geomechanics of subsurface water withdrawal and injection land subsidence and uplift ground ruptures and induced seismicity are the principal geomechanic effects of groundwater withdrawal and injection the major environmental consequence of groundwater pumping is anthropogenic land subsidence the first observation concerning land settlement linked to subsurface processes was made in 1926 by the american geologists pratt and johnson who wrote that the cause of subsidence is to be found in the extensive extraction of fluid from beneath the affected area since then impressive progress has been made in terms of a recognizing the basic hydrologic and geomechanic principles underlying the occurrence b measuring aquifer compaction and ground displacements both vertical and horizontal c modeling and predicting the past and future event and d mitigating environmental impact through aquifer recharge and or surface water injection the first milestone in the theory of pumped aquifer consolidation was reached in 1923 by terzaghi who introduced the principle of effective intergranular stress in the early 1970s the emerging computer technology facilitated development of the first mathematical model of the subsidence of venice made by gambolati and freeze since then the comprehension measuring and simulation of the occurrence have improved dramatically more challenging today are the issues of ground ruptures and induced triggered seismicity which call for a shift from the classical continuum approach to discontinuous mechanics although well known for decades anthropogenic land subsidence is still threatening large urban centers and deltaic areas worldwide such as bangkok jakarta and mexico city at rates in the order of 10 cm yr

land subsidence in central mexico detected by alos insar time series abstract massive groundwater extraction is common throughout mexico and is well known to result in land subsidence however most land subsidence surveys focus on one single city mainly mexico city and thus fail to reveal the regional extent of the problem here we use 2007 2011 interferometric synthetic aperture radar insar time series analysis of alos data to resolve land subsidence in the entire central mexico region we identify land subsidence in 21 areas including 17 cities linear vertical rates over 30 cm yr are observed in mexico city while in the other locations rates of 5 10 cm yr are detected we define 3 main categories of subsidence using the averaged velocity maps in conjunction with previously published structural surface geology and land use mapping 1 rapid large scale subsidence 2 rapid local scale subsidence and 3 slow patchy subsidence the correlation between subsidence and land use confirms that groundwater extraction mainly for agricultural and urban activities is the main cause of land subsidence we observe that the boundaries of the subsiding areas are typically characterized by high velocity gradients often coinciding with pre existing faults motion on these faults being driven by water extraction rather than by tectonic activity regional surveys of this type are necessary to understand the spatial and temporal evolution of land subsidence to constrain the distribution and connectivity of water bearing units and ultimately to reach better hazard mitigation plans

groundwater flow and solute transport in fractured lacustrine clay near mexico city a network of piezometers was installed in a surficial lacustrine clay aquitard overlying a thin saline water aquifer of volcanoclastic origin at a study site near mexico city in the basin of mexico the aquifer is underlain by additional lacustrine sediments which in turn overlie a thick regional freshwater aquifer the regional aquifer provides approximately 70 of the water supply for 20 million people in the basin of mexico in the study area major ions oxygen 18 and deuterium in the pore water of the surficial aquitard exhibit large variations with depth the nature of these variations suggests that the saline pore water is being displaced downward by infiltrating meteoric water the infiltration has been induced by strong downward hydraulic gradients imposed two to three decades ago when heavy aquifer pumping of the thin saline water aquifer began one dimensional analytical models representing solute transport in both fractured and unfractured porous media were used to simulate the geochemical profiles in the surficial aquitard the fractured porous medium model using a realistic mean hydraulic gradient and fracture spacing 1 5 m and small but significant fracture aperture 30 m provide nearly an exact match to the field data from this we infer that because of vertical fractures there is a much greater potential for downward leakage of water and contaminants through the mexico city clay into underlying aquifers than has been previously thought

