advection and dispersion of contaminant in a permeable medium embedding fractures in which advection velocity is comparatively slow abstract this paper concerns the advective migration of an aqueous contaminant in a fractured permeable formation calculation and analysis refer to fractures in which advection velocity is comparatively small the slow advective velocity is created by some local cavities or almost vertical orientation of the fractures it is shown that the advective contaminant transport is characterized by two dimensionless parameters 1 the ratio between the permeable block and fracture flow rates termed the mobility number 2 the ratio between the longitudinal advection velocity of the permeable block flow and that of the fracture flow termed the advection velocity ratio for a sufficiently large domain continuum parameters can be applied to characterization of the fractured permeable formation then the mixing between the permeable block flow and the fracture flow is a mechanism leading to contaminant dispersion for very small values of the advection velocity ratio the effective dispersivity is fully determined by the mobility number its value decreases with increase of the mobility number under such conditions the equivalent porosity is constant and its value is identical to that of the permeable blocks a significant value of the advection velocity ratio increases the equivalent porosity of the fractured permeable formation with regard to the effective dispersivity of the domain if the advection velocity ratio is equal to unity then the effective dispersivity vanishes the larger the deviation of the advection velocity from unity the larger is the effective dispersivity of the fractured permeable medium

the resolving power of cross borehole tomography the data collected in a cross borehole tomography problem is inherently incomplete since the boreholes do not completely surround the media under study the ability of the experiment to resolve structure is therefore limited by poor experimental geometry we use the method of backus and gilbert to investigate the ability of this technique to resolve variations in acoustic velocity and attenuation between the two boreholes both integrals that appear in the backus gilbert formulation can be performed analytically thus expediting the calculations the resolving kernels have significant horizontal width demonstrating that the horizontal position of structures can be only poorly resolved

interpretation of field tracer tests of a single fracture using a transient solute storage model the results and interpretation of five induced gradient tracer tests performed at five different average interborehole fluid velocities in a single fracture in monzonitic gneiss are described the experiments were conducted using radioactive 82br and a fluorescent dye as conservative tracers where the tracers were pulse injected into radial convergent and injection withdrawal flow fields the flow fields were established between straddle packers isolating the fracture in three boreholes over distances of 12 7 29 8 m the tracer breakthrough curves were determined from samples of the withdrawn groundwater and were interpreted using residence time distribution rtd theory and two deterministic simulation models the rtd curves of the tracer experiments were interpreted by fitting to the field data a simple advection dispersion model and an advection dispersion model with transient solute storage in immobile fluid zones both models consider the different flow field geometries associated with injection withdrawal and radial convergent tests comparison of the fits obtained by the simulation models suggest that the initial period of solute transport in single fractures is advection dominated and with increasing tracer residence time or decreasing fluid velocity transport progresses toward more fickian like behavior during the advective dominated period the transient solute storage model is shown to adequately describe the asymmetries and long tails characteristic of the fracture rtds interpretation of the tracer experiments using both simulation models further suggests that induced gradient tracer experiments are likely to underestimate the dispersive characteristics of single fractures under natural flow conditions

seismic tomography in boreholes summary synthetic seismic tomographic data sets for cross hole and hole to surface arrays are computed and inverted inversion imaging is performed through an iterative projection solution to a matrix equation the orientation as well as the position of an anomaly relative to the source and recorder arrays affects both the rate of convergence of the solution and the resolution obtained data density and distribution determine the physical validity of the image obtained at convergence borehole tomography is apparently a viable method for imaging inter hole structure

anisotropic velocity tomography a case study in a near surface rock mass cross borehole data were acquired in the surface crown pillar of a massive sulfide ore mine the data consist of five two dimensional 2 d cross borehole panels each with approximately 900 source receiver pairs the panels were located within the crown pillar at either side of and within a major subvertical fault zone that intersects the orebody an initial analysis of the data indicates that the bedrock containing the orebody is seismically anisotropic a rigorous analysis of the traveltimes using anisotropic velocity tomography confirms the initial assessment that anisotropy exists within the crown pillar rock mass anisotropic velocity tomography is the generalization of tomographic methods to anisotropic media as in any geophysical problem the data are insufficient to completely resolve the distributions of the rock properties at all scale lengths we use external constraints on the roughness of the final solution to ensure an algebraically well posed problem plots of the data residuals the t

