soil gas survey for tracing seismogenic faults a case study in the fucino basin central italy soil gas he rn co2 and ch4 surveys were performed to test their sensitivity for locating fault or fracture systems when masked by unconsolidated lithologies and to investigate the gas bearing properties of seismogenic faults the fucino basin central italy was chosen as a test site because it displays a network of surface and shallow buried active faults within the valley floor which were partially reactivated during the 1915 avezzano earthquake ms 7 0 the highest radon values were found aligned along the most important faults especially along the san benedetto gioia dei marsi fault sbgmf to the east and in the northwestern sector where the avezzano celano fault acf meets the northwestern prolongation of the 1915 coseismic rupture moderately anomalous values of radon occur along the faults located in the depression of the historical lake trasacco fault tf and ortucchio fault of anomalous values of co2 rn and he were detected north of borgo ottomila in a zone where coseismic scarps and liquefaction phenomena were responsible for a pervasive brittle deformation during the 1915 earthquake highest helium values prevail in the western part of the plain in correspondence with a horst structure bounded by the tf and considered to be the extension of the vallelonga trasacco ridge results of this research confirm the possible usefulness of soil gas methods for locating some tectonic faults when covered by unconsolidated deposits the study provides some clues on the spatial influence of tectonics and geology on deeply seated gas migration toward the surface

rapid inverse modeling of pressure interference tests using trajectory based traveltime and amplitude sensitivities 1 this paper presents an efficient trajectory based approach to integrate transient pressure data into high resolution reservoir and aquifer models the method involves alternating traveltime and peak amplitude matching of pressure response using inverse modeling and is particularly well suited for high resolution subsurface characterization using hydraulic tomography or pressure interference tests compared to traveltime inversion only our proposed approach results in a significantly improved match of the pressure response at the wells and also better estimates of subsurface properties this is accomplished with very little increase in computational cost utilizing the concept of a diffusive time of flight derived from an asymptotic solution of the diffusivity equation we develop analytical approaches to estimate the sensitivities for traveltime and peak amplitude of pressure response to subsurface properties the sensitivities are then used in an iterative least squares minimization to match the pressure data we illustrate our approach using synthetic and field examples in the field application at a fractured limestone formation the predominant fracture patterns emerging from the inversion are shown to be consistent with independent geophysical experiments and borehole data

gravity field determination and characteristics retrospective and prospective gravimetry has had a long history using pendulums torsion balances and static spring gravimeters relative accuracy adequate for many geophysical problems was already attained by 1900 but it took another half century to build readily portable gravimeters calibration and datum definition remained problems until the 1970s when free fall absolute gravimeters were developed that now have a precision of 10 3 mgal the problems of geographic inaccessibility and field party costs notably in areas of greatest tectonic interest are now being overcome by airborne gravimetry that has already achieved accuracies of 1 3 mgal with resolutions of 10 to 20 km satellite techniques are the best way to determine the long wavelength variations of the gravity field the resolution of the models has steadily improved with the number of satellites and the precision of the observations the best current model includes tracking data from more than 30 satellites satellite altimetry and surface gravimetry and has a resolution of about 290 km harmonic degree 70 with the most recent improvements coming from doppler orbitography and radiopositioning integrated by satellite doris tracking of the spot 2 satellite and satellite laser ranging slr doris and global positioning system gps tracking of the topex poseidon satellite meanwhile radar altimetry has become the dominant technique to infer the marine geoid with a resolution of tens of kilometers or shorter similarly the gravity fields of the moon venus and mars have been determined to harmonic degrees 70 75 and 50 respectively although tracking limitations result in variations of spatial resolution modeling earth s gravity field from the abundance of precise data has become an increasingly complex task with which the development of computer capacity has kept pace contemporary solutions now entail about 10 000 parameters half of them for effects other than the fixed gravity field of earth temporal variations arising from tides have long been well modeled and nontidal changes are now being identified the improvement in gravitational models engendered corresponding advances in geophysical interpretation isostatic models were refined and expanded to account for regional thermal and tectonic histories interpretation of the long wavelength gravity field determined by satellite techniques has been mainly in terms of plate tectonics as a manifestation of mantle convection gravity has been significant in inferring that there must be a large increase in viscosity with depth most strongly from the apparent slow sinking of subducted slabs the prospects for increasing accuracy and resolution in the determination of earth s gravity field rest primarily with the development of new measurement systems airborne gravimetry is taking promising new steps using gps but significant global model improvement awaits a dedicated satellite gravimetry system and future satellite altimeter missions will do more for ocean dynamics studies than geoid improvement advances in interpretation will occur through the development of other data such as seismic tomography and larger scale computer modeling of tectonics and convection

do moderate magnitude earthquakes generate seismically induced ground effects the case study of the m w 5 16 29th december 2013 matese earthquake southern apennines italy seismically induced ground effects characterize moderate to high magnitude seismic events whereas they are not so common during seismic sequences of low to moderate magnitude a low to moderate magnitude seismic sequence with a m w 5 16 0 07 main event occurred from december 2013 to february 2014 in the matese ridge area in the southern apennines mountain chain in the epicentral area of the m w 5 16 main event which happened on december 29th 2013 in the southeastern part of the matese ridge field surveys combined with information from local people and reports allowed the recognition of several earthquake induced ground effects such ground effects include landslides hydrological variations in local springs gas flux and a flame that was observed around the main shock epicentre a coseismic rupture was identified in the sw fault scarp of a small sized intermontane basin mt airola basin to detect the nature of the coseismic rupture detail scale geological and geomorphological investigations combined with geoelectrical and soil gas prospections were carried out such a multidisciplinary study besides allowing reconstruction of the surface and subsurface architecture of the mt airola basin and suggesting the occurrence of an active fault at the sw boundary of such basin points to the gravitational nature of the coseismic ground rupture based on typology and spatial distribution of the ground effects an intensity i vii viii is estimated for the m w 5 16 earthquake according to the esi 07 scale which affected an area of at least 90 km2

co2 degassing along the san andreas fault parkfield california the fluxes concentrations and carbon isotopic compositions of soil co2 were measured along the parkfield segment of the san andreas fault saf single or double peak co2 flux anomalies 18 g m 2 d 1 were observed along 12 of 16 fault crossing transects at five sites flux anomalies did not coincide with concentration anomalies flux anomalies paralleled the fault trace suggesting zones of high diffusivity permeability one flux anomaly may have been accentuated by a 0 3 mm creep event however values of 13c 23 7 to 21 6 and 14c 110 5 to 111 9 pmc for soil gas co2 are characteristic of co2 of biogenic origin the co2 flux anomalies are therefore consistent with fault related biogenic gas flow and do not yield evidence for degassing of deeply derived co2

