shallow gravity driven flow in a poro elastic layer by combining biot s theory of poro elasticity with standard shallow layer scalings a theoretical model is developed to describe axisymmetric gravity driven flow through a shallow deformable porous medium motivated in part by observations of surface uplift around co2 sequestration sites the model is used to explore the injection of a dense fluid into a horizontal deformable porous layer that is initially saturated with another less dense fluid the layer lies between a rigid base and a flexible overburden both of which are impermeable as the injected fluid spreads under gravity the matrix deforms and the overburden lifts up the coupled model predicts the location of the injected fluid as it spreads and the resulting uplift of the overburden due to deformation of the solid matrix in general the uplift spreads diffusively far ahead of the injected fluid if fluid is injected with a constant flux and the medium is unbounded both the uplift and the injected fluid spread in a self similar fashion with the same similarity variable r t1 2 the asymptotic form of this spreading is established results from a series of laboratory experiments using polyacrylamide hydrogel particles to create a soft poro elastic material are compared qualitatively with the predictions of the model

toward mapping surface deformation in three dimensions using insar 1 one of the limitations of deformation measurements made with interferometric synthetic aperture radar insar is that an interferogram only measures one component of the surface deformation in the satellite s line of sight we investigate strategies for mapping surface deformation in three dimensions by using multiple interferograms with different imaging geometries geometries for both current and future missions are evaluated and their abilities to resolve the displacement vector are compared the north component is always the most difficult to determine using data from near polar orbiting satellites however a satellite with an inclination of about 60 120 would enable all three components to be well resolved we attempt to resolve the 3d displacements for the 23 october 2002 nenana mountain alaska earthquake the north component s error is much larger than the signal but proxies for eastward and vertical motion can be determined if the north component is assumed negligible inversions of hypothetical coseismic interferograms demonstrate that earthquake model parameters can be well recovered from two interferograms acquired on ascending and descending tracks

characteristics of the flank magnetopause themis observations the terrestrial magnetopause is the boundary that shields the earth s magnetosphere on one side from the shocked solar wind and its embedded interplanetary magnetic field on the other side in this paper we show observations from two of the time history of events and macroscales interactions during substorms themis satellites comparing dayside magnetopause crossings with flank crossings near the terminator macroscopic properties such as current sheet thickness motion and current density are examined for a large number of magnetopause crossings the results show that the flank magnetopause is typically thicker than the dayside magnetopause and has a lower current density consistent with earlier results from cluster observations we also find a persistent dawn dusk asymmetry with a thicker and more dynamic magnetopause at dawn than at dusk

geomechanical response to seasonal gas storage in depleted reservoirs a case study in the po river basin italy 1 underground gas storage ugs in depleted hydrocarbon reservoirs is a strategic practice to cope with the growing energy demand and occurs in many places in europe and north america in response to summer gas injection and winter gas withdrawal the reservoir expands and contracts essentially elastically as a major consequence of the fluid gas and water pore pressure fluctuations depending on a number of factors including the reservoir burial depth the difference between the largest and the smallest gas pore pressure and the geomechanical properties of the injected formation and the overburden the porous medium overlying the reservoir is subject to three dimensional deformation with the related cyclic motion of the land surface being both vertical and horizontal we present a methodology to evaluate the environmental impact of underground gas storage and sequestration from the geomechanical perspective particularly in relation to the ground surface displacements long term records of injected and removed gas volume and fluid pore pressure in the lombardia gas field northern italy are available together with multiyear detection of vertical and horizontal west east displacement of the land surface above the reservoir by an advanced permanent scatterer interferometric synthetic aperture radar psinsar analysis these data have been used to calibrate a 3 d fluid dynamic model and develop a 3 d transversally isotropic geomechanical model the latter has been successfully implemented and used to reproduce the vertical and horizontal cyclic displacements on the range of 8 10 mm and 6 8 mm respectively measured between 2003 and 2007 above the reservoir where a ugs program has been underway by stogit eni s p a since 1986 following a 5 year field production life because of the great economical interest to increase the working gas volume as much as possible the model addresses two ugs scenarios where the gas pore overpressure is pushed from the current 103 pi where pi is the gas pore pressure prior to the field development to 107 pi and 120 pi results of both scenarios show that there is a negligible impact on the ground surface with deformation gradients that remain well below the most restrictive admissible limits for the civil structures and infrastructures

