characterization of site specific gps errors using a short baseline network of braced monuments at yucca mountain southern nevada 1 we use a short baseline network of braced monuments to investigate site specific gps effects the network has baseline lengths of 10 100 and 1000 m baseline time series have root mean square rms residuals about a model for the seasonal cycle of 0 05 0 24 mm for the horizontal components and 0 20 0 72 mm for the radial seasonal cycles occur with amplitudes of 0 04 0 60 mm even for the horizontal components and even for the shortest baselines for many time series these lag seasonal cycles in local temperature measurements by 23 43 days this could suggest that they are related to bedrock thermal expansion both shorter period signals and seasonal cycles for shorter baselines to rep2 the one short braced monument in our network are correlated with temperature with no lag time differences between rep2 and the other stations which are deep braced should reflect processes occurring in the upper few meters of the ground these correlations may be related to thermal expansion of these upper ground layers and or thermal expansion of the monuments themselves even over these short distances we see a systematic increase in rms values with increasing baseline length this and the low rms levels suggests that site specific effects are unlikely to be the limiting factor in the use of similar gps sites for geophysical investigations

plate boundary observatory and related networks gps data analysis methods and geodetic products the geodesy advancing geosciences and earthscope gage facility global positioning system gps data analysis centers produce position times series velocities and other parameters for approximately two thousand continuously operating gps receivers spanning a quadrant of earth s surface encompassing the high arctic north america and caribbean the purpose of this review is to document the methodology for generating station positions and their evolution over time and to describe the requisite tradeoffs involved with combination of results gage gps analysis involves formal merging within a kalman filter of two independent loosely constrained solutions one is based on precise point positioning produced with the gps inferred positioning system orbit analysis simulation gipsy oasis software at central washington university cwu and the other is a network solution based on phase and range double differencing produced with the gps at mit gamit software at new mexico institute of mining and technology nmt the primary products generated are the position time series that show motions relative to a north america reference frame and secular motions of the stations represented in the velocity field the position time series themselves contain a multitude of signals in addition to the secular motions co seismic and post seismic signals seasonal signals from hydrology and transient events some understood and other not yet fully explained are all evident in the time series and ready for further analysis and interpretation we explore the impact of analysis assumptions on the reference frame realization and on the final solutions and we compare within the gage solutions and with others

tracing enhanced oil recovery signatures in casing gases from the lost hills oil field using noble gases abstract enhanced oil recovery eor and hydraulic fracturing practices are commonly used methods to improve hydrocarbon extraction efficiency however the environmental effects of such practices remain poorly understood eor is particularly prevalent in oil fields throughout california where water resources are in high demand and the disposal of large volumes of produced water may affect groundwater quality consequently it is essential to better understand the fate of injected eor fluids in california and other subsurface petroleum systems as well as any potential effect on nearby aquifer systems noble gases can be used as tracers to understand hydrocarbon generation migration and storage conditions as well as the relative proportions of oil and water present in the subsurface in addition a noble gas signature diagnostic of injected eor fluids can be readily identified we report noble gas isotope and concentration data in casing gases from oil production wells in the lost hills oil field northwest of bakersfield california and injectate gas data from the fruitvale oil field located within the city of bakersfield casing and injectate gas data are used to 1 establish pristine hydrocarbon noble gas signatures and the processes controlling noble gas distributions 2 characterize the noble gas signature of injectate fluids 3 trace injectate fluids in the subsurface and 4 construct a model to estimate eor efficiency noble gas results range from pristine to significantly modified by eor and can be best explained using a solubility exchange model between oil and connate formation fluids followed by gas exsolution upon production this model is sensitive to oil water interaction during hydrocarbon expulsion migration and storage at reservoir conditions as well as any subsequent modification by eor

el mayor cucapah mw 7 2 earthquake early near field postseismic deformation from insar and gps observations el mayor cucapah earthquake occurred on 4 april 2010 in northeastern baja california just south of the u s mexico border the earthquake ruptured several previously mapped faults as well as some unidentified ones including the pescadores borrego paso inferior and paso superior faults in the sierra cucapah and the indiviso fault in the mexicali valley and colorado river delta we conducted several global positioning system gps campaign surveys of preexisting and newly established benchmarks within 30 km of the earthquake rupture most of the benchmarks were occupied within days after the earthquake allowing us to capture the very early postseismic transient motions the gps data show postseismic displacements in the same direction as the coseismic displacements time series indicate a gradual decay in postseismic velocities with characteristic time scales of 66 9 days and 20 3 days assuming exponential and logarithmic decay respectively we also analyzed interferometric synthetic aperture radar insar data from the envisat and alos satellites the main deformation features seen in the line of sight displacement maps indicate subsidence concentrated in the southern and northern parts of the main rupture in particular at the indiviso fault at the laguna salada basin and at the paso superior fault we show that the near field gps and insar observations over a time period of 5 months after the earthquake can be explained by a combination of afterslip fault zone contraction and a possible minor contribution of poroelastic rebound far field data require an additional mechanism most likely viscoelastic relaxation in the ductile substrate

spatial variations in fault friction related to lithology from rupture and afterslip of the 2014 south napa california earthquake following earthquakes faults are often observed to continue slipping aseismically it has been proposed that this afterslip occurs on parts of the fault with rate strengthening friction that are stressed by the main shock but our understanding has been limited by a lack of immediate high resolution observations here we show that the behavior of afterslip following the 2014 south napa earthquake in california varied over distances of only a few kilometers this variability cannot be explained by coseismic stress changes alone we present daily positions from continuous and survey gps sites that we remeasured within 12 h of the main shock and surface displacements from the new sentinel 1 radar mission this unique geodetic data set constrains the distribution and evolution of coseismic and postseismic fault slip with exceptional resolution in space and time we suggest that the observed heterogeneity in behavior is caused by lithological controls on the frictional properties of the fault plane

the 2004 2008 dome building eruption at mount st helens washington epilogue the 2004 2008 dome building eruption at mount st helens ended during winter 2007 2008 at a time when field observations were hampered by persistent bad weather as a result recognizing the end of the eruption was challenging but important for scientists trying to understand how and why long lived eruptions end and for public officials and land managers responsible for hazards mitigation and access restrictions in hindsight the end of the eruption was presaged by a slight increase in seismicity in december 2007 that culminated on january 12 13 2008 with a burst of more than 500 events most of which occurred in association with several tremor like signals and a spasmodic burst of long period earthquakes at about the same time a series of regular localized small amplitude tilt events thousands of which had been recorded during earlier phases of the eruption came to an end thereafter seismicity declined to 10 20 events per day until january 27 28 when a spasmodic burst of about 50 volcano tectonic earthquakes occurred over a span of 3 h this was followed by a brief return of repetitive drumbeat earthquakes that characterized much of the eruption by january 31 however seismicity had declined to 1 2 earthquakes per day a rate similar to pre eruption levels we attribute the tilt and seismic observations to convulsive stagnation of a semisolid magma plug in the upper part of the conduit the upward movement of the plug ceased when the excess driving pressure which had gradually decreased throughout the eruption as a result of reservoir deflation and increasing overburden from the growing dome was overcome by increasing friction as a result of cooling and crystallization of the plug

