the influence of idealized heterogeneity on wet and dry planetary boundary layers coupled to the land surface abstract this manuscript describes numerical experiments investigating the influence of 2 30 km striplike heterogeneity on wet and dry convective boundary layers coupled to the land surface the striplike heterogeneity is shown to dramatically alter the structure of the convective boundary layer by inducing significant organized circulations that modify turbulent statistics the impact strength and extent of the organized motions depend critically on the scale of the heterogeneity relative to the boundary layer height zi the coupling with the land surface modifies the surface fluxes and hence the circulations resulting in some differences compared to previous studies using fixed surface forcing because of the coupling surface fluxes in the middle of the patches are small compared to the patch edges at large heterogeneity scales zi 18 horizontal surface flux gradients within each patch are strong enough to counter the surface flux gradients between wet and dry patches allowing the formation of

geodetic imaging reservoir monitoring using satellite interferometry summary fluid fluxes within subsurface reservoirs give rise to surface displacements particularly over periods of a year or more observations of such deformation provide a powerful tool for mapping fluid migration within the earth providing new insights into reservoir dynamics in this paper we use interferometric synthetic aperture radar insar range changes to infer subsurface fluid volume strain at the coso geothermal field furthermore we conduct a complete model assessment using an iterative approach to compute model parameter resolution and covariance matrices the method is a generalization of a lanczos based technique which allows us to include fairly general regularization such as roughness penalties we find that we can resolve quite detailed lateral variations in volume strain both within the reservoir depth range 0 4 2 5 km and below the geothermal production zone 2 5 5 0 km the fractional volume change in all three layers of the model exceeds the estimated model parameter uncertainty by a factor of two or more in the reservoir depth interval 0 4 2 5 km the predominant volume change is associated with northerly and westerly oriented faults and their intersections however below the geothermal production zone proper the depth range 2 5 5 0 km there is the suggestion that both north and northeast trending faults may act as conduits for fluid flow

spatiotemporal characterization of land subsidence and uplift in phoenix using insar time series and wavelet transforms the effects of land subsidence pose a significant hazard to the environment and infrastructure in the arid alluvial basins of phoenix arizona improving our understanding of the source and mechanisms of subsidence is important for planning and risk management here we employ multitemporal interferometric analysis of large synthetic aperture radar data sets acquired by ers and envisat satellites to investigate ground deformation the ers data sets from 1992 to 1996 and envisat 2003 2010 are used to generate line of sight los time series and velocities in both the ascending and descending tracks the general deformation pattern is consistent among data sets and is characterized by three zones of subsidence and a broad zone of uplift the multitrack envisat los time series of surface deformation are inverted to obtain spatiotemporal maps of the vertical and horizontal deformation fields we use observation wells to provide an in situ independent data set of hydraulic head levels then we analyze vertical interferometric synthetic aperture radar and hydraulic head level time series using continuous wavelet transform to separate periodic signal components and the long term trend the isolated signal components are used to estimate the elastic storage coefficient the inelastic skeletal storage coefficient and compaction time constants together these parameters describe the storage response of an aquifer system to changes in hydraulic head and surface elevation understanding aquifer parameters is useful for the ongoing management of groundwater resources

upper proterozoic glaciogenic rocks and their stratigraphic significance abstract among more than 300 precambrian tillites mentioned in the literature only 25 can be identified as glacial rocks tillites are known from all continents with the exception of antarctica the uneven stratigraphic distribution of tillites cannot be explained as being due to differences in knowledge roughly synchronous glacial formations and groups form wide regional glaciohorizons they are concentrated in two stratigraphic intervals named glaciocomplexes one such the canadian glaciocomplex consisting of three or four glaciohorizons occurs in the lowermost lower proterozoic in north america and south africa the second glaciocomplex the african containing four or more glaciohorizons is known in the uppermost part of the precambrian in europe asia north and south america africa australia the glaciohorizons and glaciocomplexes reflect oscillation dynamics of glaciations and show a hierarchical structure of glacial events the glaciohorizons and glaciocomplexes were deposited during glacial periods and glacial eras on and marginal to the continents in high and middle paleolatitudes of both hemispheres by comparison with late cenozoic glacial events the duration of the ancient glacioperiods can be roughly estimated at between some millions and a few tens of millions of years within these limits each glaciohorizon can be asynchronous the glaciohorizons have great importance for regional correlations of the precambrian interregional and intercontinental glacial correlations however require radiometric and biostratigraphic controls glacial units can be used in construction of a global stratigrphic scale for the precambrian

