The European Ground Motion Service (EGMS) is part of the Copernicus Land Monitoring Service (CLMS) managed by the EEA (European Environment Agency) [1]. EGMS is based on the full resolution InSAR processing of ESA Sentinel-1 (S1) acquisitions over Europe (Copernicus Participating states) [2]. The first release or baseline includes ground motion time-series between 2015 and 2020. This open data service has yearly updates.The EGMS employs persistent scatterer (PS) and distributed scatterer (DS) in combination with a Global Navigation Satellite System (GNSS) model to calibrate the ground motion products. This public dataset consists of three products levels (L2a/Basic, L2b/Calibrated and L3/Ortho). The Basic and Calibrated product levels are full resolution (20x5m) Line of sight (Los) velocity maps from ascending/descending orbits. The Ortho product offers horizontal (East-West) and vertical (Up-Down) anchored to the reference geodetic model resampled at 100x100m.The objective of this paper is to describe the independent validation of this continental scale ground motion time-series dataset. The goal is to ensure that the EGMS products are consistent with user requirements and product specifications and they cover the expected range of applications. To evaluate the fitness of the EGMS ground motion data service 7 reproducible validation activities (VA) have been developed gathering validation data from 50 sites across 12 European countries. Last but not least, a software environment has been developed to carry out all the validation activities and describe/store the data coming from the validation sites.@en

Within the Netherlands, 24 geothermal systems have been realized of which 18 added to production of 3.7 PJ of heat in 2018. The main application domain is horticulture. The ambition of the Dutch government is to increase the production of geothermal energy in the Netherlands to 15 PJ in 2030, subsequently 110 PJ in 2050 and to expand the application domain to district heating and industry. Kramers et al. (2012) published an article on the direct heat resource assessment stating that the recoverable heat amounts to just over 63000 PJ, assuming a reinjection temperature of 35 °C. This resource estimate combines all direct heat projects regardless of their maturity. A state-of-the-art resource assessment can support the Dutch government policy to realize its ambition by classifying the resources based on project maturity, including reference to the obstructing issues in the maturation of projects such as technical, financing, licensing and/or social and environmental complexities. In January 2019, 78 exploration licenses are active or have been applied for. At least one geothermal project is defined in each of these licenses, at different levels of advancement. Outside the existing licenses and licenses applied for, The Netherlands provides ample space for geothermal development by geothermal projects, yet in a conceptual stage. At the moment, there are no tools or practical methodology to integrate all the available information in a coherent and automated manner. Furthermore, a method to quantify the geothermal energy resources of projects ‘not yet realized’ using the United Nations Framework Classification (UNFC) resource classification system, would help policymakers to decide upon the most appropriate measures to relieve the obstruction issues to reach the 2030-2050 geothermal ambitions. In this study, we show the results of a resource assessment and classification system for geothermal energy while incorporating environmental and social issues in the classification, as required by the UNFC-2009. As basis for this resource assessment, we use the webtool ThermoGIS. ThermoGIS which uses information on the Dutch subsurface derived from the regional mapping by the Geological Survey and which is updated by incorporating newly gained insights and data, provides a comprehensive overview of the geothermal potential for a selected set of aquifers. The resource estimate, including the uncertainty range related to these figures, at the status date 1-1-2019 of the Dutch geothermal “project portfolio” is classified using UNFC, resulting in a set of resource figures per resource class according to project maturity: commercial, potentially commercial, non-commercial and exploration projects. Furthermore, some additional development options are introduced like installing heat pumps on relevant projects and stimulation on projects with poor productivity to increase the resource potential. Next level analysis envisages that future projects are given an attractivity attribute reflecting, amongst others, proximity to areas of favourable heat demand, proximity to heat network, which will guide the order of the exploration drilling sequence. An estimate on the geothermal portfolio maturation speed will then reflect on the minimum number of wells to be drilled to reach the geothermal ambition. @en