excessive groundwater withdrawal and resultant land subsidence in the su xi chang area china excessive groundwater withdrawal has caused severe land subsidence in the su xi chang sxc area china the restriction and prohibition on groundwater pumping have been carried out since the late 1990s based on the latest updated field data the changing pattern of groundwater level and the distribution of land subsidence are analyzed the distribution of land subsidence in sxc is closely related to that of the cone of depression in the second confined aquifer in time and space but land subsidence is not in synchronization with the changing groundwater level both aquitards and aquifers compacted continuously in the early period of groundwater level rising and behaved as creep materials a series of laboratory tests were conducted on aquifer sands which indicated that the creep deformation under virgin compression is much greater than that under recompression and unloading and that the creep of sands decreases rapidly with the cycles of repeating load the test results reveal the mechanism of sand creep under the condition of long term groundwater pumpage as a consequence of the restriction and prohibition on groundwater pumping groundwater level has obviously recovered in the vast majority of the sxc area and land subsidence has slowed down and even a little rebound has occurred in some sites in suzhou and changzhou if the pumpage is strictly limited continuously the groundwater level will not decline below the historical lowest value but fluctuate within a certain range in such a case land subsidence in sxc will no longer develop obviously

three dimensional structure of the torngat orogen ne canada from active seismic tomography the crustal velocity structure and the moho depth of the proterozoic torngat orogen ne canada is determined by active seismic tomography using travel times of crustal turning rays and moho reflections the orogen developed during oblique convergence of the archean superior and nain provinces which trapped an interior belt of archean crust core zone between them with the torngat orogen evolving between the core zone and the nain province beneath the central orogen a crustal root is found with a preserved depth of 52 km and a width of 100 km to the north the root shallows to 44 km and narrows to a width of 45 km the root correlates with a set of major late orogenic shear zones that accommodated oblique convergence of the superior and nain provinces this correlation suggests that the transpressional shearing focused strain in the region of the root and contributed to the crustal thickening absence of postorogenic magmatic activity prevented reworking or thermal relaxation of the root the lack of late magmatism is probably related to the depleted and refractory nature of the archean lithosphere underlying the orogen upper crustal velocities are lowest in the core zone 5 7 km s at the surface and are compatible with laboratory measurements carried out on gneissic rock samples from that area higher velocities in the nain province 5 9 km s correlate with felsic gneiss and anorthosite rock samples a high velocity region immediately to the north of the crustal root is associated with a moho uplift 34 km this is explained by extension along the ungava transform fault and possibly in hudson strait at 55 ma when rifting in the labrador sea was transferred into baffin bay

evaluation and analysis of surface deformation in west chapala basin central mexico vertical deformation was measured at 14 benchmarks within the urban area of jocotepec mexico using first order leveling methods and then spatially analyzed in relation to land subsidence and soil discontinuity patterns the study area is located within the western portion of the chapala basin middle west mexico observations of vertical surficial deformation were made at each benchmark september and november 2012 relative to a fixed station and compared to an initial survey of each benchmark april 2012 results indicate that a maximum subsidence of 7 16 cm over the 8 month measurement interval occurs near downtown coincident with the largest levels of drawdown and translates to a maximum subsidence rate of 0 89 cm month for the sampling period two benchmarks located northwest and southeast of the urban area exhibited uplift of 2 8 and 0 76 cm respectively suggesting a complex mechanical response between the sedimentary soil units and the factors causing deformation a potential spatial relationship exists between subsidence patterns and soil discontinuities four separate cones of groundwater depression were observed with two being coincident with subsidence bowls downtown and south of the urban area however there is no clear relationship between drawdown and subsidence in the remaining areas hydrogeologic reconstructions reveal alternating sequences of alluvial aquifers and highly deformable lacustrine aquitards an analysis of the soil discontinuities reveals that they are directly aligned with the patterns of vertical deformation

hydraulic response of highly compressible aquitards during consolidation the transient hydraulic behavior of highly compressible aquitards is investigated through numerical analysis and field studies variations in the hydraulic parameters of an aquitard during consolidation are accounted for by incorporating empirical relationships derived from standard consolidation tests into the one dimensional flow equation the resulting equation is highly nonlinear the hydraulic response of an aquitard with physical properties typical of the compressible clays of mexico city is evaluated with both standard linear analysis and with a nonlinear approach where the hydraulic parameters are stress dependent the results indicate that decreases in the hydraulic diffusivity of the aquitard due to consolidation lead to diminished leakage flux slower groundwater velocities and solute transport rates longer transient response periods and less land subsidence than would be predicted by classical linear theory evaluation of field data from a site near mexico city indicates that significant interpretive errors may arise if the stress dependence of the hydraulic parameters is ignored in these types of systems