the late proterozoic glacial era abstract the late proterozoic glacial record is reviewed on a global basis as a setting and introduction for that part of the symposium concerned with west african tillites no unequivocal glacial deposits have yet been recorded in the interval 1 0 2 0 ga late proterozoic glacial epochs have been grouped into three main periods namely lower congo c 0 9 ga sturtian c 0 8 ga and varangian c 0 65 ga and a possible final late sinian epoch near the precambrian cambrian boundary the ediacaran epoch with its metazoan fauna follows varangian and in part at least precedes late sinian the sturtian and varangian glacial periods each comprise at least two main glacial epochs the tillites of which are widespread chronometric ages are currently disputed and the values given are for identification in the literature rather than to provide chronometric definition of all the glacial epochs only those of the varangian glacial period appear to be represented in west africa it has been argued that varangian tillites were of global extent many forming in tropical latitudes though some authors prefer a hypothesis of polar wandering to limit glaciation to polar latitudes

glacial facies associations in a neoproterozoic back arc setting zavkhan basin western mongolia diamictites many of glacial origin are globally distributed in the neoproterozoic recently two relatively thin diamictites in the maikhan uul member at the base of the neoproterozoic tsagaan oloom formation from the zavkhan basin of western mongolia have been identified as being of glacial origin the mongolian diamictites form a series of backstepping units within the transgressive systems tract of two major depositional sequences associated with sea level changes in each case the diamictites of the transgressive systems tract are abruptly overlain by deeper water upward shoaling highstand systems tracts consisting of thinly bedded sandstones and shales in sequence 1 and thinly bedded dark carbonates in sequence 3 the fact that the sequences conform closely to depositional models established at other localities suggests that all are related to major ice ages and that the depositional sequences they have generated provide a valuable tool for global correlation in this part of the stratigraphic column available stratigraphic and isotope geochemical information presented by brasier et al 1996 this issue suggests that both diamictites are likely to be of sturtian age a riftogenic setting and sturtian age for the diamictites provide a link with eastern australia and western america it is possible therefore that these diamictites formed during the breakup of a supercontinental assembly including siberia australia and laurentia c 750 725 ma bp

history and controls of subsidence in the late cretaceous tertiary great valley forearc basin california abstract analysis of the upper cretaceous tertiary fill of the great valley forearc basin of california reveals a complicated history of subsidence partitioned in time and space western oceanward parts of the basin record subsidence then uplift in apparent response to the angle and rate of descent of the underlying subducting plate specifically uplift in the forearc basin corresponds to the onset of the laramide orogeny and inferred low angles of subduction in contrast eastern arcward parts of the basin display subsidence histories suggestive of thermal contraction and compatible with continentward migration of sierran arc magmatism in the late cretaceous these results imply that subsidence histories of forearc basins are likely to be much more complicated and less predictable than those of rifted continental margins and foreland basins where single subsidence mechanisms predominate and time varying subduction is not an underlying controlling factor

velocity and q structure of the great valley california based on synthetic seismogram modeling of seismic refraction data the modified reflectivity method is used here to interpret seismic refraction data from the west side of the great valley california in terms of a onedimensional compressional wave velocity model of the crust in addition the apparent attenuation qp has been estimated for the 6 km thick sedimentary section the reflectivity method was used to calculate the prominent free surface multiples that propagate in this sedimentary section modeling of the normalized amplitudes of these multiples yielded average qp values of 100 from 0 to 2 83 km depth and 200 from 2 93 to 6 20 km depth the velocity structure in the crust is complicated it is characterized by positive velocity gradients within the sediment to a depth of 4 8 km and by a 1 4 kin thick low velocity zone below this depth the sediment overlies a basement with a velocity of 5 7 km sec at its top which increases to 6 3 km sec at 12 km depth ambiguity of the data in critical regions leads to two equally valid interpretations of the lower crust at depths of 16 to 27 km simple step increases or a more complex structure consisting of alternating high and low velocity zones