inversion of tracer test data using tomographic constraints 1 we have developed a methodology for inverting tracer test data using zonation information obtained from two dimensional radar tomograms to improve the typically overly smooth hydraulic conductivity fields obtained from conventional inversion of tracer test data the method simultaneously yields two dimensional estimates of hydraulic conductivity as well as petrophysical relationships that relate hydraulic conductivity to radar velocity these relationships can be assumed to be stationary throughout the area of investigation or to vary as a function of zonation using a synthetic three dimensional hydraulic conductivity field we apply the developed inversion methodology and explore the impact of the strength and stationarity of the petrophysical relationship as well as the impact of errors that are often associated with radar data acquisition such as unknown borehole deviation we find that adding radar tomographic data to tracer test data improves hydrogeological site characterization even in the presence of minor radar data errors the results are contingent on the assumption that a relationship between radar velocity and hydraulic conductivity exists therefore the applicability of the proposed method may be limited to field sites where this condition is partially or fully satisfied

contaminant advection and spreading in a fractured permeable formation part 1 parametric evaluation and analytical solution abstract this paper concerns contaminant transport phenomena in aquifers comprising fractured permeable formations in contrast to deep rock formations with tight almost impermeable matrix rock we consider fractures embedded in permeable rock blocks it is shown that in many cases e g in sandstone formations the advective transport of contaminants in permeable blocks can be identified as the major process leading to contaminant exchange between fractures and blocks in the framework of the present study a simplified conceptual model of the fractured formation is adopted the conceptual model is formulated by sets of space linear differential equations subject to time dependent boundary conditions a closed form analytical solution of these sets of differential equations is developed calculations of the contaminant distribution along the fracture network are utilized to obtain breakthrough curves concerning the time variation of the average contaminant concentration in certain cross sections of the fractured permeable medium characteristics of the contaminant transport phenomena originating from the contaminant advection and the mixing between the fracture flow and the permeable block flow are determined and possibilities of considering the fractured permeable formation as a continuum are discussed

an analytical model for solute transport through a water saturated single fracture and permeable rock matrix an analytical model for solute transport through a water saturated single fracture and permeable rock matrix j e houseworth 1 d asahina 1 and j t birkholzer 1 the problem of solute transport through a water saturated single fracture in a permeable rock matrix is examined using an analytical modeling approach a closed form analytical solution is obtained that accounts for transverse and longitudinal advective transport in the fracture and matrix and transverse diffusion in the matrix the solution also accounts for both diffusive and advective solute exchange between the fracture and matrix and a general solute source position in either the fracture or matrix the novel features are the incorporation of advective transport in the matrix and a general source position into a closed form solution for the solute transport problem examples of the solution behavior are presented which demonstrate the effects of matrix advection in combination with advection along the fracture transverse diffusion in the matrix for solute release in the fracture and matrix a semianalytical solution in the form of a superposition integral is also derived that includes these transport features plus independent levels of longitudinal diffusion and dispersion in the matrix and fracture respectively examples are presented that include advective transport in the fracture and matrix longitudinal and transverse diffusion in the matrix longitudinal dispersion in the fracture as well as solute release from the fracture and matrix an approximate criterion is proposed to evaluate the significance of longitudinal diffusion and dispersion relative to longitudinal spreading caused by fracture matrix interaction flow through fractures displays highly heterogeneous and complex flow patterns controlled by small scale fracture features furthermore transport processes at small scales that govern fracture matrix exchange can dramatically influence larger scale transport behavior grisak and pick ens 1980 transport through saturated fractured rock was first investigated in an analytical model by neretnieks 1980 tang et al 1981 extended this work to include the effects of longitudinal dispersion in the fracture and sudicky and frind 1982 and maloszewski and zuber 1985 further generalized the transport problem from a single fracture to a system of parallel fractures with interceding rock matrix sharifi haddad et al 2012 developed a semianalytical model of solute transport in a system of parallel fractures for a radially symmetric flow field associated with well injection maloszewski and zuber 1990 considered the effects of linear kinetic interactions between solute and the rock for a single fracture and rock matrix all of these mod els were restricted to advective transport in the fracture transverse diffusion in the matrix and diffusive fracture matrix solute exchange a review of these modeling approaches among others is provided by bodin et al 2003a 2003b cihan and tyner 2011 developed exact analytical solutions for advective transport through cylin drical macropores and diffusive exchange with a soil ma trix for an instantaneous release of solute into a macropore a constant concentration of solute at the top of a macropore and a pulse release of solute into a macropore 1 introduction solute transport in groundwater flow through frac tured rock is a subject that has been investigated for nuclear waste disposal and other environmental groundwater con tamination problems national research council 1996 fractures are a common feature of consolidated rock sys tems and typically present much higher permeability than unfractured rock matrix such that flow through fractures often dominates overall flow behavior matrix on the other hand typically dominates the overall pore volume of a fractured rock these attributes often lead to much higher solute transport velocities through fractures than in unfrac tured rock or unconsolidated soils berkowitz 2002 this behavior often makes fracture flow and transport critical characteristics to examine for any geologic site where sol ute transport is a concern however despite their impor tance fractures remain a difficult feature to represent accurately in mathematical models for groundwater flow and transport matth ai et al 2009 wu and pruess 2000 earth sciences division lawrence berkeley national laboratory berkeley california usa corresponding author j e houseworth earth sciences division law rence berkeley national laboratory berkeley ca 94720 usa jehouseworth lbl gov

