dune forming winds on titan and the influence of topography abstract numerous extended dunes on saturn s moon titan detected by the cassini radar constrain the long term pattern of surface winds we analyse the statistics of surface wind speed and direction and their spatial and temporal variability predicted by a general circulation model gcm in order to constrain surface wind predictions of this gcm by dune observations the model shows that modern winds are sufficient for saltation and dune formation at low latitudes in agreement with the presence of dunes there the best condition for the dune forming wind occurs with a threshold friction speed of 0 02 m s 1 or slightly less the equatorial region is conducive to longitudinal dunes because of a combined effect of a high sand drift potential and obtuse bimodal wind pattern oblique to the equator caused by the seasonal reversal of the hadley circulation the cross equatorial wind is steady and is characterised by a high weibull shape parameter k 4 the wind pattern at higher latitudes is more complex and gusty and neither longitudinal nor transversal dunes would be able to form putative large scale topography is found to have a profound influence on the near surface wind pattern generally mountains cause a convergence and speeding up on the flank while basins weaken the wind and cause a divergent flow longitudinal dunes can be deflected on the foot of mountains by up to 90 if xanadu is a hypothetical large mountain a wind pattern converging in xanadu that entirely disagrees with the dune observations is predicted if instead xanadu is a large basin the wind arcs clockwise north of xanadu and anti clockwise west and southwest of xanadu in agreement with the dune orientations in the vicinity of xanadu the albedo pattern has comparatively little influence on the wind field isolated mountain chains cause only local scale change in the wind pattern however the persistent surface easterlies in belet which are in conflict with the dune orientations do not disappear by any combination of large scale topography

shape topography gravity anomalies and tidal deformation of titan abstract gravity measurements and elevation data from the cassini mission have been used to create shape global topography and gravity anomaly models of titan that enable an improved understanding of its outer ice i shell structure we provide constraints on the averaged ice shell thickness and its long wavelength lateral variations as well as the density of the subsurface ocean using gravity anomalies the tidal love number k2 measurement and long wavelength topography we found that titan s surface topography is consistent with an approximate isostatically compensated ice shell of variable thickness likely in a thermally conductive or in a subcritical convective state overlying a relatively dense subsurface ocean

slope and deep sea fan facies and paleogeography of upper cretaceous chatsworth formation simi hills california the upper cretaceous chatsworth formation is a sand rich deep sea fan deposit consisting of thick channelized sequences and interchannel deposits typical of middle fan facies it has poorly developed outer fan lobes and slope facies petrographic and x ray diffraction xrd data indicate the arkosic deposits of the chatsworth formation were derived from an uplifted granitic terrane paleocurrent studies indicate northward sediment transport and an east trending slope regional comparisons of the simi hills with the santa monica and santa ana mountains suggest these terranes were once contiguous and covered part of a deep sea fan system that comprised much of the southern california area subsequently these terranes have been offset along the malibu cucamonga and elsinore faults and rotated in response to the opening of the los angeles basin and to other adjustments in the tectonic framework of the area the chatsworth formation is thought to be part of a forearc basin deposit similar to the great valley sequence and not part of the salinian borderland block the original geographic position of the forearc basin was to the south of the sierra nevada mountains and the great valley sequence

characteristics of high resolution hydraulic head profiles and vertical gradients in fractured sedimentary rocks summary accurately identifying the position of vertical hydraulic conductivity k v contrasts is critical to the delineation of hydrogeologic units that serve as the basis for conceptual and numerical models of groundwater flow high resolution head profiles have identified the position and thickness of k v contrasts in clayey aquitards but this potential has not yet been thoroughly evaluated in sedimentary rocks this paper describes an experiment in which head profiles with the highest technically feasible resolution were obtained using westbay multilevel systems mls installed in 15 cored holes at three sedimentary rock research sites with contrasting geologic and flow system conditions mlss were installed to maximum depths between 90 and 260 m with 2 5 monitoring zones per 10 m head profiles were measured over multiyear periods the vertical component of hydraulic gradient i e vertical gradient was calculated for each pair of adjacent monitoring intervals in every mls and then categorized based on its repeatability to facilitate interpretation of k v contrasts and comparisons within boreholes between boreholes at the same site and between sites the head and vertical gradient profiles from all three sites display systematic i e simple geometric shapes defined by repeatable intervals of no to minimal vertical gradient indicating relatively high k v units bounded by shorter depth intervals with large up to 50 m m vertical gradients indicating relatively low k v units the systematic nature of the profiles suggests flow in regular and interconnected fracture networks rather than dominated by a few key fractures with irregular orientations the low k v units were typically thin with their positions and thicknesses not predicted by lithostratigraphy or detailed lithologic geophysical and horizontal hydraulic conductivity data hence the position and thickness of units with contrasting k v would not be evident if mlss with the conventional number of monitoring zones had been used furthermore the detailed profiles can be strongly diagnostic of hydrogeologic unit boundaries or layers and can be used to improve the quantitative assessment of flow system conditions that is foundational to understanding contaminant plume migration

