persistent scatterer interferometric synthetic aperture radar for crustal deformation analysis with application to volcan alcedo galapagos 1 while conventional interferometric synthetic aperture radar insar is a very effective technique for measuring crustal deformation almost any interferogram includes large areas where the signals decorrelate and no measurement is possible persistent scatterer ps insar overcomes the decorrelation problem by identifying resolution elements whose echo is dominated by a single scatterer in a series of interferograms existing ps methods have been very successful in analysis of urban areas where stable angular structures produce efficient reflectors that dominate background scattering however man made structures are absent from most of the earth s surface furthermore existing methods identify ps pixels based on the similarity of their phase history to an assumed model for how deformation varies with time whereas characterizing the temporal pattern of deformation is commonly one of the aims of any deformation study we describe here a method for ps analysis stamps that uses spatial correlation of interferogram phase to find pixels with low phase variance in all terrains with or without buildings prior knowledge of temporal variations in the deformation rate is not required for their identification we apply stamps to volcan alcedo where conventional insar fails because of dense vegetation on the upper volcano flanks that causes most pixels to decorrelate with time we detect two sources of deformation the first we model as a contracting pipe like body which we interpret to be a crystallizing magma chamber the second is downward and lateral motion on the inner slopes of the caldera which we interpret as landsliding

inverse modeling of interbed storage parameters using land subsidence observations antelope valley california 1 we use land subsidence observations from repeatedly surveyed benchmarks and interferometric synthetic aperture radar insar in antelope valley california to estimate spatially varying compaction time constants and inelastic specific skeletal storage coefficients s kv in a previously calibrated regional groundwater flow and subsidence model the observed subsidence patterns reflect both the spatial distribution of head declines and the spatially variable inelastic skeletal storage coefficient using the nonlinear parameter estimation program ucode we estimate compaction time constants between 3 8 and 285 years the s kv values are estimated by linear estimation and range from 0 to almost 0 09 we find that subsidence observations over long time periods are necessary to constrain estimates of the large compaction time constants in antelope valley the insar data used in this study cover only a three year period limiting their usefulness in constraining these time constants this problem will be alleviated as more sar data become available in the future or where time constants are small by incorporating the resulting parameter estimates in the previously calibrated regional model of groundwater flow and land subsidence we can significantly improve the agreement between simulated and observed land subsidence both in terms of magnitude and spatial extent the sum of weighted squared subsidence residuals a common measure of model fit was reduced by 73 with respect to the original model however the ability of the model to adequately reproduce the subsidence observed over only a few years is impaired by the fact that the simulated hydraulic heads over small time periods are often not representative of the actual aquifer hydraulic heads errors in the simulated hydraulic aquifer heads constitute the primary limitation of the approach presented here

sensing the ups and downs of las vegas insar reveals structural control of land subsidence and aquifer system deformation land subsidence in las vegas nevada united states between april 1992 and december 1997 was measured using spaceborne interferometric synthetic aperture radar the detailed deformation maps clearly show that the spatial extent of subsidence is controlled by geologic structures faults and sediment composition clay thickness the maximum detected subsidence during the 5 75 yr period is 19 cm comparison with leveling data indicates that the subsidence rates declined during the past decade as a result of rising ground water levels brought about by a net reduction in ground water extraction temporal analysis also detects seasonal subsidence and uplift patterns which provide information about the elastic and inelastic properties of the aquifer system and their spatial variability

