the influence of clay content salinity stress and wettability on the dielectric properties of brine saturated rocks 10 hz to 10 mhz complex impedance measurements have been performed on 14 shaly sand samples berea sandstone and ottawa sand bentonite packs in a frequency range of 10 hz to 10 mhz using both the two and four electrode techniques measurements have been conducted at an effective radial stress varying from ambient pressure to 4000 psi for brine saturated oil wet and water wet samples the dielectric permittivity is found to correlate with the clay volume fraction the cation exchange capacity and electrochemical potential of the rock samples and to depend strongly on the salinity of the brine used stress and wettability are shown to have a small influence on the dielectric constant of fully brine saturated rocks a lower critical frequency is found to characterize the geometry of the pore space empirical correlations between the dielectric constant frequency permeability cation exchange capacity and porosity are presented for the shaly sands used in this study these correlations provide a means of estimating important petrophysical parameters such as the permeability and the clay content from a nondestructive complex impedance sweep of shaly sands fully saturated with brine

a two dimensional spectral analysis of short period gravity waves imaged in the oi 557 7 nm and near infra red oh nightglow emissions over arecibo puerto rico in january 1993 an extensive set of radar and optical data was gathered from various key sites around the world during a coordinated 10 day run designed to investigate the coupled dynamic behavior of the upper atmosphere on a large medium and small scale as part of this campaign an all sky ccd imaging system was operated at arecibo observatory puerto rico to help quantify the response of the low latitude mesosphere thermosphere system to short period 1 hour gravity waves measurements of the oi 557 7 nm and near infrared oh nightglow emissions were made in conjunction with photometric and isr radar soundings and revealed an abundance of small scale structure in the 80 100 km range in this letter we apply two dimensional spectral analysis techniques to aid in the interpretation of a complex set of image data that consisted of two intersecting quasi monochromatic gravity wave patterns progressing on approximately orthogonal headings an investigation of the spectral content and temporal evolution of these wave motions at each emission altitude is presented

electrical impedance variation with water saturation in rock we measured the electrical impedances of 22 sandstone samples during oil driving water tests using the two electrode method experiments show that the imaginary part x of the impedance r ix of rock may respond well to water saturation in the frequency range 100 hz 15 mhz we found that the maximum x values and their corresponding interfacial polarization frequencies are linear with water saturation the lower critical frequency is found to vary with water saturation in an unclear relationship with the characteristic length of rock the dissipation factor at the interfacial polarization frequency remains quite stable and may be an indicator of the pore structure of rock we used an equivalent circuit to explain the dispersive behavior of rock more than one interfacial polarization frequency in the impedance argand plot is predicted and can be observed if the measurement frequency range is wide enough

fracture anisotropy characterization in crystalline bedrock using field scale azimuthal self potential gradient the potential for the geophysical characterization of fractured rock bulk anisotropy using azimuthal self potential gradient aspg method was investigated at four fractured rock field sites in the new jersey highlands njh province a visual from polar plots and empirical from linear regression of cross plots correlation exists between aspg measurements and dominant fracture strike orientations mapped at three of the four study sites with the magnitude of the sp signal positively correlated to the number of fractures n along the same azimuth this result is consistent with recent electrokinetic theory that invokes a dependence of the streaming potential coupling coefficient on microgeometry in addition to hydraulic gradient based on local surface drainage patterns and regional fracture orientations the direction of the positive lobe of the aspg signal appears indicative of the likely flow direction within fracture sets three repeat measurements at one site over a one year period consistently reproduced the aspg lobes along major and minor fracture sets although the magnitude of the self potential varied along the major strike set possibly due to variable rates of groundwater flow whereas aspg captured hydraulic anisotropy at three of four sites resistivity anisotropy only dominated azimuthal resistivity surveys ars data at one site our results suggest that aspg is a surprisingly simple effective tool for characterization of fracture dominated media in addition to defining the fracture induced hydraulic anisotropy the direction of fracture controlled flow is evident from the polarity of the sp signal

near bed mass flux profiles in aeolian sand transport high resolution measurements in a wind tunnel vertical profiles of the streamwise mass flux of blown sand in the near bed 17 mm region are analysed from high resolution measurements made using an optical sensor in a wind tunnel this analysis is complemented by detailed measurements of mass flux and mean velocity profiles throughout the boundary layer depth 0 17 m using passive chambered sand traps of small dimensions and armoured thermal anemometers respectively the data permit a preliminary analysis of the relations between the observed forms of the profiles of near bed fluid stress and horizontal mass flux within a carefully conditioned boundary layer profiles of mass flux density are found to be characterized by three regions of differing gradient with transitions at about 2 mm and 19 mm above the bed the exponential decay of mass flux with height is confirmed for elevations above 19 mm and when plotted as a function of u 2 g a parameter of mean vertical trajectory height in saltation the gradient of mass flux in this region scales with the wake corrected friction velocity u where u 0 30 m s 1 a separate near bed region of more intense transport below 19 mm is identified which carries 80 per cent of the total mass flux this region is evident in some previous field and wind tunnel data but not in profiles simulated by numerical models ventilated passive sand traps underestimate mass flux in this region by 37 per cent at slow or moderate wind speeds a third significant region below 2 mm is observed these regions are likely to be related to grain populations in successive saltation low energy ejections and intermittent bed contact respectively optical measurements reveal locally high grain concentrations at some elevations below 5 mm these heights scale with transport rate mass flux gradient and wind speed copyright 1999 john wiley sons ltd

caribbean ionosphere campaign year one airglow and plasma observations during two intense mid latitude spread f events a series of campaigns has been carried out in the caribbean over a one year period to study intense mid latitude spread f events using a cluster of diversified instrumentation these events are relatively rare but a number of them have now been captured and will be discussed in this and several companion papers this paper focuses on 630 nm airglow images obtained by the cornell all sky imager for two of the more spectacular cases that began on february 17 1998 and february 17 1999 in the latter case and for the first time a poleward surge of depletion enhancement airglow zones was captured by radar as well as an airglow imager in the former case structures grew in place overhead and produced strong vhf f region backscatter as observed by the cupri and university of illinois radars the other event exactly one year later did not result in detectable 3 m backscatter the two data sets show quantitatively that the low airglow region is elevated in height and depleted in plasma density and pedersen conductivity we suggest an enhanced eastward electric field inside the low conductivity zone may be responsible for the surge the data also suggest small scale turbulence can only be observed in developing structures