flow bearing structures of fractured rocks insights from hydraulic property scalings revealed by a pumping test abstract a long duration pumping test conducted over 151 days in a fractured sandstone and shale formation displays a nonstandard drawdown response and anomalous pressure diffusion which cannot be properly interpreted using existing frameworks e g homogeneous double porosity boundary conditions and fractal models an alternative framework with simple geometry and more complex hydraulic properties is thus proposed to interpret such kind of drawdown responses the analytical development allows first to demonstrate all scaling relations in this interpretation framework then and most importantly the multi scale hydraulic test provides consistent scalings of transmissivity t to storativity s over distances ranging from 83 to 383 m in a faulted area drawdown analysis in several monitoring wells shows persistent decrease of transmissivity in highly channelized fracture flow structures in one structure the cubic dependency of transmissivity to storativity identifies a well defined fault and also demonstrates the validity of poiseuille flow at a scale rarely investigated in the other structure the linear dependency of transmissivity to storativity indicates that the flow bearing structure is the surrounding fracture network well designed pumping tests combined with scaling analysis driven by geological evidence thus provide essential information on flow bearing structures for site characterization and modeling tasks at least for moderate to low permeable fractured rocks the scaling of transmissivity to storativity appears to be more informative than any separate interpretation of hydraulic property scaling exponents

earth tide analysis specifics in case of unstable aquifer regime we consider the main factors that affect underground water flow including aquifer supply collector state and distant earthquakes seismic waves passage in geodynamically stable conditions underground inflow change can significantly distort hydrogeological response to earth tides which leads to the incorrect estimation of phase shift between tidal harmonics of ground displacement and water level variations in a wellbore besides an original approach to phase shift estimation that allows us to get one value per day for the semidiurnal m2 wave we offer the empirical method of excluding periods of time that are strongly affected by high inflow in spite of rather strong ground motion during earthquake waves passage we did not observe corresponding phase shift change against the background on significant recurrent variations due to fluctuating inflow influence though inflow variations do not look like the only important parameter that must be taken into consideration while performing phase shift analysis permeability estimation is not adequate without correction based on background alternations of aquifer parameters due to natural and anthropogenic reasons

transient surface liquid in titan s polar regions from cassini cassini radar images of titan s south polar region acquired during southern summer contain lake features which disappear between observations these features show a tenfold increases in backscatter cross section between images acquired one year apart which is inconsistent with common scattering models without invoking temporal variability the morphologic boundaries are transient further supporting changes in lake level these observations are consistent with the exposure of diffusely scattering lakebeds that were previously hidden by an attenuating liquid medium we use a two layer model to explain backscatter variations and estimate a drop in liquid depth of approximately 1 m per year on larger scales we observe shoreline recession between iss and radar images of ontario lacus the largest lake in titan s south polar region the recession occurring between june 2005 and july 2009 is inversely proportional to slopes estimated from altimetric profiles and the exponential decay of near shore backscatter consistent with a uniform reduction of 4 1 3 m in lake depth of the potential explanations for observed surface changes we favor evaporation and infiltration the disappearance of dark features and the recession of ontario s shoreline represents volatile transport in an active methane based hydrologic cycle observed loss rates are compared and shown to be consistent with available global circulation models to date no unambiguous changes in lake level have been observed between repeat images in the north polar region although further investigation is warranted these observations constrain volatile flux rates in titan s hydrologic system and demonstrate that the surface plays an active role in its evolution constraining these seasonal changes represents the first step toward our understanding of longer climate cycles that may determine liquid distribution on titan over orbital time periods

morphology of fluvial networks on titan evidence for structural control abstract although titan s surface shows clear evidence of erosional modification such as fluvial incision evidence for tectonism has been less apparent on earth fluvial networks with strongly preferred orientations are often associated with structural features such as faults or joints that influence flow or erodibility we delineated and classified the morphologies of fluvial drainages on titan and discovered evidence of structural control fluvial networks were delineated both on synthetic aperture radar sar images covering 40 of titan from the cassini titan radar mapper up through t71 and on visible light images of the huygens landing site collected by the descent imager spectral radiometer disr the delineated networks were assigned to one of three morphologic classes dendritic parallel or rectangular using a quantitative terrestrial drainage pattern classification algorithm modified for use with titan data we validated our modified algorithm by applying it to synthetic fluvial networks produced by a landscape evolution model with no structural control of drainage orientations and confirmed that only a small fraction of the networks are falsely identified as structurally controlled as a second validation we confirmed that our modified algorithm correctly classifies terrestrial networks that are classified in multiple previous works as rectangular application of this modified algorithm to our titan networks results in a classification of rectangular for one half of the sar and disr networks a review of the geological context of the four terrestrial rectangular networks indicates that tensional stresses formed the structures controlling those terrestrial drainages based on the similar brittle response of rock and cryogenic ice to stress we infer that structures formed under tension are the most likely cause of the rectangular titan networks delineated here the distribution of these rectangular networks suggests that tensional stresses on titan may have been widespread