quantifying ground deformation in the los angeles and santa ana coastal basins due to groundwater withdrawal we investigate complex surface deformation within the los angeles and santa ana coastal basins due to groundwater withdrawal and subsequent aquifer compaction expansion we analyze an 18 year interferometric synthetic aperture radar insar time series of 881 interferograms in conjunction with global positioning system gps data within the groundwater basins the large data set required the development of a distributed time series analysis framework able to automatically decompose both the insar and gps time series into short term and long term signals we find that short term seasonal oscillations of ground elevations due to annual groundwater withdrawal and recharge are unsteady due to changes in seasonal withdrawal by major water districts the spatial pattern of seasonal ground deformation near the center of the basin corresponds to a diffusion process with peak deformation occurring at locations with highest groundwater production long term signals occur over broader areas and are ultimately caused by long term changes in groundwater production comparison of the geodetic data with hydraulic head data from major water districts suggests that different regions of the groundwater system are responsible for different temporal components in the observed ground deformation short term seasonal ground deformation is caused by compaction of shallower aquifers used for the majority of groundwater production whereas long term ground deformation is correlated with delayed compaction of deeper aquifers and potential compressible clay layers these results demonstrate the potential for geodetic analysis to be an important tool for groundwater management to maintain sustainable pumping practices

field observations of the fluid granular boundary layer under near breaking waves numerous synchronized time series from video cameras pressure sensors current meters and hot film anemometers on natural beaches show that boundary layer development under the crest of near breaking waves can be idealized as a process composed of three distinct regimes here referred to as streaking roiling and pluming the roiling and pluming regimes fail to develop under the trough as a consequence there is a pronounced asymmetry in instantaneous sand transport and boundary layer phenomena between the wave crest and trough however laboratory waves with field scale periods and wave heights over thin sand beds do not exhibit this crest trough boundary layer asymmetry indicating that a critical element of similitude is absent in laboratory experiments we suggest that wave induced boundary ventilation is responsible

displacement of surface monuments vertical motion several measurements of vertical ground motion at pinon flat observatory california indicate the overall weakness and instability of the earth s weathered surface with respect to the underlying rock cumulative long period motions of order 0 5 mm per year dominate these records though smaller elastic deformations caused by precipitation loading atmospheric loading and tidal strains are evident at higher frequencies all of these help to characterize the near surface material the long period records suggest that near surface weathering is the dominant influence on monument motion at least at this site on crystalline rock in a semi arid environment rainfall loading gives an average vertical modulus of 2 6 gpa for the material in the uppermost 26 m of the ground compared with 88 gpa for granite under moderate confining stress atmospheric loading gives similar results but indicates the ground is permeable to airflow at periods longer than a few hours earth tide records show poisson s ratio to be 0 09 in contrast to the normative range of 0 2 0 25 establishing that horizontal strains couple only weakly into vertical ones so that vertical strains near the surface are a poor measure of areal strain the form of the ground surface displacement power spectrum indicates that analyses of geodetic surveys would be improved with the inclusion of a monument positioning error budget that increases with time because of ground instability and the generally small rate of crustal tectonic motions deeply emplaced monuments will be needed for observational programs designed to detect short term changes in crustal deformation over baselengths of order 10 km and less

the geochemistry of naturally occurring methane and saline groundwater in an area of unconventional shale gas development abstract since naturally occurring methane and saline groundwater are nearly ubiquitous in many sedimentary basins delineating the effects of anthropogenic contamination sources is a major challenge for evaluating the impact of unconventional shale gas development on water quality this study investigates the geochemical variations of groundwater and surface water before during and after hydraulic fracturing and in relation to various geospatial parameters in an area of shale gas development in northwestern west virginia united states to our knowledge we are the first to report a broadly integrated study of various geochemical techniques designed to distinguish natural from anthropogenic sources of natural gas and salt contaminants both before and after drilling these measurements include inorganic geochemistry major cations and anions stable isotopes of select inorganic constituents including strontium 87sr 86sr boron 11b lithium 7li and carbon 13c dic select hydrocarbon molecular methane ethane propane butane and pentane and isotopic tracers 13c ch4 13c c2h6 tritium 3h and noble gas elemental and isotopic composition helium neon argon in 105 drinking water wells with repeat testing in 33 of the wells total samples 145 in a subset of wells n 20 we investigated the variations in water quality before and after the installation of nearby 50 mg l the integrated geochemical data indicate that the saline groundwater originated via naturally occurring processes presumably from the migration of deeper methane rich brines that have interacted extensively with coal lithologies these observations were consistent with the lack of changes in water quality observed in drinking water wells following the installation of nearby shale gas wells in contrast to groundwater samples that showed no evidence of anthropogenic contamination the chemistry and isotope ratios of surface waters n 8 near known spills or leaks occurring at disposal sites mimicked the composition of marcellus flowback fluids and show direct evidence for impact on surface water by fluids accidentally released from nearby shale gas well pads and oil and gas wastewater disposal sites overall this study presents a comprehensive geochemical framework that can be used as a template for assessing the sources of elevated hydrocarbons and salts to water resources in areas potentially impacted by oil and gas development

sediment suspension in oscillatory flow measurements of instantaneous concentration at high shear abstract different syphon type suspended load probes were used together with a specially developed carousel sampler for measurements of the instantaneous sediment concentration in turbulent oscillatory flow over a sand bed shields parameters were well above the ripple flat bed transition region resulting in intense sediment transport over a flat bed the measurements were performed at different levels in a large oscillating water tunnel they showed some characteristic features of the temporal concentration variation at fixed levels including a pronounced effect of the orientation of the suction tube relative to the flow the variation with height of the average concentration is reasonably well described assuming a constant turbulent diffusivity and the magnitude of this can be predicted relatively well using simple turbulence arguments two empirical formulae for the extrapolated bed concentration are also presented the analysis is partly based on wilson s finding that in sheet flow the equivalent bed roughness is nearly proportional with the shields parameter resulting in a roughness grain diameter ratio much larger than 2 5 the figure often adopted for a flat bed but without sheet flow

evolution of coal bed methane in southeast qinshui basin china insights from stable and noble gas isotopes abstract the late carboniferous early permian coal seams of the qinshui basin in shanxi province are the most prolific producer of coalbed methane cbm in china methane formed in the late triassic during deep burial and reheating in late jurassic early cretaceous driven by magmatic underplating basin inversion brought the coal seams to 400 700 m from the surface in the mid late cenozoic here we present results of a study aimed at understanding the origin of the methane and how it was affected by cenozoic exhumation of the basin methane from a 12 km traverse perpendicular to the basin margin in the southeast part of the basin have stable isotope compositions 13c 30 2 to 35 2 and d 155 to 194 indicating a thermogenic origin with limited biogenic input they are however lighter than expected based on coal maturity and c1 c2 c3 1000 are significantly higher than typical thermogenic methane 90 of the radiogenic 4he produced in the coals has been lost prior to equilibrium between gas and water phase in the reservoir this likely occurred in response to gas loss process during rapid exhumation in cenozoic showing that the he and ar content of natural gases is a sensitive indicator of gas loss event caused by recent basin inversion the event may have led to the loss of up to 44 of the methane from the coal seams this study demonstrates the importance of basin inversion on gas preservation in shallow cbm and shows that in contrast to 13cch4 the light noble gases are essential for tracing such a process

