acoustic facies on the inner kara sea shelf implications for late weichselian to holocene sediment dynamics abstract we studied the impact of the last glacial late weichselian sea level cycle on sediment architecture in the inner kara sea using high resolution acoustic sub bottom profiling the acoustic lines were ground truthed with dated sediment cores furthermore we refined the location of the eastern lgm ice margin by new sub bottom profiles new model results of post last glacial maximum lgm isostatic rebound for this area allow a well constrained interpretation of acoustic units in terms of sequence stratigraphy the lowstand or regressive system tract sediments are absent but are represented by an unconformity atop of pleistocene sediments on the shelf and by a major incised dendritic paleo river network the subsequent transgressive and highstand system tracts are best preserved in the incised channels and the recent estuaries while only minor sediment accumulation on the adjacent shelf areas is documented the kara sea can be subdivided into three areas estuaries a the shelf b and c deeper lying areas that accumulated a total of 114 1010 t of holocene sediments

three dimensional deformation and strain induced by municipal pumping part 1 analysis of field data a 62 day controlled aquifer test was performed at the site of a new municipal well that penetrates a thick sequence of compressible basin fill deposits in mesquite nevada observation data were acquired from a high precision global positioning system gps network to accompany the water level data from the pumped well and a nearby observation well the purpose of the investigation was to quantify and characterize three dimensional surface deformation and strain associated with cyclic pumping and to evaluate aquifer properties on the basis of these data results indicate that both horizontal 8 mm total displacement with 0 2 mm precision and vertical deformation 12 mm total displacement with 2 mm precision were measuredwithinthefirst22daysofpumpingwithaslowlymigratingoutwardwaveofcompressionalstraininspiteofthefactthat an 83 m brittle unsaturated zone resided over the dynamically active aquifer the hydraulic head and strain data indicate that steady state pumping conditions were likely reached after 35 40 days results also indicate that vertical mechanical rebound occurs after about 35 days even though the rate of pumping remains unchanged strain analyses indicate that this result is due to the changing shape in the pore structure of the pumped aquifer as an elongation occurs in the horizontal direction to more than accommodateasmallcompressionalstrainintheverticaldirection uniaxialspecificstoragewasestimatedfromtime subsidence

worldwide initiation of holocene marine deltas by deceleration of sea level rise radiocarbon dated deltaic sequences of holocene age from different parts of the world began to accumulate within a restricted time range from about 8500 to 6500 years ago evaluation of major delta processes indicates that deceleration in sea level rise was the key factor in holocene delta formation within many deltas there is as much as a 2000 year age range between basal deposits in seaward and landward cores this age difference records the progressive landward migration of near mean sea level depositional environments during the lower to mid holocene establishment of a chronostratigraphic framework for holocene delta development provides a fundamental global baseline for distinguishing sea level change from vertical land motion by tectonism and isostasy and for evaluating rates of future marine incursion into low lying deltas

observation of glacial isostatic adjustment in stable north america with gps 1 motions of three hundred and sixty global positioning system gps sites in canada and the united states yield a detailed image of the vertical and horizontal velocity fields within the nominally stable interior of the north american plate by far the strongest signal is the effect of glacial isostatic adjustment gia due to ice mass unloading during deglaciation vertical velocities show present day uplift 10 mm yr near hudson bay the site of thickest ice at the last glacial maximum the uplift rates generally decrease with distance from hudson bay and change to subsidence 1 2 mm yr south of the great lakes the hinge line separating uplift from subsidence is consistent with data from water level gauges along the great lakes showing uplift along the northern shores and subsidence along the southern ones horizontal motions show outward motion from hudson bay with complex local variations especially in the far field although the vertical motions are generally consistent with the predictions of gia models the horizontal data illustrate the need and opportunity to improve the models via more accurate descriptions of the ice load and laterally variable mantle viscosity

isostatic uplift driven by karstification and sea level oscillation modeling landscape evolution in north florida isostatic uplift of tectonically stable passive margin lithosphere can preserve a record of paleo shoreline position by elevating coastal geomorphic features above the influence of nearshore wave activity conversely depositional ages and modern elevations of these features can provide valuable information about the uplift history of a region we present a numerical model that combines sea level oscillation subaerial exposure a precipitation karstification function and isostatic uplift to explore the dynamic geomorphic behavior of coastal carbonate landscapes over multiple sea level cycles the model is used to estimate ages of coastal highstand depositional features along the atlantic coast of north florida numerical simulations using current best estimates for pleistocene sea level and precipitation histories suggest ages for trail ridge 1 44 ma the penholoway terrace 408 ka and the talbot terrace 120 ka that are in agreement with fossil evidence in addition model results indicate that the rate of karstification void space creation or equivalent surface lowering rate within the north florida platform is 3 5 times that of previous estimates 1 m 11 2 k y vs 1 m 38 k y and uplift rate is 2 times as high as previously thought 0 047 mm yr vs 0 024 mm yr this process has implications for landscape evolution in other carbonate settings and may play an underappreciated role within the global carbon cycle

analytical solutions to coupled hm problems to highlight the nonlocal nature of aquifer storage specific storage reflects the volumetric deformation capacity of permeable media classical groundwater hydrology equates elastic storage to medium compressibility plus fluid compressibility times porosity however it is unclear if storage behavior can be represented by a single parameter hydraulic gradients act as body forces that push the medium in the direction of flow causing it to deform instantaneously everywhere i e even in regions where pressure would not have changed according to conventional fluid flow therefore actual deformation depends not only on the mechanical properties of the medium but also on aquifer geometry and on surrounding strata which act like constraints to displacements here we discuss the question and highlight the nonlocal nature of storage i e the volume of water released at a point depends on the poroelastic response over the whole aquifer proper evaluation of transient pressure and water release from storage requires acknowledging the hydromechanical coupling which generally involves the use of numerical methods we propose analytical solutions to the hm problem of fluid injection extraction into finite aquifers with one dimensional or cylindrical geometries we find that pressure response is much faster virtually instantaneous and larger than expected from traditional purely hydraulic solutions when aquifer deformation is restrained whereas the pressure response is reversed i e pressure drop in response to injection when the permeable medium is free to deform these findings suggest that accounting for hydromechanical coupling may be required when hydraulic testing is performed in low permeability media which is becoming increasingly demanded for energy related applications