warm ocean is eroding west antarctic ice sheet 1 satellite radar measurements show that ice shelves in pine island bay have thinned by up to 5 5 m yr 1 over the past decade the pattern of shelf thinning mirrors that of their grounded tributaries the pine island thwaites and smith glaciers and ocean currents on average 0 5 c warmer than freezing appear to be the source the synchronised imbalance of the inland glaciers is the result of reduced lateral and basal tractions at their termini and the drawdown of grounded ice shows that antarctica is more sensitive to changing climates than was previously considered

monitoring the fate of injected co2 using geodetic techniques author s vasco dw dixon th ferretti a samsonov sv abstract 2020 by the society of exploration geophysicists geodetic methods comprise one class of geophysical data that are sensitive to changes in effective pressure within operating reservoirs albeit indirectly through induced deformation geodetic observations which have observation intervals that vary from seconds to days weeks or months generally provide more frequent sampling compared to existing geophysical methodologies such as seismic time lapse monitoring which typically invoke repeat times of months to years these differences in sampling intervals are primarily due to the extensive effort and hence cost of conducting geophysical field operations which often precludes executing a large number of surveys satellite based interferometric synthetic aperture radar insar is cost effective and used in many applications including monitoring the injection of carbon dioxide co2 for both long term storage and enhanced oil production an application to the geologic sequestration of co2 in algeria revealed northwest migration along a fault fracture zone intersected by the injection well a study in a texas field demonstrated that enhanced oil recovery utilizing co2 leads to observable surface deformation that may be used to characterize the sequestered co2 and to estimate the pressure changes within the reservoir induced by injection and production

time dependent brittle creep in darley dale sandstone 1 the characterization of time dependent brittle rock deformation is fundamental to understanding the long term evolution and dynamics of the earth s crust the chemical influence of pore water promotes time dependent deformation through stress corrosion cracking that allows rocks to deform at stresses far below their short term failure strength here we report results from a study of time dependent brittle creep in water saturated samples of darley dale sandstone initial porosity 13 under triaxial stress conditions results from conventional creep experiments show that axial strain rate is heavily dependent on the applied differential stress a reduction of only 10 in differential stress results in a decrease in strain rate of more than two orders of magnitude however natural sample variability means that multiple experiments must be performed to yield consistent results hence we also demonstrate that the use of stress stepping creep experiments can successfully overcome this issue we have used the stress stepping technique to investigate the influence of confining pressure at effective confining pressures of 10 30 and 50 mpa while maintaining a constant 20 mpa pore fluid pressure our results demonstrate that the stress corrosion process appears to be significantly inhibited at higher effective pressures with the creep strain rate reduced by multiple orders of magnitude the influence of doubling the pore fluid pressure however while maintaining a constant effective confining pressure is shown to influence the rate of stress corrosion within the range expected from sample variability we discuss these results in the context of microstructural analysis acoustic emission hypocenter locations and fits to proposed macroscopic creep laws

surface displacements and source parameters of the 2003 bam iran earthquake from envisat advanced synthetic aperture radar imagery 1 the mw 6 6 26 december 2003 bam iran earthquake was one of the first earthquakes for which envisat advanced synthetic aperture radar asar data were available using interferograms and azimuth offsets from ascending and descending tracks we construct a three dimensional displacement field of the deformation due to the earthquake elastic dislocation modeling shows that the observed deformation pattern cannot be explained by slip on a single planar fault which significantly underestimates eastward and upward motions se of bam we find that the deformation pattern observed can be best explained by slip on two subparallel faults eighty five percent of moment release occurred on a previously unknown strike slip fault running into the center of bam with peak slip of over 2 m occurring at a depth of 5 km the remainder occurred as a combination of strike slip and thrusting motion on a southward extension of the previously mapped bam fault 5 km to the east