kinematic gps as a source for airborne gravity reduction in the airborne gravity survey of switzerland an airborne gravity survey of switzerland was performed in a joint project between the swiss federal institute of technology zurich and lacoste and romberg gravity meters inc the survey was flown in a twin otter aircraft equipped by the swiss federal directorate of cadastral surveying the aircraft was outfitted with three global positioning system receivers one for navigational purpose and two as sources of positioning velocity and vertical acceleration for airborne gravity reduction four receivers were installed on the ground as reference stations the gravity data were recorded with a modified lacoste and romberg marine gravimeter at a sampling rate of 1 s modifications included anti alias filters and an absolute encoder for the measuring screw the flights were performed at a barometric altitude of 5100 m above sea level an airborne bouguer anomaly map computed at flight altitude with topographic corrections of up to 167 km and a density of 2670 kg m3 is presented bouguer anomaly values at crossing points between lines flown at comparable altitudes h 10 m show differences varying between 1 1 and 2 7 mgal 10 5 m s2 comparison of the ground bouguer anomaly map upward continued to 5100 m and the one computed from airborne data shows a strong similarity both in amplitude and wavelength

soil gas method for tracing neotectonic faults in clay basins the pisticci field southern italy abstract two soil gas surveys were performed in 1991 and 1993 over an area of 95 km 2 at pisticci southern italy the research was aimed at assessing the relationship between soil gas distribution and fracture systems in a plio pleistocene clay basin located in the bradanic trough more than 400 samples were collected to measure the he co 2 and 222 rn concentration in soil atmosphere very large helium anomalies he up to 21 000 ppb above atmospheric reference were detected in 1991 in correspondence with the youngest fractures reported in the literature in order to verify the persistence of such soil gas anomalies a survey was conducted again in 1993 in subareas where major helium anomalies were previously detected the values of co 2 and 222 rn have shown about the same average as that in the 1991 survey while he values have revealed a sharp decrease with maximum values not exceeding 3000 ppb this considerable difference is tentatively related to the seismic activity that occurred just before the 1991 survey whereas no appreciable seismic activity was reported in 1993 the results of the soil gas surveys show that the shape and spatial distribution of the gas anomalies are related to the structural pattern of the area whereas the magnitude of gas leakage is controlled by the occurrence of deep gas bearing traps hydrocarbon reservoirs and possibly triggered by seismic activity

impulsive radon emanation on a creeping segment of the san andreas fault california radon emanation was continuously monitored for several months at two locations along a creeping segment of the san andreas fault in central california the recorded emanations showed several impulsive increases that lasted as much as five hours with amplitudes considerably larger than meteorologically induced diurnal variations some of the radon increases were accompanied or followed by earthquakes or fault creep events they were possibly the result of some sudden outbursts of relatively radon rich ground gas sometimes triggered by crustal deformation or vibration

spatial and temporal variations of co2 emissions from the active fault zones in the capital area of china abstract the chemical and isotopic composition of 26 soil gas wells and 11 springs along the active fault zones in the capital area of china was determined to investigate the origin of co2 the spatial and temporal variations of co2 emission and their mechanisms the chemical and isotopic data indicated that biogenic co2 was the primary source for co2 from the soil gas wells in both the basin and orogen regions the crust derived and mantle derived co2 could have ascended through the deep cut faults and got into the springs with a few diffusing into the soil gas wells minor air could have intruded into the soil gas wells in the orogen region through the faults cutting the surface owing to the barometric pressure fluctuation relatively high he concentration co2 concentration and flux of soil gas from wells were observed in the basin region than those in the orogen region a significant amount of co2 is produced during the process of oxidation of organic matter in the basin where the organic matter accumulates in thick clayey strata further amounts of co2 are produced by interactions between groundwaters and carbonates which are widely represented in the basin region and by intruded air into the soil gas wells in the orogen region due to barometric pressure fluctuations temporal variations of co2 concentration and co2 flux were observed in soil gas wells in the basin region where seismic activity is more frequent compared to those in the orogen indicating that seismic activity could be responsible for the jumpily temporal variations of co2 concentration and flux in wells monitoring activities of soil gas co2 concentrations and co2 fluxes in active fault zones should be carried out

study of soil gas radon variations in the tectonically active dharamshala and chamba regions himachal pradesh india soil gas radon measurements were made in chamba and dharamshala regions of himachal pradesh india to study the correlation if any between the soil gas radon radium activity concentration of soil and the geology active tectonics of the study region soil gas radon surveys were conducted around the local fault zones to check their tectonic activities using the soil gas technique soil gas radon activity concentration at thirty five different locations in dharamshala region has been found to be varying from 13 2 1 5 to 110 8 5 0 kbq m 3 with a geometrical mean of 35 9 kbq m 3 and geometrical standard deviation of 1 8 radon activity concentration observed in the thirty seven soil gas samples collected from the chamba region of himachal pradesh varies from 5 2 1 0 to 35 6 2 5 kbq m 3 with geometrical mean of 15 8 kbq m 3 and geometrical standard deviation of 1 6 average radium activity concentrations in thirty four soil samples collected from different geological formations of dharamshala region and chamba region are found to be 40 4 17 and 38 6 1 7 bq kg 1 respectively it has been observed that soil gas radon activity concentration has a wide range of variation in both dharamshala and chamba regions while radium activity concentrations in soil samples are more or less same in both the regions moreover soil gas radon activity concentration has a better positive correlation with the radium activity concentration in soil samples collected from chamba region as compared to dharamshala region

estimation of fracture zone geometry from steady state hydraulic head data using iterative sequential cokriging the hydrogeology of fractured crystalline rock is often controlled by a few highly conductive features such as faults and or fractures zones accurate modeling of fluid flow and transport in these systems requires that the geometry of these conductive features be characterized explicitly a new method for estimating the geometry of these features is presented the method is an extension of the recently developed geostatistical technique of sequential cokriging in this extension the geometry of the fracture zone is iteratively updated until an update increases the discrepancy between the estimated and observed hydraulic heads results from two hypothetical examples demonstrate that the method can accurately estimate the geometry of highly conductive fracture zones

soil gas radon emanometry a tool for delineation of fractures for groundwater in granitic terrains in several arid and semi arid hard rock areas of the world overexploitation of groundwater has caused de saturation of the phreatic weathered zone attempts are now underway to draw supplies from deeper fracture zones but random drilling often fails to encounter such productive zones further currently available hydrogeological and geophysical methods are of limited applicability alternative geochemical methods employing soil gas 222radon rn and helium 4he have been explored but not investigated sufficiently this paper reports the results of a systematic survey of 222rn concentration in soil gas at a depth of 60 and 160 cm in a watershed located in a semi arid granitic area in india we were able to demarcate three high 222rn anomalies which were supplemented by 4he measurements drilling was carried out on the sites of these high 222rn anomalies as well as on low 222rn anomalies the bore wells drilled at the site of high 222rn concentration were found to be quite productive and those drilled on low 222rn concentration sites were dry those sites of the intermediate 222rn concentrations had intermediate yields these preliminary results suggest that 222rn emanometry method may turn out to be useful the method still needs to be investigated in detail and its usefulness in various settings still needs to be established on a statistical basis we have made an attempt to understand the process that may cause such 222rn anomalies our observations of 222rn concentration in the soil gas and of 222rn emanation rates from the soil and uranium concentrations in the soil indicate that fracturing of the rock rather than advection of 222rn from deeper strata may be responsible for such 222rn anomalies