characteristics and genesis mechanism of ground fissures in taiyuan basin northern china abstract since the 1980s ground fissures in the taiyuan basin have experienced blowouts resulting in a significant but hidden danger to cities in the basin this paper describes the plane and damage characteristics of the ground fissures based on the findings of field investigations and mapping most ground fissures in the basin were determined as linear with pinch out reappearances on the surface they were characterized by both horizontal tension with maximum widths and vertical offsets of up to 40 and 15 cm respectively the ground fissure strikes in the basin were observed to be consistent with those of nearby active faults and the long axis direction of the groundwater depression funnel the roads and houses that lie across the fissures were determined to be the most affected by ground fissure disasters in the basin the primary damage modes for the roads were vertical offset and surface collapse whereas buildings experienced foundation failure and tensile damage profiles obtained through geological drilling and trench exploration further revealed obvious tension and synsedimentary characteristics of the ground fissures correlated with existing faults correlation analysis shows that the formation of ground fissures in taiyuan basin is mainly related to faults and excessive groundwater extraction theoretical analysis revealed that the size and activity of ground fissures in the basin were positively correlated with four factors the dip of faults in an area regional tensile stress difference between the thicknesses of aquifers on either side of a fault and groundwater exploitation the significant increase in ground fissure activity since the 1980s mainly reflects uncontrolled groundwater discharge hence prevention of excessive groundwater exploitation in the basin would mitigate the destructive effects of the ground fissures

settlements around pumping wells analysis of influential factors and a simple calculation procedure abstract estimated and measured settlements caused by pumping rarely agree several reasons could explain this mismatch including the influence of layering the mechanical parameters used in the predictions or the relationship between settlements and drawdown we analyze the influence of the above issues by investigating the mechanical response of pumped elastic porous media under different conditions a radially symmetric conceptual model is considered and several hydro mechanical simulations are performed varying the boundary conditions the size of the modeled domain and the presence or not of an overlying layer the simplicity of the considered problem allows us to compare our results with existing analytical solutions to identify the role of each variable on pumping settlements and to generalize the results the most relevant results are as follows 1 settlements are proportional to drawdown only outside a circle of radius equal to 0 7 times the thickness of the pumped porous medium inside they are virtually constant which leads to two simple procedures for computing pumping settlements 2 poorly conductive layers located above or below a pumped porous medium with higher hydraulic conductivity reduce and smooth settlements 3 boundary constraints affect the local specific storage coefficient and the displacements occurred 4 the specific storage coefficient evaluated by interpreting pumping tests with the cooper and jacob method 1946 leads to overestimation of the actual young s modulus of the soil the main conclusion is that settlements are less differential than expected near pumping wells still they must always be evaluated acknowledging the nature of layering the boundary constraints and carefully selecting the mechanical parameters of the soil

land subsidence and earth fissures due to groundwater withdrawal in the southern yangtse delta china excessive extraction of groundwater has caused severe land subsidence and earth fissures in the southern yangtse delta china based on field data the temporal and spatial distribution of land subsidence is investigated and the causes for earth fissures are analyzed the areal distribution of the land subsidence is closely related to the cones of depression in the main exploited aquifers the compaction of a hydrostratigraphic unit depends on its mechanical behavior thickness compressibility and the piezometric level changing the primary subsidence layers in shanghai have been the first aquitard before 1990 and the third confined aquifer since then but the second aquitard unit was the primary subsidence layer in changzhou earth fissures trending in several directions occurred in the husu tectonic zone they were mainly caused by differential subsidence and horizontal displacement that resulted from tensile stress and shear stress in units the majority of fissures in the study area are tensile

how stable is the mississippi delta large deltas are commonly believed to exhibit rapid rates of tectonic subsidence largely due to sediment loading of the lithosphere as a result deltaic plains are prone to accelerated relative sea level rise coastal erosion and wetland loss hurricane katrina s devastation testifies to the severe threat that these processes pose to the mississippi delta but the relative role of tectonics versus other mechanisms causing land subsidence remains elusive relative sea level records derived from basal peat have the potential to quantify differential crustal movements over holocene time scales with exceptionally high accuracy and precision here we present new sea level index points from two study areas in the southwestern mississippi delta that essentially coincide with a recently published detailed relative sea level record from the eastern part of the delta our results show that differential vertical movements among the three study areas have been only 0 1 mm yr 1 w e compare our evidence with a recent sea level compilation from the caribbean to a large extent based on data from areas that are tectonically stable our sea level index points nearly coincide with the caribbean data showing surprising tectonic stability for considerable sections of the mississippi delta however the well documented high subsidence rates in and near the birdfoot of the mississippi delta indicate that different conditions prevail there the rapid wetland loss in coastal louisiana is likely due to a considerable extent to the compaction of holocene strata

vertical land motion from present day deglaciation in the wider arctic vertical land motion vlm from past and ongoing glacial changes can amplify or mitigate ongoing relative sea level change we present a high resolution vlm model for the wider arctic that include

delimitation of ground failure zones due to land subsidence using gravity data and finite element modeling in the queretaro valley mexico abstract sedimentary basins of arid and semiarid zones are often subject to regimes of intense ground water withdrawal as it is normally the only source of water for development of communities an associated phenomenon is land subsidence which can develop to ground failures and consequently damage to infrastructure aquifer deformation can be analyzed using a stress strain or a flux force approach depending on the aquifer material compact or loose and on whether the water withdrawal forms a predominant flow direction toward a cone of depression geometry of the aquifer system also plays an important role as uneven thickness induces differential compaction and hence tensional and shear stresses on the ground mass in this work we present a stress strain approach to analyze subsidence for an unconfined aquifer of varying thickness this is done in two steps namely when the aquifer is in equilibrium and when it is totally depleted using this scheme in a region where ground failure is evident a portion of the aquifer system of the queretaro valley is analyzed the geometry of the hydrologic basement is first modeled using gravity measurements properly correlated with wells and field data then a stress analysis is implemented using the finite element method in order to identify probable zones of ground weakness which are calibrated with known ground failures the results indicate that both tensional and shear stress are present which induce ground failure in the form of surface faults

detection of aquifer system compaction and land subsidence using interferometric synthetic aperture radar antelope valley mojave desert california interferometric synthetic aperture radar insar has great potential to detect and quantify land subsidence caused by aquifer system compaction insar maps with high spatial detail and resolution of range displacement 10 mm in change of land surface elevation were developed for a groundwater basin 103 km2 in antelope valley california using radar data collected from the ers 1 satellite these data allow comprehensive comparison between recent 1993 1995 subsidence patterns and those detected historically 1926 1992 by more traditional methods the changed subsidence patterns are generally compatible with recent shifts in land and water use the insar detected patterns are generally consistent with predictions based on a coupled model of groundwater flow and aquifer system compaction the minor inconsistencies may reflect our imperfect knowledge of the distribution and properties of compressible sediments when used in conjunction with coincident measurements of groundwater levels and other geologic information insar data may be useful for constraining parameter estimates in simulations of aquifer system compaction