an evaluation of the scale at which topographical features affect the convective boundary layer using large eddy simulations abstract the major objective of this study was to evaluate at which scale topography starts to significantly affect the mean characteristics and structure of turbulence in the convective boundary layer cbl the large eddy simulation option of the regional atmospheric modeling system developed at colorado state university was used for that purpose it is found that turbulence is nonlinearly dependent on the scale of the topographical features at a horizontal length scale of less than about 5 km topography has very little impact on the mean properties of the cbl even with hills as high as 30 of the height of the cbl however it has a significant impact on the organization of the eddies at larger horizontal scales topographical features as small as about 10 of the height of the cbl have some effect on the mean characteristics of the cbl in particular a pronounced impact on the dispersion statistics i e horizontal and vertical velocity variances and higher moments is noticed furthermore th

a california statewide three dimensional seismic velocity model from both absolute and differential times abstract we obtain a seismic velocity model of the california crust and uppermost mantle using a regional scale double difference tomography algorithm we begin by using absolute arrival time picks to solve for a coarse three dimensional 3d p velocity v p model with a uniform 30 km horizontal node spacing which we then use as the starting model for a finer scale inversion using double difference tomography applied to absolute and differential pick times for computational reasons we split the state into 5 subregions with a grid spacing of 10 to 20 km and assemble our final statewide v p model by stitching together these local models we also solve for a statewide s wave model using s picks from both the southern california seismic network and usarray assuming a starting model based on the v p results and a v p v s ratio of 1 732 our new model has improved areal coverage compared with previous models extending 570 km in the sw ne direction and 1320 km in the nw se direction it also extends to greater depth due to the inclusion of substantial data at large epicentral distances our v p model generally agrees with previous separate regional models for northern and southern california but we also observe some new features such as high velocity anomalies at shallow depths in the klamath mountains and mount shasta area somewhat slow velocities in the northern coast ranges and slow anomalies beneath the sierra nevada at midcrustal and greater depths this model can be applied to a variety of regional scale studies in california such as developing a unified statewide earthquake location catalog and performing regional waveform modeling

detection of a locked zone at depth on the parkfield california segment of the san andreas fault the parkfield california segment of the san andreas fault is transitional in character between the creeping segment of the fault to the northwest and the locked carrizo plain segment to the southeast the rate of shallow fault slip decreases from 25 30 mm yr northwest of the epicenter of the 1966 parkfield earthquake to zero at the southeastern end of the 1966 rupture zone data from a network of trilateration lines spanning the san andreas fault near parkfield and extending to the pacific coast near san luis obispo shed light on the rate of fault slip at depth since the 1966 earthquake in this study average rates of line length change and shallow fault slip were inverted to determine the slip rate at depth on the parkfield fault segment the fault is taken to be a vertical surface with unknown distribution of strike slip displacement in an elastic half space a striking result of the inversions is that all solutions providing acceptable fits to the data exhibit a locked zone essentially coincident with the rupture surface of the 1966 parkfield earthquake the data require that the locked zone extend nearly as far north as the 1966 epicenter however the vertical extent of the locked zone is not well resolved over much of the parkfield segment the fault is slipping faster at the earth s surface than it is at seismogenic depths in order to fit the trilateration measurements it is necessary to include a component of contraction normal to the trend of the san andreas the inversion results suggest a spatially uniform normal strain of 0 06 strain yr the orientation of the contraction is compatible with geologic and seismic evidence of active folding and reverse faulting in the region the magnitude of the contraction is consistent with convergence rates inferred from global plate motion models

scales of response of the convective boundary layer to land surface heterogeneity the convective boundary layer cbl over domains with meso scale 2 20 km heterogeneity is characterized by preferentially located organized rolls of characteristic size equivalent to the length scale of the heterogeneity additionally random turbulent thermals also develop when the length scale of the heterogeneity exceeds 5 10 km this is due to a complex interaction between the horizontal pressure gradient generated by the heterogeneity and the buoyancy forcing consequently the corresponding wavelet spectrum exhibits two peaks one representing the turbulent thermals at a characteristic scale of about 1 5 times the cbl height and another denoting the organized eddies at a scale similar to that of the heterogeneity this implies that subgrid scale parameterizations in models with grid size larger than 5 10 km which account only for random turbulence are inadequate for heterogeneous domains also this study may provide a more objective classification of scales of atmospheric processes