The Netherlands is subject to anthropogenic and natural subsidence with rates for which the relative contribution of each process to total subsidence (i.e. natural plus anthropogenic) is still unclear. Such information is important for stakeholders to support decision making on subsidence mitigation and it should be substantiated with independent scientific studies. We present the outline of a hybrid Artificial Intelligence (AI) and knowledge-based physical model (geomechanical models) workflow to disentangle different subsidence forcing. We use static (structural model) and time-dependent data for both surface (geodetic measurements: GPS, levelling and InSAR) and subsurface (phreatic groundwater level, reservoir pressure). We show preliminary results of the approach for an area covering a gas field in the Friesland coastal plain and an area in the peat-rich central Rhine-Meuse delta plain. @en

The proposal for a Program for the requalification of Lisbon's "priority intervention Neighborhoods or Zones" (hereon, BIP/ZIP, original acronym in Portuguese) comes within the scope of the objectives of the Local Housing Program (PLH), approved by the autarchic bodies at the end of 2009. The first task implied the construction of the concept of Priority Intervention Neighborhood, which was worked on the definition of "Critical Neighborhood" (Resolution of the Council of Ministers 142/2005 of August 2), in conjunction with the research of socio- economic, urban and environmental. It was then moved to a finer definition, which includes not only Priority Intervention Districts (BIPs), but also Priority Intervention Zones (ZIP). As a first approach to the BIP / ZIP delimitation, several existing municipal boundaries that could be included in the Priority Neighborhood concept and that had already been identified within the scope of the PLH were transposed to cartographic support. The delimitations considered were as follows: 1.ACRRU - Critical Area of Urban Recovery and Reconversion 2. AUGI - Urban Area of Illegal Genesis 3. Municipal Districts (under GEBALIS management) with special problems 4. Remaining Areas of PIMP and PER (Special Rehabilitation Programs) 5. Neighborhoods ex-SAAL with serious problems pending 6. Area of intervention of the Western SRU - Western Urban Rehabilitation Assistance 7. Area of intervention of the Viver Marvila Program As a second approach to the BIP / ZIP delimitation, the following analytical method was used: several relevant indicators were selected to identify the most critical situations in the socio-economic, urban and environmental dimensions, which allowed the construction of a social index and an urban index with graphic expression at the block scale (statistical subsection). The cartographic analysis was complemented with data to the scale of the parish. It was not possible, with the available data, to build an environmental index. The social index and the urban index were worked together, duly filtered, allowing the creation of a composite index that synthesizes the most critical occurrences in the socioeconomic and urbanistic dimensions. From the cartographic overlap of this composite index with the municipal boundaries already analyzed, it results in the determination of a "spot" in the city that defines its socio-territorial fracture, thus showing the areas of the city where, more likely, are the neighborhoods and zones intervention. On this spot was made an empirical first identification of 50 neighborhoods. The methodology used and the list of neighborhoods identified were subject to three participatory workshops, involving municipal services and companies, permanent committees of the Municipal Housing and Urban Planning Council, parish councils and associations of residents of the identified neighborhoods. in the end, an extension of the initial list to the current 6 61 Districts and Priority Intervention Areas included in the C Letter of the BIP-ZIP approved by the CML for submission to public consultation until September 30.@en