land subsidence by groundwater over exploitation from aquifers in tectonic valleys of central mexico a review abstract structurally controlled differential subsidence scds is the gradual sinking of the ground characterized by the development of a damage band terrain discontinuities and collapses aligned according to the strike of a controlling geological structure scds has been reported since the 1980s in several cities settled on tectonic valleys in central mexico although groundwater abstraction is the main trigger recent research efforts also point out a tectonic component as a driving force the monitoring and quantification of scds has been done through a variety of techniques such as extensometry gps and insar furthermore the associated hazards endangering the population are floods aquifer pollution cracking and housing collapse this paper presents a comprehensive review of the current state of scds allowing for the first time the standardization of its definition mechanisms and triggering factors additionally this helps to avoid misinterpretation in the cases of sinking produced by the mexico city subsidence type mcst and thus provides the elements for proper methodological study of scds finally the review includes future research directions that need to be improved in order to reduce the impact of the phenomenon

joint inversion in coupled quasi static poroelasticity geodetic surveys now provide detailed time series maps of anthropogenic land subsidence and uplift due to injection and withdrawal of pore fluids from the subsurface a coupled poroelastic model allows the integration of geodetic and hydraulic data in a joint inversion and has therefore the potential to improve the characterization of the subsurface and our ability to monitor pore pressure evolution we formulate a bayesian inverse problem to infer the lateral permeability variation in an aquifer from geodetic and hydraulic data and from prior information we compute the maximum a posteriori map estimate of the posterior permeability distribution and a gaussian approximation of the posterior computing the map estimate requires the solution of a large scale minimization problem subject to the poroelastic equations for which we propose an efficient newton conjugate gradient optimization algorithm the covariance matrix of the gaussian approximation of the posterior is given by the inverse hessian of the log posterior which we construct by exploiting low rank properties of the data misfit hessian first and second derivatives are computed using adjoints of the time dependent poroelastic equations allowing us to fully exploit transient data using three increasingly complex model problems we find the following general properties of poroelastic inversions augmenting standard hydraulic well data by surface deformation data improves the aquifer characterization surface deformation contributes the most in shallow aquifers but provides useful information even for the characterization of aquifers down to 1 km in general it is more difficult to infer high permeability regions and their characterization requires frequent measurement to resolve the associated short response timescales in horizontal aquifers the vertical component of the surface deformation provides a smoothed image of the pressure distribution in the aquifer provided that the mechanical properties are known coupled poroelastic inversion is therefore a promising approach to detect flow barriers and to monitor pore pressure evolution

a probabilistic approach to soil layer and bedrock level modeling for risk assessment of groundwater drawdown induced land subsidence sub surface construction in urban areas generally involves drainage of groundwater which can induce subsidence in soil deposits knowledge of where compressible sediments are located and how thick these are is essential for estimating subsidence risk a probabilistic method for coupled bedrock level and soil layer modeling to detect compressible sediments is presented the method is applied in an area in central stockholm where clay is the compressible sediment layer first a bedrock level model was constructed from three sources of information a geotechnical drillings reaching the bedrock b drillings not reaching the bedrock and c mapped bedrock outcrops input data for the probabilistic bedrock level model was generated by a stepwise kriging procedure second a three layer soil model was constructed including the following materials a coarse grained post glacial and filling material below the ground surface b glacial and post glacial clays and c coarse grained glaciofluvial and glacial till deposits above the bedrock layer thicknesses were transformed to proportions of the total soil thickness since kriging requires data to be normally distributed the proportions were transformed from proportions p to standard normal quantiles z in each iteration of a monte carlo simulation a spatial distribution of the bedrock level was simulated together with the transformed values for the soil layer proportions from the iterations the probability density of the clay thickness compressible sediments at each grid cell was calculated the results of the case study map the expected value mean and the 95th percentile of the probability of compressible sediments at specific locations the resulting model is geologically realistic and validated through a cross validation procedure in order to be in good agreement with a reference dataset the case study showed that the method can efficiently handle large amounts of data and requires little manual adjustment moreover the mapped results can provide useful decision support when planning risk reducing measures and when communicating with stakeholders although this novel method is developed for risk assessment of groundwater drawdown induced subsidence it is useful for other applications involving spatial soil strata modeling

