hydrologically induced slope deformations detected by gps and clinometric surveys in the cansiglio plateau southern alps abstract changes in groundwater or surface water level may cause observable deformation of the drainage basins in different ways we describe an active slope deformation monitored with gps and tiltmeter stations in a karstic limestone plateau in southeastern alps cansiglio plateau the observed transient gps deformation clearly correlates with the rainfall both gps and tiltmeter equipments react instantly to heavy rains displaying abrupt offsets but with different time constants demonstrating the response to different catchment volumes the gps movement is mostly confined in the horizontal plane ssw direction showing a systematic tendency to rebound in the weeks following the rain four gps stations concur to define a coherent deformation pattern of a wide area 12 5 km 2 concerning the whole southeastern slope of the plateau the plateau expands and rebounds radially after rain by an amount up to a few centimeters and causing only small vertical deformation the effect is largest where karstic features are mostly developed at the margin of the plateau where a thick succession of cretaceous peritidal carbonates faces the venetian lowland a couple of tiltmeters installed in a cave at the top of the plateau detect a much faster deformation that has the tendency to rebound in less than 6 h the correlation to rainfall is less straightforward and shows a more complex behavior during rainy weather the different responses demonstrate a fast hydrologic flow in the more permeable epikarst for the tiltmeters drained by open fractures and fissures in the neighborhood of the cave and a rapid tensile dislocation of the bedrock measured at the gps stations that affect the whole slope of the mountain in the days following the rain both tiltmeter and gps data show a tendency to retrieve the displacement which is consistent with the phreatic discharge curve we propose that hydrologically active fractures recharged by rainfall are the most likely features capable to induce the observed strain variations

land subsidence in mashhad valley northeast iran results from insar levelling and gps summary significant land subsidence was recently recognized in northeast iran near the city of mashhad precise levelling surveys performed in 1995 2002 and 2005 indicate as much as 90 cm of subsidence during the 1995 2005 period continuous gps monitoring approximately 8 km northwest of mashhad city shows more than 20 cm yr 1 subsidence between 2005 and 2006 we use interferometric synthetic aperture radar insar measurements to detect the temporal and spatial pattern of this surface deformation 13 interferograms from 10 c band sar images acquired by the enivsat satellite from 2003 to 2005 are analysed and stacked our insar mapping suggests that subsidence occurs within a northwest southeast elongated ellipticshaped bowl along the axis of the mashhad valley with a peak amplitude of 28 30 cm yr 1 for the 2003 2005 time period the insar data indicate that approximately 70 km 2 in the valley floor including the northwestern part of mashhad city subsided at a rate exceeding 15 cm yr 1 between 2003 and 2005 and that the subsidence area is structurally controlled by the trends of quaternary faults cutting the valley floor analysis of piezometric records suggests that subsidence likely results from extensive overdrafting of the aquifer system in the valley that has caused as much as 65 m of water table decline since 1960s

space geodetic observation of expansion of the san gabriel valley california aquifer system during heavy rainfall in winter 2004 2005 1 starting early in 2005 the positions of gps stations in the san gabriel valley region of southern california showed statistically significant departures from their previous behavior station long moved up by about 47 mm and nearby stations moved away from long by about 10 mm these changes began during an extremely rainy season in southern california and coincided with a 16 m increase in water level at a nearby well in baldwin park and a regional uplift detected by interferometric synthetic aperture radar no equivalent signals were seen in gps station position time series elsewhere in southern california our preferred explanation supported by the timing and by a hydrologic simulation is deformation due to recharging of aquifers after near record rainfall in 2004 2005 we cannot rule out an aseismic slip event but we consider such an event unlikely because it requires slip on multiple faults and predicts other signals that are not observed

transient signal detection using gps measurements transient inflation at akutan volcano alaska during early 2008 1 continuous global positioning system gps networks record station position changes with millimeter level accuracy and have revealed transient deformations on various spatial and temporal scales however the transient deformation may not be easily identified from the position time series because of the large number of sites in a network low signal to noise ratios snr and correlated noise in space and time here we apply state estimation and principal component analysis to the daily gps position time series measured in alaska sites of the plate boundary observatory network our algorithm detects a transient signal whose maximum displacement is 9 mm in horizontal and 11 mm in vertical that occurred at akutan volcano during the first half of 2008 a simple mogi source inversion suggests inflation at shallow depth 3 9 km beneath the volcano although the detection was not easy because the signal was aseismic non eruptive and weak not apparent in raw daily time series our detection method improves the snr and therefore provides higher resolution for detecting the transient signal