coseismic and postseismic slip of the 2004 parkfield earthquake from space geodetic data we invert interferometric synthetic aperture radar insar data jointly with campaign and continuous global positioning system gps data for slip in the coseismic and postseismic periods of the 2004 parkfield earthquake the insar dataset consists of eight interferograms from data collected by the envisat and radarsat satellites spanning the time of the earthquake and variable amounts of the postseismic period the two datasets complement each other with the insar providing dense sampling of motion in the range direction of the satellite and the gps providing more sparse but three dimensional measurements of ground motion the model assumes exponential decay of the postseismic slip with a decay time constant of 0 087 years determined from time series modeling of continuous gps and creepmeter data we find a geodetic moment magnitude of m 6 2 for a 1 day coseismic model and m w 6 1 for the entire postseismic period the coseismic rupture occurred mainly in two slip asperities one near the hypocenter and the other 15 20 km north postseismic slip occurred on the shallow portions of the fault and near the rupture areas of two m 5 0 aftershocks a comparison of the geodetic slip models with seismic moment estimates suggests that the coseismic moment release of the parkfield earthquake is as little as 25 of the total this underlines the importance of aseismic slip in the slip budget for the parkfield segment online material complete data tables and supplemental tables

mantle flow beneath a continental strike slip fault postseismic deformation after the 1999 hector mine earthquake two recent large earthquakes in the mojave desert california the magnitude 7 3 1992 landers and magnitude 7 1 1999 hector mine earthquakes have each been followed by elevated crustal strain rates over periods of months and years geodetic data collected after the hector mine earthquake exhibit a temporally decaying horizontal velocity field and a quadrant uplift pattern opposite to that expected for localized shear beneath the earthquake rupture we interpret the origin of this accelerated crustal deformation to be vigorous flow in the upper mantle in response to the stress changes generated by the earthquake our results suggest that transient flow in the upper mantle is a fundamental component of the earthquake cycle and that the lower crust is a coherent stress guide coupling the upper crust with the upper mantle

tectonic contraction across los angeles after removal of groundwater pumping effects after the 1987 whittier narrows and 1994 northridge earthquakes revealed that blind thrust faults represent a significant threat to metropolitan los angeles a network of 250 continuously recording global positioning system gps stations was deployed to monitor displacements associated with deep slip on both blind and surface faults here we augment this gps data with interferometric synthetic aperture radar imagery to take into account the deformation associated with groundwater pumping and strike slip faulting after removing these non tectonic signals we are left with 4 4 mm yr 1 of uniaxial contraction across the los angeles basin oriented n 36 degrees e perpendicular to the major strike slip faults in the area this indicates that the contraction is primarily accommodated on thrust faults rather than on the northeast trending strike slip faults we have found that widespread groundwater and oil pumping obscures and in some cases mimics the tectonic signals expected from the blind thrust faults in the 40 km long santa ana basin groundwater withdrawal and re injection produces 12 mm yr 1 of long term subsidence accompanied by an unprecedented seasonal oscillation of 55 mm in the vertical direction and 7 mm horizontally

helium accumulation in groundwater ii a model for the accumulation of the crustal 4he degassing flux abstract a model of 4 he accumulation in a confined aquifer is presented which includes in situ production and a crustal degassing flux of 4 he into the bottom of a confined aquifer the model is consistent with the measurements of 4 he concentration in the great artesian basin australia torgersen and clarke 1985 and also with the measurements of 4 he concentration in the auob sandstone of namibia heaton 1981 the measured value of the crustal degassing flux of 4 he from these two areas is comparable with the 4 he degassing flux calculated from the atmospheric budget of 4 he wasserburg et al 1963 ozima and podosek 1983 a literature review suggests that a crustal degassing 4 he source may account for the 4 he accumulation in many other groundwater systems it is concluded from the literature review the detailed modelling of 4 he accumulation in gab and the auob sandstone and the atmospheric budget that crustal degassing of 4 he may be a common and widespread phenomena

correlation between changes in groundwater levels and surface deformation from gps measurements in the san gabriel valley california 1 changes in groundwater levels cause water bearing basins to deform here we provide a detailed history of horizontal surface displacements in the san gabriel valley california which we show are highly correlated with the water level changes measured at a nearby well correlation coefficient of 0 96 0 01 we use the surface response from a one year period during which water level change in the nearby well was over 16 m to monitor the deformations over a 14 year period from 1998 to 2011 the water level changes lead surface deformation by 21 days but the significance of the offset is only weakly supported p value 0 129 the projection method can be used as a real time monitoring or detection system for deformation caused by a variety of mechanisms such as fluid injection and removal groundwater development oil production carbon sequestration and by seismic and volcanic activity

displacement of surface monuments horizontal motion measurements of tectonic deformation depend on both accurate instrumentation and adequate coupling of the apparatus to the earth s crust existing techniques capable of resolving the signals of interest strain rates of 10 n yr are mainly observatory based the limitation in the baselength of these instruments 1 km results in a requirement that the reference monuments be exceptionally stable 10 tzm yr however records from pition flat observatory california show that the actual horizontal displacements for massive near surface monuments eraplaced in competent weathered granite are of the order of 50 tzm yr the low noise level of the strain measurements at this site indicates that this magnitude of monument displacement is abnormally small until high accuracy geodetic techniques are developed sophisticated monuments or monument monitoring devices will be necessary to record faithfully continuous crustal deformation

noise in gps displacement measurements from southern california and southern nevada 1 time series of position changes estimated from data from 236 continuously recording gps receivers operating in southern california and southern nevada are evaluated for noise models that characterize their temporal correlations the lengths of the time series range between 3 5 and 10 years after adjusting these data for postseismic deformation offsets and annual periodicities i find that about one half of the time series have temporal correlations that are categorized as either flicker or random walk noise the remaining time series can be best categorized as either a combination of flicker and random walk power law noise first order gauss markov plus random walk noise or power law plus broadband seasonal noise a variety of geodetic monuments are used in southern california and nevada including deeply braced designs cement piers pins drilled in outcrop and buildings when i evaluate the noise for each time series in terms of an estimate of the standard error in velocity i find that the sites with the smallest errors are those located in nevada using deeply braced monuments sites that are installed within regions of active pumping both for groundwater and oil had the largest standard errors in velocity comparison of monument stability as measured by standard error in rate with average annual rainfall nearby indicates a marginally significant correlation in addition even though regional filtering removed much of the common mode signals in these time series there still remains a common mode seasonal signal which can and should be removed