probing the mechanical properties of seismically active crust with space geodesy study of the coseismic deformation due to the 1992 mw7 3 landers southern california earthquake 1 the coseismic deformation due to the 1992 m w 7 3 landers earthquake southern california is investigated using synthetic aperture radar sar and global positioning system gps measurements the ers 1 satellite data from the ascending and descending orbits are used to generate contiguous maps of three orthogonal components east north up of the coseismic surface displacement field the coseismic displacement field exhibits symmetries with respect to the rupture plane that are suggestive of a linear relationship between stress and strain in the crust interferometric synthetic aperture radar insar data show small scale deformation on nearby faults of the eastern california shear zone some of these faults in particular the calico rodman and pinto mountain faults were also subsequently strained by the 1999 m w 7 1 hector mine earthquake i test the hypothesis that the anomalous fault strain represents essentially an elastic response of kilometer scale compliant fault zones to stressing by nearby earthquakes fialko et al 2002 the coseismic stress perturbations due to the landers earthquake are computed using a slip model derived from inversions of the insar and gps data calculations are performed for both homogeneous and transversely isotropic half space models the compliant zone model that best explains the deformation on the calico and pinto mountain faults due to the hector mine earthquake successfully predicts the coseismic displacements on these faults induced by the landers earthquake deformation on the calico and pinto mountain faults implies about a factor of 2 reduction in the effective shear modulus within the similar to 2 km wide fault zones the depth extent of the low rigidity zones is poorly constrained but is likely in excess of a few kilometers the same type of structure is able to explain high gradients in the radar line of sight displacements observed on other faults adjacent to the landers rupture in particular the lenwood fault north of the soggy lake has likely experienced a few centimeters of left lateral motion across 1 km wide compliant fault zone having the rigidity reduction of more than a factor of 2 the inferred compliant fault zones are interpreted to be a result of extensive damage due to past earthquakes

time dependent land uplift and subsidence in the santa clara valley california from a large interferometric synthetic aperture radar data set 1 we invert 115 differential interferograms derived from 47 synthetic aperture radar sar scenes for a time dependent deformation signal in the santa clara valley california the time dependent deformation is calculated by performing a linear inversion that solves for the incremental range change between sar scene acquisitions a nonlinear range change signal is extracted from the ers insar data without imposing a model of the expected deformation in the santa clara valley cumulative land uplift is observed during the period from 1992 to 2000 with a maximum uplift of 41 18 mm centered north of sunnyvale uplift is also observed east of san jose seasonal uplift and subsidence dominate west of the silver creek fault near san jose with a maximum peak to trough amplitude of 35 mm the pattern of seasonal versus long term uplift provides constraints on the spatial and temporal characteristics of water bearing units within the aquifer the silver creek fault partitions the uplift behavior of the basin suggesting that it acts as a hydrologic barrier to groundwater flow while no tectonic creep is observed along the fault the development of a low permeability barrier that bisects the alluvium suggests that the fault has been active since the deposition of quaternary units

an apparent shear zone trending north northwest across the mojave desert into owens valley eastern california strain rates measured at four geodetic networks in eastern california situated between northern owens valley and transverse ranges along a small circle drawn about the pacific north america pole of rotation are remarkably consistent each exhibits 0 14 mu rad yr simple right lateral engineering shear strain accumulation across the local vertical plane tangent to the small circle local faults e g owens valley garlock helendale traversing these networks are not as closely aligned with the vertical planes of maximum shear strain accumulation as is the local tangent to the small circle a fifth network slightly east of the small circle shows no significant strain accumulation thus a shear zone trending n35 degree w from near the eastern end of the big bend of the san andreas fault to northern owens valley is indicated by these data this corresponds to the eastern california shear zone proposed on geological evidence by dokka and travis the shear zone carries approximately 8 mm yr of the pacific north america relative plate motion from the san andreas fault north northwest across the mojave desert into owens valley and the northern basin and range province the shear zone observed at the surface may be a manifestation of a through going subcrustal fault

on the use of quasi static deformation to understand reservoir fluid flow deformation above a producing reservoir provides a valuable source of information concerning fluid flow and flow properties quasi static deformation occurs when the displacements are so slow that we may neglect inertial terms in the equations of motion we present a method for inferring reservoir volume change and flow properties such as permeability from observations of quasi static deformation such displacements may represent surface deformation such as tilt leveling interferometric synthetic aperture radar insar or bathymetry observations or subsurface deformation as inferred from time lapse seismic surveys in our approach the equation for fluid flow in a deforming reservoir provides a mapping from estimated fractional volume changes to reservoir permeability variations if the reservoir behaves poroelastically over the interval of interest all the steps in this approach are linear thus the inference of reservoir permeability from deformation data becomes a linear inverse problem in an application to the wilmington oil field in california we find that observed surface displacements obtained by leveling and insar are indeed compatible with measured reservoir volume fluxes we find that the permeability variations in certain layers coincide with fault block boundaries suggesting that in some cases faults are controlling fluid flow at depth

