resolving three dimensional surface displacements from insar measurements a review abstract one dimensional measurement along the line of sight los direction has greatly limited the capability of insar technique in the investigation of surface displacements and their dynamics in recent years great efforts have been made to resolve complete three dimensional 3 d displacements from insar measurements this contribution is intended to provide a systematic review of the progress achieved in this field based on an analysis of the insar los measurements we first cover two commonly used techniques i e offset tracking and multi aperture insar mai with which the surface displacement in the azimuth direction can be measured together with the los displacement several methods for mapping 3 d displacements using insar measurements are subsequently presented and categorized into three groups i combination of multi pass los and azimuth measurements ii integration of insar and gps data and iii prior information assisted approaches the strengths and weaknesses of each method are analyzed to show the applicability of each method to specific 3 d displacement mapping cases in hope to provide a useful guidance in choosing a suitable approach accordingly finally suggestions for resolving the challenging issues and outlook of future research are given

using fractal crustal magnetization models in magnetic interpretation1 evidence from borehole susceptibility logs and the spectral analysis of aeromagnetic data suggests that the three dimensional distribution of magnetization within the crust can be described as fractal this property can be exploited in magnetic interpretation methods which explicitly require statistical information on the spatial variation of magnetization specifically we address the problem of magnetic source depth estimation through downward continuation and gridding aeromagnetic survey data using the method of kriging when magnetic data are continued downwards the depth at which the power spectrum flattens out the white depth can be taken to be an estimate of the top of the source distribution this procedure assumes that individual sources are uncorrelated with each other taking into account the correlation of the magnetization using a fractal description leads to a reduction in this depth estimate gridding of randomly distributed magnetic measurements using kriging requires an estimate of the covariance of the data compared with the assumption of a white uncorrelated magnetization distribution using fractal covariances for kriging produces gridded estimates which more closely reflect the statistics of the underlying magnetization process and produce maps with a justifiable degree of smoothness

using cosmo skymed x band and envisat c band sar interferometry for landslides analysis abstract we explore new possibilities offered by the recently available x band satellite radar sensors for landslide hazard assessments on a detailed scale with particular reference to the exploitation of persistent scatterers interferometry psi techniques special attention is paid to the impact of the improved resolution of new x band radar imagery on the psi results in terms of quality and quantity of useful information this evaluation is supported by theoretical modelling as well as by the comparison of results from x band csk and c band envisat psi for two areas of interest one in italy and the other in switzerland it is demonstrated that with respect to medium resolution envisat ps processing fewer csk high resolution images are sufficient to achieve comparable precision of the mean displacement velocity estimates this together with the shorter revisit times provided by the csk constellation can be very important when dealing with emergency situations furthermore it is quantified that from about 3 to 11 times greater ps densities are obtained with the higher resolution x band data this implies more information about ground surface displacements as well as improved landslide monitoring and slope instability investigation capabilities furthermore ground displacement measurements can be interpreted without local knowledge of the focus area or in situ controls and nonetheless guide single hillslope instability assessments with support of google earth and its high resolution optical imagery this blind approach will allow one to monitor remote and poorly known regions at high risk of potentially disastrous slope failures

scaling nature of crustal susceptibilities scale invariant or self similar properties have been demonstrated for a wide range of geophysical processes and rock properties evidence from well logs and inferences from aeromagnetic field power spectra suggest that crustal susceptibility also shows this behaviour with a power spectrum proportional to the 4 power of the spatial frequency we examine two large susceptibility measurement data sets and find that they both support the scaling hypothesis