target oriented interferometric tomography for gpr data an interferometric form of fermat s principle and traveltime tomography is used to invert ground penetrating radar gpr data for the subsurface velocity distribution the input data consist of gpr traveltimes of reflections from two buried interfaces a reference and b target where the data are excited and recorded by gpr antennas at the surface fermat s interferometric principle is then used to redatum the surface transmitters and receivers to interface a so the associated reflection traveltimes correspond to localized transit times between interfaces a and b the overburden velocity model above interface a is not required the result after tomographic inversion is a high resolution estimate of the velocity between interfaces a and b that does not depend on the velocity model above interface a a motivation for introducing interferometric traveltime tomography is that typical layer stripping approaches will see the slowness error increase with depth as the layers are inverted this suggests that

high resolution aquifer characterization using seismic cross hole tomography an evaluation experiment in a gravel delta we performed field experiments at a well studied aquifer test site to evaluate the geophysical method of seismic cross hole tomography for high resolution aquifer characterization we address the challenge of finding meaningful relationships between seismic velocity and hydraulic conductivity at the field scale for hydraulic conductivity estimation the resolution of seismic cross hole data is limited by inversion ambiguities and diffraction effects which are not accounted for using conventional ray based inversion algorithms for velocity reconstruction we investigate the impact of diffraction effects on seismic velocity inversion and implications for hydraulic modelling our ray based seismic tomograms correlate well with sedimentary cores and hydraulic conductivity logs allowing us to interpret a zone model with distinct geophysical hydraulic zones we use this zone model to constrain seismic inversions using two approaches for forward modelling ray tracing infinite frequency approximation and wavefield modelling at a realistic frequency which accounts for diffraction we show that using the common ray tracing approach seismic velocities in low velocity zones may be significantly overestimated based on the available data we observe a negative linear relationship between logarithmic hydraulic conductivity and seismic velocity this relationship is used to parameterize hydraulic models based on seismic velocity models computer simulations of advective contaminant transport demonstrate that their results are extremely sensitive to an accurate determination of seismic low velocity zones we conclude that seismic tomography is indeed very useful for high resolution aquifer characterization however an inversion approach that accounts for diffraction effects a priori knowledge of the subsurface structure and additional well data should be applied for quantitative interpretations