transient radial movement of a confined leaky aquifer due to variable well flow rates the present paper investigates aquifer horizontal movement driven by hydraulic forces new analytic solutions are found for the velocity and displacement fields describing aquifer radial transient movement caused by well discharge and recharge within a confined leaky aquifer the development of the new solutions is based on linear momentum of bulk mass flux mass conservation of bulk mass flux the darcy gersevanov law and the analytic hydraulic drawdown if the hantush jacob carslaw jaeger and theis analytic drawdowns are applied respectively a corresponding aquifer transient movement is found within the new solutions three sets of simplified solutions based on the carslaw jaeger drawdown have been applied to three schemes of well flow rates that are power periodic and exponential functions of time for all three schemes the dimensionless relations of aquifer displacement versus radial distance show the zones and locations where possible tensile stress may occur and cause potential earth fissuring for the well flow rates varying as a power or periodic function tensile stress may be generated when inertial forces change directions based on the dimensionless relations of aquifer velocity versus time analysis of effects that vertical leaky flow have on aquifer horizontal movement shows that the vertical water flow plays a significant role in aquifer radial movement and that aquifer radial velocity is much more responsive to the vertical flow than is aquifer displacement

late quaternary ice sheet history of northern eurasia the maximum limits of the eurasian ice sheets during four glaciations have been reconstructed 1 the late saalian 140 ka 2 the early weichselian 100 80 ka 3 the middle weichselian 60 50 ka and 4 the late weichselian 25 15 ka the reconstructed ice limits are based on satellite data and aerial photographs combined with geological field investigations in russia and siberia and with marine seismic and sediment core data the barents kara ice sheet got progressively smaller during each glaciation whereas the dimensions of the scandinavian ice sheet increased during the last ice age the barents kara ice sheet attained its maximum size as early as 90 80 000 years ago when the ice front reached far onto the continent a regrowth of the ice sheets occurred during the early middle weichselian culminating about 60 50 000 years ago during the late weichselian the barents kara ice sheet did not reach the mainland east of the kanin peninsula with the exception of the nw fringe of taimyr a numerical ice sheet model forced by global sea level and solar changes was run through the full weichselian glacial cycle the modeling results are roughly compatible with the geological record of ice growth but the model underpredicts the glaciations in the eurasian arctic during the early and middle weichselian one reason for this is that the climate in the eurasian arctic was not as dry then as during the late weichselian glacial maximum

horizontal aquifer movement in a theis thiem confined system the skeletal matrix of an aquifer is known to move laterally toward a discharging well the mechanisms by which it moves relative to the well have been only partially studied in the past examining the relation of drawdown to volume strain for an assumed poroelastic solid has been a common approach by way of contrast the present study examines the relation of the velocity of solids aquifer matrix to their hydraulic driving forces the present approach can be considered darcian and allows the displacement field of the aquifer matrix to be calculated directly a new formulation of the darcy gersevanov law of water flowing relative to moving solids is applied to a theis thiem confined aquifer the aquifer is found to start with a maximum velocity when the pump is turned on and then to decelerate as time progresses dimensionless type curves of horizontal movement of the skeletal matrix are calculated the resulting equation of aquifer deformation is checked against 1 results from alternatively using the standard poroelastic stress strain approach and 2 the fundamental storage equation for transient groundwater flow

the 2016 mw5 1 fairview oklahoma earthquakes evidence for long range poroelastic triggering at 40 km from fluid disposal wells abstract wastewater disposal in the central u s is likely responsible for an unprecedented surge in earthquake activity much of this activity is thought to be driven by induced pore pressure changes and slip on pre stressed faults which requires a hydraulic connection between faults and injection wells however direct pressure effects and hydraulic connectivity are questionable for earthquakes located at large distances and depths from the injectors here we examine triggering mechanisms of induced earthquakes which occurred at more than 40 km from wastewater disposal wells in the greater fairview region northwest oklahoma employing numerical and semi analytical poroelastic models the region exhibited few earthquakes before 2013 when background seismicity started to accelerate rapidly culminating in the mw5 1 fairview earthquake in february 2016 injection rates in the 2 2 5 km deep arbuckle formation started to increase rapidly in 2012 about two years before the start of seismicity increase most of the injection activity was concentrated toward the northeast of the study region generating a relatively cohesive zone of pressure perturbations between 0 1 and 1 mpa much of the near injection seismicity was likely triggered by pressure effects and fault assisted pressure diffusion to seismogenic depth outside of the high pressure zone we observed two remarkably detached linear seismicity clusters which occurred at 20 to 50 km distance from the initial seismicity and 10 to 40 km from the nearest high rate injector semi analytical models reveal that poroelastically induced coulomb stress changes surpass pore pressure changes at these distances providing a plausible triggering mechanism in the far field of injection wells these results indicate that both pore pressures and poroelastic stresses can play a significant role in triggering deep and distant earthquakes by fluid injection and should be considered for seismic hazard assessment beyond the targeted reservoir

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

on post glacial sea level i general theory summary modern analyses of sea level changes due to glacial isostatic adjustment gia are based on the classic sea level equation derived by farrell clark 1976 geophys j r astr soc 46 647 667 the connection between global sea level variations and changes to ocean height that is assumed within this equation breaks down in the presence of a time varying shoreline geometry we present a generalized sea level equation that overcomes this difficulty we also derive analytic expressions for and present schematic illustrations of the error in the ocean height change over finite time intervals introduced in published efforts to incorporate shoreline evolution into the theory of gia induced sea level change this comparison includes studies of shoreline migration due to either local sea level changes or the growth and ablation of marine based ice we conclude that the theories applied by johnston 1993 geophys j int 114 615 634 milne 1998 phd thesis university of toronto toronto and co workers are more accurate than the procedure advocated by peltier 1994 science 265 195 201 1998a geophys res lett 25 3955 3958 1998b rev geophys 114 615 634 although an improvement in the latter has recently been reported peltier drummond 2002 geophys res lett 29 10 1029 2001gl014273 our generalized theory is valid for any earth model in a companion paper we derive the equations necessary to treat the special case of a spherically symmetric linear viscoelastic and rotating earth and we quantify errors associated with previous work