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

seasonal and long term groundwater unloading in the central valley modifies crustal stress changes in terrestrial water content cause elastic deformation of the earth s crust this deformation is thought to play a role in modulating crustal stress and seismicity in regions where large water storage fluctuations occur groundwater is an important component of total water storage change in california helping to drive annual water storage fluctuations and loss during periods of drought here we use direct estimates of groundwater volume loss during the 2007 2010 drought in california s central valley obtained from high resolution interferometric synthetic aperture radar based vertical land motion data to investigate the effect of groundwater volume change on the evolution of the stress field we show that gps derived elastic load models may not capture the contribution of groundwater to terrestrial water loading resulting in an underestimation of nontectonic crustal stress change we find that groundwater unloading during the drought causes coulomb stress change of up to 5 5 kpa and seasonal fluctuations of up to 2 6 kpa at seismogenic depth we find that faults near the valley show the largest stress change and the san andreas fault experiences only 40 pa of coulomb stress change over the course of a year from groundwater storage change annual coulomb stress change peaks dominantly in the fall when the groundwater level is low however some faults experience peak stress in the spring when groundwater levels are higher additionally we find that periods of increased stress correlate with higher than average seismic moment release but are not correlated with an increase in the number of earthquakes this indicates groundwater loading likely contributes to nontectonic loading of faults especially near the valley edge but is not a dominant factor in modulation of seismicity in california because the amplitude of stress change declines rapidly with distance from the valley by carefully quantifying and spatially locating groundwater fluctuations we will improve our understanding of what drives nontectonic stress and forces that modulate seismicity in california

topography correlated atmospheric delay correction in radar interferometry using wavelet transforms 1 atmospheric delay is one of the major sources of error in repeat pass interferometry we propose a new approach for correcting the topography correlated components of this artifact to this aim we use multiresolution wavelet analysis to identify the components of the unwrapped interferogram that correlate with topography by using a forward wavelet transform we break down the digital elevation model and the unwrapped interferogram into their building blocks based on their frequency properties we apply a cross correlation analysis to identify correlated coefficients that represent the effect of the atmospheric delay thus the correction to the unwrapped interferogram is obtained by down weighting the correlated coefficients during inverse wavelet transform we test this approach on real and synthetic data sets that are generated over the san francisco bay area we find that even in the presence of tectonic signals this method is able to reduce the correlated component of the atmospheric delay by up to 75 and improves the signal in areas of high relief the remaining part is most likely due to 3d heterogeneities of the atmosphere and can be reduced by integrating temporal information or using complementary observations or models of atmospheric delay

volume strain within the geysers geothermal field during the 1970s and 1980s the geysers geothermal region was rapidly developed as a site of geothermal power production the likelihood that this could cause significant strain within the reservoir with corresponding surface displacements led to a series of deformation monitoring surveys in 1973 1975 1977 and 1980 the geysers region was surveyed using first order class i spirit leveling in 1994 1995 and 1996 many of the leveling control monuments were resurveyed using high precision global positioning system receivers the two survey methods are reconciled using the geoid96 geoid model the displacements are inverted to determine volume strain within the reservoir for the period 1980 1994 peak volume strains in excess of 5x10 sup 4 are imaged there is an excellent correlation between the observed changes in reservoir steam pressures and the imaged volume strain if reservoir pressure changes are inducing volume strain then the reservoir quasi static bulk modulus k must be 4 6x10 sup 9 pa however seismic velocities indicate a much stiffer reservoir with k 3 4x10 sup 10 pa this apparent discrepancy is shown to be consistent with predicted frequency dependence in k for fractured and water saturated rock inversion of surface deformation data therefore appears to be a powerful method for imaging pressure change withinmore the body of the reservoir correlation between induced seismicity at the geysers and volume strain is observed however earthquake distribution does not appear to have a simple relationship with volume strain rate c 1999 american geophysical union less

fault slip distribution of the 1999 mw 7 1 hector mine california earthquake estimated from satellite radar and gps measurements we use a combination of satellite radar and gps data to estimate the slip distribution of the 1999 m w 7 1 hector mine earthquake a right lateral strikeslip earthquake that occurred on a northwest southeast striking fault in the southern california mojave desert the data include synthetic aperture radar interferograms insar from both ascending and descending orbits radar amplitude image offset fields sario for both ascending and descending azimuth directions and campaign gps observations from 55 stations provided by agnew et al 2002 we model the fault with nine segments derived from the field mapped fault rupture the sario data and aftershock locations we first estimate the dip of each fault segment as well as a single constant strike slip component across each segment resulting in an average dip of 83 to the northeast and slip of up to 5 6 m then we fix the optimal fault segment dip discretize the fault segments into 1 5 km 1 5 km patches and solve for the variable slip distribution using a nonnegative least squares method that includes an appropriate degree of smoothing our preferred solution has both right lateral strike slip and reverse faulting the estimated geodetic moment is 5 93 10 19 n m m w 7 1 similar to seismological estimates indicating that there are insignificant interseismic and postseismic deformation signals in the data we find strike slip displacements of up to 6 0 m and reverse faulting of up to 1 6 m with the maximum slip located just northwest of the epicenter most of the slip is concentrated northwest and south of the epicenter little slip is found on the northeastern branch of the fault the sario data and our modeling indicate that the amount and extent of surface fault rupture were underestimated in the field