broad band trajectory mechanics author s vasco dw nihei k abstract 2019 published by oxford university press on behalf of the royal astronomical society we present a trajectory based solution to the elastodynamic equation of motion that is valid across a wide range of seismic frequencies that is the derivation of the solution does not invoke a high frequency assumption or require that the medium have smoothly varying properties the approach adopted from techniques used in quantum dynamics produces a set of coupled ordinary differential equations for the trajectory the slowness vector and the elastic wave amplitude along the ray path the trajectories may be determined by a direct solution of the governing equations or derived as the by product of a numerical wavefield simulation synthetic tests with interfaces and layers containing increasingly narrow transition zones indicate that the conventional high frequency trajectories associated with the eikonal equation bend too sharply into high velocity regions as the wavelength exceeds the transition zone width tests in a velocity model based upon mapped structural surfaces from the geysers geothermal field in california indicate that discrepancies between high frequency and broad band trajectories can exceed several hundred metres at wavelengths of 1 hz an application to a crosswell tomographic imaging experiment demonstrates that the technique provides a basis for the seismic monitoring of fluid flow along narrow features such as fracture zones

crosswell seismic imaging in a contaminated basalt aquifer multiple seismic crosswell surveys have been acquired and analyzed in a fractured basalt aquifer at idaho national engineering and environmental laboratory most of these surveys used a high frequency 1000 10 000 hz piezoelectric seismic source to obtain p wave velocity tomograms the p wave velocities range from less than 3200 m s to more than 5000 m s additionally a new type of borehole seismic source was deployed as part of the subsurface characterization program at this contaminated groundwater site this source known as an orbital vibrator allows simultaneous acquisition of p and s waves at frequencies of 100 to 400 hz and acquisition over larger distances the velocity tomograms show a relationship to contaminant transport in the groundwater zones of high contaminant concentration are coincident with zones of low velocity and high attenuation and are interpreted to be fracture zones at the boundaries between basalt flows the orbital vibrator data show high vp vs values from 1 8 to 2 8 in

contaminant advection and spreading in a fractured permeable formation part 2 numerical simulation abstract in a companion paper referred to as paper i the transport of contaminants in a fractured permeable formation was characterized and formulated it was shown that advective movements in the fracture flow and the permeable block flow as well as mixing between these two types of flow are the most significant factors affecting contaminant transport and spreading in such formations the basic formulation and the closed form analytical solution developed in paper i invite the use of numerical schemes for a further analysis of the contaminant transport processes in the framework of the present paper this target is achieved a numerical solution scheme stemming from the conceptual model of paper i is developed simulations are performed by considering the various properties of the discrete fracture flow and the permeable block flow the results of the present study indicate that fractured permeable formations can be represented by single continuum models provided that a sufficiently large number of sectors is included in the representative elementary volume rev the minimum number of sectors depends on the ratio between the specific discharge of the permeable block flow and that imposed by the fracture presence this ratio is named the mobility number the larger the mobility number the smaller the number of sectors which should be incorporated in the rev equivalent properties of the continuum representing the fractured permeable formation such as the equivalent porosity and dispersivity are determined and evaluated

