seismic damage and behavior analysis of earth dams during the 2008 wenchuan earthquake china abstract the may 12 2008 ms 8 0 wenchuan great earthquake china caused earthquake damages of 2666 earth dams these damaged dams are in medium and small scale located in 8 provinces or municipalities of which 69 dams were at dam break risk and 331 were at high risk there were 1996 damaged dams located in sichuan province including all the 69 at dam break risk and 310 at high risk through a detailed scientific investigation earthquake damage and emergency data were collected and the isoseismal map of wenchuan earthquake with damaged dams marked on it was given also distribution feature of the above 69 dams along the fault zones were discussed typical damage types of earth dams were analyzed and the action of rare great earthquake poor quality of dam construction adverse running state of earth dams before earthquake and frequent aftershocks were concluded as four main reasons of dam damages taking 147 dams with complete geometric parameters as statistical samples some empirical graphic formulas were proposed to make rapid evaluation of damage degree finally some useful practical measures were provided to serve the post earthquake emergency danger removal also it may improve the seismic performance of dams in view of the insufficiency of local geology site effect and soil property data of damaged dams application of the qualitative results and empirical relationships to other sites should be very prudent

decorrelation in interferometric radar echoes a radar interferometric technique for topographic mapping of surfaces implemented utilizing a single synthetic aperture radar sar system in a nearly repeating orbit is discussed the authors characterize the various sources contributing to the echo correlation statistics and isolate the term which most closely describes surficial change they then examine the application of this approach to topographic mapping of vegetated surfaces which may be expected to possess varying backscatter over time it is found that there is decorrelation increasing with time but that digital terrain model generation remains feasible the authors present such a map of a forested area in oregon which also includes some nearly unvegetated lava flows such a technique could provide a global digital terrain map

kinematic behaviour and velocity characteristics of a complex deep seated crystalline rockslide system in relation to its interaction with a dam reservoir abstract this paper presents the geometry kinematics and temporal deformation characteristics of a deep seated rockslide system the hochmais atemkopf situated above the gepatsch dam reservoir in northern tyrol austria results from surface and subsurface geological investigations and deformation monitoring indicate that the hochmais atemkopf rockslide system involves several sliding masses one on top of the other characterized by different velocity characteristics with displacements being greater for the shallower slide bodies during the initial impounding phases of the gepatsch reservoir uplift forces beneath the foot of the slope led to the activation of one of these shallower slide bodies moving it more than 10 m downslope in 2 years after continuous deceleration of the sliding mass the deformation rates reduced to about 2 to 4 cm per year these were found to show seasonal fluctuations that correlated with reservoir levels and drawdown conditions with induced slope accelerations peaking when reservoir levels were at their lowest this suggests in part a controlling mechanism based on seepage forces where reservoir drawdown drives the episodic rockslide deformation behaviour together the data and analyses presented demonstrate the importance of integrating detailed geology and monitoring data to derive a basic understanding of the kinematics and controlling mechanisms of a deep seated rockslide system in advance of undertaking comprehensive numerical modelling

correlating paleomagnetic geochemical and petrographic evidence to date diagenetic and fluid flow events in the mississippian turner valley formation moose field alberta canada abstract petrographic geochemical and paleomagnetic analyses of the mississippian turner valley formation provide constraints on diagenesis and fluid flow events in the western canada sedimentary basin paleomagnetic plugs and companion geochemical samples were taken from two drillcores with fullbore microimage log orientations dolomite from both wells yielded two magnetization directions the low temperature low coercivity direction is a drilling induced remanence rather than a viscous remanent magnetization the high temperature high coercivity remanence direction is cretaceous and there is no sign of a primary mississippian direction geochemical analyses of matrix dolomite yield 18o values ranging from 0 65 to 3 34 vpdb standard and 13c values ranging from 1 77 to 3 05 vpdb the least depleted samples have stable isotope values consistent with or only slightly depleted from postulated mississippian dolomite values the remaining sample values exhibit a negative covariant trend consistent with either mixing with another diagenetic fluid or recrystallization during burial petrographic analysis reveals the presence of a recrystallization event that caused zoning and a gradual increase size of the dolomite crystals this event is thought to have caused both the cretaceous paleomagnetic remanence and the altered geochemical values the minor enrichment in sr radiogenic isotopes relative to coeval seawater values suggests that both an extrabasinal source for any fluid and large scale fluid flow are unlikely the results also indicate that magnetic remanences are very sensitive to visually minor changes in carbonate recrystallization from heat or pressure so that great care must be taken in correlating paleomagnetic and geochemical data