gregarious behaviour among non avian theropods inferred from trackways a case study from the cretaceous cenomanian candeleros formation of patagonia argentina abstract gregarious behaviour among dinosaurs has been inferred from several lines of evidence monospecific bonebeds skeletal morphology phylogenetic inferences comparison with modern ecosystems and parallel trackways with particular characteristics but is relatively poorly documented for non avian theropods here we report five parallel theropod trackways of large track size average length of 28 cm in the cretaceous cenomanian candeleros formation from northwestern patagonia argentina the tracks are provisionally assigned to aff asianopodus pulvinicalx and considering the autopod morphology of the theropod taxa documented in the candeleros formation abelisaurid theropods are suggested as trackmakers the trackways possess similar stride speed estimation direction and preservational features and track show uniform depth and do not overlap physical barriers i e large fluvial channels or perennial lake that could influence the direction of the theropod trackmaker gaits were not recognized in the section taking into account these considerations a gregarious behaviour for the abelisaurid theropod trackmakers is proposed the tracks are preserved as shallow undertracks in a medium grained sandstone bed deposited in a floodplain setting the tracking surface is interpreted as the overlaying layer of muddy siltstone the occurrence of swelling clays and microbial mats in the track bearing level could have contributed to the substrate stabilization and their role in the preservation is discussed

inversion of deformation fields time series from optical images and application to the long term kinematics of slow moving landslides in peru abstract slow moving landslides are numerous in mountainous areas and pose a large threat to populations many observations show that their kinematics is driven by climatic forcings and earthquakes in this study we document the complex interaction between those two forcings on the slow moving landslide kinematics based on the retrieval of landslide displacements over 28 years using optical satellite images to overcome the decorrelation effect over this large time span and possible misalignment between images we develop a method that uses the redundancy of displacement fields from image pairs to derive a robust time series of displacement the method is tested on the 28 year long spot1 5 pleiades archive over an area in peru affected by both earthquakes and rainfall errors are estimated on stable areas and by comparison with one 13 year long and eleven 3 year long gps time series on the maca landslide the methodology diminishes by up to 30 the uncertainty and reduces significantly the gaps due to decorrelation the data set allows detecting 3 major landslides moving at a rate of 35 to 50 m over 28 years and smaller landslides with lower displacement rates time series obtained over the three main landslides provide interesting results of their long term kinematics primarily driven by precipitation we propose simple statistical hydro kinematic models relating yearly motion to seasonal rainfall to explain the observed time series we found that annual precipitation is controlling the landslide displacements after a certain rainfall threshold is reached besides this control we show the possible impact of a local mw 5 4 earthquake in 1991 on the kinematics of the maca landslide our results suggest that the earthquake accelerated the landslide and has an effect during several years on the precipitation threshold required for triggering a motion these results suggest that the rainfall threshold can vary in time following strong earthquakes shaking

pre and post failure spatial temporal deformation pattern of the baige landslide retrieved from multiple radar and optical satellite images abstract the baige landslide in southwest china has been active for at least 50 years and experienced two failure events on oct 10 and nov 3 2018 the rock mass and debris of the slope failure formed a landslide dam the discharge of the dammed lake plus the failure events caused significant socio economic losses many slow moving areas appeared after the two failure events and potential landslide risk still exists retrieving the long term spatial temporal pattern of landslide activity can help us to understand and mitigate landslide disasters however it is difficult to monitor all movement episodes of some landslides using single satellite dataset and method due to the different deformation characteristics employing multiple radar and optical images may solve this problem in this study the landsat 8 the alos palsar and alos 2 palsar 2 images are used to obtain the surface displacements before the first failure event by using the cross correlation technique for landsat 8 images and the pixel offset tracking technique the displacement velocity map after the second failure is derived by the multi temporal synthetic aperture radar interferometry mt insar method from the alos 2 palsar 2 and the sentinel 1 images the maximum radar line of sight los average velocity is 3 m yr between jan 2007 and feb 2011 and 12 m yr between jul 2015 and jul 2018 from oct 2013 to feb 2018 the maximum horizontal average velocity is 5 8 m yr the movement accelerated from jul 2017 a large deformation area appeared on the south of the failed slope after the second failure the unstable area observed by the mt insar is much larger than that obtained through the field measurements in the first month after the second failure the maximum los displacements are more than 20 cm the depletion area and the neighboring zones of the landslide are unstable even one year after the second failure this study shows how to use multiple satellite images and hybrid remote sensing techniques to investigate the landslide deformation history and illustrates the benefits of landslide monitoring based on images from multiple satellite sensors