sea level change glacial rebound and mantle viscosity fornorthern europe northwestern europe remains a key region for testing models of glacial isostasy because of the good geological record of crustal response to the glacial unloading since the time of the last glacial maximum models for this rebound and associated sea level change require a detailed knowledge of the ice sheet geometry including the ice thickness through time existing ice sheet reconstructions are strongly model dependent and inversions of sea level data for the mantle response may be a function of the model assumptions thus inverse solutions for the sea level data are sought that include both ice and earth model parameters as unknowns sea level data from fennoscandia the north sea the british isles and the atlantic and english channel coasts have been evaluated and incorporated into the solutions the starting ice sheet for fennoscandia is based on a reconstruction of a model by denton hughes 1981 that is characterized by quasi parabolic cross sections and symmetry about the load centre both global northwestern europe as a whole and regional subsets of the data solutions have been made for earth model parameters and ice height scaling parameters the key results are as follows 1 the response of the upper mantle to the changing ice and water loads is spatially relatively homogenous across scandinavia the north sea and the british isles 2 this response can be adequately modelled by an effective elastic lithosphere of thickness 65 85 km and by an effective upper mantle viscosity from the base of the lithosphere to the 670 km depth seismic discontinuity of about 3 4 1020 pa s the effective lower mantle viscosity is at least an order of magnitude greater 3 the ice thickness over scandinavia at the time of maximum glaciation was only about 2000 m much less than the 3400 m assumed in the denton hughes model 4 the ice profiles are asymmetric about the centre of the ice sheet with those over the western part being consistent with quasi parabolic functions whereas the ice heights over the eastern and southern regions increase much more slowly with distance inwards from the ice margin

decontaminating tide gauge records for the influence of glacial isostatic adjustment the potential impact of 3 d earth structure 1 we investigate the potential impact of lateral variations in mantle viscosity and lithospheric thickness on predictions of present day relative sea level change due to glacial isostatic adjustment gia we consider three viscoelastic earth models the first is a 1 d model with a lithospheric thickness of 120 km and upper and lower mantle viscosities of 5 1020 pa s and 5 1021 pa s respectively the second model includes global lithospheric thickness variations and lateral heterogeneities in upper mantle viscosity ranging over three orders of magnitude while the third model includes lateral variations in lower mantle viscosity alone we find that the impact of 3 d structure is significant indeed the difference between the 3 d and 1 d model predictions at 300 sites with tide gauge records longer than 40 years duration is greater than 0 2 mm yr and 0 5 mm yr for 50 and 25 of the sites respectively the maximum difference exceeds several mm yr we conclude that efforts to decontaminate tide gauge records for ongoing gia to determine the rate and origin of global sea level rise should incorporate 3 d mantle structure into the gia modelling

geodetic tools for hydrogeological surveys 3d displacements above a fractured aquifer from gps time series deep porous reservoirs are subject to charge and discharge of fluids oil gas or water either naturally or induced by human exploitation this leads to a variation in pressure inside the reservoir and consequently to a deformation of the overlying material the knowledge of the ground surface displacements allows inferring the fluid migrations and the hydromechanical properties in the porous reservoir different kinds of geodetic tools are able to measure this ground deformation gps radar interferometry insar tiltmeters or leveling each of them has its own spatial and time characteristics and accuracies that conduct to different kind of applications after a review of the geodetic studies applied to hydrogeological processes we describe two examples of gps time series measurements above the granitic fractured aquifer of ploemeur located in french brittany these time series records the 3d displacements induced by the sum of different processes in this site the involved processes are mainly the ground deformation related to piezometric level variations in the aquifer that we are looking for and the ocean tide loading that can reach several centimeters in the study area we present the protocol of the gps data survey and the processing strategy applied to extract the effect of hydrogeological process with sufficient accuracy two different experiments were studied the long term deformation corresponding to seasonal hydrological cycle and the short term deformation associated to a pumping test for a same variation in piezometric levels the vertical ground displacements show larger amplitude for long term signal than for short one indicating a behavior depending on the duration of the hydrogeological load this difference of reactivity in time can be related to the heterogeneity of the studied aquifer finally this work shows that geodetic measurements provide important constraints for characterizing aquifer system response

deformation of linfen yuncheng basin china and its mechanisms revealed by π rate insar technique abstract the linfen yuncheng basin lyb in china is a region possessing severe geo hazards including active tectonic fault movement land subsidence and ground fissures among others interferometric synthetic aperture radar insar technique is applied to map surface deformation associated with various geo hazards in this basin the poly interferogram rate and time series estimator algorithm rate is used over forty nine scenes of sar data to generate the deformation maps over the entire lyb the precision of insar results is around 3 mm yr some active faults and ground fissures are successfully detected the spatiotemporal characteristics of tableland uplift faults displacement and basin subsidence are quantitatively monitored with insar technique ranging from 2 mm yr to 142 mm yr finally the mechanisms of surface deformation regarding large scale zhongtiaoshan fault middle scale basin land subsidence and small scale ground fissures are discussed in terms of interseismic movement underground water level changes and hydrostratigraphic heterogeneity

continuous gps measurements of postglacial adjustment in fennoscandia 1 geodetic results 1 data collected under the auspices of the bifrost gps project yield a geographically dense suite of estimates of present day three dimensional 3 d crustal deformation rates in fennoscandia johansson et al 2002 a preliminary forward analysis of these estimates milne et al 2001 has indicated that models of ongoing glacial isostatic adjustment gia in response to the final deglaciation event of the current ice age are able to provide an excellent fit to the observed 3 d velocity field in this study we revisit our previous gia analysis by considering a more extensive suite of forward calculations and by performing the first formal joint inversion of the bifrost rate estimates to establish insight into the physics of the gia response in the region we begin by decomposing a forward prediction into the three contributions associated with the ice ocean and rotational forcings from this analysis we demonstrate that recent advances in postglacial sea level theory in particular the inclusion of rotational effects and improvements in the treatment of the ocean load in the vicinity of an evolving continental margin involve peak signals that are larger than the observational uncertainties in the bifrost network the forward analysis is completed by presenting predictions for a pair of fennoscandian ice histories and an extensive suite of viscoelastic earth models the former indicates that the bifrost data set provides a powerful discriminant of such histories the latter yields bounds on the assumed constant upper and lower mantle viscosity nu um nu lm specifically we derive a 95 confidence interval of 5 x 10 20 less than or equal to nu um less than or equal to 10 21 pa s and 5 x 10 21 less than or equal to nu lm less than or equal to 5 x 10 22 pa s with some preference for elastic lithospheric thickness in excess of 100 km the main goal of the bayesian inverse analysis is to estimate the radial resolving power of the bifrost gps data as a function of depth in the mantle assuming a reasonably accurate ice history we demonstrate that this resolving power varies from similar to 200 km near the base of the upper mantle to similar to 700 km in the top portion of the lower mantle we conclude that the bifrost data are able to resolve structure on radial length scale significantly smaller than a single upper mantle layer however these data provide little constraint on viscosity in the bottom half of the mantle finally elements of both the forward and inverse analyses indicate that radial and horizontal velocity estimates provide distinct constraints on mantle viscosity

