diviner lunar radiometer observations of cold traps in the moon s south polar region diviner lunar radiometer experiment surface temperature maps reveal the existence of widespread surface and near surface cryogenic regions that extend beyond the boundaries of persistent shadow the lunar crater observation and sensing satellite lcross struck one of the coldest of these regions where subsurface temperatures are estimated to be 38 kelvin large areas of the lunar polar regions are currently cold enough to cold trap water ice as well as a range of both more volatile and less volatile species the diverse mixture of water and high volatility compounds detected in the lcross ejecta plume is strong evidence for the impact delivery and cold trapping of volatiles derived from primitive outer solar system bodies

geophysical investigation of the denali fault and alaska range orogen within the aftershock zone of the october november 2002 m 7 9 denali fault earthquake the aftershock zone of the 3 november 2002 m 7 9 earthquake that ruptured along the right slip denali fault in south central alaska has been investigated by using gravity and magnetic magnetotelluric and deep crustal seismic reflection data as well as outcrop geology and earthquake seismology strong seismic reflections from within the alaska range orogen north of the denali fault dip as steeply as 25 n and extend to depths as great as 20 km these reflections outline a relict crustal architecture that in the past 20 yr has produced little seismicity the denali fault is nonreflective probably because this fault dips steeply to vertical the most intriguing finding from geophysical data is that earthquake aftershocks occurred above a rock body with low electrical resistivity 10 m that is at depths below 10 km aftershocks of the denali fault earthquake have mainly occurred shallower than 10 km a high geothermal gradient may cause the shallow seismicity another possibility is that the low resistivity results from fluids which could have played a role in locating the aftershock zone by reducing rock friction within the middle and lower crust

seismic velocity models for the denali fault zone along the richardson highway alaska crustal scale seismic velocity models across the denali fault zone along the richardson highway show a 50 km thick crust a near vertical fault trace and a 5 km wide damage zone associated with the fault near trans alaska pipeline pump station 10 which provided the closest strong ground motion recordings of the 2002 denali fault earthquake we compare models derived from seismic reflection and refraction surveys acquired in 1986 and 1987 to laboratory measurements of seismic velocities for typical metamorphic rocks exposed along the profiles our model for the 1986 seismic reflection profile indicates a 5 km wide low velocity zone in the upper 1 km of the denali fault zone which we interpret as fault gouge deeper refractions from our 1987 line image a 40 km wide 5 km deep low velocity zone along the denali fault and nearby associated fault strands which we attribute to a composite damage zone along several strands of the denali fault zone and to the obliquity of the seismic line to the fault zone our velocity model and other geophysical data indicate a nearly vertical denali fault zone to a depth of 30 km aftershocks of the 2002 denali fault earthquake and our velocity model provide evidence for a flower structure along the fault zone consisting of faults dipping toward and truncated by the denali fault wide angle reflections indicate that the crustal thickness beneath the denali fault is transitional between the 60 km thick crust beneath the alaska range to the south and the extended 30 km thick crust of the yukon tanana terrane to the north online material tables of locations for the tact 1986 and tact 1987 lines

identification of high permeability subsurface structures with multiple point geostatistics and normal score ensemble kalman filter abstract alluvial aquifers are often characterized by the presence of braided high permeable paleo riverbeds which constitute an interconnected preferential flow network whose localization is of fundamental importance to predict flow and transport dynamics classic geostatistical approaches based on two point correlation i e the variogram cannot describe such particular shapes in contrast multiple point geostatistics can describe almost any kind of shape using the empirical probability distribution derived from a training image however even with a correct training image the exact positions of the channels are uncertain state information like groundwater levels can constrain the channel positions using inverse modeling or data assimilation but the method should be able to handle non gaussianity of the parameter distribution here the normal score ensemble kalman filter ns enkf was chosen as the inverse conditioning algorithm to tackle this issue multiple point geostatistics and ns enkf have already been tested in synthetic examples but in this study they are used for the first time in a real world case study the test site is an alluvial unconfined aquifer in northeastern italy with an extension of approximately 3 km 2 a satellite training image showing the braid shapes of the nearby river and electrical resistivity tomography ert images were used as conditioning data to provide information on channel shape size and position measured groundwater levels were assimilated with the ns enkf to update the spatially distributed groundwater parameters hydraulic conductivity and storage coefficients results from the study show that the inversion based on multiple point geostatistics does not outperform the one with a multigaussian model and that the information from the ert images did not improve site characterization these results were further evaluated with a synthetic study that mimics the experimental site the synthetic results showed that only for a much larger number of conditioning piezometric heads multiple point geostatistics and ert could improve aquifer characterization this shows that state of the art stochastic methods need to be supported by abundant and high quality subsurface data

rupture process of the 2002 mw 7 9 denali earthquake alaska using a newly devised hybrid blind deconvolution method this paper investigates the kinematics of the rupture process of the main event of the mw 7 9 denali alaska earthquake of 3 november 2002 a newly devised hybrid blind deconvolution method is applied to deconvolve teleseismic broadband s wave displacement recordings of the earthquake so as to determine the apparent source time functions astfs at 10 stations located around the epicenter the derived azimuthal angle of slip strongly indicates that the event ruptured unilaterally in an east southeasterly direction as determined by the calculated astfs the total duration of the rupture process was about 74 sec based on the images of the static slip dis tribution three slip concentrated areas were located at depths of less than 10 km maximum slip was about 13 4 m centered at 170 km east of the hypocenter and the average slip on the observed rupture area reached 4 1 m one concentrated rupture velocity area located at 160 180 km east of the hypocenter coincided with a slip concentrated area of maximum slip amplitude strongly suggesting that seismic energy was released rapidly a region of the fault along the strike direction with high rupture velocity 80 120 km also had very low levels of slip indicating that this portion of the fault may well have been relatively weak maximum and minimum rupture velo cities were respectively 3 32 and 2 64 km sec while the average rupture velocity was about 2 95 km sec based on the average rupture velocity and the source duration it is suggested that the principal rupture length of the denali fault must have been greater than 210 km