quantifying the helium and hydrocarbon accumulation processes using noble gases in the north qaidam basin china abstract limited reserves and insecure resource supply have led to global shortage crises in helium a vital gas for cryogenic engineering and other countless industrial manufacturing processes despite the attention drawn by global supply disruptions the helium accumulation mechanism in natural gas fields remains poorly understood noble gases are excellent tracers for studying migration and accumulation processes of fluids in the subsurface and can be used to investigate the influence of subsurface fluids on helium accumulation we present noble gas isotope and abundance data as well as major gas compositional data from 10 producing wells in three gas fields in the north qaidam basin china helium is more concentrated in the mabei and dongping gas fields 2 06 48 4 10 4 cm3 stp cm3 than in the niudong gas field 1 15 1 42 10 4 cm3 stp cm3 the helium is mainly radiogenic with 3he 4he ratios of 0 01 0 05 ra where ra is the atmospheric value of 3he 4he and lacks significant contribution from the mantle 0 03 0 67 the noble gases derived from air saturated water 20ne 36ar 84kr and 130xe can be explained by an oil modified groundwater exsolution model with excess heavy noble gases the calculated voil vwater and vgas vwater ratios indicate that the mabei region is the most oil rich area and the dongping region has the driest natural gas which is consistent with the geological context these ratios further support the fractionation models the strong linear relationship between 4he and 20ne r2 0 98 suggested that 4he was dissolved into groundwater before migrating into the oil or gas phase the initial 4he concentrations in groundwater can accumulate within 0 31 2 78 myr assuming a 4he flux from the entire crustal section according to the fractionation model helium in groundwater partitions into the gas phase when contacting hydrocarbons the different volume ratios among oil gas and water during the equilibration process cause much greater variability in the helium concentrations in the gas phase e g 6 08 10 4 to 2 01 10 3 cm3 stp cm3 in mabei than those in the groundwater phase e g 9 18 10 3 to 1 39 10 2 cm3 4he stp cm3 h2o in mabei hydrocarbons play a critical role in helium accumulation and dilution helium rich natural gas fields are characterized by old groundwater systems and moderate hydrocarbon abundance this study has succeeded in quantitatively assessing the helium accumulation process in natural gas fields in the north qaidam basin and revealed that both groundwater and hydrocarbon phases control the helium accumulation in the subsurface environment this outcome has broad implications for the prediction of hydrocarbon and helium as resources

postseismic deformation following the 2010 m 7 2 el mayor cucapah earthquake observations kinematic inversions and dynamic models due to its location on a transtensional section of the pacific north american plate boundary the salton trough is a region featuring large strike slip earthquakes within a regime of shallow asthenosphere high heat flow and complex faulting and so postseismic deformation there may feature enhanced viscoelastic relaxation and afterslip that is particularly detectable at the surface the 2010 m 7 2 el mayor cucapah earthquake was the largest shock in the salton trough since 1892 and occurred close to the us mexico border and so the postseismic deformation recorded by the continuous gps network of southern california provides an opportunity to study the rheology of this region three year postseismic transients extracted from gps displacement time series show four key features 1 1 2 cm of cumulative uplift in the imperial valley and sim 1 cm of subsidence in the peninsular ranges 2 relatively large cumulative horizontal displacements 150 km from the rupture in the peninsular ranges 3 rapidly decaying horizontal displacement rates in the first few months after the earthquake in the imperial valley and 4 sustained horizontal velocities following the rapid early motions that were still visibly ongoing 3 years after the earthquake kinematic inversions show that the cumulative 3 year postseismic displacement field can be well fit by afterslip on and below the coseismic rupture though these solutions require afterslip with a total moment equivalent to at least a m 7 2 earthquake and higher slip magnitudes than those predicted by coseismic stress changes forward modeling shows that stress driven afterslip and viscoelastic relaxation in various configurations within the lithosphere can reproduce the early and later horizontal velocities in the imperial valley while newtonian viscoelastic relaxation in the asthenosphere can reproduce the uplift in the imperial valley and the subsidence and large westward displacements in the peninsular ranges we present two forward models of dynamically coupled deformation mechanisms that fit the postseismic transient well a model combining afterslip in the lower crust newtonian viscoelastic relaxation in a localized zone in the lower crust beneath areas of high heat flow and geothermal activity and newtonian viscoelastic relaxation in the asthenosphere and a second model that replaces the afterslip in the first model with viscoelastic relaxation with a stress dependent viscosity in the mantle the rheology of this high heat flow high strain rate region may incorporate elements of both these models and may well be more complex than either of them

correlated errors in geodetic time series implications for time dependent deformation analysis of frequent trilateration observations from the two color electronic distance measuring networks in california demonstrate that the noise power spectra are dominated by white noise at higher frequencies and power law behavior at lower frequencies in contrast earth scientists typically have assumed that only white noise is present in a geodetic time series since a combination of infrequent measurements and low precision usually preclude identifying the time correlated signature in such data after removing a linear trend from the two color data it becomes evident that there are primarily two recognizable types of time correlated noise present in the residuals the first type is a seasonal variation in displacement which is probably a result of measuring to shallow surface monuments installed in clayey soil which responds to seasonally occurring rainfall this noise is significant only for a small fraction of the sites analyzed the second type of correlated noise becomes evident only after spectral analysis of line length changes and shows a functional relation at long periods between power and frequency of 1 where is frequency and 2 with 2 this type of correlated noise is termed random walk noise and its source is mainly thought to be small random motions of geodetic monuments with respect to the earth s crust though other sources are possible because the line length changes in the two color networks are measured at irregular intervals power spectral techniques cannot reliably estimate the level of 1 noise rather we also use here a maximum likelihood estimation technique which assumes that there are only two sources of noise in the residual time series white noise and random walk noise and estimates the amount of each from this analysis we find that the random walk noise level averages about 1 3 mm yr and that our estimates of the white noise component confirm theoretical limitations of the measurement technique in addition the seasonal noise can be as large as 3 mm in amplitude but typically is less than 0 5 mm because of the presence of random walk noise in these time series modeling and interpretation of the geodetic data must account for this source of error by way of example we show that estimating the time varying strain tensor a form of spatial averaging from geodetic data having both random walk and white noise error components results in seemingly significant variations in the rate of strain accumulation spatial averaging does reduce the size of both noise components but not their relative influence on the resulting strain accumulation model

noise properties of continuous gps data from concrete pillar geodetic monuments in new zealand and comparison with data from u s deep drilled braced monuments 1 reducing noise levels in geodetic data is critical for the interpretation and modeling of geophysically interesting signals in this paper i estimate noise properties of continuous gps time series collected on concrete pillar monuments and compare them with similar data from deep drilled braced monuments that are considered the most stable three dimensional monuments available i show that the time series noise properties are very similar between the monument types at least for time series up to 4 5 years duration differences between the monument types are therefore not a dominant influence on these time series implying that the less expensive concrete pillar monuments are a valid choice for recording many signals of geophysical interest

coseismic and initial postseismic deformation from the 2004 parkfield california earthquake observed by global positioning system electronic distance meter creepmeters and borehole strainmeters global positioning system gps electronic distance meter creepmeter and strainmeter measurements spanning the m 6 0 parkfield california earthquake are examined using these data from 100 sec through 9 months following the mainshock the omori s law with rate inversely related to time 1 t p and p ranging between 0 7 and 1 3 characterizes the time dependent deformation during the postseismic period these results are consistent with creep models for elastic solids with an accurate function of postseismic response the coseismic displacements can be estimated from the high rate 1 min sampling gps and the coseismic displacements are approximately 75 of those estimated from the daily solutions consequently fault slip models using daily solutions overestimate coseismic slip in addition at 2 months and at 8 months following the mainshock postseismic displacements are modeled as slip on the san andreas fault with a lower bound on the moment exceeding that of the coseismic moment online material data description and supplementary figures tables and data used in models and time series analysis