In autumn 2017 a network of 14 broadband seismic stations was deployed at the Theistareykir high temperature geothermal field (NE Iceland). This experiment was conducted as part of the current efforts to characterize the field's main structures, and possible short and long term stress variations due to the ongoing fluid injection and extraction operations which started in autumn 2017. In this work, we use two years of continuous seismic records (October 2017–October 2019) to compute a 3D shear wave velocity model of the geothermal field and to detect possible crustal stress changes related to the injection and production activities. From phase cross-correlations of the vertical component recordings, we measure the Rayleigh wave group velocity dispersion curves to obtain 2D group velocity maps between 1 and 5 s. Subsequently, we use a neighborhood algorithm to retrieve the 3D shear wave velocity model of Theistareykir. Mainly, two sets of elongated high and low velocity anomalies can be observed oriented in a NW/WNW direction, parallel to the lineaments of the active Tjörnes fracture zone. Velocity reductions west of Ketilfjall and at Baerjafjall could indicate the location of upflow zones of the magmatic reservoir or hydrothermal system. We analyzed the temporal evolution of phase and amplitude of phase auto-correlations using the stretching technique and discuss their behavior in relation to the geothermal field operations. We notice a slightly stronger long-term velocity decrease in the reservoir region compared to outer regions. This could be related to the mass depletion in that area (higher fluid extraction compared to the water reinjection). In summary, our findings show how a monitoring network can be set up to enable a detailed imaging and monitoring of reservoir behavior in general.@en

Surface deformation due to fluid extraction can be detected by satellite-based geodetic sensors, providing important insights on subsurface geomechanical properties. In this study, we use Differential Interferometric Synthetic Aperture Radar (DInSAR) observations to measure ground deformation due to fluid extraction at the Los Humeros Geothermal Field (Puebla, Mexico). Our main goal is to reveal the pressure distribution in the reservoir and to identify reservoir compartmentalization, which can be important aspects for optimizing the production of the field. The result of the PS-InSAR (Persistent Scatterer by Synthetic Aperture Radar Interferometry) analysis shows that the subsidence at the LHGF was up to 8 mm/year between April 2003 and March 2007, which is small relative to the produced volume of 5×106 m3/year. The subsidence pattern indicates that the geothermal field is controlled by sealing faults separating the reservoir into several blocks. To assess if this is the case, we relate surface movements with volume changes in the reservoir through analytical solutions for different types of nuclei of strain. We constrain our models with the movements of the PS points as target observations. Our models imply small volume changes in the reservoir, and the different nuclei of strain solutions differ only slightly. These findings suggest that the pressure within the reservoir is well supported and that reservoir recharge is taking place.@en

In recent years, new algorithms have been proposed to retrieve maximum available information in synthetic aperture radar (SAR) interferometric stacks with focus on distributed scatterers. The key step in these algorithms is to optimally estimate single-master (SM) wrapped phases for each pixel from all possible interferometric combinations, preserving useful information and filtering noise. In this paper, we propose a new method for SM-phase estimation based on the integer least squares principle. We model the SM-phase estimation problem in a linear form by introducing additional integer ambiguities and use a bootstrap estimator for joint estimation of SM-phases and the integer unknowns. In addition, a full error propagation scheme is introduced in order to evaluate the precision of the final SM-phase estimates. The main advantages of the proposed method are the flexibility to be applied on any (connected) subset of interferograms and the quality description via the provision of a full covariance matrix of the estimates. Results from both synthetic experiments and a case study over the Torfajökull volcano in Iceland demonstrate that the proposed method can efficiently filter noise from wrapped multibaseline interferometric stacks, resulting in doubling the number of detected coherent pixels with respect to conventional persistent scatterer interferometry.@en