high resolution insar constraints on flood related subsidence and evaporite dissolution along the dead sea shores interplay between hydrology and rheology abstract sinkhole generation and land subsidence are commonly attributed to dissolution of subsurface layers by under saturated groundwater and formation of cavities along the dead sea ds shorelines this process also involves seasonal flash floods that are drained into the subsurface by existing and newly formed sinkholes we quantify the contribution of flash floods to salt dissolution and land subsidence using high resolution interferometric synthetic aperture radar insar subsidence rates during a 3 year period 2012 2015 were calculated from 57 cosmo skymed x band interferograms bracketing major flood events and intra flood periods in 21 sinkhole sites the sites are located within channels and alluvial fans along the western shores of the dead sea israel the observed subsidence reaches maximum rates of 2 5 mm day accumulating in specific sites to 500 mm year in most of the sinkhole sites a gradual increase in the annual subsidence rate is observed during the 3 year study period three different modes of response to floods were observed 1 sites where floodwater is not directly channeled into sinkholes do not respond to floods 2 sites adjacent to active channels with sinkholes are unaffected by specific floods but their subsidence rates increase gradually from early winter to mid summer and decay gradually until the following winter and 3 sites in active channels with sinkholes are characterized by an abrupt increase in subsidence rates immediately after each flood by a factor of up to 20 and by a subsequent quasi exponential subsidence decay over periods of several months in these latter sites subsidence rates after each flood are temporally correlated with alternating groundwater levels in adjacent boreholes the rapid rise in groundwater head following floods increases the hydraulic gradient of the under saturated groundwater and hence also the groundwater discharge and the dissolution rate of the subsurface salt layer a subsequent quasi exponential water level drop results in similar deceleration in dissolution and subsidence rates with a similar characteristic decay time of about 150 days the observed subsidence decay pattern may also be explained by viscoelastic relaxation of the overburden in response to instantaneously formed dissolution cavities utilizing a kelvin viscoelastic model we show that the contribution of this process is most probably

sinkhole monitoring and early warning an experimental and successful gb insar application abstract sinkholes represent a natural risk that may hit catastrophically without clearly detectible precursors however they are often overlooked by people and administrators therefore sinkhole monitoring and associated early warnings constitute important research topics but currently only a few papers about sinkhole prediction can be found in this paper an experience of sinkhole monitoring and early warning with gb insar is described the latter is a highly precise instrument that is able to produce displacement maps with metric spatial resolution the described activities were carried out on elba island central italy where karstified limestone set off the occurrence of nine sinkholes since 2008 all within less than 3000 m2 causing major damage to an important road and many indirect losses in 1 year of monitoring two deforming areas were detected and the point where a sinkhole was about to propagate to the street level was predicted thus permitting the preventive closure of the road the deformation area was larger than the hole generated by the sinkhole thus showing a subsidence that continued for a prolonged time even after the cavity was filled up the occurrence of a 1 5 m wide sinkhole undetected by the gb insar also showed the lower detection limit of the instrument

mapping ground movements caused by mining induced earthquakes applying satellite radar interferometry abstract anthropogenic activity related to the extraction of gas and oil raw materials or water pumping leads to slow or rapid ground deformation the ground motion rate is related to the type of the mined material geological conditions mining methods and other factors ground subsidence resulting from the collapse of underground post mining voids occurs gradually mining induced earthquakes and seismic earthquakes are largely unpredictable and have an adverse impact on the local inhabitants and buildings for this reason monitoring of this phenomenon is a challenge the application of interferometric sar for the evaluation of ground movement has brought satisfactory results over the past twenty years mainly in the regions where no other measurements were conducted during ground subsidence in this paper we have examined a mining induced earthquake with a magnitude 4 5 which occurred in an underground copper ore mine in poland on 29th november 2016 and caused eight fatalities it also had an impact on ground surface deformation in the vicinity of the mine tailings an assessment of the earthquake related impact on surface movement was carried out by sentinel 1 tops time series interferometry the velocity of ground movement and the scale of the phenomenon were investigated in addition the impact of the mining induced earthquake on zelazny most mine tailings site was analyzed moreover the process of dynamic ground compaction was also investigated in detail ground movement following the mine earthquake was explored two time phases of the movements were determined the first phase of dynamic ground displacement was rapid and 90 of total ground deformation appeared on the surface within 7 days the second phase of displacement was a vanishing one it lasted for approx 3 weeks and 10 of ground deformation appeared on the surface the study revealed that the maximum observed ground subsidence did not exceed 9 cm the presented results contribute to a better understanding of post earthquake ground deformations in the light of their spatial distribution in time