aquifer deformation and active faulting in salt lake valley utah usa abstract aquifers and fault zones may interact through groundwater flow and stress redistribution yet their spatiotemporal relationship remains enigmatic here we quantify changes in water storage and associated stress along the wasatch fault zone in salt lake valley recently shaken by a m5 7 earthquake on march 18th 2020 ground deformation mapped by sentinel 1 sar imagery 2014 2019 reveals an elongated area with 50 mm seasonal uplift corresponding to 0 03 0 06 km3 water storage cycles phase shifts across active faults in both water level and deformation suggest control by the low permeability structures the seasonal stress changes on the adjoining faults from poroelastic volume strain are two orders of magnitude larger than those from hydrological surface loading but both are small compared to the annual increase of tectonic loading at seismogenic depths historic seismic events limited in number do not exhibit statistically significant annual periodicity and hydrological modulation of microseismicity or triggering of the recent m5 7 event is not evident

continuous deformation of the tibetan plateau from global positioning system data global positioning system velocities from 553 control points within the tibetan plateau and on its margins show that the present day tectonics in the plateau is best described as deformation of a continuous medium at least when averaged over distances of 100 km deformation occurs throughout the plateau interior by ese wnw extension and slightly slower nne ssw shortening relative to eurasia material within the plateau interior moves roughly eastward with speeds that increase toward the east and then flows southward around the eastern end of the himalaya crustal thickening on the northeast ern and eastern margins of the plateau occurs over a zone 400 km wide and cannot be the result of elastic strain on a single major thrust fault shortening there accommodates much of india s penetration into eurasia a description in terms of movements of rigid blocks with elastic strain associated with slip on faults between them cannot match the velocity field

glacial isostatic adjustment as a control on coastal processes an example from the siberian arctic the geomorphology of the western siberian arctic coast represents a significant departure from the global trend of holocene delta formation by major rivers the ob and yenisei rivers in western siberia drain into the arctic ocean via estuaries 900 and 500 km long respectively eastern siberian rivers such as the lena indigirka and kolyma terminate at significant marine deltas we show that this spatial variation in coastal geomorphology can be explained by the glacial isostatic adjustment of the region the development and collapse of a peripheral bulge in western siberia associated with the glaciation and subsequent deglaciation of the eurasian ice sheets led to a distinct spatial variation in sea level change that continues to this day in particular since the marked decrease in global scale ice melting ca 7 ka our model predicts a sea level rise at the mouth of the ob river of 14 m compared to a rise of 6 m at the mouth of the lena river which ceased at 3 ka we propose that the enhanced sea level rise in the western siberian arctic associated with peripheral bulge subsidence has prevented the establishment of marine deltas at the mouths of the ob and yenisei rivers we conclude that regional variations in relative sea level change driven by glacial isostatic adjustment should be considered when interpreting large scale coastal morphology and deltaic stratigraphy which is normally assumed to correlate with eustatic fluctuations

coastal changes in the arctic the arctic s climate system is changing air temperatures major river discharges and open water season length have increased and storm intensities and tracks are changing thirteen quantitative studies of the rates of coastline position change throughout the arctic show that recently observed changes have not increased coastal erosion rates which currently range between 0 and 2 m yr when averaged for the arctic shelf seas current data is probably insufficient both spatially and temporally however to capture change at decadal to sub decadal time scales in this context we describe the current understanding of arctic coastal geomorphodynamics with an emphasis on erosional regimes of coasts with ice rich sedimentary deposits in the laptev east siberian and beaufort seas where local coastal erosion can reach 30 m yr we also examine coasts with lithified rocky substrates where geomorphodynamics are intensified by rapid glacial retreat coastlines of svalbard greenland and the canadian archipelago are less frequently studied than ice rich continental coasts of north america and siberia and studies often focus on coastal sections composed of unlithified material as air temperature and sea ice duration and extent change longer thaw and wave seasons will intensify coastal dynamics in the arctic

aftershock deficiency of induced earthquake sequences during rapid mitigation efforts in oklahoma abstract induced seismicity provides a rare opportunity to study earthquake triggering and underlying stress perturbations triggering can be a direct result of induced stress changes or indirect due to elastic stress transfer from preceding events leading to aftershocks both of these processes are observable in areas with larger magnitude induced events such as oklahoma we study aftershock sequences of m2 5 to m5 8 earthquakes and examine the impact of targeted injection rate reductions in comparing aftershock productivity between california and oklahoma we find similar exponential scaling statistics between mainshock magnitude and average number of aftershocks for events with m 4 5 oklahoma exhibits several mainshocks with total number of aftershocks significantly below the average scaling behavior the sequences with deficient aftershock numbers also experienced rapid strong mitigation and reduced injection rates whereas two events with m4 8 and m5 0 with weak mitigation exhibit normal aftershock productivity the timing of when aftershock activity is reduced correlates with drops in injection rates with a lag time of several days large mainshocks with significantly reduced aftershocks may explain decreasing seismicity rates while seismic moment release was still increasing in oklahoma in 2016 we investigate the expected poroelastic stress perturbations due to injection rate changes within a layered axisymmetric model and find that stresses are lowered by 10s to 100s kpa within the injection affected zone for earthquakes induced by poroelastic stress increase at several kilometers from wells the rapid shut in of wells may lead to elastic stress reductions sufficiently high to arrest unfolding aftershock sequences within days after mitigation starts

the small effect of poroelastic pressure transients on triggering of production induced earthquakes in the groningen natural gas field over the past decade a steep increase in the number of seismic events has been observed in the groningen gas field the netherlands it is generally accepted that these are induced by compaction of the reservoir rock due to extensive depletion causing a buildup of strain energy in faults that may be released seismically we address the possible triggering of fault slip by the transient pressure field surrounding a well that has undergone a sudden rate change assuming a unilateral decoupling between displacement and pressure numerical experiments are conducted using a sequential finite volume finite element solution strategy that fully incorporates second order terms in the radial flow equation we investigate an idealized groningen like geometry to discover whether the hypothesized possibility of triggering induced seismicity exists explore how some controllable and uncontrollable variables influence its severity and possibly provide clues on how production strategy might be able to avoid its occurrence the results demonstrate that sudden production changes can indeed trigger near well seismic events but that the effect is very small compared to other potential causes changing from sudden to gradual changes in well rates is therefore not expected to lead to a significant reduction in the number or magnitude of production induced earthquakes in the groningen field