velocities and shear stresses in wave current flows a model is presented for the velocity distributions in combined wave current flows over rough beds the model is based on a new analysis of turbulence measurements in oscillatory flow the resulting formulas for the velocity distribution are remarkably simple and show good agreement with experiment the formula derived for friction factor also shows good agreement with experiment

improved stability of a deeply anchored geodetic monument for deformation monitoring a test of two different monument designs used in geodetic networks shows that monuments installed to depths of 5 to 10 meters and laterally braced exhibit less environmentally caused displacement than those installed to 2 meters depth at parkfield california we have been monitoring the lengths of 17 baselines over the past decade with a 2 to 3 day interval between measurements using a two color geodimeter with a nominal precision of 0 5 mm over 5 km long baselines significant variations are observed on many of these baselines which appear to be related to the seasonally occurring rainfall with the larger variations approaching 10 mm over the past decade to test whether we could improve upon the measurements on some of the more susceptible lines at two sites we installed new monuments within about 30 meters of the original monuments after 1 5 years of measurements it is evident that the new monuments significantly attenuate the seasonal displacements to less than 1 mm the use of deeply anchored monuments should improve the ability of fault scale geodetic monitoring arrays to detect small tectonic displacements

gps constraints on 34 slow slip events within the cascadia subduction zone 1997 2005 1 refinements to gps analyses in which we factor geodetic time series to better estimate both reference frames and transient deformation resolve 34 slow slip events located throughout the cascadia subduction zone from 1997 through 2005 timing of transient onset is determined with wavelet transformation of geodetic time series thirty continuous stations are included in this study ranging from northern california to southwestern british columbia our improvements in analysis better resolve the largest creep events and also identify many smaller events at 48 5 n latitude a 14 month average recurrence interval has been observed over eight events since 1997 farther north along vancouver island a host of smaller events with a distinct 14 month periodicity also occurs in southern washington state some of the largest transient displacements are observed but lack any obvious periodicity in their recurrence along central oregon an 18 month recurrence is evident while in northern california an 11 month periodicity continues through 2005 we invert gps offsets of the 12 best recorded events for thrust slip along the plate interface using a cross validation scheme to derive optimal smoothing parameters these 12 events have equivalent moment magnitudes between 6 3 and 6 8 and have 2 3 cm of slip unlike other subduction zones no long duration events are observed and cumulative surface deformation is consistently less than 0 6 cm the many newly resolved smaller transient events in cascadia show that slow slip events occur frequently with gps best capturing only the largest events it is likely that slow slip events occur more frequently at levels not detectable with gps

using cluster analysis to organize and explore regional gps velocities 1 cluster analysis offers a simple visual exploratory tool for the initial investigation of regional global positioning system gps velocity observations which are providing increasingly precise mappings of actively deforming continental lithosphere the deformation fields from dense regional gps networks can often be concisely described in terms of relatively coherent blocks bounded by active faults although the choice of blocks their number and size can be subjective and is often guided by the distribution of known faults to illustrate our method we apply cluster analysis to gps velocities from the san francisco bay region california to search for spatially coherent patterns of deformation including evidence of block like behavior the clustering process identifies four robust groupings of velocities that we identify with four crustal blocks although the analysis uses no prior geologic information other than the gps velocities the cluster block boundaries track three major faults both locked and creeping

air xe enrichments in elk hills oil field gases role of water in migration and storage hydrocarbons from the elk hills naval petroleum reserve npr 1 bakersfield ca are enriched in heavy noble gases the 132xe 36ar ratios are as high as 576 times the ratio in air and represent the largest relative xe enrichments ever observed in terrestrial fluids the xe isotopic composition is indistinguishable from air we show that these samples cannot be explained by equilibration of oil with air saturated water and secondary enrichment via a rayleigh distillation gas stripping process based on laboratory studies of others with potential petroleum source rocks we believe the source of this enriched heavy noble gas component was adsorbed air initially trapped in on the source rocks that was expelled and mixed with the hydrocarbons during expulsion and primary migration kr and xe enrichments decrease with increasing 36ar concentration we propose a model in which an initial kr xe enriched hydrocarbon becomes diluted with noble gases extracted from air saturated groundwater during expulsion migration and storage the model generates an integrated water hydrocarbon ratio for the production fluid which indicates a minimal role for water in hydrocarbon expulsion and migration the results are interpreted to provide time geometrical constraints on the mechanisms by which hydrocarbons can migrate as a separate phase

helium concentrations and isotope compositions in 10 km deep groundwaters abstract helium isotopes are useful for tracing terrestrial water movement and calculating residence times which have important implications for radioactive waste disposal and carbon capture and storage projects helium concentrations are generally measured directly in water samples however this is not always possible in this scenario the he concentration equilibrium between pore waters and he accessible volumes e g fluid inclusions hereafter hav in minerals e g quartz can be utilized to determine he concentrations in this study the he partial pressure was measured in havs of quartz grains collected from cores of the kola super deep borehole ksdb using isothermal he extraction saturation experiments a large fraction of he was released from these samples during the first interval of isothermal heating indicating a destruction of the unstable havs likely due to decrepitation of fluid inclusions we present a new approach to calculate he partial pressures using only the he fraction released from the stable havs this approach gives a he partial pressure phe of 1 5 atm at depths of 10 km when combined with solubility data this value suggests a high he concentration in the deep pore waters nearby the ksdb 1 3 10 6 mol cc h2o 1 indicating a long residence time of he atoms in a deep water mineral system close to the age of the regional metamorphism 1700 ma the 3he 4he in the deep ksdb quartz samples and the pore waters are 3 10 8 typical of radiogenic he generated in 10 km deep archean rocks of the ksdb importantly external fluxes are not needed to explain he isotope abundances in rocks minerals and pore waters at these depths

ongoing drought induced uplift in the western united states the western united states has been experiencing severe drought since 2013 the solid earth response to the accompanying loss of surface and near surface water mass should be a broad region of uplift we use seasonally adjusted time series from continuously operating gps stations to measure this uplift which we invert to estimate mass loss the median uplift is 4 mm with values up to 15 mm in california s mountains the associated pattern of mass loss which ranges up to 50 cm of water equivalent is consistent with observed decreases in precipitation and streamflow we estimate the total deficit to be about 240 gt equivalent to a 10 cm layer of water over the entire region or the annual mass loss from the greenland ice sheet

the complete 3 d surface displacement field in the epicentral area of the 1999 mw7 1 hector mine earthquake california from space geodetic observations we use interferometric synthetic aperture radar insar data to derive continuous maps for three orthogonal components of the co seismic surface displacement field due to the 1999 m w7 1 hector mine earthquake in southern california vertical and horizontal displacements are both predominantly antisymmetric with respect to the fault plane consistent with predictions of linear elastic models of deformation for a strike slip fault some deviations from symmetry apparent in the surface displacement data may result from complexity in the fault geometry