the 2002 denali fault earthquake alaska a large magnitude slip partitioned event the mw moment magnitude 7 9 denali fault earthquake on 3 november 2002 was associated with 340 kilometers of surface rupture and was the largest strike slip earthquake in north america in almost 150 years it illuminates earthquake mechanics and hazards of large strike slip faults it began with thrusting on the previously unrecognized susitna glacier fault continued with right slip on the denali fault then took a right step and continued with right slip on the totschunda fault there is good correlation between geologically observed and geophysically inferred moment release the earthquake produced unusually strong distal effects in the rupture propagation direction including triggered seismicity

recent large fold nucleation in the upper crust insight from gravity magnetic magnetotelluric and seismicity data sierra de los filabres sierra de las estancias internal zones betic cordillera abstract rheological heterogeneities in the upper crust have a close relationship with the fold position where rigid bodies could constitute initial perturbations that allow the nucleation of folds consequently establish the position and geometry of anomalous rocks located in the upper crust by geophysical studies help to understand the folded structure observed on surface new geological observations in the field along with gravity magnetic magnetotelluric and seismicity data reveal the subsurface structure in the sierra de los filabres sierra de las estancias folded region part of the alpine belt in southern spain the geometry of the upper crust is determined by geological field data 2d gravity models 2d magnetic models and 2d mt resistivity model while seismicity evidences the location of the deep active structures these results allow us to propose that a basic rock body at 4 to 9 km depth has determined the nucleation and development of the sierra de los filabres kilometric antiform n vergent large late folds are subjected to a variable present day stress field earthquake focal mechanisms suggest the presence in depth of a regional nw se compressive stress field however most of the seismogenetic structures do not extend up to the surface where nw se and wnw ese outcropping active normal faults are observed thus indicating a ne sw extension in the upper crust simultaneous to orthogonal nw se compression related to reverse faults and minor folds developed in the eastern almanzora corridor and in the nearby huercal overa basin the recent and active tectonic studies of cordilleras hinterland subjected to late folding greatly benefits from the integration of surface observations together with geophysical data

the gravina sequence remnants of a mid mesozoic oceanic arc in southern southeast alaska fragments of upper jurassic to lower cretaceous volcanic and basinal strata constitute the gravina belt in southeast alaska in the ketchikan area the gravina belt is made up of two lithotectonic units the lower unit consists of coarse marine pyroclastic and volcaniclastic strata mafic flows breccia and fine grained tuff which are locally intruded by hypabyssal bodies of diorite and quartz diorite the volcanic rocks are characterized by tholeiitic arc basalts lack felsic volcanic strata and overlie upper triassic and older strata of the alexander terrane augite and or hornblende bearing porphyritic rocks are common and locally intrude the alexander terrane basement where they are thought to represent the intrusive equivalents of lavas within the section age constraints for the volcanic unit based on structural and stratigraphic relations with adjacent units are late middle to late jurassic the gravina belt upper unit consists of fine to coarse grained turbidites and related conglomeratic channel fill deposits the basinal rocks unconformably overlie permian and triassic rocks of the taku terrane and remnants of the lower volcanic part of the gravina sequence which overlie the alexander terrane the conglomerate units contain mostly volcanic and plutonic lithic clasts some of which yield pb u zircon ages of 154 158 ma the predominance of pyroclastic deposits interbedded with massive flows tuff breccia and argillaceous turbidites and the lithologic and chemical composition of the volcanic rocks indicate a submarine volcanic arc setting for the gravina sequence the basinal pyroclastic rocks are inferred to have been shed from submarine stratovolcanos during the late jurassic epiclastic rocks were deposited as submarine fans derived in part from erosion of a magmatic arc the presence of fine grained tuffaceous turbidites implies ongoing but distant volcanism the pyroclastic and volcaniclastic rocks represent remnants of a late jurassic oceanic arc constructed on a composite basement consisting of the alexander and taku terranes the strata accumulated in an intra arc basin on the eastern edge of the alexander terrane the volcanic and basinal rocks were deformed during a major mid cretaceous intra arc contractional event in conjunction with the emplacement of a distinctly younger arc related plutonic suite