radar interferometry and its application to changes in the earth s surface geophysical applications of radar interferometry to measure changes in the earth s surface have exploded in the early 1990s this new geodetic technique calculates the interference pattern caused by the difference in phase between two images acquired by a spaceborne synthetic aperture radar at two distinct times the resulting interferogram is a contour map of the change in distance between the ground and the radar instrument these maps provide an unsurpassed spatial sampling density 100 pixels km 2 a competitive precision 1 cm and a useful observation cadence 1 pass month 1 they record movements in the crust perturbations in the atmosphere dielectric modifications in the soil and relief in the topography they are also sensitive to technical effects such as relative variations in the radar s trajectory or variations in its frequency standard we describe how all these phenomena contribute to an interferogram then a practical summary explains the techniques for calculating and manipulating interferograms from various radar instruments including the four satellites currently in orbit ers 1 ers 2 jers 1 and radarsat the next chapter suggests some guidelines for interpreting an interferogram as a geophysical measurement respecting the limits of the technique assessing its uncertainty recognizing artifacts and discriminating different types of signal we then review the geophysical applications published to date most of which study deformation related to earthquakes volcanoes and glaciers using ers 1 data we also show examples of monitoring natural hazards and environmental alterations related to landslides subsidence and agriculture in addition we consider subtler geophysical signals such as postseismic relaxation tidal loading of coastal areas and interseismic strain accumulation we conclude with our perspectives on the future of radar interferometry the objective of the review is for the reader to develop the physical understanding necessary to calculate an interferogram and the geophysical intuition necessary to interpret it

influence of temperature on brittle creep in sandstones the characterization of time dependent brittle creep promoted by chemically active pore fluids is fundamental to our understanding of the long term evolution and dynamics of the earth s crust here we report results from a study of the influence of temperature on both short term strength and time dependent brittle creep in three sandstones under triaxial stress conditions we show that an increase in temperature from 20 degrees to 75 degrees c significantly enhances stress corrosion cracking in all three sandstones leading to 1 a systematic reduction in strength during constant strain rate experiments and 2 an increase by several orders of magnitude in brittle creep strain rates during stress stepping creep experiments we also show that a conventional creep experiment performed at 75 degrees c exhibits a qualitatively similar three stage brittle creep curve as that observed at ambient temperature extrapolation of our results suggests that temperature is likely to be the dominant influence on the evolution of creep strain rate with depth in the shallow crust citation heap m j p baud and p g meredith 2009 influence of temperature on brittle creep in sandstones geophys res lett 36 l19305 doi 10 1029 2009gl039373

synthetic aperture radar interferometry to measure earth s surface topography and its deformation synthetic aperture radar interferometry insar from earth orbiting spacecraft provides a new tool to map global topography and deformation of the earth s surface radar images taken from slightly different viewing directions allow the construction of digital elevation models of meter scale accuracy these data sets aid in the analysis and interpretation of tectonic and volcanic landscapes if the earth s surface deformed between two radar image acquisitions a map of the surface dis placement with tens of meters resolution and subcentimeter accuracy can be con structed this review gives a basic overview of insar for earth scientists and presents a selection of geologic applications that demonstrate the unique capabilities of insar for mapping the topography and deformation of the earth

co seismic slip from the 1995 july 30 mw 8 1 antofagasta chile earthquake as constrained by insar and gps observations summary we analyse radar interferometric and gps observations of the displacement field from the 1995 july 30 mw 8 1 antofagasta chile earthquake and invert for the distribution of slip along the co seismic fault plane using a fixed fault geometry we compare the use of singular value decomposition and constrained linear inversion to invert for the slip distribution and find that the latter approach is better resolved and more physically reasonable separate inversions using only gps data only insar data from descending orbits and insar data from both ascending and descending orbits without the gps data illustrate the complimentary nature of gps and the presently available insar data the gps data resolve slip near gps benchmarks well while the insar provides greater spatial sampling the combination of ascending and descending insar data contributes greatly to the ability of insar to resolve the slip model thereby emphasizing the need to acquire this data for future earthquakes the rake distribution of slip and seismic moment of our preferred model are generally consistent with previous seismic and geodetic inversions although significant differences do exist gps data projected in the radar line of sight los and corresponding insar pixels have a root mean square rms difference of about 3 cm comparison of our predictions of vertical displacement and observed uplift from corraline algae have an rms of 10 cm our inversion and previous results reveal that the location of slip might be influenced by the 1987 mw 7 5 event our analysis further reveals that the 1995 slip distribution was affected by a 1988 mw 7 2 event and might have influenced a 1998 mw 7 0 earthquake that occurred downdip of the 1995 rupture our slip inversion reveals a potential change in mechanism in the southern portion of the rupture consistent with seismic results predictions of the satellite los displacement from a seismic inversion and a joint seismic gps inversion do not compare favourably with the insar observations