depth estimation from the scaling power spectrum of potential fields summary depth estimation from potential field power spectra requires a realistic assumption of the statistical properties of the source distributions density and susceptibility distributions in the earth s crust exhibit a long range dependence which is adequately described by scaling random fields with a spectral density proportional to some power of the wavenumber the theoretical power spectrum for a half space model of scaling sources explains the shape of observed power spectra of real potential field data very well minimizing the misfit between the model and the observed power spectrum yields an estimate for the depth to the top of the sources after demonstrating this approach on synthetic magnetic data we reinterpret power spectra of gravity and aeromagnetic data from utah hawaii and saskatchewan finding depth values that differ significantly from earlier interpretations all three power spectra are best explained by source distributions starting at surface level even the power spectrum from an aeromagnetic survey of a sedimentary basin with virtually non magnetic basin fill in the latter case a priori information on the intensity and the scaling exponent of the field caused by the basement had to be included to obtain an approximate estimate of the basin depth in general potential field power spectra are dominated by scaling properties of their source distributions and contain only limited depth information

post failure evolution analysis of a rainfall triggered landslide by multi temporal interferometry sar approaches integrated with geotechnical analysis persistent scatterers interferometry psi represents one of the most powerful techniques for earth s surface deformation processes monitoring especially for long term evolution phenomena in this work a dataset of 34 terrasar x stripmap images october 2013 october 2014 has been processed by two psi techniques coherent pixel technique temporal sublook coherence cpt tsc and small baseline subset sbas in order to study the evolution of a slow moving landslide which occurred on february 23 2012 in the papanice hamlet crotone municipality southern italy and induced by a significant rainfall event 185 mm in three days the mass movement caused structural damage buildings collapse and destruction of utility lines gas water and electricity and roads the results showed analogous displacement rates 30 40 mm yr along the line of sight los of the satellite with respect to the pre failure phase 2008 2010 analyzed in previous works both approaches allowed detect the landslide affected area however the higher density of targets identified by means of cpt tsc enabled to analyze in detail the slope behavior in order to design possible mitigation interventions for this aim a slope stability analysis has been carried out considering the comparison between groundwater oscillations and time series of displacement hence the crucial role of the interaction between rainfall and groundwater level has been inferred for the landslide triggering in conclusion we showed that the integration of geotechnical and remote sensing approaches can be seen as the best practice to support stakeholders to design remedial works

characterization of pre and post failure displacements of the huangnibazi landslide in li county with multi source satellite observations abstract the huangnibazi landslide in li county of southwest china began to slide rapidly since 8 august 2017 it received little attention before the failure event the fast motion of the slope posed great threats to the safety of nearby villages and the national highway g317 at the foot of the mountain in this study synthetic aperture radar sar datasets collected by c band sentinel 1 and x band terrasar x tsx as well as optical images acquired by sentinel 2 multi spectral instrument msi over the landslide site were analyzed to characterize the evolution of the slope before and after the failure event firstly the surface change of the sliding area was qualitatively evaluated using the sentinel 2 true color images and pseudo colored terrasar x amplitude images next the slow movement of the slope before the failure event was detected by interferometry using both terrasar x and sentinel 1 data stacks the maximum displacement rate estimated was larger than 45 mm year along the radar line of sight los direction finally the large post failure displacements of the landslide were successfully retrieved with meter level accuracy from terrasar x observations using adaptive amplitude offset tracking method the maximum displacement decreased from about 30 m in 11 days in august 2017 to 1 2 m in 22 days in january 2018 in both los and azimuth directions according to the recent measurements of surface displacement the landslide body is becoming stabilized gradually which suggests that the risk of catastrophic collapse of the slope has been largely reduced