electrical conductivity and carbon in metamorphic rocks of the yukon tanana terrane alaska electrical conductivity of a water saturated quartz mica garnet schist collected from a surface outcrop near the denali fault zone in the yukon tanana terrane of east central alaska increases slightly with pressure to about 200 mpa this behavior is unlike that exhibited by other yukon tanana samples or by most rocks from other locations detailed petrographic examination of the sample revealed the presence of a stringer of carbonaceous material generally less than 10 m thick enclosed in and intergrown with one of the muscovite layers and extending for about 2 cm along the foliation the stringer is probably responsible for the anomalous conductivity change with pressure making the sample the first for which anomalous electrical conductivity behavior can be attributed to carbon associated with a specific feature the carbonaceous stringer together with its host muscovite layer are deformed and broken around a rotated garnet porphyroclast the deformation was accommodated by plastic deformation of quartz and therefore occurred in the ductile regime under conditions at least equivalent to greenschist facies metamorphism we interpret the textural relations to indicate that the carbonaceous material was formed by fluid deposition in a fracture formed within the muscovite layer possibly during the main phase of metamorphism and deformation and that the mica and carbon stringer were then deformed by the noncoaxial deformation responsible for rotation of the garnet porphyroclasts together the facts that the deformation resulting in garnet rotation was ductile and that the garnet rotation disrupted the stringer demonstrate that the carbonaceous stringer was present at depth i e 10 km brittle deformation on the microscopic scale is observed to have broken the connectivity of the carbon stringer explaining in part why the rock does not exhibit anomalously high conductivity at 0 1 mpa 1 atm pressure the brittle deformation is interpreted to have been caused by unloading due to uplift the observations indicate that carbonaceous material may exert a primary control on crustal electrical conductivity because it may be present as interconnected arrays in grain boundaries or microfractures or in megascopic throughgoing fractures

testing polar spots of water rich permafrost on the moon lend observations onboard lro 1 results are presented for the lend instrument onboard lro for the detection of local spots of suppression and excess of epithermal neutron emission at the lunar poles twelve local neutron suppression regions nsrs and neutron excess regions ners are detected it is shown using the data from the lola and diviner instruments that six nsrs have the empirical property less local irradiation and lower temperature fewer local neutrons these nsrs may be identified with spots of water ice rich permafrost on the moon it is shown that detected nsrs are include in both permanently shadowed and illuminated areas and they are not coincident with permanently shadowed regions psrs at the bottom of polar craters as has been commonly expected before lend presented neutron data with high spatial resolution

the cenozoic denali fault system and the cretaceous accretionary development of southern alaska the juxtaposition of disparate geologic terranes in southern alaska has been previously interpreted to be mainly the result of several hundred kilometers of right lateral offset along the denali fault system in cenozoic time recent geologic investigations in the healy quadrangle strongly suggest that cenozoic horizontal displacements of such magnitude along the denali fault system do not exist in the healy quadrangle isograds and metamorphic facies boundaries of an early late cretaceous metamorphic belt trend across the cenozoic mckinley strand of the denali system without significant horizontal offsets the present geologic makeup of most of southern alaska is primarily the result of the talkeetna superterrane consisting of the previously assembled peninsular terrane and wrangellia colliding with and subsequently being thrust upon the yukon tanana and nixon fork terranes of the ancient north american continent in about middle cretaceous time the leading edge of the talkeetna superterrane faces a wide complexly deformed zone that contains numerous northwestward thrust miniterranes tectonically intermixed with jurassic and cretaceous flysch the flysch is interpreted to have been deposited mostly in the narrowing and subsequently collapsed oceanic basin between the converging continental blocks the postcollisional denali fault system developed in cenozoic time across the already accreted continental margin in eastern alaska along an older cretaceous suture

the global albedo of the moon at 1064 nm from lola the lunar orbiter laser altimeter lola measures the backscattered energy of the returning altimetric laser pulse at its wavelength of 1064 nm and these data are used to map the reflectivity of the moon at zero phase angle with a photometrically uniform data set global maps have been produced at 4 pixels per degree about 8 km at the equator and 2 km resolution within 20 latitude of each pole the zero phase geometry is insensitive to lunar topography so these data enable characterization of subtle variations in lunar albedo even at high latitudes where such measurements are not possible with the sun as the illumination source the geometric albedo of the moon at 1064 nm was estimated from these data with absolute calibration derived from the kaguya multiband imager and extrapolated to visual wavelengths the lola estimates are within 2 of historical measurements of geometric albedo no consistent latitude dependent variations in reflectance are observed suggesting that solar wind does not dominate space weathering processes that modify lunar reflectance the average normal albedo of the moon is found to be much higher than that of mercury consistent with prior measurements but the normal albedo of the lunar maria is similar to that of mercury suggesting a similar abundance of space weathering products regions within permanent shadow in the polar regions are found to be more reflective than polar surfaces that are sometimes illuminated limiting analysis to data with slopes less than 10 eliminates variations in reflectance due to mass wasting and shows a similar increased reflectivity within permanent polar shadow steep slopes within permanent shadow are also more reflective than similar slopes that experience at least some illumination water frost and a reduction in effectiveness of space weathering are offered as possible explanations for the increased reflectivity of permanent shadow porosity is largely ruled out as the sole explanation the south polar crater shackleton is found to be among the most reflective craters in its size range globally but is not the most reflective so mass wasting cannot be ruled out as a cause for the crater s anomalous reflectance models of the abundance of ice needed to account for the reflectance anomaly range from 3 to 14 by weight or area depending on assumptions regarding the effects of porosity on reflectance and whether ice is present as patches or is well mixed in the regolith if differences in nanophase iron abundances are responsible for the anomaly the permanently shadowed regions have between 50 and 80 the abundance of nanophase iron in mature lunar soil