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

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

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

postearthquake relaxation evidence for laterally variable viscoelastic structure and water content in the southern california mantle i reexamine the lower crust and mantle relaxation following two large events in the mojave desert the 1992 m7 3 landers and 1999 m7 1 hector mine california earthquakes time series from continuous gps sites out to 300 km from the ruptures are used to constrain models of postseismic relaxation crustal motions in the mojave desert region are elevated above background for several years following each event to account for broadscale relaxation of the lower crust and mantle the burgers body model is employed involving transient and steady state viscosities joint afterslip postseismic relaxation modeling of the gps time series up to one decade following the hector mine earthquake reveals a significant rheological contrast between a northwest trending southwest domain that envelopes the san andreas fault system and western mojave desert and an adjacent northeast domain that envelopes the landers and hector mine rupture areas in the central mojave desert the steady state viscosity of the northeast domain mantle asthenosphere is inferred to be 4 times greater than that of the southwest domain this pattern is counter to that expected for regional heat flow which is higher in the northeast domain but it is explicable by means of a nonlinear rheology that includes dependence on both strain rate and water concentration i infer that the southwest domain mantle has a relatively low steady state viscosity because of its high strain rate and water content the relatively low mantle water content of the northeast domain is interpreted to result from the continual extraction of water through igneous and volcanic activity over the past 20 myr

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

interseismic strain accumulation and anthropogenic motion in metropolitan los angeles 1 we use global positioning system gps geodesy and synthetic aperture radar sar interferometry to distinguish between interseismic strain accumulation and anthropogenic motion in metropolitan los angeles we establish a relationship between horizontal and vertical seasonal oscillations of the santa ana aquifer use this relationship to infer cumulative horizontal anthropogenic motions from cumulative vertical motions caused by water and oil resource management and estimate horizontal interseismic velocities corrected for anthropogenic effects vertical anthropogenic rates from 1992 to 1999 are slower than 3 mm yr 1 in the santa ana and san gabriel aquifers and faster than 5 mm yr 1 in the chino aquifer and in many oil fields inferred horizontal anthropogenic velocities are faster than 1 mm yr 1 at 18 of 46 gps sites northern metropolitan los angeles is contracting with the 25 km south of the san gabriel mountains shortening at 4 5 1 mm yr 1 95 confidence limits the thrust fault in an elastic edge dislocation model of the observed strain is creeping at 9 2 mm yr 1 beneath and north of a position 6 2 km deep and 8 8 km north of downtown los angeles the model fault is near the los angeles segment of the puente hills thrust but south of the sante fe springs segment of the thrust disagreement between the 6 km locking depth in the model and the 15 km seismogenic depth inferred from earthquakes suggests that the elastic continuum model may be unsatisfactory models with different stiffnesses of sedimentary basin and crystalline basement must be investigated

episodic inflation events at akutan volcano alaska during 2005 2017 detection of weak volcano deformation helps constrain characteristics of eruption cycles we have developed a signal detection technique called the targeted projection operator tpo to monitor surface deformation with global positioning system gps data we have applied the tpo to gps data collected at akutan volcano from june 2005 to march 2017 and detected four inflation events that occurred in 2008 2011 2014 and 2016 with inflation rates of about 8 22 mm yr above the background trend at a near source site av13 numerical modeling suggests that the events should be driven by closely located sources or a single source in a shallow magma chamber at a depth of about 4 km the inflation events suggest that magma has episodically accumulated in a shallow magma chamber

geophones on a board we examined the feasibility of using seismic reflections to image the upper 10 m of the earth s surface quickly and effectively by rigidly attaching geophones to a wooden board at 5 cm intervals the shallow seismic reflection information obtained was equivalent to control test data gathered using classic single geophone plants with identical 5 cm intervals tests were conducted using both a 22 caliber rifle source and a 30 06 rifle source in both cases the results were unexpected in response to our use of small high resolution seismic sources at offsets of a few meters we found little intergeophone interference that could be attributed to the presence of the board furthermore we noted very little difference in a 60 ms intra alluvial reflection obtained using standard geophone plants versus that obtained using board mounted geophones for both sources amplitude spectra were nearly identical for data gathered with and without the board with the 30 06 source filtering at high frequency passbands