on the accuracy of topographic residuals retrieved by mtinsar topographic residuals in differential interferometric synthetic aperture radar insar measurements are mainly caused by inaccurate external digital elevation model dem accurate separation of the phase component contributed by topographic residuals plays an important role in the retrieval of deformation time series from insar observations even though the residuals can be modeled and estimated in the framework of multitemporal sar interferometry mtinsar it is not clear what an optimal processing strategy is and how accurate the estimation can reach we analyze here the factors that affect the accuracy of the retrieved dem residuals by applying four commonly used mtinsar methods in a series of simulated scenarios the results indicate that besides the quality of interferometric observations the thresholds of spatial and temporal baselines the diversity of spatial baseline lengths the connectivity of interferogram network and improper deformation model also fluctuate the accuracy of the retrieved topographic residuals according to these affecting factors this paper sheds light on an optimal approach to reliably retrieve accurate topographic residuals under mtinsar framework

fluid pressure arrival time tomography estimation and assessment in the presence of inequality constraints with an application to production at the krechba field algeria deformation in the overburden proves useful in deducing spatial and temporal changes in the volume of a producing reservoir based on these changes we have estimated diffusive traveltimes associated with the transient flow due to production and then as the solution of a linear inverse problem the effective permeability of the reservoir an advantage of the approach based on traveltimes as opposed to one based on the amplitude of surface deformation is that it is much less sensitive to the exact geomechanical properties of the reservoir and overburden inequalities constrain the inversion under the assumption that the fluid production only results in pore volume decreases within the reservoir the formulation has been applied to satellite based estimates of deformation in the material overlying a thin gas production zone at the krechba field in algeria the peak displacement after three years of gas production is found to be approximately 0 5 cm overlying the eastern margin of the anticlinal structure defining the gas field using data from 15 irregularly spaced images of range change we have calculated the diffusive traveltimes associated with the startup of a gas production well the inequality constraints were incorporated into the estimates of model parameter resolution and covariance improving the resolution by roughly 30 to 40

utilizing the onset of time lapse changes a robust basis for reservoir monitoring and characterization time lapse monitoring is useful for imaging changes in geophysical attributes due to fluid flow in trying to use time lapse data for reservoir characterization difficulties often arise when relating changes in geophysical observations to changes in fluid saturation and pressure as an alternative approach for reservoir monitoring and characterization we introduce the idea of an onset time the time at which a measured quantity such as a seismic traveltime or a reflection amplitude begins to deviate from its background value we illustrate the idea and demonstrate its utility through the consideration of traveltimes recorded by the continuous active source seismic monitoring system at the frio pilot site near houston texas the system which transmits an elastic wave every 15 min is used to monitor the movement of carbon dioxide injected into a permeable sand formation from these data we can estimate the onset of changes in seismic traveltimes to six receivers in an adjacent borehole numerical simulation and synthetic tests indicate that the onset times are not very sensitive to the method used to compute the effective fluid bulk modulus and correspondingly the seismic compressional velocity rather the onset times are strongly influenced by saturation changes within the formation specifically by the break through time of the injected fluid phase by means of an iterative inversion algorithm we use the onset times to estimate permeability variations between the boreholes at the frio pilot site the authors 2014 published by oxford university press on behalf of the royal astronomical society

mapping surface deformation in open pit iron mines of carajas province amazon region using an integrated sar analysis abstract the carajas mineral province encompasses the world s largest iron reserves with excavation carried out through open pit benching mining operations in the area have significant areas of rock mass movements and surface displacements that potentially lead to slope instabilities with risks to personnel equipment and production instabilities can be expected due to deep excavations in rock masses of low geomechanical quality blasting practices and heavy precipitation in this paper ground instabilities are monitored through an integrated sar analysis based on a data stack of 33 terrasar x images this approach was designed to monitor distinct displacement regimes ranging from small to high deformation rates and to map surface changes based on variations of radar reflectivity results were compared with field information total station prisms ground based radar geological and geomechanical maps and the approach showed to be effective for monitoring ground deformation in the region due to its capabilities synoptic view high accuracy dense grid sampling the complementary use of space based sar with field monitoring systems proved to be strategic for operational mining planning and risk assessment in this challenging environment