Torfajökull is the largest silicic volcanic centre in Iceland lying at the intersection of the rift zone (MidAtlantic Ridge) and the transform zone that connects to Reykjanes peninsula. It erupts infrequently,with only two eruptions in the last 1200 years, the latest of which was over 5 centuries ago. Yet, itsactive tectonic setting, persistent high and low frequency seismicity, deformation and geothermalactivity within its large caldera (18x12 km diameter) indicate the continued presence of a long-lasting magma chamber. Here we speculate on possible geometry, size and depth of the Torfajökullmagma chamber by using radar interferometry (InSAR) and seismic interferometry (SI).Using InSAR time series analysis we detect a surface subsidence pattern at rates of up to ~13 mm yr-1in the SW region of Torfajökull ́s caldera, on-going since at least 1993. The subsidence rate isconstant in time, and perhaps due to a cooling magma chamber. The data can be fit reasonably wellusing a model of a NE-SW oriented spheroidal body at ~5 km depth. As the deflating area correlatesspatially with the area of geothermal activity, deflation may also be the surface response due to anactive hydrothermal circulation.To gain more insight into the geometry of Torfajökull’s magmatic system and rock properties of thesubsurface, we apply ambient noise seismic interferometry (SI) by cross-correlation of ambient noise.With this technique we can detect velocity variations, which can correspond to the edges of dikes ormolten magma bodies. Our tomographic results give reliable results of velocity variations within adepth range of 2 km to 7.5 km. We find high velocity zones that we interpret as old dike intrusions.Low velocity anomalies (>5%), which usually indicate the presence of warmer material, are locatedon the southeast and southwest part of the volcano, outside the volcano caldera.Finally we compare both InSAR and SI results. The hypothesis of a magma chamber under thesubsidence area detected by InSAR does not seem to fit the tomographic results, as the expectededges of a magma body modelled by InSAR are not clearly identified by the SI results. If there is anestablished magma chamber within Torfajökull caldera this is likely to be bellow 7km depth.@en

After decades of oil, gas, and coal exploitation, we have learned about some of the unpleasant aftereffects of subsurface resource exploration. Adverse long-term impacts, some known during exploration periods, others only afterwards, may include induced seismicity, land subsidence, or even sinkholes. While geothermal is currently seen as a sustainable source of energy, seismicity induced by inappropriate operational procedures or lack of knowledge of the subsurface may incite doubt and public sensitivity about its future use. A problem frequently posed before and during geothermal exploration is the cost of geophysical measurements for resource assessment, subsurface characterization during the prospection phase, and monitoring accompanying production. In this study, we investigate and discuss the potential of two economic geophysical measurement techniques for geothermal reservoir characterization and monitoring: passive seismic interferometry for better subsurface characterization through seismic imaging (static model), and satellite-based radar interferometry for geodetic imaging (dynamic model). Seismic imaging using passive seismic techniques allows for subsurface characterization via Ambient Noise Tomography, and supports the assessment of geothermal resources without requiring the use of shooting, which reduces the cost compared to active seismics. Geodetic imaging, by measuring the surface displacements during and after production, allows for the monitoring of the effects of production and constrains reservoir modelling, and can be achieved through the use of (freely available) satellite imagery. We discuss the results of both techniques over two high enthalpy geothermal sites in Iceland: Reykjanes Peninsula and Torfajökull volcano. While the Reykjanes Peninsula has geothermal fields that have been producing for decades, Torfajökull’s geothermal field, despite being the largest in Iceland, is not producing. For the subsurface characterization, we use S-wave velocity tomographic images derived from ambient noise seismic interferometry over the two geothermal sites. Within the tomographic images, low- and high-velocity anomalies are used to characterize subsurface structures, which complement current geological models with information at greater depths. From the monitoring point of view, radar satellite deformation measurements over both areas show displacements (subsidence) due to production (Reykjanes) and due to natural phenomena (Torfajökull). Finally, we summarize the lessons learnt and discuss outcomes on each technique.@en

We investigate ground movements induced by the 8 February 2016, Mw=4.2 earthquake at the Los Humeros Geothermal Field (Mexico) using Sentinel-1 radar interferometry. Previous estimated focal mechanism solution based on seismic data with a hypocentral depth of 1900 m could not resolve the measured coseismic surface deformation pattern. In this study, we applied inverse elastic dislocation models to estimate the source parameters of the seismic event. Our models suggest the reverse reactivation of the Los Humeros normal fault at a shallower depth (<1000 m), with a more significant left lateral component below ~400 m depth. The occurrence of such shallow events at Los Humeros pose increased risks for the neighboring communities and infrastructure. Therefore, continuous monitoring of seismicity and cautious planning of field operations are crucial. A NNW-SSE striking fault swarm, including the Los Humeros fault, acts as a major boundary of the subsiding area observed by InSAR time-series between February 2016 and May 2019. A potential explanation of the reverse reactivation of the Los Humeros fault and following downward movement of the eastern fault block is the depressurization of the whole hydrothermal system. Such depressurization can occur due to the exploitation of the geothermal field and/or due to natural pressure/temperature changes related to magmatic activity.@en