modelling holocene relative sea level observations from the caribbean and south america abstract holocene data from the caribbean and the atlantic coast of south america have been critically assessed and a subset of the best quality data are presented these data cover a large north south geographic extent and display a distinct spatial variation we make the first comparisons of this data set to predictions based on a realistic model of glaciation induced sea level change with the main aims of understanding the cause of the observed spatial trend and estimating a eustatic signal for the holocene the spatial variation is dominated by the influence of the ice and ocean mass redistribution on sea level change with the ice induced effect dominating the observed north south trend a best fitting model is applied to estimate a holocene eustatic signal from the observations we find that the model corrected data are consistent with a relatively rapid rise of 7 8 mm yr in the early holocene with a marked reduction in this rate around 7 cal kyr bp from this time until present the model corrected data suggest that the volume of mass transfer between ice sheets and oceans was no more than 1 m eustatic sea level equivalent

differential compaction mechanism for earth fissures near casa grande arizona precise gravity measurements indicate that earth fissures or tension cracks caused by ground water withdrawal within a 10 km 2 area southeast of casa grande arizona are associated with relief on the buried interface between the alluvial aquifer and underlying bedrock all of the fissure zones which have a cumulative length of 8 7 km occur above either ridges or steps in the bedrock surface intersecting fissure zones overlie intersecting bedrock features and the angle of intersection of the zones accurately reflects the angle between the bedrock features these relations suggest that the fissures are forming in response to localized differential compaction caused by localized variations of aquifer system thickness topographic profiles across fissures on undisturbed desert floor confirm differential compaction proportional to the variations in aquifer thickness the occurrence of the fissures at points of maximum convex upward curvature in profiles of both the topographic and buried bedrock surfaces indicates that the fissures result from tensile strains caused by bending of the strata above the buried bedrock features in response to the differential compaction tensile strains at failure are estimated to range from 0 02 to 0 2 on the basis of modeling of the bending process

ice sheet and solid earth influences on far field sea level histories previous predictions of sea level change subsequent to the last glacial maximum show significant systematic discrepancies between observations at tahiti huon peninsula and sunda shelf during lateglacial time 14 000 to 9000 calibrated years before the present we demonstrate that a model of glacial isostatic adjustment characterized by both a high viscosity lower mantle 4 1022 pa s and a large contribution from the antarctic ice sheet to meltwater pulse ia 15 meters eustatic equivalent resolves these discrepancies this result supports arguments that an early and rapid antarctic deglaciation contributed to a sequence of climatic events that ended the most recent glacial period of the current ice age

ice 3g a new global model of late pleistocene deglaciation based upon geophysical predictions of post glacial relative sea level change a new high resolution global model of late pleistocene deglaciation is inferred on the basis of geophysical predictions of postglacial relative sea level variations in which the ice ocean solid earth interaction is treated in a gravitationally self consistent fashion for the purpose of these analyses the radial viscoelastic structure of the planet is assumed known on the basis of previously published sensitivity tests on solutions of the forward problem only radiocarbon controlled relative sea level histories from sites that were actually ice covered with one or two additions are employed to constrain the model leaving relative sea level rsl data from sites that were not ice covered to be employed to confirm its consistency results for these confirmatory analyses are reported elsewhere here the new deglaciation model referred to as ice 3g is compared to previous models derived by several independent means and tested against a number of additional observations other than sea level histories including geologically controlled retreat isochrones oxygen isotope data from deep sea sedimentary cores and coral terrace elevations the latter two observations strongly constrain the net sea level rise that has occurred since the onset of deglaciation and therefore the mass of ice that melted during the last glacial interglacial transition

constraints on the late weichselian ice sheet over the barents sea from observations of raised shorelines abstract direct evidence for late weichselian grounded glacier ice over extensive areas of the barents sea is based largely on indirect observations including elevations of old shorelines on svalbard and arguments of isostatic rebound such isostatic models are discussed here for two cases representing maximum and minimum ice sheet reconstructions in the former model the ice extends over the kara sea whereas in the latter the ice is limited to the barents sea and island archipelagos comparisons of predictions with observations from a number of areas including spitsbergen nordaustlandet edgeoya kong karls land franz josef land novaya zemlya and finnmark support arguments for the existence of a large ice sheet over the region at the time of the last glacial maximum this ice sheet is likely to have had the following characteristics conclusions that are independent of assumptions made about the earth s rheological parameters i the maximum thickness of this ice was about 1500 2000 m with the centre of the load occurring to the south and east of kong karls land ii the ice sheet extended out to the western edge of the continental shelf and its maximum thickness over western spitsbergen was about 800 m iii to the north of svalberg and frans josef land the ice sheet extended out to the northern shelf edge iv retreat of the grounded ice across the southern barents sea occurred relatively early such that this region was largely ice free by about 15 000 bp v by 12 000 bp the grounded ice had retreated to the northern archipelagos and was largely gone by 10 000 bp vi the ice sheet may have extended to the kara sea but ice thicknesses were only a fraction of those proposed in those reconstructions where the maximum ice thickness is centered on novaya zemlya models for the palaeobathymetry for the barents sea at the time of the last glacial maximum indicate that large parts of the barents sea were either very shallow or above sea level providing the opportunity for ice growth on the emerged plateaux as well as on the islands but only towards the end of the period of fennoscandian ice sheet build up

late quaternary sedimentation history of the lena delta abstract core and outcrop analysis from lena mouth deposits have been used to reconstruct the late quaternary sedimentation history of the lena delta sediment properties heavy mineral composition grain size characteristics organic carbon content and age determinations 14c ams and ir osl are applied to discriminate the main sedimentary units of the three major geomorphic terraces which form the delta the development of the terraces is controlled by complex interactions among the following four factors 1 channel migration according to the distribution of 14c and ir osl age determinations of lena mouth sediments the major river runoff direction shifted from the west during marine isotope stages 5 3 third terrace deposits towards the northwest during marine isotope stage 2 and transition to stage 1 second terrace to the northeast and east during the holocene first terrace deposits 2 eustasy sea level rise from last glacial lowstand to the modern sea level position reached at 6 5 ka bp resulted in back filling and flooding of the palaeovalleys 3 neotectonics the extension of the arctic mid ocean ridge into the laptev sea shelf acted as a halfgraben showing dilatation movements with different subsidence rates from the continent side differential neotectonics with uplift and transpression in the siberian coast ridges are active both likely have influenced river behavior by providing sites for preservation with uplift in particular allowing accumulation of deposits in the second terrace in the western sector the actual delta setting comprises only the eastern sector of the lena delta 4 peat formation polygenetic formation of ice rich peaty sand ice complex was most extensive 7 11 m in thickness in the southern part of the delta area between 43 and 14 ka bp third terrace deposits in recent times alluvial peat 5 6 m in thickness is accumulated on top of the deltaic sequences in the eastern sector first terrace