investigations of thermospheric ionospheric dynamics with 6300 a images from the arecibo observatory pilot observations were conducted at arecibo puerto rico using an all sky image intensified ccd camera system in conjunction with radar ionosonde and global positioning system gps diagnostic systems during the periods january 19 28 1993 and february 21 to august 22 1995 these represent the first use of campaign mode operations of an imager at arecibo for extended periods of f region observations the january 1993 period the so called 10 day run yielded a rich data set of gravity wave signatures perhaps the first case of direct imaging of thermospheric wave train properties in the f region the 6 month 1995 campaign revealed two additional optical signatures of f region dynamics a brightness wave in 6300 a passing rapidly through the field of view fov has been linked to meridional winds driven by the midnight temperature maximum mtm pressure bulge on may 3 1995 during a period of geomagnetic activity a 6300 a airglow depletion pattern entered the arecibo fov such effects represent the optical signatures of equatorial spread f instabilities that rise above the equator to heights near 2500 km thereby affecting arecibo s l 1 4 flux tube

theoretical analysis of particle number density in steady aeolian saltation abstract particle number density or particle concentration in aeolian saltation is one important input parameter to calculate the sand flux kinetic energy and mid air collision probability in the aeolian saltation and particle concentration is also related to the wind erosion capacity hence in the present paper the vertical distribution of particle number density in steady aeolian saltation is analyzed based on two different types of probability density functions of vertical lift off velocity of saltating particles one is the pdf probability density function of vertical velocity of lift off particles in the three dimensional space defined as a type a pdf which considers the number of particles in various velocity bins per unit volume and the other is the pdf of vertical velocity of lift off particles ejected from the sand bed surface in a period of time as a type b pdf which considers the number flux of particles in various velocity bins per unit surface area these two types of pdfs are from two different perspectives i e volume and surface based perspectives respectively and can be deduced from each other the half normal and exponential distributions are recommended for the type a pdf and the corresponding type b pdf is expressed by rayleigh and gamma 2 distributions the pdf distribution pattern of vertical velocity of lift off particles has an important influence on the vertical profile of particle number density if the type a pdf of vertical velocity of ejected particles is a half normal distribution the particle number density decays exponentially with height if the type a pdf is an exponential distribution the particle number density also decreases with height if the type a pdf is gamma 3 and rayleigh distributions the particle number density first increases then decreases with height the type a and type b height parameters which are calculated according to the mean vertical lift off velocity from the type a and type b pdfs respectively are not simply considered as the actual mean saltation height although if the type a pdf of vertical lift off velocity is half normal pdf the mean dispersion height of particle concentration equals the mean saltation height the vertical distribution of particle number density can determine the dislodgement rate on bed surface which further affects the surface bedforms

nature of surface electrical conductivity in natural sands sandstones and clays the electrical conductivity of rocks results from conduction through the bulk solution occupying the pores and from surface conduction occurring at the fluid grain interface the nature of the surface electrical conductivity of shaly and clean sands and sandstones is examined surface conduction is characterized by the specific surface conductance which is the sum of three contributions i conduction within the electrical diffuse layer which makes a negligible contribution to the total specific surface conductance ii conduction in the stern layer which is shown to vary significantly with the salinity of the pore fluid at low salinities 10 6 to 10 3 mol 1 1 but becomes independent of salinity at higher salinities iii a mechanism operating directly on the mineral surface independent of salinity and perhaps associated with proton transfer at salinities higher than 10 3 mol 1 1 and at 25 c the specific surface conductance of quartz and clays is equal to 8 9 10 9 s and 2 5 10 9 s respectively equations describing the influence of surface conductivity and microstructure upon the macroscopic electrical conductivity of sands sandstones and shales are also developed

the characteristics of aeolian sediment flux profiles in the south eastern tengger desert deserts are one of the most important dust sources in the world because dust content changes as a function of height at low levels in the atmosphere this affects long term dust transport in this paper field data measured above shifting sands in the south eastern tengger desert were used to analyse the vertical distribution of sediment fluxes in the near surface layer 0 to 48 m it was possible to express horizontal sediment flux as a power function but aeolian deposition as a function of height could be expressed as an exponential function there are two curve types for the particle size distributions in the horizontal sediment flux and aeolian deposition bimodal and unimodal curves for the horizontal sediment flux and aeolian deposition heights of 24 m and 32 m respectively were the key heights in the size distribution curve below these heights the curve was bimodal whereas above these heights it was unimodal at heights of 4 to 16 m and especially between 8 m and 12 m the data were particularly interesting because the sediment size transport mode degree of sorting and the skewness and kurtosis change for the horizontal sediment flux wind turbulence moved saltating particles higher than expected

self potential monitoring of a salt plume nonintrusively monitoring the spread of contaminants in real time with a geophysical method is an important task in hydrogeophysics we have developed a sandbox experiment showing that the self potential method can locate both the source of leakage and the front of a contaminant plume we monitored the leakage of a plume of salty water from a hole at the bottom of a small tank located at the top of a main sandbox initially the sand was saturated by tap water at a given time a hole was opened at the bottom of the tank allowing the salty water to migrate by diffusion and buoyancy driven flow in the main sandbox the bottom of the sandbox contained a network of 32 nonpolarizing silver silver chloride electrodes with amplifiers connected to a multichannel voltmeter the self potential response associated withthe migration of the salt plume in the sandbox was recorded over time a self potential anomaly was observed with amplitude varying from a few millivolts at the start of the leak to a few tens of mi

thermophysical properties of the earth s crust in situ measurements from continental and ocean drilling knowledge of the variation of thermal conductivity and heat production with depth is critical to understanding the thermal state of the crust continental and oceanic drill holes provide unique opportunities for the calibration of empirical and theoretical models relating crustal thermal properties to physical and chemical properties these calibrations are based on more than 30 000 well log measurements of acoustic velocity both compressional and shear density porosity radioelement concentrations k u th and major element chemistry al si ca fe s mg na in formations ranging in age from 5 to 620 ma and in composition from granitic to gabbroic the mineralogical data available from induced gamma ray spectroscopy logs when combined with known mineral thermal conductivities in a model for the thermal conductivity of a crystalline aggregate enable the in situ application of a laboratory estimation technique and yield continuous conductivity profiles however mineralogy based conductivity models cannot account for the anisotropic conductivity observed in foliated metamorphic rocks a phonon conduction model which utilizes acoustic velocity and bulk density measurements is accurate within 15 in both isotropic and anisotropic formations of the upper continental crust and in oceanic crustal layers 2c and 3 in oceanic crustal layers 2a and 2b however the effects of fracturing on compressional and shear velocities lead to inaccurate results the heat flow heat production relationship which provides one method of determining subsurface heat production has well documented limitations allis 1979 and rybach and buntebarth 1982 1984 on the basis of laboratory measurements have proposed quantitative relationships between heat production and rock compositional and physical properties the well log k u and th data indicate that heat production can be predicted from compositional data within a factor of 2 or 3 predictions of heat production from acoustic velocity and bulk density measurements are only accurate to within an order of magnitude three factors account for these results 1 the natural variability of velocity and density for a given rock composition 2 the tendency of u and th to associate with secondary rather than primary minerals and 3 u and th redistribution through fluid flow and metamorphism thus seismic velocity based heat production profiles can at best be taken as first order estimates which may misrepresent the complexity of the continental crust however the correlation of formations of known heat production with subsurface structures when combined with a suite of existing techniques for estimating heat production may lead to more accurate results