on the simultaneity of substorm onset between two hemispheres simultaneous observations of auroral kilometric radiation from the northern and southern hemispheres showed some cases in which the buildup of field aligned acceleration occurred only in one hemisphere at the substorm onset this indicates that a substorm does not always complete the current system by connecting the cross tail current with both northern and southern ionospheric currents conjugate auroral observations showed that in one case the auroral breakup in the northern and southern hemispheres was not simultaneous rather they occurred a few minutes apart this time difference in the breakup between two hemispheres suggests that the local auroral ionosphere controls auroral breakup in each hemisphere independently the evidence in this study may indicate that the buildup of the field aligned acceleration region at the auroral breakup does not result only from the magnetospheric process and that the auroral ionosphere finally controls and or ignites the substorm onset that is the auroral breakup

groundwater pumping and land subsidence in the emilia romagna coastland italy modeling the past occurrence and the future trend 1 the emilia romagna coastland south of the po river delta italy has experienced a dramatic land settlement mainly due to the large groundwater withdrawal related to the local economic and tourist development started in the early 1950s although the use of surface water has reduced the settlement rate over the last three decades anthropogenic land subsidence still continues in a few kilometer wide coastal strip at a rate larger than the natural one the occurrence is reconstructed since 1946 with the aid of advanced finite element flow and poromechanical models implemented with a realistically detailed geology of the regional shallow multiaquifer system the models have been calibrated against the piezometric leveling and extensometer records observed over the last 50 years and a land subsidence prediction in 2016 is performed the results show that the extensive groundwater pumping that occurred in the past is most likely the main cause of the recent land settlement as well because of the delayed compaction of the clay aquitards comprised between the depleted aquifers however the available pumping data do not allow for a thorough understanding of the current local settlement process along the coastline which is the most vulnerable area of the emilia romagna region from an environmental viewpoint if the planned scenario of groundwater resource management will be implemented anthropogenic land subsidence is bound to become a marginal problem for the central and northern portion of the emilia romagna coastland

consolidation settlement in aquifers caused by pumping abstractequations are derived to calculate one dimensional vertical consolidation settlement in aquifers caused by groundwater extraction the settlement equations capture the effect that the decline in pore water pressure caused by groundwater extraction has on increased vertical effective stress the settlement equations for single layered confined or unconfined aquifers and multiple layered aquifers are derived by linking the increase in vertical effective stress to the reduction of the void ratio using the reconstructed field consolidation curve of aquifer sediments this paper s approach blends groundwater hydraulics with the classical theory of one dimensional consolidation widely used in geotechnical engineering closed form consolidation settlement equations are presented for single layer homogeneous isotropic confined aquifers with steady state or transient groundwater flow and for single layer homogeneous isotropic unconfined aquifers under steady state flow the consolidation equations f

analysis of long term land subsidence near mexico city field investigations and predictive modeling the mexico city region has several flat plains formed on exceptionally porous 60 90 lacustrine deposits overlying a highly productive regional aquifer severe land subsidence due to consolidation of the lacustrine aquitard caused by aquifer exploitation has resulted in restrictions on pumping in the core of mexico city this has led to large increases in aquifer pumping in the outlying lacustrine plains where satellite communities are rapidly expanding the chalco basin is one of these lacustrine areas where pumping began in the 1950s and greatly increased in the 1980s the lacustrine sequence in the chalco area is significantly thicker than anywhere else in the basin of mexico averaging 100 m and reaching a maximum thickness of 300 m consequently this area is susceptible to the highest potential land subsidence effects as a result of groundwater extraction of anywhere in the basin land subsidence in the central part of the chalco basin has increased to 0 4 m yr since 1984 and by 1991 total subsidence had reached 8 m the rapid land subsidence in this area is causing the accumulation of meteoric waters during the rainy season resulting in extensive flooding of farmland this study first demonstrates a methodology for combining hydraulic data from a network of monitoring wells geotechnical data from core samples and a compilation of historical information on land surface elevation to quantify groundwater flow and land subsidence phenomena within the rapidly subsiding chalco basin then a one dimensional mathematical model is employed to develop predictions of future land subsidence under a range of pumping conditions the model permits the hydraulic properties of the aquitard to vary as transient functions of hydraulic head and porosity simulations suggest that under current pumping rates total land subsidence in the area of thickest lacustrine sediment will reach 15 m by the year 2010 if pumping is reduced to the extent that further decline in the potentiometric surface is prevented total maximum subsidence would be significantly less 10 m and the rate would nearly cease by 2010