coupled hydrogeophysical inversion to identify non gaussian hydraulic conductivity field by jointly assimilating geochemical and time lapse geophysical data abstract reliable inversion of spatial heterogeneity of hydraulic conductivity is crucial to understand subsurface fluids migration the ensemble smoother direct sampling method es ds has proven to be an effective method to identify non gaussian hydraulic conductivity distributions by incorporating a variety of traditional hydrodynamic measurements e g piezometric head however inversion problems for non gaussian parameters often suffer from a sparsity of the available data from direct sampling in boreholes as a non intrusive cost effective and high sampling density method time lapse geophysical technique has not yet drawn much attention as a useful source of information for delineating the underlying non gaussian heterogeneity in this study we integrated coupled hydrogeophysical modeling and the es ds algorithm to estimate non gaussian hydraulic conductivity field by assimilating both geochemical and time lapse geophysical datasets four synthetic cases for a salt injection experiment monitored by both sampling analysis and electrical resistivity tomography are conducted to assess the ability of the proposed approach to characterize hydraulic properties by assimilating different types of data results show that using geochemical or geophysical data alone only allow a rough reconstruction of subsurface heterogeneity of aquifers but might lose the fine structure by incorporating multi source datasets the main patterns of the non gaussian reference fields can be reflected with an improved resolution the time lapse geophysical methods open up new opportunities to accurately characterize non gaussian aquifers and monitor the dynamic processes of subsurface fluids

a real time model of the seasonal temperature of lunar polar region and data validation a small tilt in the spin axis of the moon over the ecliptic plane causes seasonal incidence variation of solar illumination and especially causes significant temperature difference at the polar region in this article following the position of the subsolar point the real time model of solar illumination incidence over the moon polar region is developed based on this model with solving the 1 d heat conduction equation the seasonal temperature of the lunar surface is obtained and is in agreement with the diviner infrared ir data meanwhile using the fluctuation dissipation theorem and the wentzel kramers brillouin wkb approach for lunar regolith media the seasonal microwave mw brightness temperature tb is also obtained and validated by chang e 2 ce 2 37 ghz tb data these data also show that the lunar surface temperature and the mw tb even in the permanent shaded region psr undergo seasonal variation as well it might be due to the seasonal thermal radiation on the topographic psr coming from the sunlit crater walls caused by seasonal temperature variation the diviner ir data show that the highest temperature in the hermite a crater at the north polar psr can reach 109 k in summer

reinterpretation of lower mesozoic rocks on the chilkat peninsula alaska as a displaced fragment of wrangellia the southern chilkat peninsula is underlain by low grade metamorphic rocks consisting of a thick unit of greenstone in part of carnian age that is locally overlain by an attenuated section of calcareous sedimentary rocks and chart of latest carnian to late norian age and a thick flysch unit of jurassic and or cretaceous age the triassic part of this sequence has previously been inferred to be part of the taku terrane however its lithology age fossils and regional distribution indicate that it is probably a sliver of wrangellia that was offset from the eastern alaska range to its present position by at least 350 km dextral displacement on the denali fault

thermal stability of volatiles in the north polar region of mercury thermal models for the north polar region of mercury calculated from topographic measurements made by the mercury surface space environment geochemistry and ranging messenger spacecraft show that the spatial distribution of regions of high radar backscatter is well matched by the predicted distribution of thermally stable water ice messenger measurements of near infrared surface reflectance indicate bright surfaces in the coldest areas where water ice is predicted to be stable at the surface and dark surfaces within and surrounding warmer areas where water ice is predicted to be stable only in the near subsurface we propose that the dark surface layer is a sublimation lag deposit that may be rich in impact derived organic material

the southern kahiltna terrane implications for the tectonic evolution of southwestern alaska regionally extensive and highly deformed jurassic to cretaceous basinal turbidite deposits occur along most of the inboard boundary of the talkeetna superterrane in southern alaska and western canada the southern kahiltna terrane of southwestern alaska consists largely of such basinal deposits regional and detailed studies in and adjacent to this terrane suggest several new conclusions regarding the origin of the basin and its role in the tectonic evolution of southwestern alaska stratigraphic sedimentologic compositional and structural evidence suggests that the upper jurassic to lower cretaceous strata of the southern kahiltna terrane were derived from and deposited on rocks of the adjacent talkeetna superterrane deposition of these clastic rocks apparently postdated arc magmatism in the talkeetna superterrane suggesting deposition in a basin developed on the suture between the talkeetna superterrane and north america if true this observation implies that collision of the talkeetna superterrane with north america began prior to latest jurassic time probably at a more southerly location the superterrane has since been translated northward probably by coast parallel strike slip displacement to its present location where it was structurally juxtaposed with middle to upper creteceous rocks of the kuskokwim group a magmatic overprint indicates that the talkeetna superterrane was in approximately its present location by latest cretaceous to paleocene time

magnetotelluric imaging of the creeping segment of the san andreas fault near hollister 1 fluids may play a significant role in the earthquake rupture process since fluids can dramatically change the electrical resistivity of crustal rocks electromagnetic exploration methods can image in situ fault zone fluids magnetotelluric mt data has been collected on segments of the san andreas fault saf in central california exhibiting a range of seismic behavior from locked to creeping this paper describes mt data from the creeping segment of the saf near hollister california inversion models image a zone of enhanced conductivity beneath the surface trace of the saf that has similar geometry and greater depth extent than the fault zone conductor at parkfield comparison with geologic and seismic tomographic studies show this zone is bounded by the san andreas and calaveras faults and coincident with a zone of low seismic p wave velocities combined with previous mt studies this indicates a correlation between seismicity and the presence of fault zone fluids