experimental investigation of mass flux and transport rate of different size particles in mixed sand transport by wind abstract sand transport by wind in arid regions is a geomorphic process affected by the grain size distribution knowledge of the transport behavior of each size group in mixed sand transport is important for understanding the saltation dynamics in dune migration this paper focuses on the characteristics of mass flux mass concentration horizontal velocity and transport rate of different particle size groups and the relation to their mass proportion in air experiments were carried out to analyze these relations in a wind tunnel by particle tracking velocimetry the mass flux of different size particles usually decays exponentially with height for larger size groups and deviates from exponential decay for smaller size groups the trend of mass concentration of different size groups with height is similar to the mass flux the mean horizontal velocity of different size groups generally increases with increasing height and decreases with the increase of particle size at the same height with increasing height the ratio of mass flux of each size group to the total mass flux increases for the smaller size group but decreases for the larger size group and the transition diameter of particles is about 0 14 mm for the 0 16 mm sand sample and about 0 21 0 27 mm for the 0 24 mm sand sample for the smaller size group the ratio of the mass weighted average horizontal velocity of each size group to that of all particle sizes is 1 0 and the ratio of the transport rate of each size group to the total transport rate is usually larger than its mass proportion in air this is the opposite for the larger size groups the maximum deviation of mass flux proportion of each size group from its mass proportion in air is about 15 which is determined by the mass weighted average horizontal velocity of each size group

permeability of illite bearing shale 2 influence of fluid chemistry on flow and functionally connected pores 1 bedding parallel permeability of illite rich shale of the wilcox formation has been investigated using distilled water and 1 m solutions of nacl kcl and cacl2 as pore fluids despite low modal concentrations of swelling clays specimens expand upon fluid saturation and permeabilities depend on fluid composition permeabilities to flow of 1 m cacl2 are 3 5 times greater than values measured for the other pore fluids suggesting sensitivity to exchange of divalent cations for monovalent cations at clay mineral surfaces permeabilities of individual samples exhibit nonrecoverable changes with sequential changes in composition of incoming fluid permeabilities k at varying effective pressure pe fit a cubic law k k0 1 pe p1 m 3 where m and p1 are independent of fluid composition and k0 is greater for transport of 1 m cacl2 than that for transport of the other pore fluids assuming that fluid conduits have crack like dimensions the lack of sensitivity of m and p1 to fluid composition suggests that surface roughness and asperity stiffness of conduits are unaffected by cation exchange while changes in k0 reflect changes in the clay fluid interfaces of the connected pore space index terms 5114 physical properties of rocks permeability and porosity 5139 physical properties of rocks transport properties 1832 hydrology groundwater transport 3947 mineral physics surfaces and interfaces 1045 geochemistry low temperature geochemistry keywords permeability shale fluid chemistry citation kwon o b e herbert and a k kronenberg 2004 permeability of illite bearing shale 2 influence of fluid chemistry on flow and functionally connected pores j geophys res 109 b10206 doi 10 1029 2004jb003055

hydraulic and chemical pulse tests in a shut in chamber imbedded in an argillaceous formation numerical and experimental approaches hydraulic and chemical pulse tests were performed in four shut in chambers to obtain hydraulic and chemical parameters of the callovo oxfordian shale the osmotic tests i e chemical pulses were carried out by exchange of the formation water for a different solution either more or less concentrated two sets of two osmotic tests were done in march and october 2006 these osmotic tests are superimposed on a purely hydraulic response because of the drilling of the well causing a pressure drop the pressure records hydraulic and osmotic responses were interpreted using a 2 d model to obtain the hydraulic and chemical parameters the osmotic efficiency inferred for the callovo oxfordian shale is on the order of 0 012 for a concentration of 0 43 mol l 1 and 0 12 for a concentration of 0 086 mol l 1 these results suggest that the callovo oxfordian shale behaves as a weakly semipermeable membrane and only 0 1 0 15 mpa of the 0 2 0 5 mpa can be explained by these osmotic efficiency values

laboratory studies of aeolian sediment transport processes on planetary surfaces abstract we review selected experimental saltation studies performed in laboratory wind tunnels and collision experiments performed in splash laboratory facilities that allow detailed observations between impinging particles on a stationary bed we also discuss progress in understanding aeolian transport in nonterrestrial environments saltation studies in terrestrial wind tunnels can be divided into two groups the first group comprises studies using a short test bed typically 1 4 m long and focuses on the transitional behavior near the upwind roughness discontinuity where saltation starts the other group focuses on studies using long test beds typically 6 m or more where the saturated saltation takes place under equilibrium conditions between wind flow and the underlying rough bed splash studies using upscaled model experiments allow collision simulations with large spherical particles to be recorded with a high speed video camera the findings indicate that the number of ejected particles per impact scales linearly with the impact velocity of the saltating particles studies of saturated saltation in several facilities using predominantly particle tracking velocimetry or laser doppler velocimetry indicate that the velocity of the few particles having high trajectories increases with increasing friction velocity however the speed of the majority of particles that do not reach much higher than bagnold s focal point is virtually independent of shields parameter at least for low or intermediate u values in this case mass flux depends on friction velocity squared and not cubed as originally suggested by bagnold over short beds particle velocity shows stronger dependence on friction velocity and profiles of particle velocity deviate from those obtained over long beds measurements using horizontally segmented traps give average saltation jump lengths near 60 70 mm and appear to be only weakly dependent on friction velocity which is in agreement with some but not all older or recent wind tunnel observations similarly some measurements performed with uniform sand samples having grain diameters of the order of 0 25 0 40 mm indicate that ripple spacing depends on friction velocity in a similar way as particle jump length the observations are thus in agreement with a recent ripple model that link the typical jump length to ripple spacing a possible explanation for contradictory observations in some experiments may be that long observation sequences are required in order to assure that equilibrium exists between ripple geometry and wind flow quantitative understanding of saltation characteristics on mars still lacks important elements based upon image analysis and numerical predictions aeolian ripples have been thought to consist of relatively large grains diameter 0 6 mm and that saltation occurs at high wind speeds 26 m s involving trajectories that are significantly longer than those on earth by a factor of 10 100 however this is not supported by recent observations from the surface of mars which shows that active ripples in their geometry and composition have characteristics compatible with those of terrestrial ripples sullivan et al 2008 also the highest average wind speeds on mars have been measured to be electrification is seen as a dominant factor in the transport dynamics of dust on mars affecting the structure adhesive properties and detachment entrainment mechanisms specifically through the formation of aggregates merrison et al 2012 conversely for terrestrial conditions electric fields typically observed are not intense enough to significantly affect sand transport rates while little is known in the case of extra terrestrial environments