Torfajökull volcano, Iceland, has not erupted since 1477. However, intense geothermal activity, deformation, and seismicity suggest a long‐lasting magmatic system. In this paper, we use ambient noise tomography to image the magmatic system beneath Torfajökull volcano. One hundred days of ambient noise data from 23 broadband seismometers show the consistent presence of double‐frequency microseism noise with significant power between ∼0.1 and 0.5 Hz. Beamforming results indicate microseism noise with persistent higher energy propagating from west and SE directions and apparent velocities below 3 km/s. We use ambient noise seismic interferometry to retrieve Rayleigh waves, and we introduce a method to estimate the reliability of the retrieved surface waves. We find stable estimation of surface wave phase velocities between 0.16 and 0.38 Hz. Azimuthal velocity variations show a trend of higher velocities in the NE/SW direction, the strike of the rift zone intersecting Torfajökull, and orientation of erupted lavas on a NE‐SW fissure swarm. Tomographic results indicate low‐velocity anomalies beneath the volcano caldera (between −5% and −10%) and even lower velocity variations in the southeast and southwest study area (below −10%), outside the volcano caldera. Low anomalies may indicate the existence of hot material, more prominent outside the caldera outskirts. High‐velocity variations (between 5% and 10%) outline the volcano caldera between 4‐ and 5‐km depth and more pronounced velocities (between 10% and 15%) up to 5‐km depth in the north of the volcano caldera. We interpret the former as possible caldera collapse structure and the latest as solidified intrusive magma from the old preferred magma paths.@en

On the 8th of February 2016, a Mw 4.2 earthquake was detected inside the Los Humeros caldera, located in the eastern sector of the Trans-Mexican Volcanic Belt. The event occurred after a sharp increase in the injection rate at the Los Humeros Geothermal Field and it was recorded by the seismic monitoring network of the power plant. The earthquake was felt by the local population and it caused damage in the power plant infrastructure. The focal mechanism solution of a previous study based on seismological data shows a reverse movement with a minor left-lateral component: Mw=4.2, depth=1500m, strike=169°, dip=61°, rake=42°. We have performed a geodetic and geomechanical analysis of the seismic source event based on ground deformation inferred from DInSAR. We used ascending and descending Sentinel-1 differential interferograms to retrieve the horizontal and vertical components of the co-seismic deformation. Subsequently, we inverted the estimated deformation to obtain the solution of an activated fault using the Okada model. These results shed light on the geomechanical aspects of the event and can help to understand the effects of field operations interacting with pre-existing structural features and active tectonic processes in the Los Humeros caldera.@en

Tomographic imaging based on ambient seismic noise measurements has shown to be a powerful tool, especially in areas like Iceland, where the microseism illumination is excellent. In this paper, we produce a 3D S-wave tomographic image over the western Reykjanes Peninsula high-enthalpy geothermal fields and evaluate the reliability of the tomographic results for different resolutions through simulated and real data. We use 30 broadband stations operating for approximately one-and-a-half year and apply ambient noise seismic interferometry for each station-pair. This results in empirical Green's functions in which especially the ballistic surface waves (BSW) are well resolved. The retrieved BSW exhibit a high signal-to-noise ratio between 0.1 and 0.5 Hz, and the beamforming analysis indicates an apparent surface-wave velocity of 3 km/s over a broad azimuthal range. For the tomographic inversion, we invert the estimated phase velocities between all station pairs to frequency-dependent phase velocity maps in four different resolutions (1, 2, 3, and 4 km) using a Tikhonov regularisation. With the estimated regularisation parameter per frequency per resolution, we invert simulated data for checkerboard sensitivity tests per frequency for different combinations of velocity anomaly sizes and resolutions. Finally, after the inversion to depth, we detect S-wave velocity anomalies with variations between −15% and 15% with reference to an estimated average velocity using 1 km and 3 km of lateral resolutions and 1 km of vertical resolution. This study shows the potential of ambient noise tomography as complementary seismological tool for reservoir characterization.@en

