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Silicic magmatic systems are the most dangerous volcanoes on Earth, capable of large and catastrophic eruptions, yet their low eruptive frequency makes it challenging to interpret their short-term unrest. Here we present a decade-plus analysis that integrates, for the first time, time series of satellite interferometric synthetic aperture radar (InSAR) surface deformation and satellite thermal infrared edifice-scale surface warming at a large silicic system: Domuyo volcano, in Argentina. We find that deformation and warming are highly correlated, and depending on the sign and lag between the time series, either shallow sealing or magma influx could drive Domuyo’s ongoing inflation (~ 0.15 m/year; from an InSAR-derived tabular source, ~ 11 × 8 × 1 km; ~ 6.5 km depth; ~ 0.037 km3/year volume-change rate) and warming (0.3–0.4 °C/year). This study shows the potential that combined satellite surface deformation and edifice-scale surface warming time series have on assessing the physical mechanisms of silicic volcanic systems and for constraining deterministic models.

Geodetic methods comprise one class of geophysical data that are sensitive to changes in effective pressure within operating reservoirs, albeit indirectly through induced deformation. Geodetic observations, which have observation intervals that vary from seconds to days, weeks, or months, generally provide more frequent sampling compared to existing geophysical methodologies (such as seismic time-lapse monitoring), which typically invoke repeat times of months to years. These differences in sampling intervals are primarily due to the extensive effort, and hence cost, of conducting geophysical field operations, which often precludes executing a large number of surveys. Satellite-based interferometric synthetic aperture radar (InSAR) is cost effective and used in many applications, including monitoring the injection of carbon dioxide (CO2) for both long-term storage and enhanced oil production. An application to the geologic sequestration of CO2 in Algeria revealed northwest migration along a fault/fracture zone intersected by the injection well. A study in a Texas field demonstrated that enhanced oil recovery utilizing CO2 leads to observable surface deformation that may be used to characterize the sequestered CO2 and to estimate the pressure changes within the reservoir induced by injection and production.

The previously presented Multidimensional Small Baseline Subset (MSBAS-2D) technique computes two-dimensional (2D), east and vertical, ground deformation time series from two or more ascending and descending Differential Interferometric Synthetic Aperture Radar (DInSAR) data sets by assuming that the contribution of the north deformation component is negligible. DInSAR data sets can be acquired with different temporal and spatial resolutions, viewing geometries and wavelengths. The MSBAS-2D technique has previously been used for mapping deformation due to mining, urban development, carbon sequestration, permafrost aggradation and pingo growth, and volcanic activities. In the case of glacier ice flow, the north deformation component is often too large to be negligible. Historically, the surface-parallel flow (SPF) constraint was used to compute the static three-dimensional (3D) velocity field at various glaciers. A novel MSBAS-3D technique has been developed for computing 3D deformation time series where the SPF constraint is utilized. This technique is used for mapping 3D deformation at the Barnes Ice Cap, Baffin Island, Nunavut, Canada, during January–March 2015, and the MSBAS-2D and MSBAS-3D solutions are compared. The MSBAS-3D technique can be used for studying glacier ice flow at other glaciers and other surface deformation processes with large north deformation component, such as landslides. The software implementation of MSBAS-3D technique can be downloaded from http://insar.ca/.