case studies of coupling between the e and f regions during unstable sporadic e conditions 1 simultaneous f region airglow e region coherent scatter radar and ionosonde observations were made in greece during the summer sporadic e season in 2002 in this paper we report on two case studies during which patchy sporadic e layers were accompanied by midlatitude spread f coherent vhf radar echoes including two stream echoes and traveling ionospheric disturbances registered by the airglow instrument we argue that these events give strong evidence that polarization electric fields are built up in the e region and are mapped upward to the f region creating rising and falling regions in the bottomside plasma the resulting structure creates conditions for midlatitude spread f as detected by the ionosonde this correlation between patchy sporadic e and midlatitude spread f is further supported in a companion paper upward coupling of this sort is particularly efficient in regions of f region plasma uplift and airglow depletion since the f region pedersen conductivity is low which reduces the electrical load on the e region generator

streaming electrical potential anomaly along faults in geothermal areas electrical potential anomalies are often measured associated with geothermal areas and volcanoes in these systems fluid flow is usually mostly restricted to faults and fracture networks an equation describing electrical potential anomalies of electrokinetic nature associated with fluid upflow induced by a thermal source along faults is derived the electrical potential anomaly is related to the depth of the thermal reservoir the temperature difference between the surface and the reservoir of the geothermal area the thermal expansion of water and the streaming electrical potential coupling coefficient in the fault zone a quantitative calculation of the electrokinetic anomaly is provided by comparing this model to a self potential survey of the cerro prieto geothermal field fitterman and corwin 1982 the predictions of the model agree well with the field measurements

localization and quantification of leakages in dams using time lapse self potential measurements associated with salt tracer injection the self potential method is the only non intrusive method that is directly sensitive to the flow of the pore water in a porous material we propose the use of a new protocol of self potential measurements associated with a brine injection to locate leakages in earth dams and to quantify their permeability indeed a brine solution injection upstream of an earth dam in the assumed leakage zone is able to change the electrical conductivity of the medium in turn this decreases the magnitude of the electrokinetic contribution of the self potential signals that are related to the flow of the seepage water the evolution of this anomalous self potential signal expected to be positive with respect to a reference state prior the salt injection can be measured at the ground surface with a network of non polarizing electrodes the seepage flow inside the dam is localized from the evolution in space and time of the resulting transient self potential signals associated with the transport of the brine the mean permeability of the preferential flowpath can be determined this method is first applied to a laboratory test to show how the passage of a salt tracer affects the self potential response then we apply this new methodology to a field test site a dam with a proven leakage located in the south of france at this test site self potential mapping was first performed to locate the preferential flow path then a network of non polarizing electrodes was used to perform time lapse self potential measurements at the dam crest during a brine injection occurring upstream of the seepage zone we used two lines of 16 non polarizing electrodes each from the time lapse data the permeability of the leaking area was estimated inside one order of magnitude

thermal conductivity of unconsolidated sediments with geophysical applications a theoretical model for the prediction of the thermal conductivity of unconsolidated granular sediments with application to sand shale mixtures is presented the sediment is modeled as an assemblage of grains of thermal conductivity s immersed in a pore fluid of thermal conductivity in order to take into account for the thermal interactions between the grains a differential effective medium approach is used to provide a relationship between the effective thermal conductivity of the isotropic mixtures of grains saturated by the pore fluid the porosity and the thermal conductivities of the grains and pore fluid the influence of the topology of the interconnected pore space is accounted for through the use of the electrical cementation exponent m which is related to the electrical formation factor f by f m where is the interconnected porosity the main assumption of the model lies in the small contiguity between the grains this assumption holds well for unconsolidated sand shale mixture sediments as demonstrated by comparing the model to available experimental data the model offers the possibility to derive thermal conductivity profiles from downholes measurements of natural radioactivity electrical resistivity and bulk density

effects of fluid displacement pattern on complex electrical impedance in berea sandstone over frequency range 104 106 hz to better understand the effect of fluid distribution on the electric response of rocks saturated with oil and brine we conducted experimental studies on the complex electrical impedance in a berea sandstone together with in situ acquisitions of oil distribution images employing a high resolution medical x ray computed tomography we performed two tests of brine displacement by oil under high 10 mpa and low 5 mpa pressures which were accompanied by fingering and stable displacement patterns respectively the measured complex impedance data were fitted to the cole model to obtain the resistance capacitance peak frequency of the imaginary impedance and the exponent of the rock fluid system with increasing oil saturation the resistance showed an increasing trend whereas the other three parameters decreased the fingering displacement exhibited lower resistance and capacitance than the stable displacement the analysis of the resistance changes using a simple parallel connection model indicates that there are more components of residual brine in parallel connections in the fingering pattern than in the stable displacement pattern at the same saturation we also interpreted the normalised changes in the capacitance or apparent dielectric constant with respect to the oil saturation via an analysis of the shape factor of fluid distribution based on the maxwell wagner brugermann hanai model the changes in the shape factor suggest that the pinch off of the brine in parallel connection by the oil is a dominant mechanism reducing the capacitance in the stable displacement most of the connections in the brine phase are immediately pinched off by oil displacement front at a local oil saturation of 65 conversely in the fingering displacement there is a transition from the bulk or layered brine to the pinched off at a local oil saturation below 60 the analyses indicate that the difference in the fluid distribution under different fluid conditions is responsible for the non archie behaviour

turbulent upwelling of the mid latitude ionosphere 1 observational results by the mu radar in this paper we present the detailed results of a series of experiments designed to study the coherent backscatter of 50 mhz radar waves from the mid latitude f region data were obtained with the active phased array mu radar in japan and include some auxiliary e region coherent echoes as well as in other turbulent ionospheric phenomena the intense nonthermal scatter comes from irregularities oriented parallel to b the strongest echoes correspond to irregularities at least 20 db stronger than thermal backscatter at the same frequency from typical f region densities at the same range simultaneous observations with ionosondes show that these echoes occur during strong mid latitude spread f as defined by ionosondes the latter phenomenon is certainly much more widespread than the turbulent upwelling events described here but we believe that in some sense these correspond to the most violent mid latitude spread f the strongest echoes occur in large patches which display away doppler shifts corresponding to irregularity motion upward and northward from the radar at the edges of these patches there is often a brief period of toward doppler before the echoing region ceases on rare occasions comparable patches of strong away and toward doppler are detected although in such cases the doppler width of the toward echoes is much narrower than that of the away echoes the away patches often are characterized by mean velocities well over 250 m s and doppler widths full width at half maximum of 50 m s the multiple beam capability at mu allowed us to track the patches in the zonal direction on two days the patches moved east to west in both cases at velocities of 125 m s and 185 m s respectively there is a distinct tendency for the bottom contour of the scattering region to be modulated at the same period as the patch occurrence frequency as well as at higher frequencies this higher frequency component may correspond to substructures in the large patches and to the e region coherent scatter patches which were detected simultaneously in several multiple beam experiments in the companion paper kelley and fukao this issue we explore a number of possible explanations for this phenomenon in more detail