determination of aquifer transmissivity from earth tide analysis the water level in an open well tapping an artesian aquifer responds to pressure head disturbance caused by earth tide dilatation of the aquifer because a finite amount of time is needed for water to flow into and out of the well there exists a phase shift or time lag between the tidal dilatation of the aquifer and the water level response in the well we derive an analytical solution that expresses the phase shift as a function of the aquifer transmissivity storage coefficient well radius and the period of the harmonic disturbance this solution is rather insensitive to the storage coefficient thus if the phase shift is known for a harmonic disturbance the transmissivity can be calculated given a rough estimate of the storage coefficient theoretical analysis shows that a significant phase shift may be present even if the disturbance is slowly varying as in the case of earth tides this opens the possibility of estimating aquifer transmissivity from water level records that show earth tide fluctuations a case study using data from a site near parkfield california is presented to illustrate application of the theory phase shifts of the o1 25 82 hour period and m2 12 42 hour period tidal constituents are chosen for analysis because they are free of systematic contamination by fluctuations in barometric pressure a brief error analysis suggests that the computed o1 phase shift is subject to large uncertainty while the computed m2 phase shift is substantially more accurate based on an assumed storage coefficient range of 10 4 to 10 6 the estimated transmissivity range is 8 10 6 to 2 10 5 m2 s while hydraulic tests have not been performed to validate these estimates the range is consistent with the transmissivity value determined by other investigators from analysis of the water level response to an earthquake

structural and statistical characterization of joints and multi scale faults in an alternating sandstone and shale turbidite sequence at the santa susana field laboratory implications for their effects on groundwater flow and contaminant transport abstract this paper describes the properties of faults and fractures in the upper cretaceous chatsworth formation exposed at santa susana field laboratory and its surroundings simi hills california where groundwater flow and contamination have been studied for over three decades the complex depositional architecture of this turbidite consisting of alternating sandstones and shales interacting with formative stress conditions are responsible for multi scale fault hierarchies and permeable fractures in which nearly all groundwater flow occurs intensity and distribution of background fractures and their relation to bedding thickness are established for sandstones the dominant lithology the architecture of faults with increasing displacement is described and relationships among fault dimensional parameters captured data from 400 boreholes and piezometers reveal the effect of faults and fractures on groundwater flow large hydraulic head differences observed across fault zones with shale rich cores indicate these structures as cross flow barriers moreover hydraulic head profiles under ambient conditions and pumping tests suggest strong hydraulic connectivity in all directions to depth of hundreds of meters this outcrop based structural characterization relates the horizontal hydraulic conductivity to the observed well connected fracture network and explains the strong vertical connectivity across low hydraulic conductivity shales as faults and sheared fractures provide flow pathways

migration of contaminants in groundwater at a landfill a case study 2 groundwater monitoring devices abstract six types of devices for groundwater monitoring were used on an experimental basis in the investigation of the plume of contamination in the unconfined sandy aquifer at the borden landfill these include standpipe piezometers water table standpipes an auger head sampler suction type and positive displacement type multilevel point samplers and bundle piezometers with the exception of the first two each of these devices provides a means of obtaining vertical sample profiles of groundwater from a single borehole the auger head sampler which is a device that is attached to the cutting head of conventional continuous flight hollow stem augers yields samples from relatively undisturbed aquifer zones as the augers are advanced downward in the borehole from one depth of sampling to another this method is a rapid means of aquiring water quality profiles for mapping the distribution of a contaminant plume the other three profiling devices can be used to establish permanent networks for groundwater quality monitoring a suction type multilevel sampler consists of twenty or more narrow polyethylene or polypropylene tubes contained in a pvc casing that is capped at the bottom each tube extends to a different depth and is attached to a small screened sampling point that extends through the casing to draw water from the aquifer when suction is applied a positive displacement multilevel sampler is similar except that each sampling point is connected to a positive displacement pumping device located inside the pvc casing adjacent to the screen use of the suction type multilevel sampler is limited to zones where the water table is less than the suction lift depth of 8 or 9 m the positive displacement sampler can be used even if the water table is at a much greater depth a bundle piezometer consists of 1 2 cm o d flexible polyethylene tubes each with a short screened section at the bottom fastened as a bundle around a semi rigid center piezometer constructed of thick walled 2 cm o d pvc pipe in shallow water table areas water is withdrawn from each of the tubes and from the pvc piezometer by suction in areas with a deep water table samples are obtained by bailing with a narrow tube with a check valve on the bottom or by displacement using a double or triple tube gas drive sampler the positive displacement multilevel sampler or use of the gas drive samplers in the bundle piezometers provide the best opportunities for collecting samples that can be filtered and have preservatives added without the water being influenced excessively by degassing or by oxygen invasion networks of these three types of devices for multilevel groundwater monitoring were installed in the borden aquifer by means of hollow stem augers the devices are particularly well suited for use in aquifers composed of cohesionless sand or gravel that have little or no clay and groundwater flow that is primarily horizontal when 8 cm diameter hollow stem augers are used as many as eight polyethylene tubes are included conveniently in each bundle piezometer if augers with a larger hollow stem are used more tubes can be assembled in each bundle