Integration of results from active seismic, passive seismic and well data reduces the uncertainties of several subsurface parameters that are of interest for cost-effective geothermal production operations in Los Humeros. In this study, we present results from the application of ambient noise seismic interferometry (ANSI) to retrieve zero-offset reflected P-waves from continuous seismic data recorded at the Los Humeros geothermal field, Mexico. This study is inspired by encouraging results from the application of ANSI for body wave reflection retrieval that was reported in 2016 for a geothermal field located at Reykjanes peninsula, Iceland (Verdel et al., 2016). Continuous broadband and short-period seismic recordings provided insightful reflection information that corresponded well, in relevant depth intervals, with reflectivity retrieved from the correlation of coda waves from a distant but very strong earthquake. That work was carried out within the context of EU’s Seventh Framework research and innovation program IMAGE. Encouraged by these findings, it was decided to conduct a new study following a similar approach within the context of the GEMex project, a European-Mexican collaboration. The purpose of GEMex is to gain an improved understanding of the geological structure and geothermal reservoir behaviour for two geothermal fields: Los Humeros and Acoculco. In the following, we address data selection and processing aspects related to the retrieval of reflected P-waves from Los Humeros seismic noise recordings. The retrieved reflections are compared with modelled reflectivities at two station locations at a close distance from the location where the seismic interval velocities that are used in the modelling were available from the literature. The reflected P-wave information provides structural detail about the field at locations directly underneath the employed seismic stations.@en

We perform statistical analyses on spatiotemporal patterns in the magnitude distribution of induced earthquakes in the Groningen natural gas field. The seismic catalogue contains 336 earthquakes with (local) magnitudes above, observed in the period between 1 January 1995 and 1 January 2022. An exploratory moving-window analysis of maximum-likelihood b-values in both time and space does not reveal any significant variation in time, but does reveal a spatial variation that exceeds the significance level. In search for improved understanding of the observed spatial variations in physical terms we test five physical reservoir properties as possible b-value predictors. The predictors include two static (spatial, time-independent) properties: The reservoir layer thickness, and the topographic gradient (a measure of the degree of faulting intensity in the reservoir); and three dynamic (spatiotemporal, time-dependent) properties: The pressure drop due to gas extraction, the resulting reservoir compaction, and a measure for the resulting induced stress. The latter property is the one that is currently used in the seismic source models that feed into the state-of-The-Art hazard and risk assessment. We assess the predictive capabilities of the five properties by statistical evaluation of both moving window analysis, and maximum-likelihood parameter estimation for a number of simple functional forms that express the b-value as a function of the predictor. We find significant linear trends of the b-value for both topographic gradient and induced stress, but even more pronouncedly for reservoir thickness. Also for the moving window analysis and the step function fit, the reservoir thickness provides the most significant results. We conclude that reservoir thickness is a strong predictor for spatial b-value variations in the Groningen field. We propose to develop a forecasting model for Groningen magnitude distributions conditioned on reservoir thickness, to be used alongside, or as a replacement, for the current models conditioned on induced stress.@en