potential field power spectrum inversion for scaling geology we propose a method for inverting the power spectrum of gravity and magnetic data the method is demonstrated on aeromagnetic and bore well data from the german continental deep drilling project ktb density and susceptibility distributions in the earth s crust exhibit scaling behavior with power spectra proportional to f where f is the wavenumber and is the scaling exponent of the source distribution we model the sources of the potential field by a random function with scaling properties defined on a half space with its top at a specified depth beneath the observation plane comparing the theoretical power spectrum for this model with the power spectrum of the measured data we obtain the best values for the depth to source and the scaling exponent as a global minimum of the misfit function despite the simplicity of the model it offers a new understanding of the factors influencing the shape of the potential field power spectrum in particular the low wavenumber part of the power spectrum can be dominated by the scaling properties of the source distribution and not by the depth to some kind of basement the scaling exponent of the field varies with the type of surface geology the question of whether the scaling exponent can actually be used to identify different types of geology gives an interesting new aspect to power spectrum inversion

monitoring activity at the daguangbao mega landslide china using sentinel 1 tops time series interferometry abstract the daguangbao mega landslide china induced by the 2008 wenchuan earthquake m w 7 9 with an area of approximately 8 km 2 is one of the largest landslides in the world experts predicted that the potential risk and instability of the landslide might remain for many decades or even longer monitoring the activity of such a large landslide is hence critical terrain observation by progressive scans tops mode from the sentinel 1 satellite provides us with up to date high quality synthetic aperture radar sar images over a wide ground coverage 250 250 km enabling full exploitation of various insar applications however the tops mode introduces azimuth dependent doppler variations to radar signals which requires an additional processing step especially for sar interferometry sentinel 1 tops data have been widely applied to earthquakes but the performance of tops data based time series analysis requires further exploitation in this study sentinel 1 tops data were employed to investigate landslide post seismic activities for the first time to deal with the azimuth dependent doppler variations a processing chain of tops time series interferometry approach was developed since the daguangbao landslide is as a result of the collapse of a whole mountain caused by the 2008 mw 7 9 wenchuan earthquake the existing digital elevation models dems e g srtm and aster exhibit height differences of up to approximately 500 m tandem x images acquired after the earthquake were used to generate a high resolution post seismic dem the high gradient topographic errors of the srtm dem i e the differences between the pre seismic srtm and the actual post seismic elevation together with low coherence in mountainous areas make it difficult to derive a precise dem using the traditional insar processing procedure a re flattening iterative method was hence developed to generate a precise tandem x dem in this study the volume of the coseismic daguangbao landslide was estimated to be of 1 189 0 110 10 9 m 3 by comparing the postseismic tandem x dem with the preseismic srtm dem which is consistent with the engineering geological survey result the time series results from sentinel 1 show that some sectors of the daguangbao landslide are still active and displaying four sliding zones and exhibiting a maximum displacement rate of 8 cm year even eight years after the wenchuan earthquake the good performance of tops in this time series analysis indicates that up to date high quality tops data with spatiotemporal baselines offer significant potential in terms of future insar applications

a deterministic approach toward isostatic gravity residuals a case study from south america a new deterministic method for correcting isostatic effects in gravity data sets overcomes the deficiencies of empirically based methods this technique produces a superior gravity image for south america and has application to other continental scale gravity data sets the basis for the correction is the airy heiskanen isostatic model which assumes that surface topography is supported by crustal thickening the three key parameters 1 the crustal thickness at sea level 2 the surface reduction density and 3 the density contrast between the crust and the mantle are determined directly from the elevation free air gravity and bouguer gravity data sets the surface density parameter of 2 60 g cc is determined using a new fractal technique this technique assumes that the topography is fractal the best value for density is that which minimizes the fractal component caused by topographic effects the new value is substantially different than the 2 67 g cc density assumed by many previous workers for most continental scale data sets the crust mantle density contrast parameter of 0 45 g cc is determined by comparison between the densities determined from crossplots of the bouguer values versus elevation the crustal thickness parameter of 30 km is determined using a spectral method applied to the free air gravity the results of this work are not only an isostatic residual map but a methodology that cross checks the data for quality control the final isostatic residual map can be used with confidence for basin evaluation throughout the continent of south america basins at high elevations like the eastern foreland basins of the andes and the altiplano basin are imaged better by using this method