response of submarine hydrologic monitoring instruments to formation pressure changes theory and application to nankai advanced corks 1 we describe the response of a compressible submarine hydrologic monitoring instrument to formation pressure changes in low diffusivity rock the measured pressure depends on the frequency of the pressure signal the hydraulic diffusivity and the wellbore storage the nankai advanced circulation obviation retrofit kits acorks offshore japan record tide induced formation pressure changes with small amplitudes 25 the pressure measurements occur in thick homogeneous compressible low permeability sediment where in situ tidal pressure responses should approximate the seafloor tidal signal a wellbore storage of 2 10 8 m3 pa 1 can explain many of the observed tidal responses given the hydraulic diffusivities of the monitored intervals a reduced permeability around the wellbore of 1000 fold and a wellbore storage of 10 11 m3 pa 1 can also reconcile the data our analysis suggests that acork screens in the lower shikoku basin facies have a critical frequency on the order of 5 10 8 hz equivalent to a period of 250 days higher frequency formation pressure signals will be distorted in the pressure record within the lower shikoku basin facies the time for this monitoring system to record 90 of an instantaneous pressure change is on the order of 10 d we suggest that the acork instrument compliance contributes to but does not fully explain the small tidal amplitudes and large phase shifts recorded at the least permeable monitoring intervals

general solution for tidal behavior in confined and semiconfined aquifers considering skin and wellbore storage effects tidal analysis provides a cost effective way of estimating aquifer properties tidal response models that link aquifer properties with tidal signal characteristics such as phase and amplitude hav

capillary effects on groundwater response to earth tides author s wang cy zhu ay liao x manga m wang lp abstract 2019 american geophysical union all rights reserved the response of unconfined aquifers to earth s solid tides earth tides has been used to study a number of hydrogeological environmental and ecological processes the traditional interpretation of such responses has been based on a model that assumes free flow of groundwater to the water table even though capillary effects have long been recognized to influence the response of coastal aquifers to ocean tides here we study the capillary effect on the response of unconfined aquifers to earth tides using a numerical procedure that couples groundwater flow and poroelastic strain in both the saturated and the unsaturated zones we show that when the water table rises to the surface and the capillary zone disappears the predicted tidal response is identical to that predicted by the traditional model but when the capillary zone is present when the water table falls below the surface the predicted amplitude ratio and phase shift depart notably from those predicted by the traditional model we apply the model to a field case where large seasonal changes of tidal response have been documented we show that the large seasonal changes in the tidal response may be due to the change of the water table from a capillary affected state to a capillary free state when the water table rises annually to the ground surface thus the omission of the capillary effects in the interpretation of the response of unconfined aquifers to earth tides may lead to incorrect inference of subsurface processes and properties

channel morphometry sediment transport and implications for tectonic activity and surficial ages of titan basins abstract fluvial features on titan and drainage basins on earth are remarkably similar despite differences in gravity and surface composition we determined network bifurcation r b ratios for five titan and three terrestrial analog basins tectonically modified earth basins have r b values greater than the expected range 3 0 5 0 for dendritic networks comparisons with r b values determined for titan basins in conjunction with similarities in network patterns suggest that portions of titan s north polar region are modified by tectonic forces sufficient elevation data existed to calculate bed slope and potential fluvial sediment transport rates in at least one titan basin indicating that 75 mm water ice grains observed at the huygens landing site should be readily entrained given sufficient flow depths of liquid hydrocarbons volumetric sediment transport estimates suggest that 6700 10 000 titan years 2 0 3 0 10 5 earth years are required to erode this basin to its minimum relief assuming constant 1 m and 1 5 m flows these lowering rates increase to 27 000 41 000 titan years 8 0 12 0 10 5 earth years when flows in the north polar region are restricted to summer months

groundwater recharge assessment in an upland sandstone aquifer of southern california abstract the chloride mass balance cmb method was used to obtain long term recharge values for the santa susana field laboratory ssfl site which features a groundwater flow system beneath an upland ridge formed of sandstone and shale beds in the simi hills ventura county southern california this application relied on the availability of on site measurements of bulk atmospheric chloride deposition comprised of dry fallout and wet concentration a large number of groundwater samples 1490 collected over three decades from 206 wells spanning a depth range from 10 to 360 m and measurements of chloride in surface runoff during rain events the use of the cmb method is suited to the assessment of recharge for the study area because the mean chloride values in groundwater show minimal spatial trends indicating no sources other than atmospheric in addition the cl br ratio was used to exclude wells with possible anthropogenic chloride the site wide average recharge ranges between 1 8 and 9 5 of the mean annual precipitation 455 mm with a mean value of 4 2 the measured surface runoff varies from 2 3 to 10 2 with mean value of 6 1 28 mm and therefore the volume of water lost to evapotranspiration is between 95 9 and 80 3 with a mean value of 89 6 408 mm the long term recharge calculated using the cmb method is consistent with tritium distribution based on a subset of groundwater monitoring wells and with an analysis of steady flow in the groundwater mound beneath the ssfl furthermore the recharge value matches those in the literature for sandstone aquifers in arid and semi arid climates this recharge estimate has important relevance for site characterization in terms of constraining the volumetric groundwater flow rates and water balance and understanding the mechanisms of transport towards the water table moreover this is the first application of the cmb in an upland area of california hence the method is demonstrated to be robust and applicable to many upland bedrock areas in southern california and similar regions around the world and can be used to quantify groundwater flow rates and supplies relevant to water resource management