sinkhole occurrence monitoring over shallow abandoned coal mines with satellite based persistent scatterer interferometry abstract unexpectedly occurring sinkholes caused by shallow submerged voids are one of the key problems of intensively built up post mining areas five percent of poland s territory is still under the influence of post mining deformation impending sinkholes which tend to develop randomly over very large areas cannot be detected by using traditional geophysical methods moreover geodetic measurement methods like global positioning system gps analyses tachymetry laser scanning or photogrammetry may be useful only for the registration of the dimensions and locations of sinkholes that have already occurred here we investigate an area in upper silesia poland where 345 sinkholes were recorded over a period of more than 20 years 1992 2013 most of the events occurred in intensively built up areas and thus these sinkholes posed a direct threat to the population in the test area 11 sinkholes were detected with a maximum depth of 16 m and maximum dimension of 25 m the root cause of sinkhole formation was the collapse of post mining shallow voids we used satellite radar technology to detect and monitor ground movements potentially associated with the impending sinkholes the findings showed that the application of persistent scatterer interferometry can support the identification of zones where sinkholes will occur given adequate spatio temporal sampling a stack of envisat synthetic aperture radar sar images acquired between march 2003 and august 2010 was used in the analysis and the results confirmed that precursory ground movements were detectable at an early stage of sinkhole development the land subsidence rate observed prior to sinkhole collapse was not constant in time accelerated ground movements within 100 m of an observed sinkhole were detected we conclude that satellite measurements may provide significant support in the early identification of areas prone to sinkhole occurrence

review on sinkhole monitoring and performance of remediation measures by high precision leveling and terrestrial laser scanner in the salt karst of the ebro valley spain abstract the need to apply sinkhole remediation and monitoring programs is increasing concurrently with the rising engineering impacts of sinkholes in many regions however there is a significant gap in the scientific literature regarding the assessment of the performance of remedial works through subsidence monitoring monitoring techniques have experienced significant advances in the last few years thanks to the advent of new technologies this work presents a review of sinkhole monitoring methods and discusses some practical considerations about their capabilities and limitations it also documents a monitoring program high precision leveling and terrestrial laser scanner and the concurrent remedial works cement based and polyurethane grouting carried out in a highly active sinkhole that affects a flood control dike and the adjacent village of alcala ne spain the subsidence activity in the sinkhole is characterised by progressive sagging and the development of catastrophic nested collapses monitoring data reveal subsidence expansion and acceleration in the sector of the dike treated by polyurethane grouting above the main cavities in contrast subsequent cement based grouting of the large cavities significantly reduced subsidence rates displacement data also indicate substantial subsidence enhancement following flood recession and the associated water table drop buoyancy loss this case study illustrates that high precision leveling and terrestrial laser scanning are adequate complementary methods for monitoring specific sinkholes characterised by very high accuracy and detailed spatial resolution respectively

monitoring surface deformation over permafrost with an improved sbas insar algorithm with emphasis on climatic factors modeling abstract changes of permafrost not only affect regional and global water circulation carbon deposit and climate warming but also influence ground ecological geophysical and biogeochemical processes in cold region monitoring surface deformation over permafrost will help to understand the dynamics of these processes assess climate changes and prevent potential damages to engineering structures underlain by permafrost this article employs an improved small baseline subset interferometric synthetic aperture radar sbas insar technique to monitor the surface deformation over the danxiong yangbajing area in the southern qinghai tibet plateau qtp with emphasis on climatic factors modeling a new deformation model considering both the external mainly climatic and internal factors such as tectonic activities and thermal character of frozen soil is constructed and introduced into the sbas insar to estimate the surface deformation over permafrost the results show that the peak to peak annual deformation over natural surface is 3 6 5 0 cm while that along the qinghai tibet highway qth and the qinghai tibet railway qtr is 2 8 3 7 cm we also find that the surface deformation over frozen soil is negatively correlated to air temperature and precipitation with the correlation being 0 80 to 0 45 and 0 95 to 0 75 respectively the root mean squares rmss of the residual un modeled deformation got by the proposed method are much smaller than that by the existing methods we also successfully examine a time lag of about 60 days between the retrieved maximal subsidence and the highest air temperature in warm seasons from may to september after compensating for this time lag the rmss of the residual deformation reduce significantly and the correlation between the deformation and the temperature rises considerably varying from 0 95 to 0 65 the method presented in this paper is more suitable to model and analyze the surface deformation in permafrost areas