satellite based measurements of surface deformation reveal fluid flow associated with the geological storage of carbon dioxide interferometric synthetic aperture radar insar gathered over the in salah co sub 2 storage project in algeria provides an early indication that satellite based geodetic methods can be effective in monitoring the geological storage of carbon dioxide an injected volume of 3 million tons of carbon dioxide from one of the first large scale carbon sequestration efforts produces a measurable surface displacement of approximately 5 mm year using geophysical inverse techniques we are able to infer flow within the reservoir layer and within a seismically detected fracture fault zone intersecting the reservoir we find that if we use the best available elastic earth model the fluid flow need only occur in the vicinity of the reservoir layer however flow associated with the injection of the carbon dioxide does appear to extend several kilometers laterally within the reservoir following the fracture fault zone

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

interferometric estimation of three dimensional ice flow using ascending and descending passes satellite radar interferometry sri provides an important new tool for determining ice flow velocity interferometric measurements made from a single track direction are sensitive only to a single component of the three component velocity vector observations from along three different track directions would allow the full velocity vector to be determined a north south looking synthetic aperture radar sar could provide these observations over large portions of the globe but not over large areas of the polar ice sheets the authors develop and demonstrate a technique that allows the three component velocity vector to be estimated from data acquired along two track directions ascending and descending under a surface parallel flow assumption this technique requires that there are accurate estimates of the surface slope which are also determined interferometrically to demonstrate the technique the authors estimate the three component velocity field for the ryder glacier greenland their results are promising although they do not have yet ground truth data with which to determine the accuracy of their estimates

inversion of gps data for spatially variable slip rate on the san andreas fault near parkfield ca we analyze gps data collected from 1991 1998 at 35 sites near the parkeld segment of the san andreas fault inverting the resultant site velocities for the distri bution of interseismic slip rate on the san andreas reveals an area of low slip rate on thefault extendingfrom between middle mountain and carr hill to southeast of gold hill this slip rate patternis similar to thatfoundbyharris and segall 1987 using trilateration data collected between 1966 and 1984 we infer a deep slip rate 33 mm yr and depth of the transition between seismogenic and non seismogenic slip 14km thatagree betterwithindependentgeologic ev idence than those found in the 1987 study in contrast to harris and segall 1987 wendnoevidenceoffault normal contraction

circumferential strain behavior during creep tests of brittle rocks abstract creep tests were carried out on inada granite under confining pressure and on dry and wet specimens of kamisunagawa sandstone distinctive points qa the point where the axial strain rate reaches a minimum qc the point where the magnitude of circumferential strain rate reaches a minimum and rc the point where the magnitude of circumferential strain acceleration begins to increase were defined dependency of the strain values at the distinctive points on creep stress confining pressure and water presence was examined circumferential strain at qc or rc was not affected by creep stress for both rocks peak load points were observed in reloading stress strain curves when reloading was carried out before qc for kamisunagawa sandstone circumferential strain values at peak load during reloading coincided with critical extensile strain which is defined as circumferential strain value at peak load during constant strain rate tests and is insensitive to confining pressure water presence and anisotropy although slightly affected by strain rate load increased slightly or did not increase when reloading was carried out after rc for both rocks rc in creep tests scattered around unloading stress strain curves from peak load during constant strain rate tests for kamisunagawa sandstone these observations suggest that qc and rc in creep tests are closely related to the peak load points during constant strain rate tests circumferential strain would be used as a condition insensitive damage indicator of rock in creep tests as well as in constant strain rate tests