along strike variations in the electrical structure of the san andreas fault at parkfield california magnetotelluric exploration has been used to image along strike variations in the electrical resistivity structure of the san andreas fault at parkfield california a low resistivity wedge extending to a depth of several kilometers is continuous over a horizontal distance of 8 km the base of the wedge is coincident with the shallowest microearthquakes a change in the electrical and fluid connection of the san andreas fault with a low resistivity zone in the franciscan formation is observed along the parkfield segment

comparison of geoelectrical tectonic models for suture zones in the western u s a and eastern europe are black shales a possible source of high conductivities abstract large scale geoelectrical anomalies have been mapped with geomagnetic depth sounding gds and magnetotelluric mt surveys in the carpathian mountains region these anomalies are associated with the zone of closure between stable europe and a complex of microplates in front of the converging african plate the zone of closure or suture zone is largely occupied by an extensive deformed flysch belt the models derived to fit the observed geoelectrical data are useful in the study of other suture zones and carpathian structures have been compared with areas currently being studied in the western cordillera of the u s a models derived for a smaller scale suture zone mapped in western washington state have features that are similar to the carpathian models the geoelectrical models for both the carpathian and washington anomalies require dipping conductive slabs of 1 5 m material that extends to depths 20 km in both instances there is evidence that these materials may merge with lower crustal mantle conductors along the down dip margins of the slab the main conductive units are interpreted to be sedimentary rocks that have been partially subducted due to collisional processes heat flow is low in both regions and it is difficult to explain fully the deep conduction mechanisms however evidence suggests that the conduction at depth may include electronic conduction in sulfide mineral or carbon films as well as ionic conduction in fluids or partial melt

protolith relations of the gravina belt and yukon tanana terrane in central southeastern alaska metamorphic rocks west of the coast mountains batholith in central southeastern alaska are divided into the gravina belt taku terrane and newly defined ruth assemblage the ruth assemblage comprises metapelite quartzose metaclastic strata quartzite marble felsic metatuff mafic metavolcanic rocks and orthogneiss depositional and emplacement ages of 367 pm 10 ma and 345 pm 13 ma inferred from discordant u pb zircon analyses on felsic metatuff and granodioritic orthogneiss respectively require that at least portions of the ruth assemblage be late devonian and early mississippian in age the assemblage is similar in age and protolith to and thus correlated with the yukon tanana terrane the gravina belt is characterized by upper jurassic and lower cretaceous mafic volcanic rocks and tuffaceous turbiditic clastic strata that unconformably overlie the alexander terrane metamorphic rocks that structurally underlie the taku terrane and ruth assemblage are included in this assemblage trace

latitudinal variation in spectral properties of the lunar maria and implications for space weathering abstract space weathering alters the optical properties of exposed surfaces over time complicating the interpretation of spectroscopic observations of airless bodies like asteroids mercury and the moon solar wind and micrometeoroids are likely the dominant agents of space weathering but their relative contributions are not yet well understood based primarily on clementine mosaics we report a previously unrecognized systematic latitudinal variation in the near infrared spectral properties of the lunar maria and show that the characteristics of this latitudinal trend match those observed at lunar swirls where magnetic fields alter local solar wind flux without affecting the flux of micrometeoroids we show that the observed latitudinal color variations are not artifacts of phase angle effects and cannot be accounted for by compositional variation alone we propose that reduced solar wind flux which should occur both at swirls and toward higher latitudes is the common mechanism behind these color variations this model helps us quantify the distinct effects of solar wind and micrometeoroid weathering and could aid in interpreting the spectra of airless bodies throughout the solar system

enkf coupled with groundwater flow moment equations applied to lauswiesen aquifer germany summary we describe a field application of a new data assimilation method recently proposed by panzeri et al 2013 2014 the method couples a modified ensemble kalman filter enkf algorithm with stochastic moment equations mes governing space time variations of theoretical ensemble mean and covariance values of groundwater flow state variables hydraulic heads and fluxes whereas traditional enkf entails monte carlo mc simulations and suffers from inbreeding our approach obviates both synthetic case studies have shown the me based approach to be computationally efficient and accurate when compared to mc based results here we use our me based method to assimilate drawdown data recorded during cross hole pumping tests in the heterogeneous alluvial lauswiesen aquifer near tubingen germany our results include an estimate of log transmissivity distribution throughout the aquifer and corresponding measures of estimation error we validate our calibrated model by using it to predict drawdowns recorded during another pumping test at the site and compare its performance with that of standard mc based enkf

thermal stability of ice on ceres with rough topography the dwarf planet ceres may have an ice rich crust and subsurface ice exposed by impacts or endogenic activity would be subject to sublimation we model surface and subsurface temperatures on ceres to assess lifetimes of water ice and other volatiles topographic shadowing allows a small but non negligible fraction 0 4 of ceres surface to be perennially below the 110 k criterion for 1 gyr of stability these areas are found above 60 latitude other molecules ch3oh nh3 so2 co2 may be cold trapped in smaller abundances a model for the transport gravitational escape and photoionization of h2o molecules suggests net accumulation in the cold traps buried ice is stable within a meter for 1 gyr at latitudes higher than 50 an illuminated polar cap of water ice would be stable within a few degrees of the poles only if it maintained a high albedo 0 5 at present obliquity if the obliquity exceeded 5 in the geologically recent past then a putative polar cap would have been erased at latitudes 0 30 ice is stable under solar illumination only briefly 10 100 yr unless it has high albedo and thermal inertia in which case lifetimes of 104 yr are possible finally a small hemispheric asymmetry exists due to the timing of ceres perihelion passage which would lead to a detectable enhancement of ice in the northern hemisphere if the orbital elements vary slowly relative to the ice accumulation rate our model results are potentially testable during the dawn science mission