crosshole seismic tomography and borehole logging for engineering site characterization in sikeston mo usa abstract this paper presents a geophysical investigation performed in the median separating the east and west bound lanes of u s highway 60 approximately 15 km west from the town of sikeston mo usa two boreholes drilled at depth of 45 m approximately located 6 m from the wahite ditch bridge in u s highway 60 were used to carry out the geophysical tests the objective of the survey was to obtain the density distribution of soil materials and high resolution compressional and shear wave velocities of the shallow subsurface for computation of elastic engineering properties of the unconsolidated material interposed between the two investigated boreholes the studied site is located in the new madrid seismic zone nmsz one of the major seismic source zones in the eastern united states although no major seismic events have occurred in the new madrid area since the catastrophic earthquakes of 1811 1812 more intensive studies in this area are required to better understand the local soil effects and the liquefaction potential of unconsolidated earth materials on strong ground motion joint interpretation of borehole logs and velocity images obtained by p and s wave traveltime inversions outlined shallow anomalies which were interpreted as caused by variation in relative porosity and compactness of saturated unconsolidated soil materials in the interval between 17 and 19 m of depth a velocity anomaly with distinct characteristics is recognized analysis of traveltimes of p wave energy propagated from common source receiver depth positions at that depth interval delineated a low velocity zone lower than estimated p wave velocity in water in which propagated s wave energy was negligible analysis of porosity logs did not outline any porosity anomaly for that region the anomaly is interpreted as caused by the presence of a gas bearing zone extending for 1 5 m 0 76 m from the top and the bottom of the depth interval through which propagation of shear energy was almost prevented and compressional energy traveled a very low speed relative lower values of shear modulus were computed for the gas bearing zone the same depth interval also exhibited relative lower values of bulk modulus relative higher values of compressibility and relative high porosity however the low velocity anomaly is not caused by relative increased porosity but rather to replacement of water by gas in the pore volumes of this zone the presence of a shallow thin gas bearing zone is interpreted as hazardous in the occurrence of strong motion in the new madrid seismic zone shallow water table as detected by seismic and log measurements in the area increases the risk of liquefaction of the sampled soil under strong ground motions

acoustic velocities in heated block of granite subjected to uniaxial stress acoustic velocities have been measured within a 38 cm cubic block of granite isolated from the surrounding rock the block was subjected to uniaxial stresses in the range 0 24 mpa and to heating in the range 14 sup 0 to 98 sup 0 c an increase in temperature from 14 sup 0 to 72 sup 0 c in the unstressed block resulted in an increase in velocities in directions parallel and perpendicular to the applied stress a further increase in temperature to 98 sup 0 c in the unstressed block resulted in a decrease in velocities application of uniaxial stress with the block at a temperature of 98 sup 0 c resulted first in uniform increases in velocity to an applied stress of mpa and then sharp decreases from 10 to 14 mpa followed by uniform increases in velocity to a maximum stress of 24 mpa a reduction in temperature to 16 sup 0 c resulted in a sharp reduction in velocity 25 percent less than originally measured at ambient temperature it is concluded that at temperatures rising to 72 sup 0 c anisotropic thermal expansion of the crystals comprising the granite causes the closure of microcracks present in the unheated rock between 72 sup 0 and 98 supmore 0 c particularly when stress was applied irreversible mechanical changes occurred in the block less

applications of algebraic reconstruction techniques to crosshole seismic data tomographic imaging techniques were applied to two crosshole data sets to determine the velocity structures and the reliability and resolution of the algorithms on real data the experiments were carried out at the retsoff salt mine in new york and at the underground radioactive waste study site at the stripa mine facility in sweden the traveltimes at restoff were high quality and were obtained over raypaths of up to 500 m in length the structure was quite complicated with velocity contrasts up to 50 percent the stripa site was in granitic rock with velocity contrasts of only a few percent the dimensions of the experiment were small with maximum ray lengths of just over 10 m the data at this site were collected with very high accuracy source and receiver locations were measured to better than 1 0 mm and traveltimes were read to 0 001 ms a number of algorithms similar to the algebraic reconstruction techniques art used in medical imaging have been applied to the data some modifications of the algorithms such as the application of weighting schemes damping parameters and curved raypaths were performed the resulting velocity fields were compared to the known fields and with each other to determine an optimal method the algorithms were found to be a rapid reliable means of reconstructing the slowness field of real data low velocity zones were recovered with accuracy in location and value it was also found that great care was necessary in application of the techniques to ensure that proper damping parameters are used and the proper number of iterations taken otherwise poor reconstructions will result

crosshole seismology and seismic imaging in crystalline rocks a borehole to borehole audiofrequency seismic system using piezoelectric transducers as active elements has been developed and used to investigate crystalline rocks in canada high quality seismograms have been recorded for transmitter receiver distances of up to 230 meters it has been found that both travel times and signal amplitudes provide diagnostic information about rock quality two dimensional images of seismic velocity and transparency distributions between two boreholes derived from observed arrival times and amplitudes by simple back projection tomography reflect lithology and geological structure the results indicate the potential usefulness of crosshole seismic imaging as a tool for rock mass characterization