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

a new method for measuring deformation on volcanoes and other natural terrains using insar persistent scatterers 1 we present here a new insar persistent scatterer ps method for analyzing episodic crustal deformation in non urban environments with application to volcanic settings our method for identifying ps pixels in a series of interferograms is based primarily on phase characteristics and finds low amplitude pixels with phase stability that are not identified by the existing amplitude based algorithm our method also uses the spatial correlation of the phases rather than a well defined phase history so that we can observe temporally variable processes e g volcanic deformation the algorithm involves removing the residual topographic component of flattened interferogram phase for each ps then unwrapping the ps phases both spatially and temporally our method finds scatterers with stable phase characteristics independent of amplitudes associated with man made objects and is applicable to areas where conventional insar fails due to complete decorrelation of the majority of scatterers yet a few stable scatterers are present

numerical simulation and prediction of regional land subsidence caused by groundwater exploitation in the southwest plain of tehran iran abstract this study characterizes land subsidence in southwest plain of tehran using numerical modeling and predicts the trend through 2018 excessive groundwater withdrawal has caused severe land subsidence in tehran in the past 28 years 1984 2012 groundwater level has decreased 11 65 m the multi layered aquifer system in the southwestern plain of tehran contains three aquifers and three aquitard units the present model was developed simulation using pmwin modflow for windows first groundwater level and land subsidence were simulated for the end of 2004 the model was calibrated using hydraulic head measurements and insar data the simulation results were in fairly good agreement with the measurement results the calibrated and evaluated model was then used to assess the future evolution of land subsidence and for prediction of subsidence through the end of 2018 numerical results show that assuming a constant rate of pumping in the future land subsidence in the southwestern plain of tehran will reach 33 cm by 2018 the study confirmed that land subsidence caused by groundwater pumping is a serious threat to southwest tehran

fifteen years of surface deformation in western taiwan insight from sar interferometry abstract geodetically measured surface displacements are produced by a combination of underlying deformation processes acting at different spatial and temporal scales a complete history of surface measurements in an area can help discriminate contributions from tectonic hydrologic and anthropogenic processes in this study we use synthetic aperture radar sar images of the active mountain front and adjacent coastal plain of southwestern taiwan to generate time series of surface deformation from 1995 to 2001 and from 2005 to 2008 based on the insar small baseline method the insar measurements agree well with los motions estimated from continuous gps measurements of 3d displacements between 2006 and 2008 a significant range increase in line of sight los is dominated by land subsidence in the coastal area of western and southwestern taiwan subsidence rates vary with annual periods and are highly correlated with seasonal precipitation which are likely associated with groundwater recharge and withdrawal the long term deformation is dominated by long term tectonic loading in sw taiwan during the interseismic period of the earthquake cycle including elastic strain along or continuous creep on the active faults our results show the ability of insar to reveal spatiotemporal crustal deformation in western taiwan with high spatial resolution and accuracy which is potentially important for evaluating seismic hazards

model test of soil deformation response to draining recharging conditions based on dfos abstract intense groundwater exploitation and seasonal fluctuations of water level in phreatic aquifer cause land subsidence disasters to better understand the land subsidence mechanism caused by groundwater withdrawal a small scale sand clay interbedded model box was built to carry out consolidation and rebound tests during two drainage recharge cycles distributed fiber optical sensing dfos technologies were introduced for coupled monitoring of soil strain and water content to analyze response characteristics of each layer to water level changes the results indicate that soil layers were compressed during drainage and rebound during recharge with clay layer deformation more obvious than sand layer deformation deformation of the sand layer was synchronous with water content changes while that of the clay layer lagged behind water content changes due to its lower permeability coefficient the segmented compression clay layer curve shows that the water content rapidly decreased when it was lower than the liquid limit while the clay layer compression rate obviously accelerated during drainage when the water content was higher than that of the liquid limit during recharge the rebound rate significantly increased under the condition of repeated drainage and recharge the soil microstructure changed with decreasing porosity and permeability coefficient leading to a longer consolidation time with increasing cycling times the soil gradually tended toward elastic deformation the observations propose a novel technology dfos technology for monitoring land subsidence caused by seasonal water level fluctuations and dewatering projects the test results are of great significance to investigate land subsidence mechanisms and evaluate soil layer compression potential

decadal modulation of repeating slow slip event activity in the southwestern ryukyu arc possibly driven by rifting episodes at the okinawa trough we studied 38 slow slip events sses in 1997 2016 beneath the iriomote island southwestern ryukyu arc japan using continuous global navigation satellite system gnss data these sses occur biannually on the same fault patch at a depth of 30 km on the subducting philippine sea plate slab with average moment magnitudes mw of 6 6 here we show that the slip accumulation rate cumulative slip lapse time of these sses fluctuated over a decadal time scale the rate increased twice around 2002 and 2013 concurrently with earthquake swarms in the okinawa trough this suggests that episodic activations of the back arc spreading at the okinawa trough caused extra southward movement of the block south of the trough and accelerated convergence at the ryukyu trench