bright and dark polar deposits on mercury evidence for surface volatiles measurements of surface reflectance of permanently shadowed areas near mercury s north pole reveal regions of anomalously dark and bright deposits at 1064 nanometer wavelength these reflectance anomalies are concentrated on poleward facing slopes and are spatially collocated with areas of high radar backscatter postulated to be the result of near surface water ice correlation of observed reflectance with modeled temperatures indicates that the optically bright regions are consistent with surface water ice whereas dark regions are consistent with a surface layer of complex organic material that likely overlies buried ice and provides thermal insulation impacts of comets or volatile rich asteroids could have provided both dark and bright deposits

joint assimilation of piezometric heads and groundwater temperatures for improved modeling of river aquifer interactions the ensemble kalman filter enkf is increasingly used to improve the real time prediction of groundwater states and the estimation of uncertain hydraulic subsurface parameters through assimilation of measurement data like groundwater levels and concentration data at the interface between surface water and groundwater measured groundwater temperature data can provide an additional source of information for subsurface characterizations with enkf additionally an improved prediction of the temperature field itself is often desirable for groundwater management in this work we investigate the worth of a joint assimilation of hydraulic and thermal observation data on the state and parameter estimation with enkf for two different model setups i a simple synthetic model of a river aquifer system where the parameters and simulation conditions were perfectly known and ii a model of the limmat aquifer in zurich switzerland where an exhaustive set of real world observations of groundwater levels 87 and temperatures 22 was available for assimilation year 2007 and verification year 2011 results for the synthetic case suggest that a joint assimilation of piezometric heads and groundwater temperatures together with updating of uncertain hydraulic parameters gives the best estimation of states and hydraulic properties of the model for the real world case the prediction of groundwater temperatures could also be improved through data assimilation with enkf for the validation period it was found that parameter fields updated with piezometric heads reduced rmse s of states significantly heads 49 temperature 15 but an additional conditioning of parameters on groundwater temperatures only influenced the characterization of the temperature field

assessment of local hydraulic properties from electrical resistivity tomography monitoring of a three dimensional synthetic tracer test experiment 1 in recent years geophysical methods have become increasingly popular for hydrological applications time lapse electrical resistivity tomography ert represents a potentially powerful tool for subsurface solute transport characterization since a full picture of the spatiotemporal evolution of the process can be obtained however the quantitative interpretation of tracer tests is difficult because of the uncertainty related to the geoelectrical inversion the constitutive models linking geophysical and hydrological quantities and the a priori unknown heterogeneous properties of natural formations here an approach based on the lagrangian formulation of transport and the ensemble kalman filter enkf data assimilation technique is applied to assess the spatial distribution of hydraulic conductivity k by incorporating time lapse cross hole ert data electrical data consist of three dimensional cross hole ert images generated for a synthetic tracer test in a heterogeneous aquifer under the assumption that the solute spreads as a passive tracer for high peclet numbers the spatial moments of the evolving plume are dominated by the spatial distribution of the hydraulic conductivity the assimilation of the electrical conductivity 4d images allows updating of the hydrological state as well as the spatial distribution of k thus delineation of the tracer plume and estimation of the local aquifer heterogeneity can be achieved at the same time by means of this interpretation of time lapse electrical images from tracer tests we assess the impact on the performance of the hydrological inversion of i the uncertainty inherently affecting ert inversions in terms of tracer concentration and ii the choice of the prior statistics of k our findings show that realistic ert images can be integrated into a hydrological model even within an uncoupled inverse modeling framework the reconstruction of the hydraulic conductivity spatial distribution is satisfactory in the portion of the domain directly covered by the passage of the tracer aside from the issues commonly affecting inverse models the proposed approach is subject to the problem of the filter inbreeding and the retrieval performance is sensitive to the choice of k prior geostatistical parameters

illumination conditions of the lunar polar regions using lola topography abstract we use high resolution altimetry data obtained by the lunar orbiter laser altimeter instrument onboard the lunar reconnaissance orbiter to characterize present illumination conditions in the polar regions of the moon compared to previous studies both the spatial and temporal extent of the simulations are increased significantly as well as the coverage fill ratio of the topographic maps used thanks to the 28 hz firing rate of the five beam instrument we determine the horizon elevation in a number of directions based on 240 m resolution polar digital elevation models reaching down to 75 latitude the illumination of both polar regions extending to 80 can be calculated for any geometry from those horizon longitudinal profiles we validated our modeling with recent lunar reconnaissance orbiter wide angle camera images we assessed the extent of permanently shadowed regions psrs defined as areas that never receive direct solar illumination and obtained total areas generally larger than previous studies 12 866 and 16 055 km2 in the north and south respectively we extended our direct illumination model to account for singly scattered light and found that every psr does receive some amount of scattered light during the year we conducted simulations over long periods several 18 6 years lunar precession cycles with a high temporal resolution 6 h and identified the most illuminated locations in the vicinity of both poles because of the importance of those sites for exploration and engineering considerations we characterized their illumination more precisely over the near future every year a location near the shackleton crater rim in the south polar region is sunlit continuously for 240 days and its longest continuous period in total darkness is about 1 5 days for some locations small height gains 10 m can dramatically improve their average illumination and reduce the night duration rendering some of those particularly attractive energy wise as possible sites for near continuous sources of solar power