seasonal subsidence and rebound in las vegas valley nevada observed by synthetic aperture radar interferometry analyses of areal variations in the subsidence and rebound occurring over stressed aquifer systems in conjunction with measurements of the hydraulic head fluctuations causing these displacements can yield valuable information about the compressibility and storage properties of the aquifer system historically stress strain relationships have been derived from paired extensometer piezometer installations which provide only point source data because of the general unavailability of spatially detailed deformation data areal stress strain relations and their variability are not commonly considered in constraining conceptual and numerical models of aquifer systems interferometric synthetic aperture radar insar techniques can map ground displacements at a spatial scale of tens of meters over 100 km wide swaths insar has been used previously to characterize larger magnitude generally permanent aquifer system compaction and land subsidence at yearly and longer timescales caused by sustained drawdown of groundwater levels that produces intergranular stresses consistently greater than the maximum historical stress we present insar measurements of the typically small magnitude generally recoverable deformations of the las vegas valley aquifer system occurring at seasonal timescales from these we derive estimates of the elastic storage coefficient for the aquifer system at several locations in las vegas valley these high resolution measurements offer great potential for future investigations into the mechanics of aquifer systems and the spatial heterogeneity of aquifer system structure and material properties as well as for monitoring ongoing aquifer system compaction and land subsidence

on postglacial sea level summary an exact method is presented for calculating the changes in sea level that occur when ice and water masses are rearranged on the surface of elastic and viscoelastic non rotating earth models the method is used to calculate the instantaneous elastic and delayed vi scoelastic sea level changes following the partial melting of late quaternary ice sheets we find that there can be large errors in the usual assumption that changes in sea level are uniform over the ocean basins if a quantity of ice equivalent to a uniform 100 m rise in sea level melts from the laurentide and fennoscandian ice sheets then in the south pacific the instantaneous rise in sea level can be as large as 120m in the north atlantic the instantaneous rise is always less than 100 m there is a zone in the north atlantic with almost no sea level change and near greenland and norway the sea level falls rather than rises by over 100 m one thousand years after the melting a forebulge migrating towards the ice loads causes water to flow from the south pacific into the north pacific suggesting that raised beaches should occur in the south pacific the gravitational attraction of an ice mass upon a nearby ocean tends to hold sea level high in the vicinity of the ice this extra load near the ice may have a significant influence on postglacial isostatic adjustment

influence of glacial isostatic adjustment on river evolution along the u s mid atlantic coast abstract long term river evolution depends partly on crustal deformation which shapes the topography crossed by rivers on glacial timescales ice sheet growth and decay can produce crustal vertical motion of 10 mm yr resulting from the solid earth s adjustment to variations in ice and water loads comparable to tectonically driven rates in the most rapidly uplifting mountains on earth this process of glacial isostatic adjustment gia can influence river courses and drainage basins substantially particularly near former ice margins we explore the extent to which gia influenced the evolution of rivers along the united states east coast during the last glacial cycle we compute gravitationally self consistent gia responses that incorporate recent constraints on the laurentide ice sheet history through the last glacial build up phase and we connect the predicted variations in topography to abrupt changes in river dynamics recorded in the hudson delaware susquehanna and potomac rivers from 40 ka to present to the extent that increases in sediment transport capacity imply increases in river incision rate the gia driven changes in slope and drainage area are consistent with episodes of erosion and sedimentation observed in the hudson delaware and potomac rivers but inconsistent with the observed accelerated river incision in the susquehanna river at 30 14 ka these analyses add to a growing body of evidence showing that gia strongly influences river evolution over millennial timescales

deformation characteristics of a clayey interbed during fluid injection surface deformation due to fluid withdrawal has long been observed at the surface above aquifers and oil reservoirs uplift associated with fluid injection has also been observed although the processes of subsidence and uplift are reversible in a poroelastic setting the presence of clayey interbeds can result in ground deformation behavior non reversible because of their low permeability and nonlinear behavior in this investigation a cam clay model is used in conjunction with a poroelastic model to simulate the presence of a laterally extensive lens shaped clayey interbed in a sandstone aquifer during fluid injection spatial and temporal changes associated with this interbed during aquifer pressurization are captured and can be clearly differentiated from the deformation of the surrounding poroelastic aquifer formation results for pore pressures and ground surface deformation patterns can be categorized into three distinct time intervals an early time interval where the aquifer is pressurized but not the interbed leading to a lower region above the interbed an intermediate time interval in which the interbed pressures slowly increase approaching the pressure of the adjacent aquifer leading to a potentially large surface uplift above the interbed and a late time interval in which pressure equilibration is achieved between the interbed and aquifer and a highly non symmetrical irregular surface deformation pattern results which may be higher or lower than the background depending on the interbed characteristics reservoir configuration is found to be an important factor influencing ground deformation behavior with more obvious deformation always occurring in a laterally confined aquifer as opposed to a laterally infinite aquifer

three dimensional deformation and strain induced by municipal pumping part 2 numerical analysis summary field measurements consisting of water levels from a municipal well and three dimensional surface deformations and strains from high precision gps measurements at various radial distances from the well were collected as part of a 62 day controlled aquifer test at mesquite nv these measurements were used as observations in several numerical models and a parameter estimation code to characterize and constrain hydraulic and mechanical properties of a 400 m thick basin fill aquifer a parsimonious approach was used in conceptualizing the aquifer system nonetheless results from the calibrated deformation and flow models accurately reproduced the observed head and deformations during the first 20 days of pumping the time at which a new equilibrium was achieved surface deformations were shown to reflect hydraulic anisotropy and direction of principal conductivity in addition the radius of influence and cone of depression from pumping was approximated in spite of the fact that no monitoring well data existed at the site sensitivity analysis indicates that cyclical head values are most sensitive to changes in horizontal hydraulic conductivity while time dependent vertical deformations are most sensitive to changes in skeletal specific storage this investigation shows that gps monitoring can be used in place of costly monitoring wells to characterize aquifers for water management purposes where skeletal deformation tends to be elastic