characteristics of the flank magnetopause cluster observations the magnetopause is a current sheet forming the boundary between the geomagnetic field on one side and the shocked solar wind on the other side this paper discusses properties of the low latitude dawn and dusk flanks of the magnetopause the reported results are based on a large number of measurements obtained by the cluster satellites during magnetopause traversals using a combination of single spacecraft and multispacecraft techniques we calculated macroscopic features such as thickness location and motion of the magnetopause the results show that the typical flank magnetopause is significantly thicker than the dayside magnetopause and also possesses a pronounced and persistent dawn dusk asymmetry thicknesses vary from 150 to 5000 km with an median thickness of around 1400 km at dawn and around 1150 km at dusk current densities are on average higher on dusk suggesting that the total current at dawn and dusk are similar solar wind conditions and the interplanetary magnetic field cannot fully explain the observed dawn dusk asymmetry for a number of crossings we were also able to derive detailed current density profiles the profiles show that the magnetopause often consists of two or more adjacent current sheets each current sheet typically several ion gyroradii thick and often with different current direction this demonstrates that the flank magnetopause has a structure that is more complex than the thin one dimensional current sheet described by a chapman ferraro layer

monitoring the geologic storage of carbon dioxide using multicomponent sar interferometry monitoring the geologic storage of carbon dioxide using multi component sar interferometry alessio rucci 1 d w vasco 2 and fabrizio novali 1 tele rilevamento europa milano italy berkeley laboratory university of california berkeley california 94720 summary combining interferometric synthetic aperture radar insar data from ascending and de scending orbits we estimate both quasi vertical and quasi east west displacements for a region in central algeria an area encompassing an active large scale carbon dioxide stor age project the in salah gas storage project the surface deformation associated with the injection into three horizontal wells is clearly visible in the insar estimates we find that the addition of the quasi horizontal displacement data enables us to discriminate between source models producing similar vertical displacements in particular predictions from a model consisting of a distribution of volume changes restricted to the reservoir depth interval satisfies the quasi vertical data but does not match the quasi east west displace ment data however aperture changes on sub vertical damage zones intersecting each of the injection wells give rise to displacements matching both the quasi east west and vertical components in all cases we can match the observations with the most significant volume and aperture changes in regions immediately surrounding the injection wells key words interferometry deformation inverse problem

2 5 d surface deformation of m6 1 earthquake near mt iwate detected by sar interferometry the two dimensional displacement vector field on the earth s surface associated with a large earthquake near iwate volcano in japan was mapped by combining satellite radar interferometry images from two different track directions the displacement reveals not only large main ruptures but details of many small faults movement of aftershocks and volcanic earthquakes the displacements of the aftershock faults coincide with a stress field reorganized by the main earthquake that accelerated the aftershock fault movements the displacements mimic the topography suggesting that repeated movements of the same faults in the quaternary have led to the presently existing topography

rapid subsidence over oil fields measured by sar interferometry the lost hills and belridge oilfields are in the san joaquin valley california the major oil reservoir is high porosity and low permeability diatomite extraction of large volumes from shallow depths causes reduction in pore pressure and subsequent compaction forming a surface subsidence bowl we measure this subsidence from space using interferometric analysis of sar synthetic aperture radar data collected by the european space agency remote sensing satellites ers 1 and ers 2 maximum subsidence rates are as high as 40 mm in 35 days or 400 mm yr measured from interferograms with time separations ranging from one day to 26 months the 8 and 26 month interferograms contain areas where the subsidence gradient exceeds the measurement possible with ers sar but shows increased detail in areas of less rapid subsidence synoptic mapping of subsidence distribution from satellite data powerfully complements ground based techniques permits measurements where access is difficult and aids identification of underlying causes

comparison of various inversion techniques as applied to the determination of a geophysical deformation model for the 1983 borah peak earthquake abstract a number of techniques are employed to overcome nonuniqueness and instability inherent in linear inverse problems to test the factors that enter into the selection of an inversion technique for fault slip distribution we used a penalty function with smoothness pf s a damped least squares method dls damped least squares method with a positivity constraint dls p and a penalty function with smoothness and a positivity constraint pf s p for inverting the elevation changes for slip associated with the 1983 borah peak earthquake unlike solving an ill posed inverse problem using a gradient technique ward and barrientos 1986 we have restored the well posed character between the elevation changes and normal slip distribution studies showed that the constraints based on sound understanding of the physical nature of the problem are crucial in the derivation of a meaningful solution and dictates primarily the selection of a particular inversion technique all available geological and geophysical information were used to determine a geophysical deformation model for the earthquake it is suggested that the pf s p solution for a fault length of 75 km is the preferred model the long wavelength features in the estimated slip distribution are similar to those obtained by ward and barrientos 1986 whereas the shorter wavelength features differ between two solutions the fault dips 49 to the southwest the slipped zones deepen from the surface at the northwest to about 20 km downdip depth at the southeast the fault extends to the southeast beyond the epicenter of the mainshock it is also shown that only the long wavelength features of the slip distribution are well resolved the resolution is better at shallower levels than at deeper levels the resolution deteriorates when the deformation sources are away from the leveling lines smoothness constraints provide better resolution than damping does at depth the addition of a positivity constraint significantly improves the model resolution