improved calibration of reflectance data from the lro lunar orbiter laser altimeter lola and implications for space weathering abstract the lunar orbiter laser altimeter lola experiment on lunar reconnaissance orbiter lro is a laser altimeter that also measures the strength of the return pulse from the lunar surface these data have been used to estimate the reflectance of the lunar surface including regions lacking direct solar illumination a new calibration of these data is presented that features lower uncertainties overall and more consistent results in the polar regions we use these data along with newly available maps of the distribution of lunar maria also derived from lro instrument data to investigate a newly discovered dependence of the albedo of the lunar maria on latitude hemingway et al 2015 we confirm that there is an increase in albedo with latitude in the lunar maria and confirm that this variation is not an artifact arising from the distribution of compositions within the lunar maria using data from the lunar prospector neutron spectrometer radiative transfer modeling of the albedo dependence within the lunar maria is consistent with the very weak to absent dependence of albedo on latitude in the lunar highlands the lower abundance of the iron source for space weathering products in the lunar highlands weakens the latitude dependence to the extent that it is only weakly detectable in current data in addition photometric models and normalization may take into account the fact that the lunar albedo is latitude dependent but this dependence can cause errors in normalized reflectance of at most 2 for the majority of near nadir geometries we also investigate whether the latitude dependent albedo may have obscured detection of small mare deposits at high latitudes we find that small regions at high latitudes with low roughness similar to the lunar maria are not mare deposits that may have been misclassified owing to high albedos imposed by the latitude dependence finally we suggest that the only modest correlations among space weathering indicators defined for the lunar samples may be due to mixing of soils from distinct latitudes

evidence for surface water ice in the lunar polar regions using reflectance measurements from the lunar orbiter laser altimeter and temperature measurements from the diviner lunar radiometer experiment abstract we find that the reflectance of the lunar surface within 5 of latitude of the south pole increases rapidly with decreasing temperature near 110 k behavior consistent with the presence of surface water ice the north polar region does not show this behavior nor do south polar surfaces at latitudes more than 5 from the pole this south pole reflectance anomaly persists when analysis is limited to surfaces with slopes less than 10 to eliminate false detection due to the brightening effect of mass wasting and also when the very bright south polar crater shackleton is excluded from the analysis we also find that south polar regions of permanent shadow that have been reported to be generally brighter at 1064 nm do not show anomalous reflectance when their annual maximum surface temperatures are too high to preserve water ice this distinction is not observed at the north pole the reflectance excursion on surfaces with maximum temperatures below 110 k is superimposed on a general trend of increasing reflectance with decreasing maximum temperature that is present throughout the polar regions in the north and south we attribute this trend to a temperature or illumination dependent space weathering effect e g hemingway et al 2015 we also find a sudden increase in reflectance with decreasing temperature superimposed on the general trend at 200 k and possibly at 300 k this may indicate the presence of other volatiles such as sulfur or organics we identified and mapped surfaces with reflectances so high as to be unlikely to be part of an ice free population in this south we find a similar distribution found by hayne et al 2015 based on uv properties in the north a cluster of pixels near that pole may represent a limited frost exposure

subsurface migration of h2o at lunar cold traps 1 permanently shaded areas near the poles of the moon and mercury may harbor water ice we develop a physical model for migration of water molecules in the regolith and discover two pathways that can lead to accumulation of h2o in the subsurface a small fraction of water molecules delivered either continuously or abruptly to permanently cold areas diffuses into the regolith and can remain there longer than on the surface higher temperatures lead to deeper burial at constant temperature this diffusive migration produces less than one molecular layer of volatile h2o on grains because it is driven by differences in surface concentrations the water is therefore expected to be in adsorbed form and the amount stored in this fashion could be at most a few hundred ppm of h2o a second pathway is pumping by diurnal temperature oscillations from a transient ice cover that may have formed during a large comet impact it can lead to high ground ice densities but the ground ice layer lasts not long beyond the disappearance of the ice cover both types of subsurface charging mechanism work best for temperatures typical of permanently shaded areas with sunlit surfaces in their field of view

crustal structure across the central alaska range anatomy of a mesozoic collisional zone a first order process in the growth of continents is the collision and accretion of terranes against continental margins collision leads to the formation of a suture zone between the accreted terrane and the former continental margin new insights on the suturing process are observed from two receiver function transects across the mesozoic alaska range suture zone three distinct crustal sections are identified from observations of crustal thickness intracrustal discontinuities and vp vs a northern section with 27 km thick crust of felsic to intermediate composition a central section that is 37 km thick that exhibits intracrustal discontinuities and has felsic to intermediate composition and a southern section that is 30 km thick and has a more mafic composition we interpret these sections to correspond with the former continental margin yukon composite terrane the suture zone proper and the allochthonous oceanic terrane wrangellia composite terrane the boundary between the yukon composite terrane and the suture zone appears to be a subhorizontal discontinuity that accommodated underthrusting of crust from the suture zone beneath the former continental margin the boundary between the suture zone and the wrangellia composite terrane in contrast appears to be a relatively discrete vertical boundary the observed variability in the crust across the alaska range suture zone is likely controlled by the differing compositions of the terranes involved which influences how each section responds to precollisional syncollisional and postcollisional deformation