near real time monitoring of volcanic surface deformation from gps measurements at long valley caldera california 1 long valley caldera in eastern california is an active volcanic area and has shown continued unrest in the last three decades we have monitored surface deformation from global positioning system gps data by using a projection method that we call targeted projection operator tpo tpo projects residual time series with secular rates and periodic terms removed onto a predefined spatial pattern we used the 2009 2010 slow deflation as a target spatial pattern the resulting tpo time series shows a detailed deformation history including the 2007 2009 inflation the 2009 2010 deflation and a recent inflation that started in late 2011 and is continuing at the present time november 2012 the recent inflation event is about four times faster than the previous 2007 2009 event a mogi source of the recent event is located beneath the resurgent dome at about 6 6 km depth at a rate of 0 009 km3 yr volume change tpo is simple and fast and can provide a near real time continuous monitoring tool without directly looking at all the data from many gps sites in this potentially eruptive volcanic system

itrf2005 a new release of the international terrestrial reference frame based on time series of station positions and earth orientation parameters 1 unlike the past international terrestrial reference frame itrf versions where global long term solutions were combined the itrf2005 uses as input data time series weekly from satellite techniques and 24 h session wise from very long baseline interferometry of station positions and daily earth orientation parameters eops the advantage of using time series of station positions is that it allows to monitor station non linear motion and discontinuities and to examine the temporal behavior of the frame physical parameters namely the origin and the scale the itrf2005 origin is defined in such a way that it has zero translations and translation rates with respect to the earth center of mass averaged by the satellite laser ranging slr time series spanning 13 years of observations its scale is defined by nullifying the scale and its rate with respect to the very long baseline interferometry vlbi time series spanning 26 years of observations the itrf2005 orientation at epoch 2000 0 and its rate are aligned to the itrf2000 using 70 stations of high geodetic quality the estimated level of consistency of the itrf2005 origin at epoch 2000 0 and its rate with respect to the itrf2000 is respectively 0 1 0 8 5 8 mm and 0 2 0 1 1 8 mm yr along the x yand z axis we estimate the formal errors on these components to be 0 3 mm and 0 3 mm yr we believe that this low level of agreement between the two frame origins is most probably due to the poor slr network geometry and its degradation over time the itrf2005 combination involving 84 co location sites revealed a scale inconsistency of 1 ppb 6 3 mm at the equator at epoch 2000 0 and 0 08 ppb yr between the slr and vlbi long term solutions as obtained by the stacking of their respective time series possible causes of this inconsistency may include the poor slr and vlbi networks and their co locations local tie uncertainties systematic effects and possible inconsistent model corrections used in the data analysis of both techniques for the first time of the itrf history the itrf2005 rigorous combination provides self consistent series of eops including polar motion from vlbi and satellite techniques and universal time and length of day from vlbi only a velocity field of 152 sites with an error less than 1 5 mm yr is used to estimate absolute rotation poles of 15 tectonic plates that are consistent with the itrf2005 frame this new absolute plate motion model supersedes and significantly improves that of the itrf2000 which involved six major tectonic plates citation altamimi z x collilieux j legrand b garayt and c boucher 2007 itrf2005 a new release of the international terrestrial reference frame based on time series of station positions and earth orientation parameters j geophys res 112 b09401

satellite interferometric observations of displacements associated with seasonal groundwater in the los angeles basin 1 the newport inglewood fault zone nifz displays interferometric synthetic aperture radar sar phase features along most of its length having amplitudes of up to 60 mm however interpretation in terms of right lateral shallow slip along the fault fails to match the range of geologic estimates of slip recently bawden et al 2001 proposed that these phase features as well as a broader deformation pattern in the los angeles basin are due to vertical motion related to annual variations in the elevation of the water table we confirm this hypothesis through the analysis of a longer span of data consisting of 26 sar images collected by the ers 1 and ers 2 spacecraft between june 1992 and june 2000 moreover we use continuous gps measurements from 1995 to the present to establish the amplitude and phase of the vertical deformation the los angeles basin becomes most inflated one quarter of the way through the year which is consistent with water table measurements as well as with the end of the rainy season when the aquifer should be at a maximum the spatial pattern of the amplitude of the annual signal derived from continuous gps measurements is consistent with the shape of the interferometric fringes gps sites both near the nifz and in a 20 by 40 km zone within the basin also show significant n s annual variations that may be related to the differential expansion across the fault since these horizontal signals have peak to trough amplitudes of 6 mm they mask the smaller tectonic signals and need to be taken into account when interpreting gps time series of site position moreover since the groundwater signal appears to have a long term vertical trend which varies in sign depending on location it will be difficult to distinguish interseismic tectonic slip along the nifz and within the affected areas in the basin