Tomographic studies based on passive seismic measurements have proven to be a powerful tool to image the subsurface. This especially holds in areas like Iceland, where the microseism coverage arriving from the ocean is excellent. In this study, we apply Ambient Noise Seismic Interferometry (ANSI) to generate a tomographic image of Rayleigh-waves velocity anomalies to further invert for S-wave anomalies at two Icelandic locations. We derive a tomographic image over Reykjanes Peninsula geothermal system using 30 Broad-Band (BB) stations deployed under the IMAGE (Integrated Methods for Advanced Geothermal Exploration) project framework and operated for approximately one year and a half. In the other case study, we derive a tomographic image of Torfajökull volcano using 23 BB seismometers that recorded ambient noise for 100 days. The later data were acquired in 2005 by Cambridge University. We retrieve the surface-wave part of the Green’s functions by cross-correlation between station pairs and consecutive stacking of the cross-correlations to obtain coherent ballistic surface waves (BSW). We pick the arrival times of the BSW, which are the input for the tomographic analysis. Both datasets show remarkably high signal-to-noise ratio of surface-wave arrivals between 0.1 and 0.5 Hz, even with only 100 days of recorded ambient noise. A beamforming analysis indicates a broad azimuthal coverage with persistent ambient noise arrivals within three azimuthal quadrants - between 90 and 360 degrees. The highly coherent surface-wave retrieval and the wide azimuthal coverage of the microseisms explain the success of ANSI techniques in Iceland. For the tomographic inversion, we use a Tikhonov and a statistical regularisation to invert the ballistic surface-wave time-arrival to 3D frequency-dependent velocity variations. After further inversion to S-wave velocity variations, we detect low- and high-velocity anomalies with changes between -15% and 15% from an estimated average velocity, we interpret these anomalies as possible old dyke intrusions and heat sources.@en

Detecting a point-like target when it is horizontally displaced is of paramount importance in target tracking and in measuring the motion of glaciers over short intervals of time. This paper performs an experimental study of the accuracy, precision and sensitivity of the horizontal motion detectable using SAR. Therefore point-like targets such as corner reflectors (CR) are moved horizontally in a controlled manner over short time intervals to reproduce the real target motion. Such CR movements are monitored using SAR and the results are compared with the ground truth to arrive at the target horizontal motion determination parameters. Towards this goal three CRs were installed each displaced by a few hundreds of metres in a farmland in Delft, The Netherlands. These corner reflectors are inclined for ERS-2 3-days ice-phase mission starting March 2011. Since the area does not exhibit horizontal motion, one of the CRs was moved horizontally stepwise in the order of a few centimeters to a few metres. At each step the CRs are imaged by SAR and also measured by campaign-style GPS (and with a few leveling campaigns) in order to provide the actual displacement in three dimensions. Then the motion is computed using SAR data and results are compared with the GPS measurements to validate the sensitivity of SAR in detection of motion of the targets. The experimental setup is such that the CRs are visible starting from March 2011 from both ascending and descending orbit TerraSAR-X satellite acquisitions over Delft. Hence similar parameters such as sensitivity, precision and accuracy of motion detection will be derived for X-band SAR as well. Further, in order to substantially verify the reliability of our computations, data from three different field experiments with stable CRs performed with ERS-1/2 in 1996, with ENVISAT from 2003 to 2007 and with ENVISAT from March 2010 to January 2011 in the areas of Groningen, Delft and Cabauw respectively were exploited. The outcome of our experiment will result in the empirical study of the sensitivity of motion detection of point-like targets in C- and X- bands. Also the influence of these parameters under varying imaging conditions such as change in Doppler and perpendicular baselines will be discussed. @en