assessing compositional variability and migration of natural gas in the antrim shale in the michigan basin using noble gas geochemistry abstract this study uses stable noble gases he ne ar kr xe volume fractions and isotopic ratios from antrim shale natural gas to assess compositional variability and vertical fluid migration within this reservoir in addition to distinguishing between the presence of thermogenic versus biogenic methane r ra values where r is the measured 3he 4he ratio and ra is the atmospheric value of 1 384 0 013 10 6 vary from 0 01 to 0 34 suggesting a largely dominant crustal 4he component with minor atmospheric and mantle contributions crustal 21ne 40ar and 136xe contributions are also present but the atmospheric component is largely dominant for these gases crustal contributions for 21ne 40ar and 136xe vary between 1 1 and 12 5 between 0 7 and 19 and between 0 1 and 2 7 respectively a few samples present higher than atmospheric 20ne 22ne ratios pointing to the presence of a small mantle ne component high horizontal and vertical variability of noble gas signatures in the antrim shale are observed these are mainly due to variable noble gas input from deep brines and to a smaller extent variable in situ production within different layers of the antrim shale in particular the lachine and norwood members estimated 4he ages considering external 4he input for antrim shale water vary between 0 9 ka and 238 2 ka and match well for most samples with the timing of the major wisconsin glaciation suggesting that antrim shale water was influenced by glaciation induced recharge consistency between measured and predicted 40ar 36ar ratios assuming ar release temperatures 250 c supports a thermogenic origin for most of the methane in these samples this thermogenic methane is likely to originate at greater depths either from the deeper portion of the antrim shale in the central portion of the michigan basin or from deeper formations given that the thermal maturity of the antrim shale in the study area is rather low

noble gas tracing of groundwater coalbed methane interaction in the san juan basin usa the san juan basin natural gas field located in northwestern new mexico and southwestern colorado in the usa is a case type coalbed methane system groundwater is thought to play a key role in both biogenic methane generation and the co2 sequestration potential of coalbed systems we show here how noble gases can be used to construct a physical model that describes the interaction between the groundwater system and the produced gas we collected 28 gas samples from producing wells in the artesian overpressured high production region of the basin together with 8 gas samples from the underpressured low production zone as a control stable isotope and major species determination clearly characterize the gas in the high production region as dominantly biogenic in origin and the underpressured low producing region as having a significant admix of thermogenic coal gas 3he 4he ratios increase from 0 0836ra at the basin margin to 0 318ra towards the center indicating a clear but small mantle he signature in all gases coherent fractionation of water derived 20ne 36ar and crustal 4he 40ar are explained by a simple rayleigh fractionation model of open system groundwater degassing low 20ne concentrations compared to the model predicted values are accounted for by dilution of the groundwater associated gas by desorbed coalbed methane this rayleigh fractionation and dilution model together with the gas production history allows us to quantify the amount of water involved in gas production at each well the quantified water volumes in both underpressured and overpressured zones range from 1 7 103 m3 to 4 2 105 m3 with no clear distinction between over and underpressured production zones these results conclusively show that the volume of groundwater seen by coal does not play a role in determining the volume of methane produced by secondary biodegradation of these coalbeds there is no requirement of continuous groundwater flow for renewing the microbes or nutrient components we furthermore observe strong mass related isotopic fractionation of 20ne 22ne and 38ar 36ar isotopic ratios this can be explained by a noble gas concentration gradient in the groundwater during gas production which causes diffusive partial re equilibration of the noble gas isotopes it is important for the study of other systems in which extensive groundwater degassing may have occurred to recognize that severe isotopic fractionation of air derived noble gases can occur when such concentration gradients are established during gas production excess air derived xe and kr in our samples are shown to be related to the diluting coalbed methane and can only be accounted for if xe and kr are preferentially and volumetrically trapped within the coal matrix and released during biodegradation to form ch4

a magnus opus helium neon and argon isotopes in a north sea oilfield this study of the magnus oilfield located in the east shetland basin northern north sea represents the most detailed investigation of noble gas isotope systematics in a liquid hydrocarbon reservoir yet undertaken samples from nine producing wells across this middle jurassic field were taken and the helium neon and argon isotopic ratios and abundances in the oil were determined both the helium and the neon isotope systematics require a contribution from a mantle source if the mantle endmember is modeled using mid ocean ridge mor values 2 3 4 5 of the 4he and 4 3 6 2 of the 21ne is mantle derived the remainder of the 4he and 9 0 12 0 of the 21ne is crustal radiogenic and the remaining 21ne is atmosphere derived the resolved mantle derived he ne ratio is quite distinct from upper mantle values estimated from mor samples but indistinguishable from values resolved in other regions of continental extension this result provides strong evidence that the subcontinental lithospheric mantle not only has a different noble gas inventory to the convecting mantle under mors but also has a near uniform composition the quantity of radiogenic noble gas associated with the magnus oil groundwater system can only be accounted for by production predominantly from outside the volume of the magnus sandstone aquifer reservoir drainage area and the associated kimmeridge clay source rock formation and together with the mantle derived noble gases provides strong evidence for cross formational communication with deeper regions of the crust the 20ne and 36ar must have been input into the oil phase by interaction with an air equilibrated groundwater noble gas partitioning between a seawater derived groundwater and the oil phase at the average magnus sandstone aquifer temperature requires a subsurface seawater oil volume ratio of 110 40 to account for both the 20ne and 36ar concentrations in the central and southern magnus samples the volume of groundwater which has equilibrated with the magnus oil is indistinguishable from the static volume of water estimated to be in the down dip magnus aquifer reservoir drainage volume this suggests that the magnus oil has obtained complete equilibrium with the groundwater in the reservoir drainage volume probably during secondary migration and further suggests that concurrent cementation of the magnus sandstone aquifer has occurred with little or no large scale movement of air equilibrated groundwater through the aquifer system higher concentrations of 20ne and 36ar in the n magnus oil cannot be accounted for by equilibration with a seawater derived groundwater this is qualitatively consistent with the earlier and more mature oil in this section equilibrating with freshwater which is known to have been trapped in the crest of the reservoir structure

an investigation of the velocity field under regular and irregular waves over a sand beach abstract near bed horizontal cross shore and vertical velocity measurements were acquired in a laboratory wave flume over a 1 8 sloping sand beach of finite depth data were acquired using a three component acoustic doppler velocimeter to measure the velocity field close to but at a fixed distance from the bed the near bed velocity field is examined as close as 1 5 cm above a trough and crest of a ripple under three different types of wave forcing stokes waves stokes groups and irregular waves although both horizontal and vertical velocity measurements were made attention is focused primarily on the vertical velocity the results clearly indicate that the measured near bed vertical velocity which was outside the wave bottom boundary layer is distinctly nonzero and not well predicted by linear theory spectral and bispectral analysis techniques indicate that the vertical velocity responds differently depending on the location over a ripple and that ripple induced effects on the velocity field are present as high as 4 8 cm above the bed for vortex ripples with wavelengths on the order of 8 cm and amplitudes on the order of 2 cm at greater heights above the bed the observed wave induced motion is adequately predicted by the linear theory