depth discrete specific storage in fractured sedimentary rock using steady state and transient single hole hydraulic tests abstract a method is presented for obtaining depth discrete values of specific storage ss from single hole hydraulic tests in fractured rock boreholes using straddle packers 1 5 17 m test intervals low flow constant head ch step tests analyzed using the thiem method provide transmissivity t values free from non darcian error short term constant rate pumping tests 0 5 2 h analyzed using the cooper jacob approximation of the theis method provide s from the hydraulic diffusivity using the darcian t value from the ch step test this synergistic use of two types of hydraulic tests avoids the common source of error when pumping tests injection or withdrawal are conducted at higher flow rates and thereby induce non darcian flow resulting in the underestimation of t other errors such as well bore storage and leakage can also substantially influence s by causing a shift in the time axis of the cooper jacob semi log plot in this approach the darcian t values from the ch step tests are used in the analysis of the transient pumping test data for calculating s throughout the pumping test using the cooper jacob approximation to minimize all of the aforementioned errors resulting in more representative s values the effect of these non idealities on the measured drawdown is illustrated using the theis equation with the darcian t and s values to calculate drawdown for comparison to measured data the ss values for tests in sandstone obtained from this approach are more consistent with confined aquifer conditions than values derived from the traditional cooper jacob method and are within the range of field and lab values presented from a compilation of literature values for fractured sandstone 10 7 10 5 m 1 this method for obtaining ss values from short interval straddle packer tests improves the estimation of both k and ss and provides opportunity to study their spatial distribution in fractured rock

dunes on titan observed by cassini radar thousands of longitudinal dunes have recently been discovered by the titan radar mapper on the surface of titan these are found mainly within 30 of the equator in optically near infrared and radar dark regions indicating a strong proportion of organics and cover well over 5 of titan s surface their longitudinal duneform interactions with topography and correlation with other aeolian forms indicate a single dominant wind direction aligned with the dune axis plus lesser off axis or seasonally alternating winds global compilations of dune orientations reveal the mean wind direction is dominantly eastwards with regional and local variations where winds are diverted around topographically high features such as mountain blocks or broad landforms global winds may carry sediments from high latitude regions to equatorial regions where relatively drier conditions prevail and the particles are reworked into dunes perhaps on timescales of thousands to tens of thousands of years on titan adequate sediment supply sufficient wind and the absence of sediment carriage and trapping by fluids are the dominant factors in the presence of dunes

combined use of straddle packer testing and flute profiling for hydraulic testing in fractured rock boreholes summary a combination of high resolution hydraulic tests using straddle packers and transmissivity t profiling using the flute flexible liner method liner profiling in densely fractured rock boreholes is shown to be efficient for the determination of the vertical distribution of t along the entire hole the liner t profiling method takes a few hours or less to scan the entire borehole length resulting in a t profile under favorable conditions this method has good reliability for identifying the highest t zones identified by distinct decreases in liner velocity when these zones are covered by the descending liner in contrast for one short test interval e g 1 2 m the multiple test straddle packer method takes a few hours to measure t with good precision and accuracy using a combination of steady state and transient tests e g constant head step tests slug tests and constant rate pumping tests because of the time consuming aspect of this multiple test method it is most efficient in each borehole to conduct straddle packer testing only in priority zones selected after assessment of other borehole data collected prior to packer testing the t profile from the liner method is instrumental in selecting high permeable zones for application of the multiple test method using straddle packers which in turn refines the t estimation from the liner profile results from three boreholes in densely fractured sandstone demonstrate this approach showing the synergistic use of the methods with emphasis on information important for determining hydraulic apertures