integrated 2d modeling and interpretation of geophysical and geotechnical data to delineate quick clays at a landslide site in southwest sweden radio magnetotellurics rmt electrical resistivity tomography ert and high resolution reflection seismic data were collected along four lines to characterize the geometry and physical properties of geologic structures at a quick clay landslide site in southwest sweden the site is situated in the gota river valley where the normally consolidated materials mainly consist of glacial and postglacial sediments geotechnical data suggest the presence of quick clays above coarse grained layers these layers play a key role in the formation of quick clays and landslide triggering the rmt and ert data were individually and jointly inverted in 2d to study the resolution of resulting models for each data set the resistivity models from the joint inversions demonstrate superior resolution and accuracy compared with individual ones the geometry and location of shallower structures resolved in the 2d resistivity models from joint rmt ert inversions correlated well with those imaged in the reflection seismic data and observed in the existing geotechnical boreholes the models were poor in resolving deeper resistive bedrock at locations where the thickness of the conductive overburden exceeds a certain limit however information from the reflection seismic data could be used to estimate the depth to the top of the bedrock along all the four lines comparison between the geotechnical data and the resistivity models suggested that quick clays overlying the coarse grained layer have higher electrical resistivity than the marine clays we further validated and refined the obtained results by performing synthetic tests we showed that integration of ertand rmt data with reflection seismic data is ideal for quick clay landslide studies especially when the clay materials are thick

highly structured tropical airglow and tec signatures during strong geomagnetic activity a remarkable set of all sky images using the 630 nm airglow emission has been taken over the arecibo observatory in puerto rico wave like structures at a height of about 250 km are commonly found to travel in the southwest direction at speeds ranging from 20 120 m s most surprising is that geomagnetic activity seems to greatly amplify them forming very intricate patterns of light and dark simultaneous observations using gps satellite transmissions on one night reveal that dark regions are severely plasma depleted while bright regions have nighttime content as large as the full noontime ionosphere this unexpected geomagnetic effect at mid latitudes has implications for trans ionospheric radiowave propagation and space weather

same night observations of spread f by the jicamarca radio observatory in peru and cupri in alcântara brazil 50 mhz echoes from equatorial spread f were observed on several nights by both the jicamarca radio observatory jro in peru and the cornell university portable radar interferometer cupri in alc ntara brazil although little detailed correlation is expected between sites separated by such large distances the night of october 17 1994 shows some remarkable similarities between peru and brazil on this night spread f commenced at both jicamarca and alc ntara as thin bottomside layers situated near 320 km altitude at nearly the same local times later major plumes erupted that reached to over 1000 km altitude at both sites since plumes normally drift west to east these are obviously not the same structures but the similarities indicate that conditions for spawning them must have been coincidentally very similar on this night the next two nights which produced plumes over brazil but only bottomside layers over peru emphasize that local conditions on the same night can be very different at the two locations the importance of having a sufficiently wide beam for exploring spread f over a large altitude range at the alc ntara site is also explored

oxygen osmium isotope systematics of west maui lavas a record of shallow level magmatic processes new 18 o and 187 os 188 os data from late shield building stage lavas from west maui volcano hawai i indicate that a range of distinct shallow level processes can affect compositions of plume generated ocean island magmas the relative ages of the samples studied were determined either on the basis of field relationships or from collection depth in a water well the stratigraphically lower lavas have os 61 399 ppt initial 187 os 188 os 0 1311 0 1324 and 18 o olivine 4 53 4 88 the stratigraphically higher lavas have os 20 273 ppt initial 187 os 188 os 0 1323 0 1390 with the exception of one low os sample with 187 os 188 os 0 1517 and 18 o olivine 4 73 5 21 these compositions are generally similar to those of kea type hawaiian lavas from mauna kea and kilauea volcanoes but in detail there are some significant differences between the west maui lavas and other kea type lavas the stratigraphically lower lavas have 187 os 188 os similar to those previously observed for mauna kea and kilauea lavas and define a nearly flat 87 sr 86 sr vs 187 os 188 os trend that is consistent with assimilation by these magmas of small degree melts of pacific oceanic crustal gabbros the stratigraphically higher west maui lavas extend to 187 os 188 os higher than observed at mauna kea or kilauea this probably results from interaction of these magmas with the hydrothermally altered volcanic edifice during the waning phases of the shield building stage this process is likely to affect the isotope systematics of os and o but will have little effect on those of hf nd pb or sr

role of unstable sporadic e layers in the generation of midlatitude spread f 1 there is growing experimental evidence to suggest that mesoscale spread f is linked to the occurrence of midlatitude coherent backscatter from patchy sporadic e layers which are unstable to the gradient drift and farley buneman plasma instabilities to validate this suggestion we have compared e region backscatter and spread f ionosonde recordings from about 100 days of joint operation during summer and found a one to one relation in the occurrence of both phenomena also midlatitude backscatter studies over the last few years have shown the existence of enhanced electric fields inside patchy sporadic e these are believed to be polarization fields set up locally by neutral winds that transport the plasma patches horizontally and by the relatively large hall to pedersen conductivity ratios at e region altitudes moreover midlatitude echoes were found to be associated with mostly westward drifting sporadic e patches with typical scale lengths from 10 to more than 100 km and perturbed eastward electric fields from a few to maybe more than 10 to 15 mv m we propose that the enhanced polarization fields set up inside unstable sporadic e patches can easily map up the magnetic field lines to the f region and thus contribute to the formation of midlatitude spread f this new mechanism for spread f generation is basically an image process that can account for key observational properties of the phenomenon these include the rapid plasma upwelling and the abrupt changes in height uplifts of the f layer as well as the scale sizes involved and morphological characteristics

first observations of coherent scatter from the mid latitude f region in the caribbean the cornell university portable radar interferometer cupri started a new series of measurements of the mid latitude ionosphere from puerto rico in july 1997 on the first day of operation coherent echoes were obtained from the f region this was the first detection of such echoes in this longitude sector this is surprising since the mu radar has seen similar eches over japan and the presence of related phenomena in the caribbean suggested they should have been seen in other vhf studies a number of f region events were subsequently observed some echoes were characterized with very narrow spectra and small mean doppler shifts two events had echoes whose range changed rapidly with time but only one of these had comparable doppler velocities such differences suggest that we caught the events in different stages of development in addition to presenting samples of the data we outline the reasons why these structures were anticipated