airborne gravimetry from a small twin engine aircraft over the long island sound in january 1990 a test of the feasibility of airborne gravimetry from a small geophysical survey aircraft a cessna 404 was conducted over the long island sound using a bell aerospace bgm 3 sea gravity meter gravity has been measured from large aircraft and specially modified de havilland twin otters but never from small standard survey aircraft the gravity field of the long island sound is dominated by an asymmetric positive 30 rngal anomaly which is well constrained by both marine and land gravity measurements using a trimble 4000 gps receiver to record the aircraft s horizontal position and radar altimeter elevations to recover the vertical accelerations gravity anomalies along a total of 65 km were successfully measured the root mean square rms difference between the airborne results and marine measurements within 2 km of the flight path was 2 6 mgai for 15 measured values the anomalies recovered from airborne gravimetry can also be compared with the gridded regional free air gravity field calculated using all available marine and land gravity measurements the rms difference between 458 airborne gravity measurements and the regional gravity field is 2 7 mgai this preliminary experiment demonstrates that gravity anomalies with wavelengthsas short as 5 km can be measured from small aircraft with accuracies of 2 7 mgal or better the gravity measurements could be improved by higher quality vertical and horizontal positioning and tuning the gravimeter s stabilized platform for aircraft use

soil gas geochemistry in relation to eruptive fissures on timanfaya volcano lanzarote island canary islands spain abstract we report herein the first results of an extensive soil gas survey performed on timanfaya volcano on may 2011 soil gas composition at timanfaya volcano indicates a main atmospheric source slightly enriched in co2 and he soil co2 concentration showed a very slight deep contribution of the timanfaya volcanic system with no clear relation to the main eruptive fissures of the studied area the existence of soil helium enrichments in timanfaya indicates a shallow degassing of crustal helium and other possible deeper sources probably form cooling magma bodies at depth the main soil helium enrichments were observed in good agreement with the main eruptive fissures of the 1730 36 eruption with the highest values located at those areas with a higher density of recent eruptive centers indicating an important structural control for the leakage of helium at timanfaya volcano atmospheric air slightly polluted by deep seated helium emissions co2 degassed from a cooling magma body and biogenic co2 might be the most plausible explanation for the existence of soil gas helium is a deep seated gas exhibiting important emission rates along the main eruptive fissure of the 1730 36 eruption of timanfaya volcano

identifying fracture zone geometry using simulated annealing and hydraulic connection data a new approach is presented to condition geostatistical simulation of high permeability zones in fractured rock to hydraulic connection data a simulated annealing algorithm generates three dimensional 3 d realizations conditioned to borehole data inferred hydraulic connections between packer isolated borehole intervals and an indicator fracture zone or background k bedrock variogram model of spatial variability we apply the method to data from the u s geological survey mirror lake site in new hampshire where connected high permeability fracture zones exert a strong control on fluid flow at the hundred meter scale single well hydraulic packer tests indicate where permeable fracture zones intersect boreholes and multiple well pumping tests indicate the degree of hydraulic connection between boreholes borehole intervals connected by a fracture zone exhibit similar hydraulic responses whereas intervals not connected by a fracture zone exhibit different responses our approach yields valuable insights into the 3 d geometry of fracture zones at mirror lake statistical analysis of the realizations yields maps of the probabilities of intersecting specific fracture zones with additional wells inverse flow modeling based on the assumption of equivalent porous media is used to estimate hydraulic conductivity and specific storage and to identify those fracture zone geometries that are consistent with hydraulic test data

an airborne gravity study of eastern north carolina the naval research laboratory nrl has developed a prototype airborne gravity measurement system the core of the system is a lacoste and romberg air sea gravity meter mounted on a three axis stable platform corrections to the gravimeter data for altitude and variations in altitude are determined from a combination of highly precise radar and pressure altimeters the original prototype system was designed for use over oceanic areas we recently incorporated the pressure measurement to extend use of the airborne system to terrestrial regions where occasional radar altitudes over points of known topographic height can be obtained the radar heights are used to relate the pressure altitudes to absolute altitudes and to determine the slopes of the isobaric surfaces vertical accelerations due to horizontal velocity over a curved rotating earth the eotvos correction and precise two dimensional positions are determined from a texas instrument p code global positioning system the updated system was tested

changes in the diffuse co2 emission and relation to seismic activity in and around el hierro canary islands significant changes in the diffuse emission of carbon dioxide were recorded in a geochemical station located at el hierro canary islands before the occurrence of several seismic events during 2004 two precursory co2 efflux increases started thirteen and nine days before two seismic events of magnitude 2 3 and 1 7 which took place near el hierro island canary islands on march 23 and april 15 reaching a maximun value of 51 1 and 46 2 g m 2 d 1 respectively five and eight days before the two seismic events other similar increases started thirteen and five days before the occurrence of two seismic events of magnitude 1 3 and 1 5 which took place on october 15 and 21 respectively reaching the maximum values four and one day before the earthquakes these changes were not related to variations in atmospheric or soil parameters the material failure forecast method ffm which analyzes the rate of precursory phenomena was successfully applied to forecast the first seismic event that took place in el hierro island in 2004

compositions and flux of soil gas in liu huang ku hydrothermal area northern taiwan abstract soil co 2 flux has been considered a useful proxy to remotely monitor volcanic activity in a hydrothermal area within a safe distance the liu huang ku lhk area which is close to the taipei basin and many existing active fumaroles and hot springs was chosen for the first systematic soil gas study in a hydrothermal area of taiwan in 2004 and 2006 the soil co 2 flux was measured by the closed chamber method with a non dispersive infrared detector soil co 2 emission rate was estimated 19 8 0 2 t day 1 and 582 t km 2 day 1 in 2004 and 22 4 0 2 t day 1 and 659 t km 2 day 1 in 2006 respectively these values are close to those reported for other active high co 2 flux hydrothermal areas of the world it implies that magmatic gases are actively degassing from subsurface in northern taiwan helium and carbon isotopic data reveal that soil gas in lhk is mainly derived from the mantle and is mixed with a small amount of crustal and air components the abundance of soil co 2 shows a positive correlation with the 3 he 4 he ratios and total sulfur contents which are considered as magmatic sensitive indicators for the fumarolic samples therefore soil co 2 could be used as a good proxy for future monitoring of magmatic activity in this area