on the impact of surface heterogeneity on a realistic convective boundary layer 1 turbulent interactions of momentum and scalars within the convective boundary layer cbl over a heterogeneous surface can have a strong influence on both local flow properties and regional weather and climate using realistic heterogeneous surface flux data as well as mean vertical soundings obtained from the soil moisture atmosphere coupling experiment 2002 smacex as boundary and initial conditions in a large eddy simulation les model this research attempts to further our understanding of the impact of surface heterogeneity on a growing cbl in a realistic environment on the basis of a newly proposed method a set of realizations precisely replicating the basic statistics mean and variance and cross correlation of surface flux boundary conditions relative to the actual fields at the smacex are used for a series of les experiments the impacts of heterogeneity on two aspects of the cbl are discussed in this study 1 the characteristic vertical profiles of cbl properties and 2 the vertical mixing scales of the cbl within the set of conditions examined in this study the potential temperature is more sensitive to the surface heterogeneity scale than to specific humidity and the variation of velocity both horizontal and vertical clearly reflects the impact of surface organization the vertical profile of the coefficient of variation calculated from the potential temperature field is introduced to identify the thermal blending height and a good agreement is obtained compared to the predicted values using formulations from the literature a commonly used formulation for the momentum blending height was found to inadequately represent the vertical mixing another stability dependent formulation combining both shear and convective characteristics is shown to provide more reasonable results

earth fissures and localized differential subsidence long linear tension cracks associated with declining groundwater levels at four sites in subsiding areas in south central arizona fremont valley california and las vegas valley nevada occur near points of maximum convex upward curvature in subsidence profiles oriented perpendicular to the cracks profiles are based on repeated precise vertical control surveys of lines of closely spaced bench marks association of these fissures with zones of localized differential subsidence indicates that linear earth fissures are caused by horizontal tensile strains probably resulting from localized differential compaction horizontal tensile strains across the fissures at the point of maximum convex upward curvature ranging from approximately 100 to 700 microstrains 0 01 to 0 07 per year were indicated based on measurements with a tape or electronic distance meter

the effect of land surface heterogeneity and background wind on shallow cumulus clouds and the transition to deeper convection abstractidealized large eddy simulations less with prescribed heterogeneous land surface heat fluxes are performed to study the impact of the heterogeneity length scale and background wind speed

a preferred scale for landscape forced mesoscale circulations 1 the regional atmospheric modeling system was used in two previous studies to simulate mesoscale circulations forced by surface heterogeneity in the central u s and amazonia in this work spectral analysis is used to compare the horizontal length scales of these simulated circulations with the scale of the surface heterogeneity for both cases the organized mesoscale circulations are confined within a preferred length scale range 10 20 km that is significantly different from the dominant length scale of the surface heterogeneity multiscale landscape patchiness in these two regions tend to produce eddies at a wide range of scales but the land atmosphere interaction processes act as a medium pass filter to select intermediate scale circulations this scale of response remains relatively unchanged despite significant day to day variations in the synoptic situation and the mean surface heat flux

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

land subsidence in houston texas measured by radar interferometry and constrained by extensometers 1 we present results from a radar interferometry study over the houston galveston texas gulf coast region from the nearly 60 potential interferograms considered an atmospheric artifact assessment is performed and a tractable set of interferograms selected for detailed processing and error analysis the subsequent interferogram time series spanning 1996 1998 is constrained by coincident extensometer data with root mean square error less than 2 5 mm the interferogram time series confirms that historic subsidence in east houston has stopped consistent with current groundwater use patterns broad scale subsidence bowls are observed in west and northwest houston where maximum subsidence rates are in excess of 2 and 4 cm yr 1 respectively linear interferogram phase signatures associated with approximately 1 cm of differential subsidence across faults including the long point fault in northwest houston are observed near the seabrook extensometer a hereto unidentified subsidence bowl with a maximum subsidence rate in excess of 3 cm yr 1 is revealed this study demonstrates that when used in conjunction with a set of traditional geodetic measurements radar interferometry can measure the spatial and temporal evolution of urban land subsidence within even the most challenging of environments