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

monitoring subsidence at messara basin using radar interferometry the messara valley is the largest and most productive region in the island of crete greece over the last 20 years extensive exploitation of the aquifer mainly for agricultural purposes has led to a 40 m decrease in the level of groundwater this investigation aims at mapping ground subsidence that might be induced by such overpumping of groundwater using conventional differential interferometry a total of 29 ers 1 and 2 sar and 7 alos palsar images have been used for forming interferograms the images used cover the period from 1992 to 2000 and 2007 to 2010 respectively processing of alos l band data 23 6 cm has revealed a ground motion away from the line of sight of the satellite los direction that amounts to at least 3 cm year for the period 2007 2010 piezometric measurements and other geological parameters have also been analyzed

the effect of clay dehydration on land subsidence in the yun lin coastal area taiwan the smectite dehydration theory developed by ransom and helgeson was applied for simulation of land subsidence in the yun lin coastal area taiwan the volumetric reduction of smectite clay at equilibrium state was computed by assuming that the dehydration of interlayer water in smectite clay can be described with a regular solid solution reaction by using the in situ stratigraphic data collected from the subsidence monitoring wells in the simulated area the amounts of land subsidence caused by smectite dehydration in three scenarios with pressure variation were calculated the results indicate that significant amounts of land subsidence can be attributed to smectite dehydration this finding reveals that smectite dehydration is of importance for assessment and prediction of land subsidence additionally the results also indicate the overburden weight has a larger effect on clay dehydration than the effective stress change resulting from over pumping although both of them induce relatively minor variations on land subsidence

on the derivation of coseismic displacement fields using differential radar interferometry the landers earthquake we present a map of the coseismic displacement field resulting from the landers california june 28 1992 earthquake derived using data acquired from an orbiting high resolution radar system we achieve results more accurate than previous space studies and similar in accuracy to those obtained by conventional field survey techniques data from the ers 1 synthetic aperture radar instrument acquired in april july and august 1992 are used to generate a high resolution wide area map of the displacements the data represent the motion in the direction of the radar line of sight to centimeter level precision of each 30 m resolution element in a 113 km by 90 km image our coseismic displacement contour map gives a lobed pattern consistent with theoretical models of the displacement field from the earthquake fine structure observed as displacement tiling in regions several kilometers from the fault appears to be the result of local surface fracturing comparison of these data with global positioning system and electronic distance measurement survey data yield a correlation of 0 96 thus the radar measurements are a means to extend the point measurements acquired by traditional techniques to an area map format the technique we use is 1 more automatic 2 more precise and 3 better validated than previous similar applications of differential radar interferometry since we require only remotely sensed satellite data with no additional requirements for ancillary information the technique is well suited for global seismic monitoring and analysis

monitoring severe aquifer system compaction and land subsidence in taiwan using multiple sensors yunlin the southern choushui river alluvial fan during 1992 2007 excessive pumping of groundwater caused large scale aquifer system compaction and land subsidence in the choshui river alluvial fan especially in the area of yunlin county the subsidence impedes surface water runoff and endangers the operation of taiwan high speed rail leveling global positioning system gps multi level compaction monitoring well and differential interferometric synthetic aperture radar dinsar are used to study the extent of subsidence in yunlin and its mechanism these sensors complement each other in spatial and temporal resolutions a leveling network totaling 434 km in length was deployed to derive subsidence at every 1 5 km along the routes and the result is accurate to few mm and shows a basin like subsidence pattern centering at tuku township four multi level compaction monitoring wells co located with gps pillars detect compactions at different depths showing that the aquifer system compaction the cause of subsidence occurs mostly below depths 200 m where reduction of groundwater pumping is most needed the vertical displacements from gps and leveling agree to within 1 cm and are larger than the cumulative compaction detected by the compaction monitoring wells suggesting that compaction also occurs below 300 m the depth of the wells the vertical displacements derived using dinsar and 8 envisat sar images agree with the leveling result to 1 2 cm