a multidisciplinary fractured rock characterization study at raymond field site raymond ca abstract a dedicated field site was developed and a suite of experiments were conducted in the sierra nevada foothills near the town of raymond ca to develop and test a multi disciplinary approach to the characterization of groundwater flow and transport in fractured rocks a wealth of geologic hydrologic and geophysical data was collected at the site using a variety of unique tools a cluster of nine approximately 90 m deep boreholes were drilled at the site in a v shaped pattern with an angle of 60 the boreholes are spaced 7 5 15 30 and 60 m from the central borehole various geophysical and hydrologic tests were conducted in and between these boreholes integration of cross hole radar and seismic tomography borehole flow surveys and images from a new digital borehole scanner indicated that groundwater flow is mainly confined to a few sub horizontal fracture zones a unique suite of hydraulic tests were conducted in which three to four intervals in each of the nine boreholes were isolated using pneumatic packers some 130 injection tests were conducted and more than 4100 cross hole transient pressure measurements were obtained a computer algorithm was developed to analyze such massive interference data systematically as a result of the analysis an image of the fracture connections emerged which is consistent with the geophysical data high precision tiltmeters were effective in remotely characterizing the preferential flow path several radial convergent tracer tests were conducted by injecting a mixture of several conservative tracers and one sorbing tracer deuterium fluorescein lithium bromide and polystyrene micro spheres some differences between the breakthrough curves are observed which may be due to possible differences among so called conservative tracers some characterization tools were found to be more effective than others in locating flowing fractures however no single tool was almighty characterization of fractured rock is extremely challenging and requires a stepwise and well thought approach which is basically a good old scientific approach prediction of transport based on the characterization results is even more challenging and one should always bear in mind that it is virtually impossible to uniquely characterize a fractured rock

soil co2 flux in hydrothermal areas of the tatun volcano group northern taiwan abstract we measured soil co2 flux in the representative hydrothermal areas of the tatun volcano group tvg to better understand the volcano s dynamic nature and to estimate its soil co2 degassing output results show that the average soil co2 fluxes obtained at da you keng dyk geng tze ping gtp she haung ping shp and tatun natural park tnp were 128 g m 2 d 1 518 g m 2 d 1 420 g m 2 d 1 and 25 g m 2 d 1 respectively the range is comparable to other active volcanic hydrothermal areas in the world along with liu huang ku lhk where the soil co2 flux is known the total soil co2 output from measured areas is evaluated at 82 t d 1 furthermore a first total soil co2 output from the whole hydrothermal areas of the tvg is roughly estimated at 113 t d 1 which includes 15 t d 1 mantle contribution considering the mantle derived co2 flux and h2o co2 ratio of fumarolic gas thermal energy associated with the diffuse degassing at the tvg hydrothermal area is estimated at 8 2 mw carbon 13c and helium 3he 4he isotopic ratios of soil samples of the studied areas ranged from 4 4 to 6 7 and 2 45 to 6 98 ra respectively the extent of air involvement in the soil degassing system as constrained by the helium and carbon isotopic compositions provides essential information for depicting regional degassing features of the hydrothermal areas

inverse modeling of partitioning interwell tracer tests a streamline approach 1 identifying the location and distribution of nonaqueous phase liquid napl in the subsurface constitutes a vital step in the design and implementation of aquifer remediation schemes in recent years partitioning interwell tracer tests pitt have gained increasing popularity as a means to characterize napl saturation distribution in situ in this method a suite of conservative and partitioning tracers are injected into the contaminated site the chromatographic separation between the conservative and the partitioning tracers can be used to infer napl saturation distribution the conventional approach to the analysis of the tracer response uses a first order method of moments to compute average napl saturation in the tracer swept regions and cannot provide detailed spatial distribution of the napl we propose a computationally efficient streamline based inverse method for analyzing partitioning interwell tracer tests to estimate three dimensional spatial variation of napl saturation in the subsurface our approach is based on an analogy between streamlines and seismic ray tracing and relies on an analytic sensitivity computation method that yields sensitivities of the partitioning tracer response to subsurface parameters such as porosity hydraulic conductivity and napl saturation in a single streamline simulation the inversion of tracer response is carried out in a manner analogous to seismic waveform inversion whereby we first match the first arrival followed by matching the amplitudes of the tracer response the power and utility of the method is illustrated using synthetic and field applications the field example is from the hill airforce base utah where partitioning tracer tests were conducted in an isolated test cell with 4 injection wells 3 extraction wells and 12 multilevel samplers tracer responses from 51 sampling locations are analyzed to determine hydraulic conductivity variations and napl saturation distribution in the test cell finally a performance comparison with simulated annealing shows that our proposed approach is faster by 3 orders of magnitude

shallow soil co2 flow along the san andreas and calaveras faults california 1 we evaluate a comprehensive soil co2 survey along the san andreas fault saf in parkfield and the calaveras fault cf in hollister california in the context of spatial and temporal variability origin and transport of co2 in fractured terrain co2 efflux was measured within grids with portable instrumentation and continuously with meteorological parameters at a fixed station in both faulted and unfaulted areas spatial and temporal variability of surface co2 effluxes was observed to be higher at faulted saf and cf sites relative to comparable background areas however 13c 23 3 to 16 4 and 14c 75 5 to 94 4 values of soil co2 in both faulted and unfaulted areas are indicative of biogenic co2 even though co2 effluxes in faulted areas reached values as high as 428 g m 2 d 1 profiles of soil co2 concentration as a function of depth were measured at multiple sites within saf and cf grids and repeatedly at two locations at the saf grid many of these profiles suggest a surprisingly high component of advective co2 flow spectral and correlation analysis of saf co2 efflux and meteorological parameter time series indicates that effects of wind speed variations on atmospheric air flow though fractures modulate surface efflux of biogenic co2 the resulting areal patterns in co2 effluxes could be erroneously attributed to a deep gas source in the absence of isotopic data a problem that must be addressed in fault zone soil gas studies

tectonic and geologic influences on soil gas radon emission along the western extension of damascus fault syria the main purpose of this work is to demonstrate the possibility of using soil gas radon survey as a promising technique for locating the trend of western extension of damascus fault where it is hidden under a cover of pliocene unconsolidated deposits the normal level of radon background was established in a stationary area away from the tectonic influence of the fault zone the sites of radon measurements were chosen according to the accessibility and suitability of the area besides some indicative geologic and tectonic evidences a total of 81 radon sampling points were analyzed and the results revealed some reasonable spatial increases with peak values of 2 3 times higher than the background level trending in accordance with what is believed to be the general direction of the fault in the bedrock however permeability properties rather than geotectonic activities seemed to be the main causes controlling the variations of radon concentration over the concerned fault zone yet the moderate level of the observed radon values could be attributed to the nature of the prevailing rock types as well as the probable effect of locked tectonic structure due to the action of high regional compressive regime which typically originates such reverse faulting further the accumulation of fill materials due to rock alteration along the plane of such dormant fault through long geologic time possibly led to increase in the ratio of clay minerals which may affect soil gas mobility through the medium