subsidence derived volumetric strain models for mapping extensional fissures and constraining rock mechanical properties in the san joaquin valley california large scale subsidence due to aquifer overdraft is an ongoing hazard in the san joaquin valley subsidence continues to cause damage to infrastructure and increases the risk of extensional fissures here we use insar derived vertical land motion vlm to model the volumetric strain rate due to groundwater storage change during the 2007 2010 drought in the san joaquin valley central valley california we then use this volumetric strain rate model to calculate surface tensile stress in order to predict regions that are at the highest risk for hazardous tensile surface fissures we find a maximum volumetric strain rate of 232 microstrain yr at a depth of 0 to 200 m in tulare and kings county california the highest risk of tensile fissure development occurs at the periphery of the largest subsiding zones particularly in tulare county and merced county finally we assume that subsidence is likely due to aquifer pressure change which is calculated using groundwater level changes observed at 300 wells during this drought we combine pressure data from selected wells with our volumetric strain maps to estimate the quasi static bulk modulus k a poroelastic parameter applicable when pressure change within the aquifer is inducing volumetric strain this parameter is reflective of a slow deformation process and is one to two orders of magnitude lower than typical values for the bulk modulus found using seismic velocity data the results of this study highlight the importance of large scale high resolution vlm measurements in evaluating aquifer system dynamics hazards associated with overdraft and in estimating important poroelastic parameters

preconsolidation stress of aquifer systems in areas of induced land subsidence aquifer systems in the eloy picacho area arizona the houston galveston area texas and the tulare wasco area and santa clara valley california appear to have been overconsolidated by an amount that ranged approximately from 1 6 to 6 2 bars 16 to 63 m of water before man began to withdraw groundwater from them the relation between land subsidence and water level decline in these areas consists of two linear segments in these areas subsidence per unit water level decline was approximately constant until water levels had declined an amount that ranged from 16 to 63 m when water levels declined past these values subsidence per unit water level decline increased to larger constant values although slow drainage from aquitards may have contributed to this response it is interpreted here to be caused primarily by natural overconsolidation of the compacting part of the aquifer system the water level decline at which the ratio of subsidence to unit water level decline changed indicates approximately the amount by which the preconsolidation stress exceeded the overburden stress on the aquifer system that existed before groundwater withdrawals began

relationships between compressional wave and shear wave velocities in clastic silicate rocks new velocity data in addition to literature data derived from sonic log seismic and laboratory measurements are analyzed for clastic silicate rocks these data demonstrate simple systematic relationships between compressional and shear wave velocities for water saturated clastic silicate rocks shear wave veloci ty is approximately linearly related to compressional wave velocity and the compressional to shear velocity ratio decreases with increasing compressional velocity laboratory data for dry sandstones indicate a nearly constant compressional to shear velocity ratio with rigidity approximately equal to bulk modulus ideal models for regular packings of spheres and cracked solids exhibit behavior similar to the observed water saturated and dry trends for dry rigidity equal to dry bulk modulus gassmann s equations predict velocities in close agreement with data from the water saturated

properties of a simulated convective boundary layer over inhomogeneous vegetation using a high resolution boundary layer model effects of heterogeneity over a mesoscale flat domain are investigated through a series of idealised model simulations in these simulations two different land surface types bare soil and vegetation are arranged in two different patterns it is found that the effect of heterogeneity remains significant with geostrophic winds of 10 m s 1 however when the geostrophic wind direction is perpendicular to the alignment of the surface heterogeneities with alignment here defined as the direction along the edges of a sequence of surface patches higher winds tend to weaken the coherent circulations caused by the surface heterogeneities the vertical winds generated by the mesoscale circulations associated with the surface heterogeneities are on the order of 0 5 cm s 1 when the geostrophic wind direction is perpendicular to the alignment of the surface heterogeneities over a three strip surface type the mesoscale pattern in horizontal velocity is also pronounced with significant fluctuations at the interfaces between two different surface patches the heights at which the heterogeneity effects on potential temperature and winds vanish are well above the convective boundary layer top and reach at least 3 3 zi under light winds but depend on the wind speed and directions as well as the orientation of surface heterogeneities finally the implications of the surface heterogeneity for initiation of deep convection have been explored for a surface consisting of two dimensional strips of alternating soil and vegetated surfaces aligned in the north south direction for this surface pattern the interaction between westerly background winds and the secondary circulation sets up conditions which favour the initiation of deep convection at the eastern downwind edge of the soil strip copyright 2010 royal meteorological society