lithosphere rheology and active tectonics in mongolia relations between earthquake source parameters gravity and gps measurements in this paper we use observations of earthquake source parameters and gravity to investigate the mechanical properties and the active faulting of the lithosphere in mongolia well determined earthquake centroid depths including 10 from inversions of p and sh waveforms that are presented here for the first time show that the seismogenic thickness ts within mongolia itself is less than 20 km however to both the east in parts of the lake baikal rift system and the west adjacent to the junggar basin and kazakhstan platform the seismogenic thickness is considerably greater and includes essentially the whole crust from the admittance between the free air gravity and the topography and also from profiles across a flexural foreland basin we determine the effective elastic thickness te in central mongolia to be 30 km in both mongolia and its surroundings te is comparable with ts and where it is well determined te ts these data are consistent with the view that the strength of the continental lithosphere resides in its seismogenic part which in mongolia is the upper crust but to both the east and west appears to be the whole crust the earthquake source parameters also allow us to ask how the active faulting in mongolia accommodates the velocity field revealed by gps measurements it is likely that the entire mongolian altay range in the west rotates counter clockwise relative to stable asia and is responsible for the distributed e w left lateral shear seen further east in central mongolia the admittance observations show no evidence at the present day for convective mantle support or a hotspot responsible for the elevated region of the hangay dome in central mongolia even though the geochemical data from nodules in late cenozoic basalts and seismic tomography studies suggest elevated temperatures at shallow depths 125 km and probably thinned lithosphere

climate induced formation of a closed basin great divide basin wyoming large closed basins are often associated with regions of active tectonics in contrast we provide the example of the great divide basin in southern wyoming where climate change through its impact on erosion and fl exure provides the primary mechanism of basin closure two and three dimensional fl exural models that incorporate the effects of local basin abandonment due to aridity as well as minor extrabasinal extension demon strate that basin closure with 40 m of base ment relief tilt could have been achieved in the great divide basin under reasonable assumptions of sediment rock density and fl exural rigidity the primary drive for ba sin abandonment was insuffi cient discharge that retarded river downcutting continued erosion in the surrounding drainage led to fl exural rebound against which erosion by the outlet from the great divide basin was unable to compete eventually the basin became detached and isolated from the sur rounding drainage and a few tens of meters of differential tilt developed between the ba sin fl oor and spillover point an extra amount of tilt up to a few meters could have been at tained by rift shoulder effects associated with minor nearby extension outside of the basin to the north hence closure of the great di vide basin took place with no internal fault ing nor did it require any extrabasinal tec tonic activity to force basin closure hence basin closure and or drainage reorganization need not record tectonic activity in all cases differential erosion provides an alternative hypothesis that does not refl ect local tectonic timing our model of the evolution of the great divide basin illustrates a mechanism by which basins can become closed by cli matic effects alone

three dimensional numerical modeling of deltaic depositional sequences 1 influence of the rate and magnitude of sea level change abstract a three dimensional numerical model of deltaic deposition is used to investigate the influence of sea level changes on delta development and sequence variability results illustrate the three dimensional morphology of key stratal surfaces and architecture of stratal units systems tracts and highlight the importance of the rate and magnitude of sea level change in controlling the evolution of deltaic depositional sequences high rates of sea level fall lead to the development of a limited number of major incised channels that focus sediment supply to a few elongate finger like forced regressive lobes separated by large areas of nondeposition in contrast low rates of sea level fall cause only minor channel incision which occurs late during sea level fall as a result sediment is supplied more uniformly to the delta front leading to an attached laterally continuous forced regressive apron during lowstand and subsequent sea level rise the delta morphology and internal geometry are strongly controlled by the rate of rise high rates lead to i poorly developed lowstand wedges that are drowned early ii high magnitude transgressions and iii the late development of maximum flooding surfaces the stratigraphy developed during sea level rise is also strongly influenced by the incised valley system created during the preceding sea level fall if deep major valleys developed that captured most of the sediment supply the resultant stratigraphy has well developed lowstand wedges that are flooded relatively late during sea level rise even within a single delta systems tracts and key stratal surfaces show three dimensional variability and two dimensional sections often lack significant elements of the stratigraphy as a result analysis of two dimensional sections can often lead to miscorrelation and erroneous interpretations of the controlling processes

mathematical model for regional land subsidence due to pumping 2 integrated aquifer subsidence equations for vertical and horizontal displacements a mathematical model for regional subsidence due to pumping from an aquifer is developed on the basis of biot s work on coupled three dimensional consolidation following biot s work on threedimensional consolidation with coupling between mass conservation and equilibrium equations a mathematical model for regional subsidence due to pumping from an aquifer is developed by averaging the three dimensional model over the thickness of the aquifer and assuming conditions of plane stress both vertical land subsidence and horizontal displacements as functions of plane coordinates and time can be estimated by solving the model equations for a given confined or leaky confined aquifer an analytical solution is presented for the special case of a single well pumping from an infinite homogeneous isotropic aquifer the solution provides estimates of changes in averaged over the vertical values of piezometric head vertical subsidence and horizontal displacement the results indicate that under the conditions of the studied case of radial flow the solution for piezometric head is identical to the one obtained by noncoupled models furthermore half the volume strain is produced by vertical subsidence while the other half by the horizontal displacement hence the vertical subsidence is only approximately half the value obtained in noncoupled models which neglect horizontal displacement a numerical example demonstrates these conclusions

fault controlled deformation and stress from pumping induced groundwater flow summary four two dimensional numerical model scenarios are developed to gain a better understanding of how earth fissures form under pumping induced stress the simulated aquifer aquitard system contains a low compressibility sub vertical 100 m wide fault zone that transects the hydrostratigraphic system that includes a 100 m thick vadose zone two scenarios represent constant and cyclical pumping over a 5 year period and two scenarios are used to evaluate the difference between using purely elastic aquitards versus elasto plastic aquitards the model provides for the analysis of the spatial distribution of deformation and normal and shear stress that potentially lead to the formation of earth fissures results indicate that this fault zone largely controls the deformation and stress regime of the system during pumping patterns of deformation and stress are similar for all scenarios with only the magnitudes being affected simulation results show that pumping induces a counterclockwise rotation of the fault plane on the footwall the distribution of deformation through the fault is damped and the deformation patterns are more subdued on the hanging wall but all deformation is directed toward the pumping well these deformation patterns result in two areas of stress accumulation that may lead to fissure formation a near the land surface in the fault zone and b near the saturated unsaturated interface on the hanging wall adjacent to the fault zone these results reveal the importance of both the fault and vadose zones in fissure genesis