turbulent upwelling of the mid latitude ionosphere 2 theoretical framework in a companion paper data from the mu radar have been presented which show that during sunspot minimum conditions in japan the mid latitude ionosphere is sometimes characterized by regions of rapid and turbulent upwelling in this paper we explore possible mechanisms for these events the most likely process seems to be the instability of the equilibrium which occurs when the mid latitude plasma is supported against gravity either by an eastward electric field component or by a southward neutral wind as was proposed by perkins 1973 we show for example that the growth rate determined by perkins is considerably higher in sunspot minimum conditions than at sunspot maximum for comparable altitudes of the ionospheric f layer the growth rate is not very large however and we argue here that the observed structures must evolve from preexisting undulations of the bottomside of the f region which are generated by gravity waves that is the gravity waves create finite amplitude structures which are amplified by the plasma instability an intriguing feature of the gravity wave role in this process is that the echoing patches detected by the mu radar and the height bands detected by the arecibo radar which we believe to be related phenomena all seem to propagate to the west this is the same direction reported for the angle of arrival measurements of classic mid latitude spread f by a number of researchers using ionosonde techniques since the mu radar detects the upwelling regions from nonthermal 3 m irregularities there must be mechanism to create such tracers we propose that secondary structures are created at intermediate scales via the e b instability operating on the dome of the upwelling structure and by the neutral wind driven process on either the west or the east wall of the structure depending on the direction of the zonal wind the 3 m waves are then created in a cascade process which brings energy into a range of k space in which the structures are linearly damped finally we discuss the fine structure of the echoing patches and suggest several plausible mechanisms two of which involve e region coupling and one which deals with the vertical structure of the gravity wave seeding process

modelling the evolution of complex conductivity during calcite precipitation on glass beads author s leroy p li s jougnot d revil a wu y abstract the authors 2017 when ph and alkalinity increase calcite frequently precipitates and hence modifies the petrophysical properties of porous media the complex conductivity method can be used to directly monitor calcite precipitation in porous media because it is sensitive to the evolution of the mineralogy pore structure and its connectivity we have developed a mechanistic grain polarization model considering the electrochemical polarization of the stern and diffuse layers surrounding calcite particles our complex conductivity model depends on the surface charge density of the stern layer and on the electrical potential at the onset of the diffuse layer which are computed using a basic stern model of the calcite water interface the complex conductivity measurements of wu et al on a column packed with glass beads where calcite precipitation occurs are reproduced by our surface complexation and complex conductivity models the evolution of the size and shape of calcite particles during the calcite precipitation experiment is estimated by our complex conductivity model at the early stage of the calcite precipitation experiment modelled particles sizes increase and calcite particles flatten with time because calcite crystals nucleate at the surface of glass beads and grow into larger calcite grains at the later stage of the calcite precipitation experiment modelled sizes and cementation exponents of calcite particles decrease with time because large calcite grains aggregate over multiple glass beads and only small calcite crystals polarize

measurement of streaming potential coupling coefficient in sandstones saturated with high salinity nacl brine 1 we present measurements of the streaming potential coupling coefficient in intact sandstone samples saturated with nacl brines at concentrations up to 5 5 moll 1 the values we record at low salinity are consistent with those reported previously as brine salinity increases the coupling coefficient decreases in magnitude but is still measureable up to the saturated concentration limit the magnitude of the zeta potential also decreases with increasing salinity but approaches a constant value at high salinity this behaviour is not captured by current models of the electrical double layer our results suggest that streaming potential measurements may be used to monitor flow in saline subsurface environments such as deep saline aquifers and hydrocarbon reservoirs however they were obtained at laboratory temperature future work will focus on the effect of elevated temperatures at high salinity

hydroelectric coupling in a clayey material the hydroelectric coupling generating self potential anomalies recorded on the earth s surface has received a considerable attention in the last four years geophysical applications include the use of this phenomenon for mapping subsurface fluid flow the study of hydrothermal activity and the use of self potential anomalies to monitor volcanic activity and the possibility still debated of seismic activity forecasting through the use of electromagnetic precursors of electrokinetic nature we model here two key parameters relevant of the hydroelectric coupling in clayey porous rocks these two parameters are the potential and the specific surface conductivity which depend on the electrochemistry of the pore water mineral interface they are modeled in the case of a kaolinite saturated by a nacl brine using a triple layer model tlm in which the parameters are optimized using the simplex algorithm

coherent and incoherent scatter radar observations during intense mid latitude spread f an intense mid latitude spread f event occurred over puerto rico during the night of february 17 1998 simultaneous observations were made with the cornell university portable radar interferometer cupri located near isabela pr the university of illinois vhf radar located at salinas pr gps receivers at isabela and st croix measuring total electron content the arecibo incoherent scatter radar and the cornell all sky imager located at the arecibo observatory this was the first time that such a broad range of complementary instrumentation captured a mid latitude spread f space weather event it was the first and still only time that a spread f event over the caribbean exhibited large doppler shifts in the vhf spectra this event was characterized with multiple filaments that initially produced receding doppler velocities exceeding 300 m s as seen by cupri and the illinois radar the arecibo incoherent scatter radar recorded line of sight velocities exceeding 100 m s that moved the f layer peak to over 400 km altitude airglow images of 630 0 nm emissions from f region heights showed depleted structures oriented southeast to northwest the large velocities observed with the radars suggest that we caught this event in a stage of explosive development it is interesting that the first fully documented caribbean event occurred during a magnetically active period

constitutive equations for ionic transport in porous shales 1 the constitutive coupled equations describing ionic transport in a porous shale are obtained at the scale of a representative elementary volume by volume averaging the local nernst planck and stokes equations the final relationships check the onsager reciprocity to the first order of perturbation of the state variables with respect to the thermostatic state this state is characterized by a modified version of the donnan equilibrium model which accounts for the partition of the counterions between the stern and diffuse gouy chapman layers after upscaling the local equations the material properties entering the macroscopic constitutive equations are explicitly related to the porosity of the shale its cation exchange capacity and some textural properties such as the electrical cementation exponent entering archie s law this new model is then applied to predict the salt filtering and electrodiffusion efficiencies of a shale layer

importance of thermo osmosis for fluid flow and transport in clay formations hosting a nuclear waste repository abstract three osmotic processes have been identified in clay rich media electro and chemo osmosis flows of water caused by salinity and electrical potential gradients have so far attracted almost exclusive attention but despite the recurring concern about the importance of thermo osmosis a flow of water driven by a temperature gradient in argillaceous media it remains largely neglected here we propose a new formalism for estimating the thermo osmotic permeability based on a theoretical analysis at the molecular and pore scale then upscaled we show that the thermo osmotic permeability can be estimated only from surface charge density temperature pore size and salinity the possible prominent role of thermo osmosis in compacted shale layers with a temperature gradient is then exemplified this first general estimate of the thermo osmotic permeability can be used to improve our understanding of the influence on fluid flow and pressure fields of the natural geothermal gradient in sedimentary basins which is required e g for safety assessments of nuclear waste repositories in shale layers