noble gas fractionation during subsurface gas migration abstract environmental monitoring of shale gas production and geological carbon dioxide co2 storage requires identification of subsurface gas sources noble gases provide a powerful tool to distinguish different sources if the modifications of the gas composition during transport can be accounted for despite the recognition of compositional changes due to gas migration in the subsurface the interpretation of geochemical data relies largely on zero dimensional mixing and fractionation models here we present two phase flow column experiments that demonstrate these changes water containing a dissolved noble gas is displaced by gas comprised of co2 and argon we observe a characteristic pattern of initial co enrichment of noble gases from both phases in banks at the gas front followed by a depletion of the dissolved noble gas the enrichment of the co injected noble gas is due to the dissolution of the more soluble major gas component while the enrichment of the dissolved noble gas is due to stripping from the groundwater these processes amount to chromatographic separations that occur during two phase flow and can be predicted by the theory of gas injection this theory provides a mechanistic basis for noble gas fractionation during gas migration and improves our ability to identify subsurface gas sources after post genetic modification finally we show that compositional changes due to two phase flow can qualitatively explain the spatial compositional trends observed within the bravo dome natural co2 reservoir and some regional compositional trends observed in drinking water wells overlying the marcellus and barnett shale regions in both cases only the migration of a gas with constant source composition is required rather than multi stage mixing and fractionation models previously proposed

helium and argon isotopes in rocks minerals and related ground waters a case study in northern switzerland abstract to address the problems related to the transfer of helium and argon isotopes from rocks into related aquifers the concentrations of u th li and k and helium and argon isotopes were measured in a sedimentary sequence from tertiary to permo carboniferous and in crystalline rocks in northern switzerland in addition to whole rock samples mineral separates have also been investigated the observed concentrations of 3 he 4 he and 40 ar in rocks minerals and groundwaters are compared to calculated values which would result from in situ radiogenic production in a closed system this comparison shows that the rocks and minerals have almost completely lost radiogenic in situ produced helium loss of 3 he and 4 he has been controlled by different retention capacities of the rock forming and accessory minerals and fillings therefore measured 3 he 4 he ratios in these rocks can differ from the calculated production ratios the deviation is generally less than a factor of 3 however in certain chemical sediments e g anhydrites elevated ratios of 3 he 4 he up to 15 10 8 which is 20 times the production ratio were observed it is postulated that 3 h the precursor of 3 he might be chemically bound in such sediments during the 12 3 years half life of 3 h and that the beta decay energy of 3 h is too small to liberate 3 he the calculated closed system concentrations of helium in groundwater exceed the measured ones by up to three orders of magnitude implying that the water rock system has not been a closed system since the time of sedimentation and that movable waters have removed helium to a discharge area and to the atmosphere stagnant old waters however could contain high concentrations of helium and supply it to younger movable waters aquitards with low permeability permian shales appear to be a more important source of helium isotopes than water bearing rocks permian sandstones high abundances of all parent elements in the shales almost complete loss of radiogenic helium and the enhanced production ratio of 3 he 4 he 7 2 10 8 in these rocks similar to the ratio observed in the neighbour permian aquifer 9 4 10 8 suggest the shale as a major source of helium isotopes for this aquifer and diffusion as a principal process for helium transfer from the stagnant porewaters in shales into the movable waters in sandstones some sedimentary rocks e g permian sandstones and shales contain more helium than could have been produced since the time of sedimentation while permian sandstones mainly have retained this excess rare gas component they have released radiogenic helium the difference in the retention of these two components most probably demonstrates that migration of radiogenic helium from damage tracks along crystal imperfections to grain boundaries is an important process controlling its loss the abundances of excess 3 he and 4 he in rocks cannot be predicted by in situ production calculations studies of rocks and minerals are required the average ratio of 40 ar 36 ar 385 in groundwaters collected from permian sediments from the weiach borehole is much higher than that in the aquifers from the crystalline basement below the sediments radiogenic 40 ar in permian sediments is mainly liberated by diagenetic water rock interactions the low contribution of radiogenic 40 ar in deep aquifers of the crystalline basement and the fact that chlorine concentrations in groundwaters from the basement are also much lower than in the overlaying permian aquifer eliminates a hypothetical upwards fluid flux from this study we envisage intrabasin sources for helium and argon isotopes in groundwaters with mainly lateral migration of waters through sedimentary layers at different rates and diffusion of helium from slower velocity older waters in more stagnant zones shales into flow passes with highervelocity younger waters in sections with higher permeability sandstones an external source for noble gases is not required in such a model

determining fluid migration and isolation times in multiphase crustal domains using noble gases geochemical characteristics in subsurface fluid systems provide a wealth of information about fluid sources migration and storage conditions determining the extent of fluid interaction aquifer hydrocarbon connectivity is important for oil and gas production and waste storage applications but is not tractable using traditional seismic methods furthermore the residence time of fluids is critical in such systems and can vary from tens of thousands to billions of years our understanding of the transport length scales in multiphase systems while equally important is more limited noble gas data from the rotliegend natural gas field northern germany are used here to determine the length scale and isolation age of the combined water gas system we show that geologically bound volume estimates i e gas to water volume ratios match closed system noble gas model predictions suggesting that the rotliegend system has remained isolated as a closed system since hydrocarbon formation radiogenic helium data show that fluid isolation occurred 63 129 m y after rock and or groundwater deposition ca 300 ma which is consistent with known hydrocarbon generation from 250 to 140 ma thus corroborating long term geologic isolation it is critical that we have the ability to distinguish between fluid systems that despite phase separation have remained closed to fluid loss from those that have lost oil or gas phases these findings are the first to demonstrate that such systems remain isolated and fully gas retentive on time scales 100 m y over 10 km length scales and have broad implications for saline aquifer co2 disposal site viability and hydrocarbon resource prediction which both require an understanding of the length and time scales of crustal fluid transport pathways

noble gases solubility models of hydrocarbon charge mechanism in the sleipner vest gas field abstract noble gases are chemically inert and variably soluble in crustal fluids they are primarily introduced into hydrocarbon reservoirs through exchange with formation waters and can be used to assess migration pathways and mechanisms as well as reservoir storage conditions of particular interest is the role groundwater plays in hydrocarbon transport which is reflected in hydrocarbon water volume ratios here we present compositional stable isotope and noble gas isotope and abundance data from the sleipner vest field in the norwegian north sea sleipner vest gases are generated from primary cracking of kerogen and the thermal cracking of oil gas was emplaced into the sleipner vest from the south and subsequently migrated to the east filling and spilling into the sleipner ost fields gases principally consist of hydrocarbons 83 93 co2 5 4 15 3 and n2 0 6 0 9 as well as trace concentrations of noble gases helium isotopes 3he 4he are predominantly radiogenic and range from 0 065 to 0 116 ra reported relative to air ra 1 4 10 6 clarke et al 1976 sano et al 1988 showing predominantly 98 crustal contributions consistent with ne 20ne 22ne from 9 70 to 9 91 21ne 22ne from 0 0290 to 0 0344 and ar isotopes 40ar 36ar from 315 to 489 air derived noble gas isotopes 20ne 36ar 84kr 132xe are introduced into the hydrocarbon system by direct exchange with air saturated water asw the distribution of air derived noble gas species are controlled by phase partitioning processes in that they preferentially partition into the gas i e methane phase due to their low solubilities in fluids therefore the extent of exchange between hydrocarbon phases and formation waters that have previously equilibrated with the atmosphere can be determined by investigating air derived noble gas species we utilize both elemental ratios to address process i e open vs closed system and concentrations to quantify the extent of hydrocarbon water exchange i e volumetric gas water ratios these data are discussed within the framework of several conceptual models i total gas stripping model which assumes all noble gases have been stripped from the water phase thus defining the minimum volume of water to have interacted with the hydrocarbon phase ii equilibrium model which assumes equilibration between groundwater and hydrocarbon phase at reservoir p t and salinity and iii open and closed system gas stripping models using concentrations and elemental ratios by applying these models to ne ar data from sleipner we estimate volumetric gas water ratios v g v w between 0 02 and 0 07 which are lower than standard geologic gas water estimates of 0 24 estimated by combining gas in place estimates with groundwater porosity estimates sleipner vest data can be best approximated by an open system model which predicts more than an order of magnitude more groundwater interaction during migration than geologic estimates indicating a dynamic aquifer system and or a hydrous migration pathway in an open system the extent of gas loss can be estimated to be between 8 and 10 reservoir volumes which have passed through the system and been lost i e filled and spilled

