The effect of stress on radon emanation from rock

Holub, R.; Brady, B. H. G.

doi:10.1029/jb086ib03p01776

Cited by 108 publications

(55 citation statements)

References 10 publications

(7 reference statements)

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“…Dissolution or alteration of fresh rock surfaces could significantly increase ion concentrations present in groundwater and would be especially noticeable in well-established aquifers where older rock surfaces have been passivated by the formation of equilibrium alteration assemblages. As noted previously, laboratory studies have shown that the rate of gas release from rocks is enhanced at stress levels associated with microfracturing (HOLUB and BRADY, 1981;SOBOLEV eta/., 1984;KATOH eta/., 1985). Field investigations have reported coincident trends in regional stress changes and groundwater radon concentrations (WAKITA et a/., 1985), and in regional deformation changes and ground gas radon activities (THOMAS and KoYANAGI, 1986).…”

Section: Increased Reactive Surface Area Modelmentioning

confidence: 74%

“…More porous rocks typically show greater volume losses; this decline is irreversible and is unlikely to account for repeated precursory anomalies or cyclic chemical changes in groundwater. Investigation of gas emanation from rocks shows that gas release declines at low to intermediate stresses, due to closure of the channels through which gases escape, and only at higher stresses does gas emanation increase appreciably (HoLUB, 1981;GIARDINI et a/., 1976;HoLUB and BRADY, 1981;HONDA et a/., 1982). The latter increase is accompanied by acoustic emissions associated with micro-fracturing and is believed to be the result of new pore volume formation associated with dilatency (SOBOLEV, 1984;.…”

Section: Pore Collapse Modelmentioning

confidence: 99%

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Geochemical precursors to seismic activity

Thomas

1988

PAGEOPH

225

112

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Abstract-Studies of earthquake precursory phenomena during the last several decades have found that significant geophysical and geochemical changes can occur prior to intermediate and large earthquakes. Among the more intensely investigated geochemical phenomena have been: (1) changes in the concentrations of dissolved ions and gases in groundwaters and (2) variations in the concentrations of crustal and mantle volatiles in ground gases. The concentration changes have typically showed no consistent trend (either increasing or decreasing), and the spatial and temporal distribution of the observed anomalies have been highly variable. As a result, there is little agreement on the physical or chemical processes responsible for the observed anomalies. Mechanisms proposed to account for precursory groundwater anomalies include ultrasonic vibration, pressure sensitive solubility, pore volume collapse, fracture induced increases in reactive surfaces, and aquifer breaching/fluid mixing. Precursory changes in soil gas composition have been suggested to result from pore volume collapse, micro-fracture induced exposure of fresh reactive silicate surfaces, and breaching of buried gas-rich horizons. An analysis of the available field and laboratory data suggests that the aquifer breaching/fluid mixing (AB/FM) model can best account for many of the reported changes in temperature, dissolved ion and dissolved gas concentrations in groundwater. Ultrasonic vibration and pressure sensitive solubility models cannot reasonably account for the geochemical variations observed and, although the pore collapse model could explain some of the observed chemical changes in groundwater and ground gas, uncertainties remain regarding its ability to generate anomalies of the magnitude observed. Other geochemical anomalies, in particular those associated with hydrogen and radon, seem best accounted for by increases in reactive surface areas (IRSA model) that may accompany precursory deformation around the epicenter of an impending earthquake. Analysis of the probable response of these models to the earthquake preparation process, as well as to other environmental factors, suggests that geochemical monitoring programs can provide information that may be valuable in forecasting the probability of an earthquake; however, because of the complexity of the earthquake preparation process, the absolute prediction of seismic events using geochemical methods alone, does not presently appear to be feasible.

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Section: Increased Reactive Surface Area Modelmentioning

confidence: 74%

Section: Pore Collapse Modelmentioning

confidence: 99%

Geochemical precursors to seismic activity

Thomas

1988

PAGEOPH

225

112

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“…Paradoxically, a few experimental studies in the history of Earth sciences have attempted to understand the relationships between radon emission rate and rock deformation. In their early and pioneer work, Holub and Brady (1981) performed uniaxial compression tests on granite samples to monitor changes in radon exhalation as a function of microfracturing. Tests were carried out by cycli-cally loading and unloading samples to increase rock damage.…”

Section: Introductionmentioning

confidence: 99%

Real-time setup to measure radon emission during rock deformation: implications for geochemical surveillance

Tuccimei

Mollo

Soligo

et al. 2015

Geosci. Instrum. Method. Data Syst.

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Abstract.Laboratory experiments can represent a valid approach to unravel the complex interplay between the geochemical behaviour of radon and rock deformation mechanisms. In light of this, we present a new real-time experimental setup for analysing in continuum the alpha-emitting 222 Rn and 220 Rn daughters over variable stress-strain regimes. The most innovative segment of this setup consists of the radon accumulation chamber obtained from a tough and durable material that can host large cylindrical rock samples. The accumulation chamber is connected, in a closed-loop configuration, to a gas-drying unit and to a RAD7 radon monitor. A recirculating pump moves the gas from the rock sample to a solid-state detector for alpha counting of radon and thoron progeny. The measured radon signal is enhanced by surrounding the accumulation chamber with a digitally controlled heating belt. As the temperature is increased, the number of effective collisions of radon atoms increases favouring the diffusion of radon through the material and reducing the analytical uncertainty. The accumulation chamber containing the sample is then placed into a uniaxial testing apparatus where the axial deformation is measured throughout a linear variable displacement transducer. A dedicated software allows obtaining a variety of stress-strain regimes from fast deformation rates to long-term creep tests. Experiments conducted with this new real-time setup have important ramifications for the interpretation of geochemical anomalies recorded prior to volcanic eruptions or earthquakes.

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“…Both mechanisms of radon transport -diffusion and advection -depend on both soil porosity and permeability, which at the same time vary as a function of the stress field (Holub & Brady, 1981). However, migration by diffusion is negligible, where a component of advective long-distance transport exists (Etiope & Martinelli, 2002).…”

Section: Anomalous Radon Concentration and Seismicitymentioning

confidence: 99%