permeability estimating from complex resistivity measurement of shaly sand reservoir summary permeability is a key parameter associated with the subsurface production and injection this paper introduces a new method which uses the complex resistivity of rock to estimate permeability in petroleum reservoirs complex resistivity measurements were carried out on 53 shaly sand samples from daqing oil filed with a wide variation in permeability and porosity in the frequency range from 100 hz to 20 mhz using a four electrode technique this paper investigates the relationship between the complex resistivity measurements and the permeabilities of the samples the imaginary part of the complex impedance shows a power law relation to the frequency ranges from 100 hz to 1 5 khz the results show that permeability can be estimated well with expressions of the form of a b c where is the slope of the bilogarthmic plot of the imaginary part versus frequency is the porosity a b and c are constants the salinity of nacl has little influence of the slope in the range of 1 10 g l 1 the isovalue maps of the error factor which show substantial regions of near minimum values of are used to analyse the behaviour of with the change of the exponents b and c the permeability estimation is more sensitive to the changes of the slopes than the porosity the slope and the porosity are not completely independent the slope is the decisive parameter for the estimation of the permeability the additional use of the porosity improves the formula fit to the data significantly

the hydroelectric problem of porous rocks inversion of the position of the water table from self potential data summary the self potential sp method is a fast and cheap reconnaissance tool sensitive to ground water flow in unconfined aquifers a model based on the use of green s functions for the coupled hydroelectric problem yields an integral equation relating the sp field to the distribution of the piezometric head describing the phreatic surface and to the electrical resistivity contrast through this phreatic surface we apply this model to sp data measured on the south flank of the piton de la fournaise volcano a large shield volcano located on reunion island indian ocean the phreatic surface inverted with the help of the simplex algorithm from the sp data agrees well with the available information in this area one borehole and electromagnetic em data this interpretation scheme which we call electrography has many applications to the crucial problem of water supply in volcanic areas where drilling is expensive

characterization of transport properties of argillaceous sediments application to the callovo oxfordian argillite 1 we consider the case of a cylindrical cored specimen of a saturated argillaceous sediment located between two reservoirs filled with an electrolyte one of the boundaries of the sample is submitted to a sharp pressure or salinity change the migration of the resulting pressure or saline front through the core specimen is responsible for the apparition of an electrical field which is called the streaming potential the diffusion potential for a salinity gradient respectively the temporal variation of this electrical field is recorded with ag agcl nonpolarizable electrodes and used to monitor the evolution of the pressure or saline front between the two reservoirs there is a finite interval of time before which the steady state condition holds through the core in both cases the electrical potentials exhibit a relaxation with a relaxation time constant depending on the square of the length of the cylindrical core specimen and on its hydraulic or ionic diffusivity the experiments described here provide new methodologies to determine the hydraulic and ionic diffusivities of clay rich materials these experiments confirm also the predictions of a transport model developed recently for such materials and illustrate a powerful geophysical method to obtain transport properties not only in the laboratory but also in the field using a network of nonpolarizable electrodes to remotely monitor dissipation processes occurring inside the investigated system

on the efficiency of vertical array aeolian field traps the efficiency of three vertical array field traps for measuring the distribution of aeolian mass transport with height was compared with measurements with an isokinetic trap the vertical traps seem to work adequately efficiency 80 at heights greater than 15 mm above the bed closer to the bed however the open array trap catches about 70 the two continuous arrays only about 50 because most of the transport takes place close to the surface the overall efficiency of the field traps ranges from 50 to 70 based on these wind tunnel tests we have developed a low single compartment wedge shaped trap its shape in combination with flow straighteners at the entrance minimizes stagnation effects so that the efficiency is 80 our data indicate that with the wedge trap used in combination with the vertical array aberdeen trap we can sample mass transport in the field during periods with unidirectional winds with an overall efficiency of the order of 80

vertical profiles of aeolian sand mass flux abstract vertical profiles of the horizontal mass flux of blown sand are investigated experimentally using a passive vertical array in a wind tunnel considering lower sampling efficiency of the sand trap in the near bed region this investigation is complemented by the measurements of the longitudinal profiles of mass flux made using a horizontal sand trap the experiments were conducted with two test sands and five different stream velocities in the upper part of the vertical profile the measured data exhibit an exponential decay distribution with a positive deviation occurring in the near bed region the measured longitudinal profiles are similar to the measured vertical profiles linking both profiles and the modes of sand transport it is possible that saltating sand grains give rise to the well known exponential decay distribution of mass flux and that creeping and reptating grains force a deviation from it a simple equation applicable for both the vertical and the longitudinal sand mass flux variations is introduced and the parameters are estimated from experimental data

characterization of electrical properties of organic rich shales at nano micro scales abstract a new experimental protocol is explored to characterize electrical properties of hydrocarbon bearing mudrocks at nano micro scales two current flow regimes of peak force tunneling atomic force microscopy pf tuna have been used 1 the vertical out of plane current regime with hundred micrometer diameter top electrodes obtains homogenized conductivity quantitatively 2 the horizontal in plane current regime was shown powerful to visualize the conductive paths related to connectivity and tortuosity for heterogeneous and anisotropic shales results show that the approach works well with one to two layers of adsorbed water 25 55 relative humidity under low frequency 0 5 20 hz for shale rocks current maps with sub nanometer resolution emphasize the dominant role of hydrated ions associated with the hydrophilic clay minerals in driving the dielectric response of shales while conductivity of pyrite and kerogen cannot be neglected for mature organic rich shale conductive network the acquired i v curves at microscale provide a reliable mean to evaluate homogenized conductivity of such multiscale multi component heterogeneous material under controlled environmental conditions the procedure discussed herein serves as a complement for fine grained rocks and minerals of ionic electronic hybrid conductive mechanism under partially water saturation these results can be used to develop accurate electrical models specifically for shale rocks with heterogeneous and sophisticated microstructure the methodology can be also extended to other micro or meso porous geomaterials such as cementitious and bituminous nanoporous media

three dimensional inversion of self potential data used to constrain the pattern of groundwater flow in geothermal fields 1 we propose an algorithm to invert self potential signals measured at the ground surface of the earth to localize hydromechanical disturbances or to the pattern of groundwater flow in geothermal systems the self potential signals result from the divergence of the streaming current density groundwater flow can be either driven by topography of the water table free convection or deformation of the medium the algorithm includes the electrical resistivity distribution of the medium obtained independently by dc resistance tomography or electromagnetic methods or by coding the assumed geology in terms of distribution of the electrical resistivity accounting for the effect of the temperature and salinity distributions and possibly constraints from borehole measurements inversion of the distribution of the source current density from ground surface and borehole self potential measurements is achieved by solving the inverse problem using tikhonov regularization solutions that are compatible with the physics of the primary flow problem by introducing assumptions regarding the smoothness or the compactness of the source and the three dimensional distribution of the electrical resistivity of the system the inverse problem can be solved in obtaining the three dimensional distribution of the current source density in the ground however an annihilator can be added to the inverted source geometry without affecting the measured self potential field annihilators can be obtained from boundary conditions synthetic models and a sandbox experiment are discussed to demonstrate the validity of the algorithm an application is presented to the geothermal field of cerro prieto baja california mexico using literature data inversion of the self potential and resistivity data allows observing a plume of hot groundwater rising to the ground surface in the central part of the investigated area and discharging to the ground surface in the southwest part the temperature anomaly associated with the existence of this plume is independently observed by interpolating borehole temperature measurements we found a good agreement between the distribution of the temperature and the inverted source current density the proposed method appears therefore as a noninvasive method for remote detection and three dimensional mapping of subsurface groundwater flow