response of leaky aquifers to earth tides interpreted with numerical simulation abstract the response of aquifers to earth s solid tides earth tides has increasingly been used as a tool for monitoring the hydraulic properties of groundwater systems recent studies of the tidal response of the arbuckle aquifer opened to a usgs deep well in oklahoma wang et al 2018 barbour et al 2019 which has been injected with an enormous amount of toxic wastewater showed evidence that this aquifer may be leaking quantitative interpretation of the tidal response of this aquifer was made with a one dimensional analytical solution wang et al 2018 that showed that substantial leakage is occurring however the analytical model has inherent simplifications such as conductivity isotropy small aquifer thickness absence of aquitard storage and no basement leakage in this study we revisit the tidal response of leaky aquifers with a finite element multi layered model where such simplifications are removed we found that the simplifications in the analytical model lead to overly conservative estimates of leakage we revisit the tidal response of the arbuckle aquifer in oklahoma with the numerical simulation and estimate an average vertical hydraulic conductivity of 2 10 6 t o 7 10 5 m s for the aquitard overlying the arbuckle thus the aquitard above the arbuckle is not confining at this location but is as conductive as the aquifer itself given the fast rise of fluid level in many arbuckle wells in response to the injection of hundreds of millions of barrels of wastewater into this aquifer across oklahoma and kansas the present result calls for vigilant monitoring of leakage of wastewater from the arbuckle aquifer into the overlying freshwater reservoirs and the surface environment plain language summary earthquakes can damage the confinement of groundwater aquifers and thus can cause seismic hazard by letting freshwater in some aquifers to be contaminated or stored toxic wastewater in other aquifers to leak out into the environment thus it is important to monitor possible leakage of aquifers in earthquake countries analysis of the aquifer response to earth s solid tides in a usgs deep well in oklahoma wang et al 2018 barbour et al 2019 which has been used as the repository of an enormous amount of injected toxic wastewater shows that the aquifer may be leaking an analytical solution wang et al 2018 that contains several simplifications was used to quantify the aquifer leakage from the tidal response here we use a two dimensional multilayered numerical simulation without these simplifications to explore the limitations of the analytical model we find that aquitard storage and basement leakage have important effects on the tidal response of aquifers and the omission of these factors in the analytical solution may have caused underestimation of the aquifer leakage we then apply the numerical model to interpret the tidal response of water level documented in a usgs deep monitoring well installed in the arbuckle aquifer in oklahoma where an enormous amount of toxic wastewater has been stored with reasonable estimates of the aquitard storage our simulations yield an estimate of 2 10 6 t o 7 10 5 m s for the vertical hydraulic conductivity of the aquitard thus the aquitard is not at all confining but is as conductive as the aquifer itself given the fast rise of fluid level in many arbuckle wells in response to the injection of hundreds of millions of barrels of wastewater into this aquifer across oklahoma and kansas the present result calls for vigilant monitoring of leakage of wastewater from the arbuckle aquifer into the overlying freshwater reservoirs and the surface environment

bedrock fracture parameters from the interpretation of well tides this paper presents a theory to account for the main features of the tidal response of an isolated plane fracture as revealed by the water level in an intersecting open borehole according to the theory the diurnal and semidiurnal tidal constituents both amplitude and phase of water level variations depend on the fracture aperture the orientation dip and strike and the radial extent of the fracture and the compressibility of the asperites the theory is applied to water level observations made in six open boreholes located in crystalline rock at a test site at the chalk river nuclear laboratories atomic energy of canada limited in chalk river ontario canada the boreholes were uncased and intersected many open fractures so that a definitive test of the theory could not be made however in four cases a fracture model could be found which fitted the observations within the experimental error

are the basins of titan s hotei regio and tui regio sites of former low latitude seas 1 features observed in the low latitude basins of hotei regio and tui regio on titan have attracted the attention of the cassini era investigators at both locations visual infrared mapping spectrometer vims observed isolated 5 m bright 500 km wide features described as lobate in shape several studies have proposed that these materials are cryo volcanic flows we propose an alternative explanation recently published topographic profiles across hotei regio and tui regio indicate these features appear to occur in large regional basins at least along the direction of the profiles cassini synthetic aperture radar sar images show that the terrains surrounding both topographically low lying 5 m bright features exhibit fluvial networks that appear to converge into the probable basins the 5 m bright features themselves correspond to fields of discrete radar bright depressions whose bounding edges are commonly rounded and cumulate in planform in sar images these fields of discrete radar bright depressions strongly resemble fields of features seen at titan s high latitudes identified as dry lakes thus the combination of 1 the resemblance to high latitude dry lakes 2 location in the centers of regional depressions and 3 convergence of fluvial networks are inferred by us to best explain the features of hotei regio and tui regio as sites of paleolake clusters and perhaps former now dry seas these low latitude paleolake clusters or former seas if real may be evidence of substantially larger inventories of liquid alkanes in titan s past

formation of gravel pavements during fluvial erosion as an explanation for persistence of ancient cratered terrain on titan and mars abstract in many terrestrial channels the gravel bed is only transported during rare floods threshold channels and rates of erosion are very slow in this paper we explore how coarse debris delivered to channels on mars and titan from erosion may inhibit further erosion once a coarse gravel channel bed develops portions of the equatorial region of titan are fluvially eroded into banded crenulated terrain some of which contains numerous circular structures that are likely highly degraded large impact craters surviving from the late heavy bombardment no mechanism that can chemically or physically break down ice likely the most important component of titans crust has been unambiguously identified this paper examines a scenario in which fluvial erosion on titan has largely involved erosion into an impact generated megaregolith that contains a modest component of gravel sized debris as the megaregolith is eroded coarse gravel gradually accumulates as a lag pavement on channel beds limiting further erosion and creating a dissected but largely inactive or senescent landscape similar development of gravel pavements occur in ancient mountain belts on earth and partially explain the persistence of appreciable relief after hundreds of millions of years likewise coarse gravel beds may have limited the degree to which erosion could modify the heavily cratered terrains on mars particularly if weathering were largely due to physical rather than chemical weathering processes in a relatively cold and or arid environment