time dependent model of aseismic slip on the central san andreas fault from insar time series and repeating earthquakes the central segment of san andreas fault csaf is characterized by a nearly continuous right lateral aseismic slip however observations of the creep rate obtained using small characteristically repeating earthquakes cres show pulses of creep along the csaf which may indicate spatially and temporally variable seismic hazard along the csaf therefore the goal of this study is to obtain a high resolution time dependent model of creep along the csaf to examine this hypothesis to this end we apply a time dependent creep modeling approach which combines interferometric synthetic aperture radar insar surface deformation time series and observations of fault creep obtained from cres the sar data set includes c band scenes acquired by the ers 2 and envisat satellites between 2003 and 2011 the resulting creep rate distribution implies a peak rate up to 32 mm yr along the central part of the csaf afterslip due to the 2004 parkfield earthquake on the southeastern segment of the csaf is also manifest in the model and there is clear evidence of creep pulsing along strike and depth of the csaf estimated annual rate of slip deficit accumulation is equivalent to a magnitude 5 6 5 7 earthquake taking advantage of the time dependence of our model we also refine the scaling relationship which associates the released seismic moment due to a cre event with the amount of creep on the fault surrounding the cre patches this study provides the first kinematic model of creep pulsing constrained using geodetic and seismic data which can enhance time dependent seismic hazard maps and improve earthquake operational forecast models

aquifer mechanical properties and decelerated compaction in tucson arizona in recent decades high groundwater extraction rates often coincident with periods of severe drought result in the widespread decline of water levels overexploitation of aquifers also causes land subsidence which poses a severe threat to infrastructure tucson arizona experiences land subsidence coupled with the depletion of groundwater a critical water resource for the desert city to understand the spatiotemporal evolution of land subsidence and its implications for aquifer properties we examine long time series of surface deformation and head levels measurements at extensometer stations indicate rapid compaction of fine grained material up to 8 5 mm yr from 1990 to 2005 which results in permanent storage volume losses up to 4 1 the analysis of densely populated sets of interferograms generated from envisat and radarsat c band acquisitions yields multitemporal maps of surface deformation at unprecedented resolution these maps reveal that subsidence significantly slows by the late 2000s corresponding with the implementation of artificial recharge efforts subsequent to groundwater level recovery we observe a brief 6 6 year interval of residual compaction suggesting a high vertical hydraulic conductivity which is then shown to be up to 9 8x10 4 m day we also estimate the average elastic and inelastic skeletal storage coefficients for the aquifer system to be 3 78x10 3 and 6 01x10 3 respectively insar shows deformation nearly ceases by 2015 likely reducing hazards associated with earth fissuring and infrastructure damage this study highlights successful outcomes of water management and conservation plans that preserve existing groundwater reserves and increase artificial recharge

seismic velocities for hydrate bearing sediments using weighted equation a weighted equation based on the three phase time average and wood equations is applied to derive a relationship between the compressional wave p wave velocity and the amount of hydrates filling the pore space the proposed theory predicts accurate p wave velocities of marine sediments in the porosity range of 40 80 and provides a practical means of estimating the amount of in situ hydrate using seismic velocity the shear s wave velocity is derived under the assumption that the p to s wave velocity ratio of the hydrated sediments is proportional to the weighted average of the p to s wave velocity ratios of the constituent components of the sediment in the case that all constituent components are known a weighted equation using multiphase time average and wood equations is possible however this study showed that a three phase equation with modified matrix velocity compensated for the clay content is sufficient to accurately predict the compressional wave velocities for the marine sediments this theory was applied to the laboratory measurements of the p and s wave velocities in permafrost samples to infer the amount of ice in the unconsolidated sediment the results are comparable to the results obtained by repeatedly applying the two phase wave scattering theory the theory predicts that the poisson s ratio of the hydrated sediments decreases as the hydrate concentration increases and the porosity decreases in consequence the amplitude versus offset avo data for the bottom simulating reflections may reveal positive negative or no avo anomalies depending on the concentration of hydrates in the sediments