using surface deformation to image reservoir dynamics the inversion of surface deformation data such as tilt displacement or strain provides a noninvasive method for monitoring subsurface volume change reservoir volume change is related directly to processes such as pressure variations induced by injection and withdrawal the inversion procedure is illustrated by an application to tiltmeter data from the hijiori test site in japan an inversion of surface tilt data allows us to image flow processes in a fractured granodiorite approximately 650 barrels of water injected 2 km below the surface produces a peak surface tilt of the order of 0 8 microradians we find that the pattern of volume change in the granodiorite is very asymmetrical elongated in a north northwesterly direction and the maximum volume change is offset by more than 0 7 km to the east of the pumping well the inversion of a suite of leveling data from the wilmington oil field in long beach california images large scale reservoir volume changes in 12 one to two year increments from 1

poroelasticity efficient modeling of strongly coupled slow deformation processes in a multilayered half space we present a fast powerful numerical scheme to compute poroelastic solutions for excess pore pressure and displacements in a multilayered half space the solutions are based on the mirror image technique and use an extension of haskell s propagator method they can be applied to assess in situ formation parameters from the surface deformation field when fluids are injected into or extracted from a subsurface reservoir or they can be used to simulate changes in pore fluid pressure resulting from matrix displacements induced by an earthquake the performance of the numerical scheme is tested through comparison with observations of the surface deformation as recorded by tiltmeters in the vicinity of an iteratively pumped well modeling of near surface tilt data around a productive well is useful in constraining hydraulic diffusivity in the layered subsurface

subcritical creep compaction of quartz sand at diagenetic conditions effects of water and grain size 1 compactional creep was measured for aggregates of quartz sand that were subjected to an effective pressure of 34 5 mpa and temperature of 150 c for times up to 6 months the effects of grain size and water on creep were determined by loading quartz aggregates of 255 60 130 18 and 35 12 m grain size under nominally dry water vapor static liquid water and flowing water conditions all aggregates displayed transient decelerating creep volume strain rates as low as 2 10 10 s 1 were achieved volume strain rate increases systematically with decrease in grain size and increase in exposure to water at comparable strain or time despite the fact that the effective pressure applied was far less than the critical pressures for short term cataclastic compaction of the quartz aggregates grain scale microstructures indicate that the underlying mechanism of creep is crack growth creep rates are explained by subcritical crack growth as governed by water silicate reactions at crack tips controlled by access of water at dry and vapor conditions and solute chemistry under static and flowing liquid water conditions extrapolation of the experimental results to natural compaction of quartz sand during burial and diagenesis over times of tens of millions of years indicates that porosity loss through subcritical cracking and grain rearrangement of medium grained porous wet quartz sands can reach 10

the use of satellite based radar interferometry to monitor production activity at the cold lake heavy oil field alberta canada the cold lake heavy oil field has been studied by geoscientists for more than 30 years and has been producing bitumen for 20 years using the cyclic steam stimulation css process future development options can be improved by the resolution of steam movement and the avoidance of areas of faults and fractures to locate these features remote sensing has recently been investigated as a cheaper alternative to four dimensional seismic surveys advances in satellite and radar technology have made it possible to measure very small movements of the earth s surface found in earthquake zones and volcanic regions the technique uses synthetic aperture radar interferometry insar allowing the measurement of deformation using a vertical resolution in optimal conditions on the order of millimeters between repeat acquisitions this accuracy has only been achieved over dry areas without significant vegetation growth at the cold lake oil field it has been reported previously that the injection of steam to mobilize the bitumen causes the pump jacks to heave and subside by as much as 30 cm during the first steam cycle the present project was instigated to determine if such small positive and negative vertical movements could be resolved over the field data from three satellite radar sensors were selected ers european remote sensing satellite jers japanese remote sensing satellite and radarsat the canadian radar satellite the present article has provided the first results of repeat pass insar using jers sar data for the land subsidence application area contrary to the widespread belief that this technology can only be used for dry areas we show that accurate results on the order of a centimeter in resolution can be obtained in a forested area such as cold lake using the jers l band spaceborne sar system begin page 782