a large scale flow and tracer experiment in granite 2 results and interpretation water and tracer flow has been monitored in a specially excavated drift in the stripa mine several new experimental techniques and equipment were developed and used the whole ceiling and the upper part of the walls were covered with 375 individual plastic sheets where the water flow into the drift could be collected eleven different tracers were injected at distances between 11 and 50 m from the ceiling of the drift the flow rate and tracer monitoring was kept up for more than 2 years the tracer breakthrough curves and flow rate distributions were used to study the flow paths velocities hydraulic conductivities dispersivities and channeling effects in the rock in a companion paper the experimental design and performed experiments are described the present paper describes the interpretation of flow and tracer movement in the rock outside the drift the tracer movement was measured by the more than 160 individual tracer curves the tracer experiments have permitted the flow porosity and dispersion to be studied the possible effects of channeling and the diffusion of tracers into stagnant waters in the rock matrix and in stagnant waters in the fractures have also been addressed

the hadley circulation as a radiative convective instability abstract hadley cell simulations over a tropical ocean are reported that suggest that the emission and absorption of thermal radiation by clouds plays an important role in the dynamics of the hadley circulation in particular inclusion of interactions between clouds and radiation causes the tropical atmosphere to become unstable to large scale convective circulations driven by differential radiative heating between cloudy and clear regions even when the sea surface temperature and the solar forcing do not vary with latitude or time zonally symmetric circulations take the form of an equatorially asymmetric convective cell with ascent in one hemisphere and descent in the other this may explain why there is usually only one intertropical convergence zone that is located away from the equator even when the sea surface temperature maximum is on or near the equator the conclusions of this paper are tentative because the treatments of convection radiation and cloudiness are highly simplified however if

a continuum approach for modeling mass transport in fractured media a continuum approach has been developed for modeling mass transport in fractured rocks it involves a new application of a particle tracking method in which physical transport is simulated in terms of velocity and the variations in velocity statistics describing the particle motion come from observing the actual pattern of particle motion in a discrete subdomain this subdomain is a small but representative piece of the much larger continuum in effect particle motion in the continuum is forced to mimic that in the discrete subdomain the model successfully duplicates patterns of anisotropic dispersion predicted by de josselin de jong 1972 and breakthrough curves simulated with a discrete fracture model applications demonstrate that the de josselin de jong approach for estimating dispersivities for idealized networks cannot generally be applied to networks formed from sets of finite irregularly spaced fractures in addition this study reinforces indications from earlier studies about the complexity of dispersion in fractured media factors that contribute to spreading in the major and minor principal directions change with the orientation of the network relative to the mean hydraulic gradient

surface to tunnel seismic tomography studies at yucca mountain nevada 1 a surface to tunnel seismic survey was conducted to estimate fracture intensity and distribution in the proposed nuclear waste repository area at yucca mountain nevada a 5 km long source line and a 3 km long receiver line were located on top of yucca mountain ridge and inside the exploratory study facility esf tunnel respectively numerical modeling showed that the first arrival p waves are mainly propagated in the repository horizon at depth therefore two dimensional travel time inversions were performed after the actual source locations on the ridge were projected onto the layer of interest at depth static corrections were applied to absorb the scatter in the new source locations and to correct for variations in source and receiver coupling and travel time shifts zero offset amplitude variations of the first arrivals across the receiver line inside the tunnel showed strong correlation with the fracture density determined by measurements along the tunnel wall wave guidance by subhorizontal fractures is suggested as a possible source for this phenomenon tomographic inversion of the travel time data revealed a low velocity zone in the south central area of the repository horizon conversion of the velocity tomography results to fracture density tomograms showed good correlation with fracture intensity mapped along tunnel walls the fractured zone extends over a large area in the southern region of the potential repository in particular southwest of the intensely fractured zone encountered in the esf tunnel the rock in the northern section of the repository appears more competent compared to the highly fractured areas in the south