landslide evolution assessment based on insar and real time monitoring of a large reactivated landslide wenchuan china abstract the upper minjiang catchment is frequently affected by a significant number of large to giant landslides in one such massive older landslide approximately 2 million m3 of sediment was reactivated threatening the safety of a pylon on the landslide and the safety of the only route that allows high speed travel from wenchuan to maoxian to trace the deformation evolution history and analyze the current deformation of the new landslide we examined sar data since 2007 carried out geological and uav surveys and designed and installed real time monitoring equipment this paper presents the main spatial and temporal characteristics of the landslide we found that the landslide has experienced creep deformation in the past five years and its sensitivity to rainfall the development process of the landslide from the formation of tensile crack at the trailing edge to the gradual pushing forward of the crack propagation was revealed the innovation of this paper is to reveal the whole process of the spatial temporal evolution from its beginning to large deformation of a real case of creep landslide which can provide a very good reference for the analysis and monitoring of such creeping landslide evolution process this representative case also shows how to combine remote sensing and in situ monitoring methods to carry out continuous monitoring and the establishment of a warning system for potential landslide sites so as to trace the evolution history derive activity maps and analyze development trend which can significantly reduce landslide risk additional mitigation procedures can be put into place if continuous monitoring of the minjiang river canyon occurs resulting in a reduction of direct losses in particular modeling of the slope deformation and failure damming process and prospective flooding can be done in advance therefore it is expected that this report can strengthen the case for the deployment of systematic monitoring of potential landslide sites by integrating earth observation methods and in situ monitoring systems as an approach to reduce risk

rapid drought induced land subsidence and its impact on the california aqueduct abstract the central valley in california is characterized by a semi arid climate prone to droughts a variable surface water supply and immense agricultural areas dependent on groundwater irrigation the groundwater is stored in a complex aquifer system composed of alternating layers of coarse sediments and fine grained sediments acting as confining materials groundwater fluctuations are coupled with both the elastic and inelastic land surface deformation historically observed in the central valley surface deformation poses a hazard to the california aqueduct which supports central valley agriculture and large urban populations in southern california the risk of reduced aqueduct efficacy and expensive repairs compels water resource managers to carefully monitor land deformation in the valley a persistent drought in the region began in 2012 intensified in 2014 and was abruptly alleviated by a wet period from dec 2016 to feb 2018 nasa s uavsar l band synthetic aperture radar acquired 31 high resolution radar images between may 2013 and nov 2018 the interferometric phase difference between acquisitions is used to develop a time series of vertical displacement and identify and track a rapidly forming subsidence feature adjacent to the california aqueduct the surface area of the feature that subsided 10 cm or more by the end of the time series reaches 4452 ha and a 10 5 km segment of the aqueduct this study also incorporates extensometer measurements precise leveling surveys sentinel 1a displacement concurrent water elevation data well construction reports nearby extensometer measurements aquifer material characterization and environmental conditions spatiotemporal data availability limits the appropriateness of calculations and models able to be performed for different sites along the aqueduct we aim to offer insight into heterogeneous subsurface properties and mechanics estimate the permanent loss of aquifer storage volume and identify additional data that would aid water management

anticipating and managing engineering problems in the complex karst environment karst environments are characterized by distinctive landforms and a peculiar hydrologic behavior dominated by subsurface drainage karst systems can be extremely complex heterogeneous and unpredictable due to the wide range of geological and hydrological controlling factors the great variability results in serious problems for engineers and in difficulties to characterize the karstified rock masses and in designing the engineering works to be performed the design and development of engineering projects in karst environments require specific approaches aimed at minimizing the detrimental effects of hazardous processes and environmental problems further karst aquifers that provide approximately 20 25 of the world s drinking water are extremely vulnerable to pollution due to the direct connection between the surface and the subsurface drainage the rapidity of the water flow in conduit networks and the very low depuration capability sinkholes are the main source of engineering problems in karst environments and may cause severe damage in any human structure the strategies and solutions that may be applied to mitigate sinkhole problems are highly variable and largely depend on the kind of engineering structure the karst setting and the typology and size of the sinkholes a sound geological model properly considering the peculiarities of karst and its interactions with the human environment is essential for the design of cost effective and successful risk reduction programs due to the unique direct interaction between surface and subsurface environments and the frequent ground instability problems related to underground karstification management of karst environments is a very delicate matter disregarding such circumstances in land use planning and development inevitably results in severe problems with high economic impacts karst environments require specific investigation methods in order to properly manage and safeguard the sensitive geo ecosystems and natural resources associated with them