origin of pore water and salinity in the lacustrine aquitard overlying the regional aquifer of mexico city abstract a series of six ancient connected lakes occupied the broad plain of the closed basin of mexico this study pertains to two of these lakes 18o 2h and chemical patterns in the pore water of the broad aquitard formed from sediment in these lakes indicate that the origin of this paleo lake water was local meteoric water which entered the ancient lakes as runoff and groundwater from springs evaporation of surface water in the former chalco lake caused concentration of dissolved salts and enrichment in the heavy isotopes 18o and 2h during high water periods the south easternmost ancient lake chalco fed partially evaporated water to the closed lake texcoco the lowest of the lakes where further evaporation occurred causing higher concentration of salts and enrichment of heavy isotopes these major ions and stable isotopes follow the evaporation trends characteristic of closed or nearly closed evaporatic basins elsewhere in the world paleo lake evaporation lines in lakes chalco and texcoco originated from the same starting water and developed as a consequence of the topographic position of the former lakes and local climatological conditions a modern evaporation line developed after the drainage of the lakes reflecting evaporation of modern infiltrating meteoric water the presence of brackish pore water in most of the chalco aquitard which has a maximum thickness of 300 m indicates that upward vertical groundwater flow has not been capable of displacing the paleo lake water this suggests that vertical advection was not significant throughout the hundreds of thousands of years of existence of the aquitard sediments one dimensional numerical simulations of the deeper part of the 18o profile representing the thicker part of the aquitard sediments 140 m showed that this profile was developed by molecular diffusion with a small upward advective flux where apparently the chalco aquitard always had enriched brackish water overlying the fresh water aquifer

adaptive explicit implicit quasi three dimensional finite element model of flow and subsidence in multiaquifer systems a quasi three dimensional finite element model is presented for the analysis of groundwater flow and land subsidence due to pumpage in multiaquifer systems in the model aquifers are simulated with the aid of two dimensional horizontal finite element grids each aquifer is connected to its neighbors above and below by one dimensional vertical finite element strings which allow leakage to take place across aquitards and aquicludes land subsidence is modeled by varying the void ratio of each vertical element according to a nonlinear version of terzaghi s one dimensional consolidation theory a major feature of the new method is its ability to solve the finite element equations explicitly in one part of the mesh and implicitly in another part depending on the ratio between the stability limit of each node and any given time step size since the hydraulic diffusivity of aquitards is usually very small compared to that of aquifers it is often possible to solve the finite element equations explicitly for most and sometimes all aquitard nodes this leads to a virtual decoupling of the aquifer equations during a given time step which results in a significant saving of computer time and storage

study on land subsidence under different plot ratios through centrifuge model test in soft soil territory since the mid 1990s multi storied buildings high rise buildings and skyscrapers have been emerging due to the new round of great scale development on the soft soil littoral land subsidence in soft soil areas caused by engineering environmental effect especially by construction of high dense building groups attracts more and more attention the plot ratio may be one of the most important factors on engineering induced land subsidence thus three geotechnical centrifugal model tests were conducted under three conditions of different plot ratios to study the ground settlement mechanism of high dense building groups in soft soil territory it is concluded that the subsidence superimposition effect is obvious in the central area of high dense building groups the settlement increases with the growth of plot ratio the urban planning department should take this subsidence situation into account when determining the construction plot ratio to utilize the earth more aptly and safely