satellite radar interferometry time series analysis of surface deformation for los angeles california 1 the los angeles california metropolitan area is a tectonically active region with surface deformation that is a combination of fault related tectonics plus a variety of natural and anthropogenic signals we apply the small baseline subset sbas algorithm to produce an interferometric synthetic aperture radar insar time series analysis for the los angeles area using data acquired by the ers satellites from late 1995 into 2002 the result is a space time deformation product that can be exploited to view not only the smoothly varying long term surface motion but also its time varying patterns large seasonal oscillations of the santa ana aquifer observed in southern california integrated gps network scign data are accurately matched in the insar time series moreover correlations of the insar time series with an annual sinusoid allows us to investigate the dynamics of the hydrologic system index terms 1243 geodesy and gravity space geodetic surveys 1294 geodesy and gravity instruments and techniques 1803 hydrology anthropogenic effects citation lanari r p lundgren m manzo and f casu 2004 satellite radar interferometry time series analysis of surface deformation for los angeles california geophys res lett 31 l23613 doi 10 1029 2004gl021294

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

long term strain oscillations related to the hydrological interaction between aquifers in intra mountain basins a case study from apennines chain italy abstract we analyze the multiyear strain cycle of a network of continuous gps stations in the l aquila intra mountain basin in central apennines italy the basin is bounded by two aquifers nuria velino and gran sasso hosted in two tectonically active mountain ranges all stations show coherent displacements mostly in the horizontal plane and orthogonal to the normal fault zones of the apennine mountain range the displacement repeats back and forth roughly every 4 5 years with elongation up to 6 mm the deformation occurs in the region bounded by the two aquifers and the displacement amplitude decreases with distance as predicted by two tensile sources acting in an elastic medium we interpret this type of deformation as induced by the opening of pre existing fractures related to two different fault systems as a response to hydrostatic pressure variations the strain cycle follows the average multiyear rainfall cycle and foresees a dilatation phase during high rainy seasons and a contraction during drier periods the estimated depth of the equivalent tensile sources ranges from 1 2 to 1 5 km affecting stations at distances up to 20 km away gps data show the cumulated movement induced by the two nearby aquifers and suggest a mutual interaction in the elastic space related to the different average annual rainfall and effective infiltration we fit two tensile sources located along the main faults affecting the aquifers the eastern source corresponds to the major active fault system affecting the gran sasso range while the western one includes the sub parallel active faults of the mt ocre in the nuria velino range where carbonate rocks show a higher structural permeability and effective infiltration these fault systems affect jurassic miocene limestones and dolomites inducing parallel fracturation style of the rock matrix and favoring a strong anisotropy allowing a prevalent lateral expansion as a reaction to pore pressure variations the recorded hydrological signal may hamper other geophysical signals in gps time series thus the measure of tectonic strains requires a careful mapping and modeling of major aquifers

limitations in identifying the equilibrium line altitude from the optical remote sensing derived snowline in the tien shan china optical remote sensing derived end of summer snowline altitude sla has long been employed on glaciers as an indicator of the equilibrium line altitude ela in the tien shan northwest china both accumulation and ablation of glaciers occur mainly in the warm season making it difficult to obtain the representative snowline highest snowline in the area the high spatio temporal resolution of hj 1 satellite images enables the highest snowline to be acquired in this paper we compare image derived sla and measured in situ ela for two adjacent glaciers in the tien shan over the period 2009 10 results indicate that 1 in 2009 there was a substantial difference between sla and ela on one glacier suggesting inconsistent applicability in using sla to identify ela over a large area and 2 in 2010 an intense ablation year the field data derived ela surpassed the glacier peak in this situation there is no theoretical relationship between sla and ela and the image derived snowline actually indicates the boundary between ice and firn from previous years in summary errors will arise from the discrepancies between individual glaciers and from intensive ablation when using sla to identify ela over a large area