an analytical study of seismoelectric signals produced by 1 d mesoscopic heterogeneities the presence of mesoscopic heterogeneities in fluid saturated porous rocks can produce measurable seismoelectric signals due to wave induced fluid flow between regions of differing compressibility the dependence of these signals on the petrophysical and structural characteristics of the probed rock mass remains largely unexplored in this work we derive an analytical solution to describe the seismoelectric response of a rock sample containing a horizontal layer at its center that is subjected to an oscillatory compressibility test we then adapt this general solution to compute the seismoelectric signature of a particular case related to a sample that is permeated by a horizontal fracture located at its center analyses of the general and particular solutions are performed to study the impact of different petrophysical and structural parameters on the seismoelectric response we find that the amplitude of the seismoelectric signal is directly proportional to the applied stress to the skempton coefficient contrast between the host rock and the layer and to a weighted average of the effective excess charge of the two materials our results also demonstrate that the frequency at which the maximum electrical potential amplitude prevails does not depend on the applied stress or the skempton coefficient contrast in presence of strong permeability variations this frequency is rather controlled by the permeability and thickness of the less permeable material the results of this study thus indicate that seismoelectric measurements can potentially be used to estimate key mechanical and hydraulic rock properties of mesoscopic heterogeneities such as compressibility permeability and fracture compliance

the brazil guara equatorial spread f campaign results of the large scale measurements the guara campaign equatorial spread f rocket was launched from alc ntara brazil on 14 october 1994 at 1955 lt 2255 ut into an active topside spread f event spread f plasma irregularities observed up to 822 km altitude correlate well with plumes observed simultaneously with a coherent backscatter radar matching 1 10 km features in the rocket and radar data over the altitude range 300 800 km implies an eastward drift speed of 110 m s versus 95 m s at 400 500 km based on radar interferometry combining these two measurements implies an average upward drift of 30 m s for the highest altitude structures the amplitude difference between low and high altitude 10 km density structures if attributed to temporal effects implies an effective diffusion coefficient decay time constant of 500 1000 m s 2 4 10 4 s 1 which agrees with previous estimates from other techniques and supports the idea that the decay of spread f turbulence occurs in a scale independent manner

relationship between spectral induced polarization and hydraulic properties of saturated and unsaturated sandstone there is growing interest in the use of geophysical methods for hydrological model parameterization empirical induced polarization ip hydraulic conductivity k relationships have been developed but these are only applicable to sediments in which the ip response shows limited variation with electrical current frequency here we examine the spectral ip response of samples taken from a uk sandstone aquifer and compare measured parameters with physical and hydraulic properties we demonstrate the limited value of existing ip k models due to the inherent ip frequency dependence of these samples our results show how the mean relaxation time is a more appropriate measure of ip response for these sediments a significant inverse correlation between the surface area to pore volume ratio and is observed suggesting that is a measure of a characteristic hydraulic length scale this is supported by a measured strong positive correlation between log and log k our measurements also reveal evidence of a relationship between and a dominant pore throat size which leads to postulations about the parallelism between the spectral ip behavior and unsaturated hydraulic characteristics additional experiments show how the relaxation time is affected by degree of fluid saturation indicating that saturation levels must be accounted for if our empirical relationships are applied to vadose zone studies our results show clear evidence of the potential value of frequency based ip measurements for parameterization of groundwater flow models

application of acoustic noise and self potential localization techniques to a buried hydrothermal vent waimangu old geyser site new zealand a seismo acoustic and self potential survey has been performed in the hydrothermal area of the old waimangu geyser new zealand which was violently erupting a century ago nowadays no surface activity is visible there we set up an array of 16 geophones and recorded a high and steady acoustic ambient noise we applied the matched field processing mfp approach to the acoustic data to locate the sources responsible for the ambient noise the white noise constraint processor reveals the presence of a unique and well focused acoustic source at a depth of 1 5 m below the seismic array for this very shallow source the application of mfp enabled the determination of both the source location and the dispersion curve of seismic velocity the study was completed by self potential sp measurements on several profiles around the acoustic noise source which displayed a large positive anomaly above it the results of the sp inversion gave an electric streaming current density source very close to the acoustic one both sources likely belong to a shallow hydrothermal structure interpreted as a small convective cell of boiling water beneath an impermeable layer the joint application of these methods is a promising technique to recognize hydrothermal structures and to study their dynamics

first vhf radar observation of midlatitude f region field aligned irregularities we describe the first midlatitude f region vhf radar observations of small scale field aligned irregularities fai looking northward at 34 elevation the locus of perpendicularity with the geomagnetic field b remains inside the radar beam such that fai can be observed at radar ranges from 350 to over 800 km or f region altitudes from 200 to 500 km approximately the preliminary results presented here show the large scale 20 km configuration of small scale 322 6 cm half the radar wavelength f region irregularities as well as typical spectral results our most important finding is that at least on some occasions there is a quasi periodic variation in time and space on scales of approximately 12 minutes and 50 km of the observed plasma instabilities

witseg sampler a segmented sand sampler for wind tunnel test the flux profile of blowing sand is the reflection of a large number of sand particles moving in different trajectories to describe the function of the flux profile requires measuring the flux of blown sand at different heights a segmented sand sampler for wind tunnel study witseg sampler has been designed and evaluated in a wind tunnel the sampler is 0 6 m high and sectioned into 60 openings that can measure the flux profile of blowing sand at 10 mm intervals special attention was paid in designing the sampler to its practicability and efficiency for the convenience of use the leading edge with inlets sand chambers and side cover are removable to maximize the sampling efficiency the leading edge is wedge shaped so that the width of the inlets is 5 mm while the width of the sand chamber is 15 mm each sand chamber has two screened vents that are connected to a vertical vent to minimize the air pressure inside the sand chamber and maximize its efficiency wind tunnel evaluation shows that the sampler is good for measuring aeolian sand flux both the measured flux profile and total flux show a reasonably good agreement with the widely accepted flux profile function and sand transport equation it has an overall efficiency of 0 91 the witseg sampler that can measure the detailed variation of blown sand flux with height proves to be a good tool for studying the flux profile of blowing sand