bayou corne louisiana sinkhole precursory deformation measured by radar interferometry catastrophic sinkholes are formed through the collapse of natural or human made subterranean caverns and are common in areas with evaporite and carbonate rock despite their danger advance warning of these events is rare we report a measurement of precursory surface deformation of as much as 260 mm derived with interferometric synthetic aperture radar insar and evident over a month before surface collapse at the site of the bayou corne louisiana usa sinkhole that formed in august 2012 data collected by the airborne uninhabited aerial vehicle sar uavsar instrument were used for the study analysis of data acquired from two flight tracks with near opposing imaging geometries reveal a deformation pattern consistent with compressive loading at the surface due to loss of support from a subterranean cavity collapse related to texas brine oxy geismar well 3 the precursor deformation was nearly entirely horizontal i e oriented along the surface and manifested as movement of surface material toward the location where the sinkhole later formed the sinkhole formed in the area with the largest gradient in surface strain but did not cover the full extent of the precursory deformation detected with radar this work suggests that insar data collected operationally for hazard monitoring could in some cases identify sinkhole development before surface collapse and decrease subsequent danger to people and property

definition of sinkhole triggers and susceptibility based on hydrogeomorphological analyses sinkholes represent a geological risk that is often underrated mainly due to its very localized nature in fact sinkholes occur only under particular circumstances and typically affect relatively small areas despite these characteristics the difficulty in forecasting the precise location and timing of their sudden collapse creates serious problems for civil protection authorities and urban planners in this framework identifying the mechanism and thus the triggering factor of sinkholes is strategically pivotal in developing management plans the present paper addresses the sinkhole prone area of il piano elba island central italy the integration of hydrogeological surveys coupled with a thorough study of historical maps and aerial photographs suggests that the main triggering factor in this area may not be related to water pumping from the karst aquifer as initially hypothesized instead sinkholes appear to be caused by ravelling and erosive processes occurring entirely in the sedimentary cover when heavy rainfall induces water overpressure within the superficial aquifer

sinkhole precursors along the dead sea israel revealed by sar interferometry the water level in the dead sea israel and jordan has been dropping at an increasing rate since the 1960s exceeding one meter per year during the last decade this drop has triggered the formation of sinkholes and widespread land subsidence along the dead sea shoreline resulting in severe economic loss and infrastructural damage in this study the spatiotemporal evolution of sinkhole related subsidence and the effect of human activities and land perturbation on sinkhole development are examined through interferometric synthetic aperture radar measurements and field surveys conducted in israel during 2012 interferograms are generated using cosmo skymed satellite images and a high resolution 0 5 m pixel elevation model obtained from lidar measurements as a result of this unique combination of high resolution data sets millimeter scale subsidence has been resolved in both natural and human disturbed environments precursory subsidence over a period of a few months occurred before the collapse of all three sinkhole sites reported in this study the centers of the subsiding areas migrated possibly due to progressive dissolution and widening of the underlying cavities filling of newly formed sinkholes with gravel and mud injections into drill holes seem to enhance land subsidence enlarge existing sinkholes and form new sinkholes apart from shedding light on the mechanical process the results of this study may pave the way for the implementation of an operational sinkhole early warning system

insar based modeling and analysis of sinkholes along the dead sea coastline sinkholes commonly form by subsurface dissolution cavities that collapse after the overlying layers become mechanically unsupported sinkholes along the dead sea shorelines are preceded by associated with and followed by gradual surface subsidence that accompanies the cavities growth we exploit satellite radar interferometry interferometric synthetic aperture radar to resolve temporal and spatial relationships between gradual subsidence and sinkhole collapse the geometry of the deflating cavity roof is determined by elastic inverse modeling of the surface displacements a coulomb failure stress criterion is applied to calculate the stress field induced by the deflating cavity at the ground surface we find that the induced stress field favors generation of sinkholes at the perimeters of the subsiding areas rather than at their centers in agreement with field observations providing important information for sinkhole hazard assessment further our analysis suggests that short term deformation in consolidated gravel layers at shallow depths could be approximated by simple elastic modeling