north america s largest dinosaur trackway site implications for morrison formation paleoecology little known exposures of the upper jurassic morrison formation from the purgatoire valley of southeastern colorado have yielded the world s largest continuously mapped assemblage of dinosaur trackways body fossils include plant invertebrate and vertebrate remains indicative of predominantly fresh water conditions the tracks occur in a lacustrine sequence characterized by 1 shallow water shales 2 micritic shoreface limestones with ooids intraclasts ripple marks mud cracks and 3 minor quartzose sandstone with salt crystal casts analysis of these sedimentary facies suggests that in southeastern colorado lakes were larger and longer lived than in other morrison paleoenvironments trackway orientations and footprint depth contours pinpoint the location of the paleoshoreline at successive levels in the section detailed mapping of 1 300 footprints in bed 2 has revealed more than 100 trackways which testify to the activity of both quadrupedal and bipedal dinosaurs the respective ratio based on trackway counts is 40 60 the quadrupedal tracks are attributed to sauropods and represent the first ever discovered in north america they also exhibit the first known manus claw impressions and are in need of formal description more than 90 of the bipedal tridactyl prints lack claw impressions and are tentatively therefore referred to the ornithopoda cf gypsichnites possibly a camptosaurus the small proportion with distinct claw impressions may represent allosaurus resulting estimates of species diversity 5 and predator prey ratio 1 30 are in general agreement with the estimates of other authors based on skeletal remains and they suggest that the purgatoire river tracks may accurately reflect the composition of the dinosaur fauna distinctive groupings of parallel non overlapping trackways suggest gregarious behavior among sauropods and tridactylous forms

new dinosaur ichnotaxa from the early jurassic of the holy cross mountains poland abstract the numerous ornithopod tracks discovered during the last four years in the holy cross mts allow the identification of two new ichnospecies anomoepus pienkovskii ichnosp nov and moyenisauropus karaszevskii ichnosp nov the moyenisauropodid structure indicates that the trackmakers may well have been hitherto unknown forms of the earliest iguanodontids newly discovered theropod footprints grallator grallator zvierzi ichnosp nov and grallator eubrontes soltykovensis ichnosp nov supplement knowledge of the early jurassic terrestrial fauna of poland the majority of the tracks occurring in the gliniany las exposure upper hettangian were left by dinosaurs which occupied the margins of a lagoonal environment the other footprints discovered in the soltykow lower hettangian outcrop were left by carnosaurs walking across the fluvial plain

variogram analysis of helicopter magnetic data to identify paleochannels of the omaruru river namibia the geomagnetic field over sedimentary basins is very sensitive to variations in basement depth therefore magnetic surveys are widely used to map basement topography in petroleum and groundwater exploration we propose variogram analysis as a more accurate alternative to power spectral methods data variograms are computed from aeromagnetic flight line data to estimate depth the data variograms are compared with model variograms for a range of source depths we use the exact space domain counterparts of a fractal power spectral model as model variograms to demonstrate the utility of this method for groundwater exploration we map the basement topography of the omaruru alluvial plains in namibia a comparison with electromagnetic em resistivities and drilling information confirms the high accuracy but also the limitations of variogram analysis depth variogram analysis makes maximum use of short wavelength contributions to the magnetic signal which is the key to the resolution of shallow basement t

dynamics of slow moving landslides from permanent scatterer analysis high resolution interferometric synthetic aperture radar insar permanent scatterer data allow us to resolve the rates and variations in the rates of slow moving landslides satellite to ground distances range changes on landslides increase at rates of 5 to 7 millimeters per year indicating average downslope sliding velocities from 27 to 38 millimeters per year time series analysis shows that displacement occurs mainly during the high precipitation season during the 1997 1998 el nino event rates of range change increased to as much as 11 millimeters per year the observed nonlinear relationship of creep and precipitation rates suggests that increased pore fluid pressures within the shallow subsurface may initiate and accelerate these features changes in the slope of a hill resulting from increases in the pore pressure and lithostatic stress gradients may then lead to landslides