real time mud gas logging during drilling of the safod pilot hole in parkfield ca 1 the real time mud gas monitoring during drilling of the 2 2 km deep safod pilot hole has proved successful a nearly complete depth profile was obtained for methane radon helium and with limitations for carbon dioxide within the sedimentary section 0 768 m mud gas yielded the highest ch4 co2 and 222rn concentrations whereas he was comparably low four major gas rich zones were identified methane is a mixture of microbial and thermogenic origin mud gas concentrations of ch4 and rn are much lower in the underlying granitic rocks and the average background level of he is higher in addition to several gas rich zones two shear zones inferred from geophysical measurements are also indicated by increased mud gas concentrations gas results permit speculation that one major shear zone is hydraulically connected to the sedimentary section above up to 9 of the helium is of mantle origin which is probably a lower limit

origin of hydrogen and carbon dioxide in fault gases and its relation to fault activity gases occluded in fracture zones of active faults are characterized by a high concentration of h 2 and or co 2 a predominant gas species h 2 or co 2 is related to the lithofacies which the fault cuts carbon dioxide concentration in sediments fluctuates with temperature this evidence and sigma 13 c of co 2 about 20 suggests that co 2 originates from organic materials carbon dioxide with sigma 13 c of 5 to 17 in brecciated gneiss containing marble may have been produced by interaction between organically derived co 2 and the marble or alternatively may have been magmatically derived hydrogen usually occurs in sheared silicate rocks and its concentration fluctuates a great deal the concentration of h 2 from active faults associated with historical earthquakes usually amounts to as high as several percent in maximum whereas the concentration of h 2 from quaternary faults not associated with historical earthquakes is at most 1

geochemical characteristics of soil radon and carbon dioxide within the dead sea fault and karasu fault in the amik basin hatay turkey abstract the study area is close to the boundary of three tectonic plates anatolian arabian and african plates and is characterized by important tectonic lineaments which consist mainly of the dead sea fault dsf the karasu fault and the east anatolian fault eaf systems to understand the origin of soil gas emanation and its relationships with the tectonics of the amik basin hatay a detailed soil gas sampling was systematically performed together with co2 flux measurements 220 soil gas samples were analyzed for rn and co2 concentrations the distribution of soil rn kbq m3 co2 concentration ppm and co2 flux g m2 day in the area appears as a point source spot and or diffuses halo anomalies along the buried faults fractures due to crustal leaks the results revealed that rn and co2 concentrations in the soil gas show anomalous values at the specific positions in the amik basin the trace of these anomalous values is coincident with the n s trending dsf co2 is believed to act as a carrier for rn gas based on the rn and co2 concentrations of soil gases at least three gas components are required to explain the observed variations in addition to the atmospheric component two other gas sources can be recognized one is the deep crust component which exhibits high rn and co2 concentrations and is considered the best indicator for the surface location of fault fracture zones in the region the other component is a shallower gas source with high rn concentration and low co2 concentration moreover he isotopic compositions of representative samples vary from 0 94 to 0 99 ra illustrating that most samples have a soil air component and may have mixed with some crustal component without significant input of the mantle component based on the repeated measurements at a few sites soil gas concentrations at the same site were observed to be higher in 2014 than in 2013 which may be associated with the activity of the dsf in 2013 2014 this suggests that soil gas variations at fault zone are closely related to the local crustal stress and hence are suitable for monitoring fault activities

interpretation of radon anomalies in seismotectonic and tectonic gravitational settings the south eastern crati graben northern calabria italy the study area is located in the south eastern part of the crati valley northern calabria italy which is a graben bordered by n s trending normal faults and crossed by nw se normal left lateral faults numerous severe crustal earthquakes have affected the area in historical time present day seismic activity is mainly related to the n s faults located along the eastern border of the graben in this area much seismically induced deep seated deformation has also been recognised in the present paper radon concentrations in soil gas have been measured and compared with a lithology b quaternary faults c historical and instrumental seismicity and d deep seated deformation the results highlight the following a there is no evidence of a strong correlation between lithology and the radon anomalies b a clear correlation between the n s geometry of radon anomalies and the orientation of main fault systems has been recognised except in the southernmost part of the area where the radon concentrations are strongly affected by the superposition of the n s and the nw se fault systems c epicentral zones of instrumental and historical earthquakes correspond to the highest values of radon concentrations probably indicating recent activated fault segments in particular high radon values occur in the zones struck by earthquakes in 1835 1854 and 1870 d deep seated gravitational deformation generally coincides with zones characterised by low radon concentrations in the studied area the anisotropic distribution of radon concentrations is congruent with the presence of neotectonic features and deep seated gravitational phenomena the method used in this study could profitably contribute towards either seismic risk or deep seated gravitational deformation analyses

flow and transport in hierarchically fractured rock we construct multiple realizations of hierarchical fracture networks with fractal dimensions between one and two then simulate single well pumping tests and natural gradient tracer tests on them we calculate averages and standard deviations of test results over the multiple realizations and show individual results for selected cases to highlight key features of flow and transport through hierarchically fractured rock these studies are intended to illustrate the range of possible behavior that can be obtained during fracture dominated hydraulic and tracer tests and provide insights into how to interpret field responses the fractal dimension of the fracture network itself is generally larger than the fractal dimension of the flow field arising during a well test the performance measures of the natural gradient tracer tests including the total flow through the fracture network tracer travel time front width and maximum breakthrough concentration can all be correlated to fractal dimension although some of the features observed in the flow and transport behavior within the hierarchically fractured rock have been observed by other authors using non fractal fracture network concepts e g channelized flow with early breakthrough times crossing breakthrough curves others arise directly from the fractal nature of the fracture network in which variability occurs on all scales e g front width and maximum breakthrough concentration that are constant over a wide range of fractal dimensions generally transport simulations show large variability within a given realization and among realizations with the same fractal dimension even in networks whose dimension is close to two this finding is consistent with the large variability in experimental results observed at fractured rock field sites

