia and Bucharest. During sampling period recorded earthquakes that occurred mostly in Vrancea epicentral region were minor-moderate of moment magnitudes in range of
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. The average radon concentration in air above the ground measured with CR-39 detectors and 10 days period recorded simultaneously at all test sites, registered the following values: (1) in Vrancea area (similar in VRI and PLOR) was 1094.58 
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 150.3 Bq/m3; (2) at Muntele Rosu-Cheia seismic station measured in a mountain tunnel laboratory was 3695.91 ± 440 Bq/m3; (3) at Bucharest station was 380.53 
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 69.17 Bq/m3, and 10 days CRn fluctuations in the range of (88 
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 40 to 912
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 130 Bq/m3). Clear radon anomalies, mostly at VRI and PLOR in Vrancea epicentral area as well as at Muntele Rosu-Cheia have been measured before seven minor earthquakes which were recorded in the range of moment magnitude
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in Vrancea area. Temporal variation of radon in air near the ground have been examined in relation with meteorological parameters like as air temperature, relative humidity, air pressure and wind velocity. Permanent monitoring of radon concentration anomalies in seismic area Vrancea is an important issue as surveillance tool in the field of earthquake hazard for Romania.
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