deformation time series generation in areas characterized by large displacement dynamics the sar amplitude pixel offset sbas technique we exploit the amplitude information of a sequence of synthetic aperture radar sar images acquired at different times in order to generate displacement time series in areas characterized by large and or rapid deformation the size of which is on the order of the image s pixel dimensions we follow the same rationale of the small baseline subset sbas differential sar interferometry dinsar approach by coupling the available sar images into pairs characterized by a small separation between the acquisition orbits we exploit the amplitudes of the selected image pairs in order to calculate the relative across track range and along track azimuth pixel offsets po finally we apply the sbas inversion strategy to retrieve the range and azimuth displacement time series this approach referred to as pixel offset po sbas technique has been applied to a set of 25 envisat sar observations of the sierra negra caldera galapagos islands spanning the 2003 2007 time interval the retrieved deformation time series show the capability of the technique to detect and measure the large displacements affecting the inner part of the caldera that in correspondence to the october 2005 eruption reached several meters moreover by comparing the po sbas results to continuous gps measurements we estimate that the accuracy of the po sbas time series is on the order of 1 30th of a pixel for both range and azimuth directions

improved ocean geoid resolution from retracked ers 1 satellite altimeter waveforms summary the ocean geoid can be inferred from the topography of the mean sea surface satellite altimeters transmit radar pulses and determine the return traveltime to measure seasurface height the ers 1 altimeter stacks 51 consecutive radar reflections on board the satellite to a single waveform tracking the time shift of the waveform gives an estimate of the distance to the sea surface we retrack the ers 1 radar traveltimes using a model that is focused on the leading edge of the waveforms while earlier methods regarded adjacent waveforms as independent statistical events we invert a whole sequence of waveforms simultaneously for a spline geoid solution smoothness is controlled by spectral constraints on the spline coeycients our geoid solutions have an average spectral density equal to the expected power spectrum of the true geoid the coherence of repeat track solutions indicates a spatial resolution of 31 km as compared to 41 km resolution for the ers 1 ocean product while the resolution of the latter deteriorates to 47 km for wave heights above 2 m our geoid solution maintains its resolution of 31 km for rough sea retracking altimeter waveform data and constraining the solution by a spectral model leads to a realistic geoid solution with significantly improved along track resolution

variogram analysis of magnetic and gravity data model variograms describe the space domain statistics of magnetic and gravity data variogram analysis can be used to map intensity depth and scaling exponent self correlation of source in previous statistical methods the measured data were gridded and transformed to the wavenumber domain then their power spectrum was analyzed using a spectral model to avoid the loss and distortion of information during gridding and wavenumber domain transform i transform the spectral model to the space domain instead variograms are the appropriate space domain counterparts of magnetic and gravity power spectra the variogram of the field above a self similar half space model is governed by three parameters intensity depth and scaling exponent these source parameters can be mapped with high resolution and accuracy by fitting model variograms directly to magnetic and gravity line data variograms