Persistent Scatterer Interferometry (PSI) has emerged over the last decade as a technique capable of very accurate (millimetric) measurements of ground deformation occurring at radar scatterers (persistent scatterers or PS) that are phase coherent over a period of time. PSI studies using C-band SAR data have shown that the PS spatial density in urban areas is usually very high (100-300 PS/km2). However, many ground deformation phenomena (e.g. tectonic motion, volcanoes, landslides, mining, gas extraction, CO2 sequestration) occur in uninhabited or rural areas with few man-made structures, leading to much lower PS density because of significant phase decorrelation between subsequent SAR acquisitions. In order for PSI to be effective in monitoring these areas, it has been found that a PS density greater than about 10 PS/km2 is required. Artificial amplitude- and phase-stable radar scatterers may thus have to be introduced in non-urbanised geodynamic areas that have too low a density of PS points. Conceptually the simplest of these artificial PS points are corner reflectors. Several experiments have been performed in the past using these reflectors, with conclusive results about their amplitude and phase stability. They suffer, however, from the disadvantage of large size (in the order of a metre in case of C-band SAR). To make these artificial PS points easy to deploy and maintain, especially in poorly accessible areas, Compact Active Transponders (CATs) have been designed to be used in lieu of corner reflectors. These CATs are small (in the order of a few tens of centimetres), lightweight (<3 kg), less obtrusive, and have the added advantage of a better link budget due to signal amplification by the transponder. They are sealed, function autonomously with internal power and over a wide temperature range, and can operate unattended for more than a year. Additionally, since a CAT is transmitter-specific and is only turned on at the time of the satellite overpass, it offers little interference to other radar or radio targets. However, it is of paramount importance in geodetic applications to ensure that the phase of the CAT remains stable in all operating and environmental conditions. Towards this goal, an experiment to validate the phase stability of CATs has been set up in a farmland in Delft (The Netherlands). The setup comprises three CATs and three corner reflectors, which are installed at distances of a couple of hundred metres from each other. SAR data from the ERS-2 Ice-Phase Mission are being acquired every three days between March and June 2011. Since the area does not exhibit steady ground deformation, some of the units are displaced vertically by a controlled amount. Levelling is performed between the CATs and the corner reflectors as close as possible to each SAR acquisition, in order to validate the height differences obtained from the radar phase information. As a second means of validation, campaign-style GPS is performed on each of the devices to accurately position them in WGS-84 coordinates. One of the CATs in the Delft field experiment has an integrated GPS antenna, to ensure millimetric coregistration and a coherent cross-reference. This novel unit called I2GPS (Integrated Interferometry and GNSS for Precision Survey) has been developed with the objective of producing a fully-integrated deformation map. In addition to providing absolute calibration for PSI data, the high temporal sampling rate of GPS data imparts the capability of accurately detecting abrupt ground motion in three dimensions. With adequate GPS/I2GPS units, the vertical components of the local velocity field can be derived from single-track InSAR line-of-sight displacements. The results and conclusions of this experiment consisting of corner reflectors, CATs and I2GPS will be presented and analysed here.@en

The coastal plains of the Netherlands are subject to anthropogenic and natural subsidence with rates which are an order of magnitude higher than sea-level rise. Because one-third of the Netherlands lies below mean sea level, subsidence may threaten the country’s subsistence with major socio-economic consequences. Subsidence is a normal natural process but is overprinted and accelerated by anthropogenic activities which drives deep or shallow processes. Deep processes are caused by the extraction of hydrocarbons and salt, whereas shallow processes are primarily caused by lowering of phreatic groundwater levels. At present, the relative contribution of each process to total subsidence (i.e. natural plus anthropogenic) is unclear. Such information is important for stakeholders to support decision making on subsidence mitigation and it should be substantiated with independent scientific studies. We present the outline of a hybrid Artificial Intelligence (AI) big data and model workflow to disentangle different subsidence forcing and we report on preliminary results for an area covering a gas field in the peat-rich Friesland coastal plain. The proposed workflow is a hybrid approach between a knowledge-based physical model and machine-learning techniques. The big input data comprises a suite of static (structural model) and time-dependent subsurface data (phreatic groundwater level, reservoir pressure), and geodetic measurements. Geomechanical models provide the connection between the drivers (groundwater levels and reservoir pressures) and the surface movement.@en