size and shape of saturn s moon titan cassini observations show that saturn s moon titan is slightly oblate a fourth order spherical harmonic expansion yields north polar south polar and mean equatorial radii of 2574 32 0 05 kilometers km 2574 36 0 03 km and 2574 91 0 11 km respectively its mean radius is 2574 73 0 09 km titan s shape approximates a hydrostatic synchronously rotating triaxial ellipsoid but is best fit by such a body orbiting closer to saturn than titan presently does titan s lack of high relief implies that most but not all of the surface features observed with the cassini imaging subsystem and synthetic aperture radar are uncorrelated with topography and elevation titan s depressed polar radii suggest that a constant geopotential hydrocarbon table could explain the confinement of the hydrocarbon lakes to high latitudes

quantifying fractured crystalline rock properties using well tests earth tides and barometric effects summary characterization of fractured rock aquifers often requires the acquisition and analysis of diverse datasets obtained from various instrumentation configurations in this investigation at the fractured rock research site in floyd county virginia a high precision borehole extensometer and tiltmeter were used during pumping to monitor deformation in the vicinity of fractures identified from borehole logging strain data obtained from earth tide analyses were used with the extensometer and tiltmeter data to quantify hydromechanical properties including fracture volumetric specific storage porosity poisson s ratio the drained formation elastic modulus and the effective dip direction of the fracture borehole tiltmeter data were used to estimate deformation caused by an aquifer test consisting of three pumping and recovery periods performed in well ex 1 during each period of the aquifer test the extensometer located in w 03 and 27 7 m from the pumping well was anchored over 2 m long sections of 1 a fracture in hydraulic communication with ex 1 2 a fracture that is not hydraulically connected with ex 1 and 3 an unfractured portion of bedrock directly above the hydraulically connected fracture results from the pumping tests yielded compressibilities of 1 3 10 11 pa 1 and 1 7 10 11 pa 1 for the lower and upper fractures respectively when coupled with areal strain calculated from earth tide analyses the volumetric specific storage values are 3 2 10 11 pa 1 and 2 8 10 11 pa 1 and the poisson s ratios are 0 26 and 0 31 respectively using this with a calculated barometric efficiency of 0 45 allows for porosity calculations of 0 02 and 0 03 respectively for the vicinity of fractures in well w 03

analysis and interpretation of cassini titan radar altimeter echoes abstract the cassini spacecraft has acquired 25 radar altimeter elevation profiles along titan s surface as of april 2008 and we have analyzed 18 of these for which there are currently reconstructed ephemeris data altimeter measurements were collected at spatial footprint sizes from 6 60 km along ground tracks of length 400 3600 km the elevation profiles yield topographic information at this resolution with a statistical height accuracy of 35 50 m and kilometer scale errors several times greater the data exhibit significant variations in terrain from flat regions with little topographic expression to very rugged titanscapes the bandwidth of the transmitted waveform admits vertical resolution of the terrain height to 35 m at each observed location on the surface variations in antenna pointing and changes in surface statistics cause the range compressed radar echoes to exhibit strong systematic and time variable biases of hundreds of meters in delay it is necessary to correct the received echoes for these changes and we have derived correction algorithms such that the derived echo profiles are accurate at the 100 m level for off nadir pointing errors of 0 3 and 0 6 for leading edge and echo centroid estimators respectively the leading edge of the echo yields the elevation of the highest points on the surface which we take to be the peaks of any terrain variation the mean value of the echo delay is more representative of the mean elevation so that the difference of these values gives an estimate of any local mountain heights finding locations where these values diverge indicates higher relief terrain elevation features are readily seen in the height profiles several of the passes show mountains of several hundred m altitude spread over 10 s or even 100 s of km in spatial extent so that slopes are very small large expanses of sub 100 m topography are commonplace on titan so it is rather smooth in many locations other areas exhibit more relief although the overall observed variation in surface height on any pass is less than about 1 km some elevation features correspond to observed changes in brightness in cassini infrared images but many do not correspondence between the imaging sar ground tracks and the altimeter paths is limited so that identifying elevation changes with higher resolution sar features is premature at present