the noble gas isotope record of hydrocarbon field formation time scales abstract noble gases may be considered as the most prominent tracers of natural fluids including hydrocarbons the atmosphere is the only source of 20ne 36ar 84kr 130xe in subsurface environments and their concentrations in pore waters after recharge are known from the solubility data this allows modelling of noble gas partitioning between coexisting gas oil and water phases in the course of hydrocarbon formation migration and storage radiogenic isotopes 4he 21ne 40ar 136xe after being released from source rocks are mixed with air derived noble gases already present in the pore space concentrations of radiogenic species in the pore space of typical hydrocarbon fields are generally so high that they can hardly be accumulated in situ and thus indicate noble gas transfer from ground waters the time bearing ratios 4he 20ne 21ne 20ne 4he 40arair 40ar 40arair in hydrocarbon fields are thus proportional to the time interval between the ground water recharge and noble gases partitioning into the hydrocarbon phase s the recharge partition interval the largest available data set allows the recharge partition intervals to be constrained for a large number of hydrocarbon fields situated in different tectonic settings ancient plates young plates mobile belts these intervals increase systematically with the ages of hydrocarbon source and trap lithologies and are comparable with these ages this important feature valid in general for different hydrocarbon fields implies i local sources of radiogenic noble gas isotopes in ground waters ii relatively recent formation of hydrocarbon fields and iii their short formation time scales in some cases the duration of formation of a hydrocarbon field can be constrained for example nearly constant 21ne 20ne 40ar 40arair ratios measured in samples from the magnus oil field north sea give an accumulation time scale 10 ma it should be emphasized that the above noble gas isotope ratios give the time estimates which are independent of geological reconstructions sometimes the noble gas inventory in a hydrocarbon field and ground waters allows characterization of the source rock volume involved in formation of the field generally this volume exceeds that of the hydrocarbon field rocks by orders of magnitude

afterslip and only afterslip following the 2004 parkfield california earthquake 1 an analysis of the first two years of postseismic surface deformations from gps reveals that afterslip is the only mechanism significantly contributing to postseismic deformation following the 2004 m6 parkfield california earthquake finite element modeling shows this event to have been too small to significantly stress the lower crust and upper mantle thus viscoelastic relaxation did not lead to detectable surface displacements similarly coseismically induced pressure changes in the upper crust were not sufficient to induce a measurable poroelastic response from 10 days to two years after the parkfield earthquake postseismic displacements at all gps stations experience the same characteristic decay time 2 weeks this suggests that only afterslip was activated and the distribution of slip remained unchanged in this time period afterslip was found to be broadly distributed in the upper 15 km of the crust and associated with a moment release of much greater magnitude than the coseismic rupture

gps applications for geodynamics and earthquake studies geodetic measurements obtained with the global positioning system gps are increasingly more widely applied in geophysical studies in this paper we review the changes to the technology of gps geodesy over the last five years that are responsible for this increased applicability we survey geophysical investigations employing gps to measure coseismic postseismic and interseismic deformation plate motion and crustal deformation at plate boundaries volcano deformation and the deformation associated with glacial isostatic adjustment and its application to sea level studies we emphasize the use of gps determinations for the modeling of this wide variety of geophysical phenomena we also discuss the recent advent of permanent gps networks for regional geophysical studies as well as the possible future of gps surveying in light of the recent advances

apparent stability of gps monumentation from short baseline time series 1 long running short 1 km gps baselines offer an insight into the accuracy budget of geophysical estimates inferred from gps coordinate time series in this paper we report on analysis of 10 short baselines using data spanning several years and examine deviations from a constant baseline length annual signals with amplitude 0 5 mm are evident in various coordinate components at 6 of the 10 sites with amplitudes exceeding 2 5 mm on two baselines these signals are largely invariant to elevation cutoff angle multipath and phase center model errors are shown to probably have negligible effects at most sites at annual periods they are therefore likely real monument motions although linear thermal expansion is negligible at most sites linear trends 0 25 mm yr 1 are evident on four baselines in at least one coordinate component subdaily signals are present at all sites at k1 and its higher harmonics time correlated noise possibly in the form of flicker noise dominates despite many common signals being eliminated as a result of the small baseline lengths although it is around 1 order of magnitude smaller than for single site ppp solutions we constrain monument random walk motion to be no more than 0 5 mm yr 1 2 if these baseline motion results were representative of the 300 currently active igs sites 180 would have annual signals 0 5 mm in at least one coordinate component 120 would have linear rates 0 25 mm yr 1 and almost all sites would have subdaily k1 k2 signals of 0 1 mm each solely due to local site effects

spatial variability of the wave bottom boundary layer over movable rippled beds observations of the spatially dependent velocity field over movable bed forms subjected to slightly skewed and asymmetric regular wave forcing were collected the dynamics between the ripple elements is dominated by coherent vortices characterized by the swirling strength and evidenced in the temporal and spectral characterization within the boundary layer spectral energy in the second harmonic 3f0 is amplified at the ripple slopes and is consistent with the location of the expected strongest pressure gradients first moment and second moment velocity statistics were used to address the spatial variability of the intra ripple hydrodynamics estimates of displacement and momentum thicknesses and mom are smaller than suggested by the higher harmonics but consistently highlight areas of adverse and favorable pressure gradients shear stress and roughness estimates were inferred by fitting a logarithmic model to first moment and second moment statistics of the velocity field the maximum shields parameter was observed to peak at the stoss slope of asymmetric ripples during the strongest and shorter half wave period onshore first moment roughness estimates are similar in magnitude to bed load parameterizations provided by li et al 1997 and about a factor of 3 larger than second moment estimates assessment of the vertical transfer of horizontal momentum derived using a reynolds decomposition suggests that stresses inferred from the logarithmic law using first moment velocity statistics appropriately reproduce the mean momentum transfer for the longer and weaker offshore half wave period