evolution of sinkholes over wink texas observed by high resolution optical and sar imagery abstract two caprock and cover collapse sinkholes wink sinks 1 and 2 in winkler county texas collapsed in 1980 and 2002 respectively they are located in a region underlain by the salado formation on the eastern edge of the delaware basin the sinkhole collapses were associated with intense hydrocarbon drilling and production activities in the hendrick oilfield production records and prior investigations imply the sinkholes developed after salt dissolution due to freshwater intrusion cavity formation roof failure and successive upward cavity migration high resolution 1 m aerial photography shows the ensuing expansion of wink sink 2 from 2002 through 2010 and relative stability of the ground surface after 2010 very high resolution 25 cm staring spotlight mode terrasar x reveals the spatiotemporal details of wink sinkhole deformations the vicinities around the two existing sinkholes wink sinks 1 2 deformed at a rate of 5 cm yr in line of sight los direction from october 2015 to march 2016 and the deformation was possibly caused by the gradual deposit of the debris from overlying unconsolidated alluvium and santa rosa sandstones infilling the cavity after the sinkhole collapse specifically the largest deformation of 53 cm yr in los direction was found 1 km east of wink sink 2 our study suggests that severe drought in 2011 widened and created fractures as well as ground fissures in the rocks overlying and underlying the salt formation due to the increased effective stress fractures ground fissures and the abandoned unplugged boreholes or improperly completed wells opened one or more vertical pathways of freshwater from groundwater flow and precipitation toward the salt bed finally causing the rapid salt dissolution and the opening of new cavities to explain the onset of a rapid subsidence near the wink sinkholes our study considers the combined effect of natural perturbation i e drought rock fractures ground fissures subsurface drainage precipitation and anthropogenic effects i e improper well control our method to explore high resolution imagery can be applied to characterize the sinkhole deformation and mitigate sinkhole related geohazards

natural versus human control on subsurface salt dissolution and development of thousands of sinkholes along the dead sea coast one of the most hazardous results of the human induced dead sea ds shrinkage is the formation of more than 6000 sinkholes over the last 25 years the ds shrinkage caused eastward retreat of underground brine replaced by fresh groundwater which in turn dissolved a subsurface salt layer to generate cavities and collapse sinkholes the areal growth rate of sinkhole clusters is considered the most pertinent proxy for sinkholes development analysis of light detection and ranging lidar digital elevation models dems and interferometric synthetic aperture radar insar allows translation of the areal growth rate to a salt dissolution rate of the salt layer revealing two peaks in the history of the salt dissolution rate these peaks cannot be attributed to the decline of the ds level instead we show that they are related to long term variations of precipitation in the groundwater source region the judea mountains and the delayed response of the aquifer system between the mountains and the ds rift this response is documented by groundwater levels and salinity variations we thus conclude that while the ds level decline is the major trigger for sinkholes formation the rainfall variations more than 30 km to the west dominate their evolution rate the influence of increasing rainfall in the judea mountains reaches the ds at a typical time lag of four years and the resulting increase in the salt dissolution rate lags by a total time of 5 6 years

rapid subsidence in damaging sinkholes measurement by high precision leveling and the role of salt dissolution abstract investigations dealing with subsidence monitoring in active sinkholes are very scarce especially when compared with other ground instability phenomena like landslides this is largely related to the catastrophic behaviour that typifies most sinkholes in carbonate karst areas active subsidence in five sinkholes up to ca 500 m across has been quantitatively characterised by means of high precision differential leveling the sinkholes occur on poorly indurated alluvium underlain by salt bearing evaporites and cause severe damage on various human structures the leveling data have provided accurate information on multiple features of the subsidence phenomena with practical implications 1 precise location of the vaguely defined edges of the subsidence zones and their spatial relationships with surveyed surface deformation features 2 spatial deformation patterns and relative contribution of subsidence mechanisms sagging versus collapse 3 accurate subsidence rates and their spatial variability with maximum and mean vertical displacement rates ranging from 1 0 to 11 8 cm yr and 1 9 to 26 1 cm yr respectively 4 identification of sinkholes that experience continuous subsidence at constant rates or with significant temporal changes and 5 rates of volumetric surface changes as an approximation to rates of dissolution induced volumetric depletion in the subsurface reaching as much as 10 900 m3 yr in the largest sinkhole the high subsidence rates as well as the annual volumetric changes are attributed to rapid dissolution of high solubility salts