a methodology to interpret cross hole tests in a granite block water flow through low permeability fractured media is often concentrated in a small number of fractures this fractures need to be characterized in order to simulate accurately the hydraulic behaviour of such media we present a methodology to identify the most significant water conductive fractures the method is based on the interpretation of cross hole tests and is supported by geology geophysics and hydraulic data the methodology has been applied to the hydrogeological characterization of a granitic block around the febex experiment at the grimsel underground laboratory switzerland geology and geophysics are used for identifying candidates to flow controlling fractures single borehole hydraulic tests help in neglecting those with low transmissivity but the only means to assess connectivity consists of performing cross hole tests the resulting geometry is later implemented into a 3d finite element mesh where the fractures are simulated as 2d elements embedded into a 3d porous medium the latter includes the effect of minor fracturing and can be heterogeneous and anisotropic the resulting model is calibrated to obtain an integrated model this methodology has proven capable of reproducing single hole and cross hole tests and steady state heads and also of quantifying groundwater flow to the experimental area of the febex tunnel

interferometric global positioning system three dimensional positioning source for airborne gravimetry the naval research laboratory nrl and the national geodetic survey recently collaborated on an experiment to test interferometric mode global positioning system gps tracking as a source of altitude and vertical acceleration for airborne gravity measurement reduction a texas instruments ti 4100 gps receiver and an extremely precise radar altimeter were installed in an nrl p 3 orion aircraft a second ti 4100 was located at a fixed base station of known location carrier phase data from four gps satellites were recorded from the fixed and airborne receivers and postprocessed to produce three dimensional displacements of the airborne station relative to the base station differences in gps and radar altimeter coordinate systems were modeled and removed the resulting gps and radar altitudes were compared the two unfiltered 1 hz data sets differed by an rms of 20 cm when aircraft dynamics were controlled by autopilot in straight and level flight during hand flown maneuvers such as turns climbs and descents rms differences varied from 40 to 80 cm a significant portion of the differences can be attributed to remaining coordinate system discrepancies and to uncompensated geometric effects due to aircraft motion we have also examined vertical acceleration time series produced by doubly differencing both data sets by applying a low pass filter which allows resolution of features with wavelengths of 20 km and greater at nominal aircraft speeds of 100 m s the rms difference between the radar and gps derived vertical accelerations was less than 2 mgal 2 10 5 m s2 during straight and level flight it should be possible to improve this accuracy and wavelength resolution with future improvements in measurement and processing techniques the results of this experiment show that the incorporation of interferometric mode gps tracking into the airborne gravity measurement system will make possible rapid and relatively inexpensive gravity surveys over any type of terrain while simultaneously providing accurate measurements of ground height profiles beneath the aircraft

what can airborne gravimetry contribute to geoid determination this paper evaluates the suitability of airborne gravimetry for geoid determination spectral analysis of gravity data is used to derive the high frequency geoid spectrum and to compare it to the error spectrum of the geoid as derived from an airborne gravity system gravity values in various areas with typical topographic features are used for the spectral analysis the achievable accuracy of airborne gravimetry in geoid determination is studied through an assessment of inertial navigation system ins and global positioning system gps errors in the spectral ranges of interest the results of these computations are presented in a number of graphs which allow the following conclusions to determine geoid undulations with an accuracy of 1 cm rms the minimum wavelength to be resolved is 14 km in flat terrain and 5 km in mountainous terrain using a flight speed of 300 km h at an altitude of 2 5 km or less above ground current hardware sensitivity is sufficient to resolve the geoid spectrum for such wavelengths the total gps ins induced geoid undulation error rms in this case is less than 1 cm for wavelengths between 5 km and 100 km and less than 10 cm for wavelengths between 5 km and 500 km the cumulative rms geoid error is less than 30 cm for wavelengths up to 1000 km the accuracy for relative geoid determination is 0 1 ppm for wavelengths up to 100 km and 0 2 ppm for 500 km the results were verified by analyzing the data collected during an airborne test the results indicate that airborne gravimetry has the potential to determine geoid undulation with centimeter level accuracy and to fill the gaps in the global gravity map in an efficient manner and with an accuracy superior to current terrestrial methods

radon concentrations in soil gas considering radioactive equilibrium conditions with application to estimating fault zone geometry a calculation method for determining the amount of rn isotopes and daughter products at the start of measurement cras is proposed as a more accurate means of estimating the initial rn concentration in soil gas the cras utilizes the decay law between 222rn and 220rn isotopes and the daughter products 218po and 216po and is applicable to scintillation counter measurements as rn is both inert and chemically stable it is useful for fault investigation based on the soil gas geochemistry however the total number of particles emitted by the decay of rn has generally been considered to be proportional to the initial rn concentration without considering the gas condition with respect to radioactive equilibrium the cras method is shown to be effective to derive rn concentration for soil gases under both nonequilibrium conditions in which the total number of decays increases with time and equilibrium conditions which are typical of normal soil under low gas flux the cras method in conjunction with finite difference method simulation is applied to the analysis of two active fault areas in japan and it is demonstrated that this combination could detect the sharp rises in 222rn concentrations associated with faults the method also allows the determination of fault geometry near the surface based on the asymmetry variation of the rn concentration distribution when coupled with a numerical simulation of 222rn transport the results for the new method as applied to the two case studies are consistent with the data collected from the geological survey it implies that the cras method is suitable for investigating the fault system and interstitial gas mobility through fractures the present analyses have also demonstrated that high rn concentrations require the recent and repeated accumulation of 222rn parents 230th and 226ra in fault gouges through deep gas release during fault movement

correlations between the radon concentrations in soil gas and the activity of the anninghe and the zemuhe faults in sichuan southwestern of china abstract the anninghe fault anhf and the zemuhe fault zmhf with left lateral strike slip located along the eastern boundary of the sichuan yunnan block southwestern of china are some of the most active faults these faults mainly control the seismicity of southwestern area of china measurement of soil gas radon rn emitted from fault along the anhf and the zmhf has been carried out for the research of tectonic activity we obtained the rn concentrations at 394 sampling points along 15 profiles across the anhf and the zmhf in 2016 the measurement results show that the values of rn in the anhf are significantly higher than that in the zmhf the relative coefficient kq of rn activity attained in profiles of the anhf ranges from 3 3 to 9 1 which are obviously higher than that of 2 1 2 5 in profiles of the zmhf the radon flow brings up the deeper and radon richer gas upward through the high level cracked strata caused by the tectonic activity accounts for the anomalously high values attained the spatial variation of rn in the concentration profile and the relative coefficient kq calculated indicate that the tectonic activity of the south segment of the anhf is significantly higher than that of the north segment of the zmhf

airborne gravity is here the achievement of practical and useful airborne gravity exploration for petroleum is a major culmination of more than twenty years of research and development commercial surveys have now been conducted for three years the precision and anomaly resolution attainable are twice as good as that of current shipborne gravity data this paper presents data to demonstrate the precision of airborne gravity and discusses its usefulness with simultaneous magnetics and topography industrial acceptance of the method portends a new era in geophysical exploration for oil and gas which gives promise to double the effectiveness of explorations on land in both time and cost