detecting rock uplift across southern taiwan mountain belt by integrated gps and leveling data abstract rock uplift on the earth surface is a key observation for studies of tectonics and geodynamic processes geodetic measurements from global positioning system gps and leveling are able to track vertical deformation over a wide range of spatial and temporal scale taiwan mountain belt is subject to a rapid uplift rate of 20 mm yr as revealed by gps and leveling measurements in previous studies the extremely high rates motivate us to analyze a set of newly processed gps and leveling data along a nw se transect across southern taiwan by considering the effects of the earthquake related deformation as well as hydrological and surface processes our estimates of rock uplift rates from gps and leveling are from 12 to 14 mm yr across the southern central range of taiwan vertical velocity changes on the small spatial scale are primary related to fault locking in the seismic cycle the large spatial feature showing the mean uplift rate of 6 mm yr between the eastern central range and the frontal thrust faults can be explained by a large scale pop up structure assuming the depth of 15 20 km in the orogenic wedge and the horizontal shortening of 30 mm yr our results draw attention to carefully study geodetic vertical deformation in the mountain belts and seek relevant causes

identifying poromechanism and spatially varying parameters of aquifer compaction in choushui river alluvial fan taiwan abstract subsidence occurs in many alluvial depositional environments causing substantial socio economic losses thick aquifers with interbedding or lens structured clay can contribute significantly to compaction the poromechanism of aquifer compaction is usually complicated and its spatial variation is poorly understood inhibiting our ability to fully explain the region wide nature of groundwater exploitation induced land subsidence in this study we explore the poromechanism of aquifer deformation in the choushui river alluvial fan taiwan groundwater level and multi layer compaction data were collected for analyses elastic plastic and viscous characteristics all appear in the deformation data to various extents a visco elasto plastic vep model composed of a visco elastic set and a visco plastic set in series which are associated with different viscous dampers is proposed to model the deformation compared with existing models the proposed model is superior in terms of simulating compaction as well as its applicability and versatility the proposed vep model is applied to observation wells in the proximal middle and distal fans of the choushui river alluvial fan to explore the spatial variation in the poromechanical properties the results show that the young s modulus of the elastic spring increases with depth and with the distance from the distal fan to the proximal fan the young s modulus of the plastic element decreases with depth the system response factor of the visco plastic set decreases with depth and with the distance from the distal fan to the proximal fan aquifer recovery incapability increases with depth both the trend and dynamic fluctuations in compaction for the choushui river alluvial fan are well captured by the proposed vep model which is essential for assessing long term land and water resource management and evaluating potential short term threats to infrastructure caused by seasonal subsidence

a new project to monitor land subsidence in the northern venice coastland italy the paper deals with the implementation of a levelling and global positioning system gps network to control land subsidence in the coastal area north of the venice lagoon about 480 km of levelling lines with 527 benchmarks 45 of which suited for differential gps measurements were established in 2004 a complete survey of the net was carried out in 2004 soon after its establishment the 2004 records have been compared with previous scattered data obtained by the use of levelling surveys dgps and sar interferometry the results show a trend in land settlement that increases from the lagoon margin to the north and jeopardize the venice coastland groundwater withdrawals for domestic agricultural and health spas uses peat oxidation of reclaimed marshlands for farming natural consolidation of the holocene deposits and tectonics of the pre quaternary basement are the causes of land subsidence in the study area since most of the area lies below the mean sea level and on account of the expected sea level rise due to global change a detailed monitoring of land displacements in the near future will be of paramount importance to plan necessary works for coastland protection

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