detection and displacement characterization of landslides using multi temporal satellite sar interferometry a case study of danba county in the dadu river basin abstract detection of potential slope instabilities across wide areas using sar interferometry insar techniques can aid prevention and mitigation of landslide disasters nevertheless the low spatial density of coherent radar targets detected by conventional time series insar methods in mountainous areas with complex topography and vegetation cover introduces considerable uncertainties into the deformation measurements and thus results in a high probability of omissions for landslide detection in this study a new time series insar method named coherent scatterers insar csi is proposed to solve this problem through the joint exploitation of persistent scatterers ps and distributed scatterers ds to increase the quantity of measurement points mps in rural environments we applied this approach to detect potentially unstable slopes at a catchment scale delineate sliding boundaries and measure the deformation of major landslides the archived alos palsar and envisat asar data stacks covering the danba county in the upper reach of the dadu river basin in southwest china were processed the palsar measured deformation rate map revealed 17 suspected landslides and their sliding boundaries by contrast only six out of these 17 landslides were detected from the asar results as the other 11 landslides were undetected due to the much lower density of coherent points these detection results were indirectly verified by two different approaches two differential interferograms for recently acquired l band alos 2 palsar 2 data pairs were visually inspected to check whether these landslides are still in active deformation the reliability of the insar results was further evaluated by comparisons against field survey and in situ gps measurements the spatial and temporal patterns of surface displacements at several slow moving landslides were analyzed in detail and general guidelines on the application of the csi method for landslide investigations were discussed and summarized

curie temperature depth estimation using a self similar magnetization model summary the earth s crust is magnetized down to the curie temperature depth at about 10 to 50 km this limited depth extent of the crustal magnetization is discernible in the power spectra of magnetic maps of south africa and central asia at short wavelengths the power increases as rapidly towards longer wavelengths as expected for a self similar magnetized crust with unlimited depth extent above wavelengths of about 100 km the power starts increasing less rapidly indicating the absence of deep seated sources to quantify this effect we derive the theoretical power spectrum due to a slab carved out of a self similar magnetization distribution this model power spectrum matches the power spectra of south africa and central asia for a self similarity parameter of 4 and curie temperature depths of 15 to 20 km

surface displacements of the heifangtai terrace in northwest china measured by x and c band insar observations abstract the heifangtai terrace located in yongjing county of gansu province in northwest china is characterized by a large number of landslides with frequent failure events related to agricultural irrigation activities thus it is a task of great importance to identify and monitor the active loess slopes and sort out the impact factors in this study we employed the time series insar method to map the active slopes in the heifangtai terrace with two terrasar x data stacks covering the year of 2016 and two sentinel 1 data stacks from 2016 to 2018 the detected active spots are mainly distributed along the edges of the terrace time series displacements derived from terrasar x and sentinel 1 observations were validated by comparisons against gps and crack gauge measurements good agreement between insar and gps was achieved at slow moving locations while unwrapping errors induced by sudden accelerations make insar underestimate the pre failure displacements with respect to gps measurements the trends of insar measured displacement and crack gauge measurements also match well with correlation higher than 0 75 insar measured displacements at the jiaojia landslide group were highly correlated with the bury of groundwater record which suggested that the rising of groundwater level may seriously decrease the stability of loess slopes

the historical development of the magnetic method in exploration the magnetic method perhaps the oldest of geophysical exploration techniques blossomed after the advent of airborne surveys in world war ii with improvements in instrumentation navigation and platform compensation it is now possible to map the entire crustal section at a variety of scales from strongly magnetic basement at regional scale to weakly magnetic sedimentary contacts at local scale methods of data filtering display and interpretation have also advanced especially with the availability of low cost high performance personal computers and color raster graphics the magnetic method is the primary exploration tool in the search for minerals in other arenas the magnetic method has evolved from its sole use for mapping basement structure to include a wide range of new applications such as locating intrasedimentary faults defining subtle lithologic contacts mapping salt domes in weakly magnetic sediments and better defining targets through 3d inversion these new applications have increased the method s utility in all realms of exploration in the search for minerals oil and gas geothermal resources and groundwater and for a variety of other purposes such as natural hazards assessment mapping impact structures and engineering and environmental studies

some observations on trackway evidence for gregarious behavior among small bipedal dinosaurs abstract although trackway evidence for social behavior herding or gregariousness has been demonstrated for large mainly quadrupedal dinosaurs until recently footprint evidence for herding among small bipedal dinosaurs has been sparse recent reports now increase the number of sites suggestive of social behavior to nine found in strata of early jurassic through mid cretaceous age in europe north america and east asia present evidence suggests that small gregarious dinosaurian bipeds included both theropod and ornithopod species