geochemical investigations applied to active fault detection in a volcanic area the north east rift on mt etna sicily italy geochemical investigations were performed on the northeast rift of mt etna a prominent volcanic structure of this volcano low temperature fumaroles were found on the upper part of this area and the isotopic compositions of c co2 and he suggest a likely magmatic origin of the emitted gases on the contrary very low degassing was found in the lower part of the ne rift with co2 concentrations generally very close to those in air this pattern is probably due to sealing of the eruptive fissures by the repeated injections of magma solidified into dikes and by consequent shallow hydrothermal alteration of the fissured rocks due to residual magma degassing high soil co2 concentrations were also found in an elongated area parallel to the ne rift and located immediately to the east of it the geometry of these anomalies suggests the existence of several hidden faults sub parallel to the ne rift and likely connected to the pernicana fault system this latter structure seems to merge with the ne rift at the altitude where the fumarole emissions are located the hidden structures together with the pernicana system and the ne rift represent the western and northern boundaries of a large eastward collapsing sector of mt etna

airborne measurement of absolute sea surface heights topographic profiles may be measured from an aircraft by differencing precise radar or laser altitudes with ellipsoidal heights obtained by means of kinematic interferometric mode gps over the ocean the difference between the two altitudes is the geoid height plus dynamic oceanographic effects such as tides currents eddies etc aircraft might provide on a local scale altimetry measurements similar to those from geosat and ers 1 such airborne measurements could be applied to the determination of a local high resolution geoid or for oceanographic studies several long over water altimetry profiles were obtained during the 1991 field campaign of the greenland aerogeophysics project gap91 kinematic interferometric gps between multiple short or zero baseline airborne receivers and several sets of stationary gps receivers on the ground provided precise three dimensional positioning for airborne gravity magnetic and topographic profiling sensor systems mounted aboard a p 3 orion aircraft the logistics of surveying a large region long gps baselines and poor satellite coverage limit the accuracy of the gps positioning but the geoid signal is clearly visible in the over water profiles in spite of gps baseline lengths of up to 1000 km differences between modeled geoid heights and measured sea surface heights ranged from about 1 2 meters r m s although the differences are primarily due to errors in the gps positions some portion is due to errors in the model geoid uncompensated tides sea ice contamination of the radar data and other errors in the radar we believe that this represents the first airborne measurement of absolute sea surface heights

gas geochemistry applied to earthquake prediction an overview terrestrial gases in groundwater and soil air have been extensively studied in recent years in seismically active areas especially in ussr china japan and united states in search of premonitory changes that might be useful for earthquake prediction concentrations of radon helium hydrogen mercury carbon dioxide and several other volatiles have been found generally to be anomalously high along active faults suggesting that the faults may be paths of least resistance for the terrestrial gases generated or stored in the earth to escape to the atmosphere temporal gas concentration changes with durations of a few hours to many months have been observed before many large earthquakes at a relatively small number of favorably situated stations at epicentral distances of up to several hundreds of kilometers these sensitive stations are generally located along active faults especially at intersections or bends of faults or some other structurally weak zones possibly because of tectonic strain concentration at such places however gas concentrations especially those measured at or near the ground surface may also be significantly affected by meteorological hydrological and other nontectonic changes in the environment the nontectonically induced variations must be carefully eliminated or recognized in the search of true earthquake related anomalies

airborne gravity and precise positioning for geologic applications airborne gravimetry has become an important geophysical tool primarily because of advancements in methodology and instrumentation made in the past decade airborne gravity is especially useful when measured in conjunction with other geophysical data such as magnetics radar and laser altimetry the aerogeophysical survey over the west antarctic ice sheet described in this paper is one such interdisciplinary study this paper outlines in detail the instrumentation survey and data processing methodology employed to perform airborne gravimetry from the multi instrumented twin otter aircraft precise positioning from carrier phase global positioning sys tem gps observations are combined with measurements of acceleration made by the gravity me ter in the aircraft to obtain the free air gravity anomaly measurement at aircraft altitude gps data are processed using the kinematic and rapid static kars software program and aircraft vertical acceleration and corrections for gravity data reduction are calculated from the gps position solu tion accuracies for the free air anomaly are determined from crossover analysis after significant editing 2 98 mgal rms and from a repeat track 1 39 mgal rms the aerogeophysical survey covered a 300 000 km 2 region in west antarctica over the course of five field seasons the grav ity data from the west antarctic survey reveal the major geologic structures of the west antarctic rift system including the whitmore mountains the byrd subglacial basin the sinuous ridge the ross embayment and siple dome these measurements in conjunction with magnetics and ice penetrating radar provide the information required to reveal the tectonic fabric and history of this important region

investigation of the 1867 lesbos ne aegean earthquake fault pattern based on soil gas geochemical data abstract in this work the soil gas method is being used to compare geochemical data with the geological and structural information on lesbos island ne aegean in particular in the aghia paraskevi kalloni region the epicentral area of an earthquake in 1867 the island belongs to an seismically active zone part of the right lateral and normal fault systems of north anatolia and north and central aegean field observations aerial photo interpretation and microearthquake distribution show two main fault systems trending ne sw to nne ssw and nw se the strongest known destructive earthquake hit the island in 1867 with its epicentral area in the central part of lesbos estimated intensity ix x for the most central and eastern part of the island and vi vii for the rest the soil gas sampling was performed in august 1996 in the aghia paraskevi area by this soil gas survey an attempt was made for the recognition of active faults using the soil gases as fault tracers high values of all the investigated gases he 222rn co2 and ch4 characterize the central and southern sector of the area the soil gas anomalous concentrations are probably linked to the very active extensional tectonic structures that cause the characteristic seismicity of lesbos especially those of 222rn and co2 after statistical processing of the data and the use of contour and dot maps of each investigated gas an important accordance was found between the interpreted linear gas anomalies and the observed faults which possibly generated the 1867 shock

spatial radon anomalies on active faults in california abstract radon emanation has been observed to be anomalously high along active faults in many parts of the world we tested this relationship by conducting and repeating soil air radon surveys with a portable radon meter across several faults in california the results confirm the existence of fault associated radon anomalies which show characteristic features that may be related to fault structures but vary in time due to other environmental changes such as rainfall across two creeping faults in san juan bautista and hollister the radon anomalies showed prominent double peaks straddling the fault gouge zone during dry summers but the peak to background ratios diminished after significant rain fall during winter across a locked segment of the san andreas fault near olema the anomaly has a single peak located several meters southwest of the slip zone associated with the 1906 san francisco earthquake across two fault segments that ruptured during the magnitude 7 5 landers earthquake in 1992 anomalously high radon concentration was found in the fractures three weeks after the earthquake we attribute the fault related anomalies to a slow vertical gas flow in or near the fault zones radon generated locally in subsurface soil has a concentration profile that increases three orders of magnitude from the surface to a depth of several meters thus an upward flow that brings up deeper and radon richer soil air to the detection level can cause a significantly higher concentration reading this explanation is consistent with concentrations of carbon dioxide and oxygen measured in soil air samples collected during one of the surveys