using earth tide induced water pressure changes to measure in situ permeability a comparison with long term pumping tests good constraints on hydrogeological properties are an important first step in any quantitative model of groundwater flow field estimation of permeability is difficult as it varies over orders of magnitude in natural systems and is scale dependent here we directly compare permeabilities inferred from tidal responses with conventional large scale long term pumping tests at the same site tidally induced water pressure changes recorded in wells are used to infer permeability at ten locations in a densely fractured sandstone unit each location is either an open hole well or a port in a multilevel monitoring well tidal response is compared at each location to the results of two conventional long term and large scale pumping tests performed at the same site we obtained consistent values between the methods for a range of site specific permeabilities varying from 10 15 m2 to 10 13 m2 for both open wells with large open intervals and multilevel monitoring well we conclude that the tidal analysis is able to capture passive and accurate estimates of permeability

titan s topography and shape at the end of the cassini mission with the conclusion of the cassini mission we present an updated topographic map of titan including all the available altimetry sartopo and stereo photogrammetry topographic datasets available from the mission we use radial basis functions to interpolate the sparse dataset which covers only 9 of titan s global area the most notable updates to the topography include higher coverage of the poles of titan improved fits to the global shape and a finer resolution of the global interpolation we also present a statistical analysis of the error in the derived products and perform a global minimization on a profile by profile basis to account for observed biases in the input dataset we find a greater flattening of titan than measured additional topographic rises in titan s southern hemisphere and better constrain the possible locations of past and present liquids on titan s surface

temporal changes of hydraulic properties of overburden aquifer induced by longwall mining in ningtiaota coalfield northwest china abstract characterizing the mining induced temporal changes of hydraulic properties of the overburden aquifer is significant for groundwater resource protection conventional hydrogeological methods e g hydraulic test physical model test and numerical simulation of determining hydraulic properties of the overburden aquifer cannot quantitatively analyze the temporal changes of the hydraulic properties induced by mining disturbances this paper demonstrates a quantitative determination for the temporal changes of parameters compressibility porosity and specific storage in the overburden aquifer influenced by the mining processes based on in situ continuous measurements of groundwater level that was affected by earth tide atmospheric loading and mining disturbances the results showed that when working face reached a certain distance 127 m from borehole j6 in this study those parameters compressibility porosity and specific storage of overburden aquifer began to show gradual decrease with approximately up to two order of magnitudes after the working face passed by the observation borehole j6 those properties of overburden aquifer recovered in about 80 days which might reflect the characteristic of elastic deformation of the aquifer those findings of the mining induced parameters temporal changes could improve our understanding of the mining effects on aquifer system and could be meaningful in groundwater resource protection

mechanisms of recharge in a fractured porous rock aquifer in a semi arid region abstract eleven porewater profiles in rock core from an upland exposed sandstone vadose zone in southern california with thickness varying between 10 and 62 m were analyzed for chloride cl concentration to examine recharge mechanisms estimate travel times in the vadose zone assess spatial and temporal variability of recharge and determine effects of land use changes on recharge as a function of their location and the local terrain the profiles were classified into four groups reflecting the range of site characteristics century to millennium average recharge varied from 4 to 23 mm y 1 corresponding to 1 moreover the temporal variability of recharge was estimated and along each profile past recharge rates calculated based on the sequence of cl concentrations in the vadose zone recharge rates increased at specific times coincident with historical changes in land use the consistency between the timing of land use modifications and changes in cl concentration and the match between observed and simulated cl concentration values in the vadose zone provide confidence in porewater age estimates travel times recharge estimates and reconstruction of recharge histories this study represents an advancement of the application of the chloride mass balance method to simultaneously determine recharge mechanisms and reconstruct location specific recharge histories in fractured porous rock aquifers the proposed approach can be applied worldwide at sites with similar climatic and geologic characteristics

fluvial erosion as a mechanism for crater modification on titan abstract there are few identifiable impact craters on titan especially in the polar regions one explanation for this observation is that the craters are being destroyed through fluvial processes such as weathering mass wasting fluvial incision and deposition in this work we use a landscape evolution model to determine whether or not this is a viable mechanism for crater destruction on titan we find that fluvial degradation can modify craters to the point where they would be unrecognizable by an orbiting spacecraft such as cassini given enough time and a large enough erosion rate a difference in the erosion rate between the equator and the poles of a factor of a few could explain the latitudinal variation in titan s crater population fluvial erosion also removes central peaks and fills in central pits possibly explaining their infrequent occurrence in titan craters although many craters on titan appear to be modified by aeolian infilling fluvial modification is necessary to explain the observed impact crater morphologies thus it is an important secondary modification process even in titan s drier equatorial regions

a global topographic map of titan abstract cassini radar sartopo and altimetry data are used to construct a global gridded 1 1 elevation map for use in global circulation models hydrological models and correlative studies the data are sparse and so most of the map domain 90 is populated with interpolated values using a spline algorithm the highest 520 m gridded point observed is at 48 s 12 w the lowest point observed 1700 m below a 2575 km sphere is at 59 s 317 w this may be a basin where liquids presently in the north could have resided in the past if the deepest point were once a sea with the areal extent of present day ligeia mare it would be 1000 m deep we find four prominent topographic rises each 200 km wide radar bright and heavily dissected distributed over a 3000 km arc in the southeastern quadrant of titan 40 60 s 15 150 w