evolution of long term land subsidence near mexico city review field investigations and predictive simulations 1 aquitard consolidation in the chalco plain is the most recent of a series of major land subsidence problems near mexico city caused by leaky aquifer pumping and involving a complex distribution of basalt flows within a lacustrine sequence this study first conducted a ground magnetic survey combined with lithologic logs to map the extension of basalts then it assessed the evolution of ground surface elevations and updated hydraulic heads in the aquifer and aquitard in order to verify the accuracy of previous simulations and develop new predictions on land subsidence employing a one dimensional nonlinear groundwater flow consolidation model results show the presence of shallow basalts that extend from sierra santa catarina into the chalco plain causing a differential consolidation that controls both the distribution of large scale fractures in the aquitard and the shape of a new lake cumulative land subsidence in the center of the chalco plain reached 13 m in 2006 thus closely matching previous numerical estimations since 1985 the ground surface decline has continued at a rate of 0 40 m yr while the potentiometric surface decline in the aquifer proceeds at an average rate of 1 5 m yr indicating that the flow system has not yet reached steady state conditions numerical predictions show that under current pumping rates where the aquitard is 300 m total land subsidence will reach 19 m by the year 2020 while where the aquitard is 140 m thick total land subsidence will reach 12 m and increase the risk of flooding and aquitard fracturing for nearby urban centers

land subsidence in china land subsidence in china occurs in different regions it is primarily caused by excessive groundwater withdrawal other reasons for the subsidence include the oil warm groundwater withdrawal and the neotectonic movement the common characteristics of land subsidence in china are slow accumulative irreversible and other unique properties the range of subsidence still keeps extending and the accumulative subsidence increasing though some measures taken adjustment of the aquifer exploitation practice is a subsidiary way to control land subsidence but it cannot solve this problem completely in a specfic way of groundwater changing the contribution of a certain soil layer to the total subsidence depends on its compressibility and thickness besides the elasticity both cohesive soil layers aquitards and sand layers aquifers are observed to be plastic and creep when the groundwater level fluctuates in a specific way which often leads to subsidence delay

modeling visco elastic plastic deformation of soil with modified merchant model eighty four to ninety eight percent of land subsidence in shanghai city is caused by the visco elastic plastic deformation of sediments numerical experiments are done on the sediments with visco elastic plastic deformation in shanghai to verify the modified merchant model mm model and land subsidence model based on the modified merchant ls mm model there are two advantages of the mm model and the ls mm model one is that only a few parameters are involved there are three parameters in the mm model and four parameters in the ls mm model the other one is that both models can describe elastic elastic plastic and visco elastic deformation in addition to visco elastic plastic deformation the corresponding models are developed by setting proper values of the three parameters of 1 and 2 the two advantages make the ls mm model flexible and applicable to the simulation of the large regional land subsidence with visco elastic plastic deformation and other different kinds of deformation the results can be improved by variable parameters especially specific storage

mechanical modeling of aquifer sands under long term groundwater withdrawal abstract long term excessive groundwater withdrawal causes severe land subsidence and considerable economic loss during the period of land subsidence aquifer sands present complex deformation characteristics field data in the southern yangtse delta china have shown that the deformation characteristics of aquifer sands are closely related to the changing patterns of groundwater level the aquifer units have experienced when the groundwater level fluctuates yearly within a certain range the aquifer unit behaves primarily as an elastic material when the groundwater level rises and falls alternatively with the average decreasing but higher than the previous lowest value the unit has experienced the aquifer unit behaves primarily as a visco elastic and elasto plastic material however when the average level decreases and is lower than the previous lowest value the unit has experienced the aquifer unit behaves primarily as a visco elastic elasto plastic and visco plastic material the plastic and creep deformation of aquifer sands is also proved through laboratory tests with the increasing cycle number of loading the creep and plastic deformation decreases and the expansion under unloading is closer to the compression under loading in a single cycle on the basis of field and laboratory data a new mechanical model is constructed which can describe various kinds of deformation characteristics under different changing patterns of groundwater level including elastic visco elastic plastic and visco plastic deformation the model includes two yielding stresses and six parameters when the appropriate field data are available the six parameters of the model can be determined through graphic methods then the deformation of aquifer units can be calculated if the changing groundwater level is known