advances in aerogeophysics and precise positioning gravity topography and high resolution applications airborne magnetic surveys have long been a primary tool for geologic mapping resource exploration hazard evaluation and tectonic studies recent advances in precise positioning have enabled other geophysical tools such as laser and radar altimeters and the gravity meter to be mounted on airplanes and contribute to geologic and environmental studies the principal advantages of airborne geophysical surveys over ground based studies result from enhanced experiment design including improved access to remote and contaminated areas optimized sampling rapid sampling rate and tremendous potential for interdisciplinary studies

an inverse technique for developing models for fluid flow in fracture systems using simulated annealing one of the characteristics of flow and transport in fractured rock is that the flow may be largely confined to a poorly connected network of fractures in order to represent this condition lawrence berkeley laboratory has been developing a new type of fracture hydrology model called an equivalent discontinuum model in this model we represent the discontinuous nature of the problem through flow on a partially filled lattice this is done through a statistical inverse technique called simulated annealing the fracture network model is annealed by continually modifying a base model or template so that with each modification the model behaves more and more like the observed system this template is constructed using geological and geophysical data to identify the regions that possibly conduct fluid and the probable orientations of channels that conduct fluid in order to see how the simulated annealing algorithm works we have developed a synthetic case in this case the geometry of the fracture network is completely known so that the results of annealing to steady state data can be evaluated absolutely we also analyze field data from the migration experiment at the grimsel rock laboratory in switzerland

a multidisciplinary statistical approach to study the relationships between helium leakage and neotectonic activity in a gas province the vasto basin abruzzo molise central italy the evaluation of a new method based on the integration of geochemical morphological and structural analyses for the study of neotectonics in clay basins is presented more than 900 helium soil gas samples were collected over an area located in the central sector of the adriatic foredeep central italy soil gas distribution has been compared with the location and orientation of the main structural features described in the literature and or characterized by field surveys and morphotectonic features obtained by air photo interpretation and drainage network analysis collected data were statistically analyzed and compared by means of rose diagram plots a geostatistical approach was used to describe the spatial behavior of the helium distribution the comparison of the morphological and structural elements with the observed geochemical anomalies shows that the northwest southeast is the most representative direction in agreement with the known apennine structural trends moreover the presence of north south and east west trends in the helium regional distribution observed in the central and southern sectors of the studied area is thought to be caused by a more recent deformation phase acting along these directions this hypothesis is strengthened by the good correspondence both at regional and local scales between geochemical data and the results of the structural and geomorphological analyses furthermore the magnitude and the anisotropic distribution of the helium anomalies in the residual maps indicate that at local scale this gas could be related with the distribution of the hydrocarbon reservoirs occurring in the area

characterizing long term radon concentration changes in a geothermal area for correlation with volcanic earthquakes and reservoir temperatures a case study from mt aso southwestern japan abstract the purpose of this study is to characterize in detail the temporal changes in rn radon 222 concentration in soil gases near fumaroles and clarify its correlation with volcanic earthquakes and temperatures in two geothermal reservoirs mt aso crater in southwest japan which has two reservoirs on its western side estimated by magnetotelluric survey to be at about 2 km in depth was selected for this study for the long term survey the scintillation counter method was used weekly for 12 5 years at the three hot springs within a 2 km range rn concentrations were calculated using the cras method a calculation method that considers radioactive equilibrium or nonequilibrium state of the soil gas rn concentrations generally showed similar fluctuation patterns among the sites cras was used as a new indicator for evaluating the age of the soil gas this age corresponds to the elapsed time determined from the generation of rn based on the measurement of the numbers of atoms of rn and its daughter 218po at the start of measurement in comparing the rn data with the history of earthquakes in the aso caldera volcanic seismicity was identified as a major controlling factor in the sudden increase and decrease in rn concentration as a function of age for more precise detections of change rn concentrations were measured continuously at one site by pumping soil gas from a borehole and using an ionization chamber over 2 5 years five chemical components he h2 n2 ch4 and co2 were then measured by gas chromatography at 1 week intervals because rn concentrations are affected strongly by atmospheric temperatures the residual components were obtained by subtracting the trend of the components from the original data chemical component data were used to estimate the temperature and pressure in the reservoir at the site temperatures ranged from 229 to 280 c average 265 c average pressure 80 mpa residual rn concentrations showed a clear correlation with temporal changes in estimated temperature and to a degree with pressure considering the migration mechanism of rn by molecular diffusion and advection under rapid gas upflow conditions change in the diffusion coefficient is regarded as a possible factor to have induced temporal changes in rn concentrations in conjunction with the temperature changes in the reservoirs in addition the increase of the amount of degassed rn from the advective convective hydrothermal fluids which is associated with wall rock fracturing is another important factor earthquakes likely enhance the permeability of a reservoir by generating fractures which in turn can cause an increase in the reservoir temperature upflow fluid velocity and gas flux this provides one possible interpretation for the significant correlation of rn concentrations with earthquakes

radon anomalies on three kinds of faults in california radon emanation is known to be anomalously high along active faults in many parts of the world we tested this relationship in california during july and early august 1992 using a portable radonmeter to conduct soil air radon surveys at 5 sites across three kinds of faults creeping locked and freshly broken along a 350 m long survey line across a creeping segment of the san andreas fault at nyland ranch in san juan bautista we found anomalous radon concentrations not in the creep zone itself as determined by a creepmeter but on the adjacent sides 10 and 30 meters from the center line of the fault the anomalous values were 5 times higher than the background values measured farther away from the fault a similar radon anomaly was observed along a 420 m long survey line across a creeping segment of the calaveras fault near 7th street in hollister there the anomalous values were about 6 to 11 times the background values and about 40 and 50 m from the center line of the fault the double peaked featire of the anomalies may be indicative of a relatively low gas permeability of the fault gouge materials in the creeping zones and high permeability of fractured rocks in the adjacent shear zones along a 144 m survey line across the currently locked segment of the san andreas fault at the earthquake trail near olema the radon concentration was indeed anomalously high in the fault zone by a factor of two above background values however the maximum values 3 to 6 times background again were recorded about 10 meters from the center line three weeks after the magnitude 7 5 landers earthquake of 28 june 1992 we conducted a survey along a 300 m line across the earthquake fault alongside encantado road in the epicenter area the radon values measured at the two main fault breaks were an order of magnitude higher than the background values a similar result was found along a 420 m line alongside reche road about 1 7 km south of encantado road