crustal heterogeneity in south australia earthquake evidence summary lateral velocity variations in the south australian crust have been mapped using the relatively new technique of seismic tomography the input data comprised p1 travel times from 1340 local earthquakes recorded on the south australian seismic network during the period 1978 1983 to reduce errors in the earthquake locations focal depths and origin times we used an averaging technique of dividing the area under consideration into a series of overlapping cylindrical cells all earthquakes and seismic stations were assigned to the centre of the nearest cell travel times between all centres were computed by averaging over all relevant cell pairs after first scaling all travel times by a factor equal to the distance between cell centres divided by the actual ray path length only ray paths appropriate to the p1 phase were considered starting with a first guess model based on the number of ray intersections with each cell the travel times were computed along all ray paths and compared with the observed averaged values the errors and residuals were back projected for each ray over all the chords along the ray and the average cell slowness adjusted in an iterative sense until the computed and observed travel times agreed within a specified error tolerance the areas with poor raypath coverage lack of earthquakes and or stations could not be imaged the area covered lies mostly within the adelaide geosyncline where there is believed to be a thick cover of proterozoic sediments the velocity image is of the upper 20 km of the crust so no direct correlation between the surface geology and the crustal velocity is to be expected results indicate a significant variation in crustal velocity from 5 9 to 6 5 km s 1 the velocities correlate remarkably with time terms computed in a separate study of moho refracted arrivals pn low time terms correspond to high crustal velocity and high time terms reflect anomalously low crustal velocity the residual component of the time terms can be explained in terms of variations in depth to the moho throughout the geosyncline of the order of 10 km the prominent features of the tomographic velocity map are a n s trending velocity low over the spencer gulf graben and a ridge of high velocity beneath the flinders ranges the velocity low can be associated with a region of low gravity aligned parallel to the torrens hinge zone which marks the western boundary of the geosyncline the northern end of the high velocity ridge coincides with a region of positive bouguer gravity teleseismic residuals from both earthquakes and nuclear explosions show a similar trend to the pn time terms and indicate lateral variability in crustal thickness and velocity a component of the residual must be attributed to mantle velocity inhomogeneity which extends to depths of 300 km

transport of a tracer slug in a fractured permeable formation abstract this paper concerns the migration of a tracer slug injected into a fractured permeable formation basic transport processes are formulated dimensionless parameters governing transport phenomena in the domain are identified and their effects are determined a simplified conceptual model is employed for the quantitative evaluation of the physical phenomena associated with tracer migration in the domain the analytical approach applied in this study provides some basic characteristics concerning the build up and decay of tracer breakthrough curves characteristics of fracture networks incorporating a large number of fracture sectors are evaluated using a numerical finite difference scheme it is shown that various time and length scales characterize the phenomena involved in tracer slug migration in a fractured permeable formation it is found that in cross sections located at a small distance from the tracer injection point two maximum values of tracer concentration are expected in the breakthrough curves in cross sections located at comparatively large distances from the tracer injection point the breakthrough curves are similar to those characterizing an ideal porous media

a large scale flow and tracer experiment in granite 1 experimental design and flow distribution this paper describes the stripa three dimensional experiment where water and tracer flow has been monitored in a specially excavated drift in the stripa mine several new experimental techniques and equipment were developed and used the experiment was performed in a specially excavated drift 100 m long at the 360 m level in granite the whole ceiling and the upper part of the walls were covered with 375 individual plastic sheets where the water flow into the drift could be collected eleven different tracers were injected at distances between 11 and 50 m from the ceiling of the drift the flow rate and tracer monitoring was kept up for more than 2 years the tracer breakthrough curves and flow rate distributions were used to study the flow paths velocities hydraulic conductivities dispersivities and channeling effects in the rock this paper describes the experimental techniques the fracture mapping the tracer and flow rate measurements and the results of the flow rate measurements the detailed observations made possible by the plastic sheeting technique have given some qualitative as well as quantitative information on flow rate distribution in fractured rock which previously has not been available these observations may be of importance for assessing the transport of dissolved species such as radionuclides through fractured rock