images of surface volatiles in mercury s polar craters acquired by the messenger spacecraft images acquired by nasa s messenger spacecraft have revealed the morphology of frozen volatiles in mercury s permanently shadowed polar craters and provide insight into the mode of emplacement and evolution of the polar deposits the images show extensive spatially continuous regions with distinctive reflectance properties a site within prokofiev crater identified as containing widespread surface water ice exhibits a cratered texture that resembles the neighboring sunlit surface except for its uniformly higher reflectance indicating that the surficial ice was emplaced after formation of the underlying craters in areas where water ice is inferred to be present but covered by a thin layer of dark organic rich volatile material regions with uniformly lower reflectance extend to the edges of the shadowed areas and terminate with sharp boundaries the sharp boundaries indicate that the volatile deposits at mercury s poles are geologically young relative to the time scale for lateral mixing by impacts and either are restored at the surface through an ongoing process or were delivered to the planet recently

coseismic slip distribution of the 2002 mw7 9 denali fault earthquake alaska determined from gps measurements 1 on 3 november 2002 an mw7 9 earthquake occurred in central alaska the earthquake ruptured portions of the susitna glacier denali and totschunda faults inversion of the gps measured displacement field indicates that the event was dominated by a complex right lateral strike slip rupture along the denali fault gps sites closest to the epicenter show the effect of thrust motion on the susitna glacier fault the preferred coseismic slip model with m w 7 8 indicates relatively low slip on the western part of the rupture and high slip from about 60 km east of the hypocenter extending to the junction of the denali and totschunda faults we find mostly shallow slip from the surface to 15 km depth but the inversion suggests one large deep slip patch about 110 km east of the hypocenter our model predicts surface slip in good agreement with surface geological observations where model resolution is good

structure of the altyn tagh fault and daxue shan from magnetotelluric surveys implications for faulting associated with the rise of the tibetan plateau magnetotelluric measurements in the foreland of the daxue shan have imaged low angle 20 thrust faults that extend to a depth of 3 km the surface projections of the faults at depth coincide with the mapped traces of the chang ma m 7 6 1932 and north hills thrusts minimum cumulative offsets of 7 km on the chang ma thrust and 14 km on the north hills thrust are estimated from the horizontal extent of underthrust sediment assuming that regional thrusting began at 5 6 ma this corresponds to minimum convergence rates of 1 3 mm yr and 2 5 mm yr on the chang ma and north hills thrusts respectively these slip rates correspond to 3 mm yr of sinistral slip on the altyn tagh fault between 96 e and 97 e this is consistent with the 4 2 mm yr of slip estimated by geological studies assuming comparable slip rates and similar fault geometry in the neighboring ranges this requires a minimum of 11 mm yr of shortening parallel to the altyn tagh fault between the dang he nan shan and qilian shan both the style of thrusting and rate of shortening are in agreement with geologic studies that favor a relatively high rate of slip on the altyn tagh fault this in turn implies that lithospheric extrusion contributes significantly in accommodating the ongoing convergence between india and asia farther west the altyn tagh fault is imaged on four magnetotelluric profiles as a vertical resistivity contrast extending to a depth of at least 8 km two strands of the north altyn tagh fault are imaged east of the asperity near subei 39 30 n 95 e

the geometry of fluvial channel bodies empirical characterization and implications for object based models of the subsurface the distribution of channel deposits in fluvial reservoirs is commonly modeled with object based techniques constrained on quantities describing the geometries of channel bodies to ensure plausible simulations it is common to define inputs to these models by referring to geologic analogs given their ability to reproduce complex geometries and to draw upon the analog experience object based models are considered inherently realistic yet this perceived realism has not hitherto been tested by assessing the outputs of these techniques against sedimentary architectures in the stratigraphic record this work presents a synthesis of data on the geometry of channel bodies derived from a sedimentologic database with the following aims 1 to provide tools for constraining stochastic models of fluvial reservoirs in data poor situations and 2 to test the intrinsic realism of object based modeling algorithms by comparing characteristics of the modeled architectures against analogs an empirical characterization of the geometry of fluvial channel bodies is undertaken that describes distributions in and relationships among channel body thickness cross stream width and planform wavelength and amplitude object based models are then built running simulations conditioned on six alternative analog informed parameter sets using four algorithms according to nine different approaches closeness of match between analogs and models is then determined on a statistical basis results indicate which modeling approaches return architectures that more closely resemble the organization of fluvial depositional systems known from nature and in what respect none of the tested algorithms fully reproduce characteristics seen in natural systems demonstrating the need for subsurface modeling methods to better incorporate geologic knowledge

constraints on the volatile distribution within shackleton crater at the lunar south pole shackleton crater is nearly coincident with the moon s south pole its interior receives almost no direct sunlight and is a perennial cold trap making shackleton a promising candidate location in which to seek sequestered volatiles however previous orbital and earth based radar mapping and orbital optical imaging have yielded conflicting interpretations about the existence of volatiles here we present observations from the lunar orbiter laser altimeter on board the lunar reconnaissance orbiter revealing shackleton to be an ancient unusually well preserved simple crater whose interior walls are fresher than its floor and rim shackleton floor deposits are nearly the same age as the rim suggesting that little floor deposition has occurred since the crater formed more than three billion years ago at a wavelength of 1 064 nanometres the floor of shackleton is brighter than the surrounding terrain and the interiors of nearby craters but not as bright as the interior walls the combined observations are explicable primarily by downslope movement of regolith on the walls exposing fresher underlying material the relatively brighter crater floor is most simply explained by decreased space weathering due to shadowing but a one micrometre thick layer containing about 20 per cent surficial ice is an alternative possibility