Author(s): Fouladi Moghaddam, N; Nourollah, H; Vasco, DW; Samsonov, SV; Rudiger, C | Abstract: This paper presents a study on geophysical inverse modelling for subsurface structural properties of an unconventional hydrocarbon site that was monitored previously by Interferometric Synthetic Aperture Radar (InSAR) technology for surface deformation. A static three-dimensional geomodel along with extracted property maps replicates the depth of each underlying stratigraphic unit and structural feature with the density of each geological layer. We examine the hypothesis that integration of elastic properties of each formation layer with InSAR observations in a stratified elastic medium will lead to a viscoelastic geophysical inverse problem that can be solved to estimate fractional volume change at the reservoir level. Moreover, we examine synthetic scenarios in which the elastic properties of the formations are perturbed before determining the resulting impact on the rate of surface deformation. The results show that although the slope of underlying formations, their density and depth can define the extent and pattern of a deformation signal, their properties have a marginal impact on volumetric change compared to the dense network of shallow depth Coal Seam Gas (CSG) mining wells. Besides, it is also demonstrated that the inversion of InSAR deformation maps can resolve the uncertainties associated with low-resolution seismic interpretation as well as filling the data gaps within seismic acquisitions. A significant contribution of this investigation to the geological basin modelling involves a) introducing a remote and non-invasive technology such as InSAR to improve geophysical mapping of subsurface structures such as faults in areas with sparse or no reflective seismic information, and b) applying a multi-layer viscoelastic geophysical source model for an unconventional hydrocarbon reservoir such as CSG.

Taking advantage of the ever-increasing amount of available SAR data requires adapted processing infrastructures. We present here the InSAR Mass processing Toolbox for Multidimensional time series (MasTer), which can combine any type of SAR data to produce unsupervised vertical and horizontal ground deformation time series. MasTer is optimized to automatically download SAR data, select the appropriate interferometric pairs, perform the interferometric mass processing, compute the geocoded deformation maps, invert and display the velocity maps and the 2D time series on a web page updated incrementally as soon as a new image is made available. MasTer also allows the production of time series of coherences or SAR amplitude images, which can be used e.g. for land use monitoring or geomorphological changes detection. The capabilities and performances of MasTer are illustrated with several examples. Software and manual are available on request to authors. To MasTer the art of InSAR mass processing.

Atmospheric heterogeneity mainly exposes itself as tropospheric-phase delay in Satellite Interferometric Synthetic Aperture radar (InSAR) observations, which smears or even overshadows the deformation component of InSAR measurements. In this study, we estimated the performance of four Global Atmospheric Models (GAMs), i.e. European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis v5 (ERA5), ERA-Interim (ERA-I), Modern-Era Retrospective analysis for Research and Applications v2 (MERRA2) and Generic Atmospheric Correction Online Service for InSAR (GACOS), for tropospheric-phase delay reduction in InSAR applications in the Tibetan plateau, of which ERA5 is the latest GAM released by ECMWF. We demonstrated the effectiveness of Atmospheric Phase Screen (APS) correction using the four GAMs for more than 700 Sentinel-1 Terrain Observation by Progressive Scans interferograms covering two study areas in the southern (R1) and northwest margins (R2) of the Tibetan plateau. Topography-correlated signals have been widely observed in these interferograms, which are most likely due to the APS effects. We calculated the Standard Deviations (SD) and Pearson’s Correlation Coefficients (r) between InSAR Line of Sight measurements and topography before and after applying APS correction. The results show that the SDs of non-deformation areas from the GAMs decrease to approximately 4 mm from around 10 mm and 12 mm originally on average for R1 and R2, respectively, and the r after the APS correction are reduced below 0.4 from around 0.8 for the selected interferometric pairs. In addition, as the newly released GAM, ERA5 has similar performance with GACOS products and outperforms other models generally. This suggests that GAMs, particularly ERA5, have great potential in the APS correction for InSAR applications in the Tibetan plateau.

We investigated an M_w ∼ 6.2 earthquake doublet on the border of the USA and Canada using ALOS2 Light-of-Sight displacements and GPS measurements. We selected three L-band ALOS-2 interfergorams with temporal baselines of one yr to extract coseismic deformation maps, in which master and slave images were both acquired in July. A subpixel-based alignment and another range spectral splitting techniques under the GAMMA InSAR software framework were applied to improve the interferometric coherence and reduce the effects of phase anomalies in two of the three interferometric pairs due to either ionospheric delay or a potential focusing issues in the generation of the ALOS2 SLC data. The updated interferograms convincingly reveal deformation fringe patterns produced by the two earthquakes. We conducted a nonlinear geophysical inversion to estimate the geometric parameters of the earthquakes with the InSAR and GPS measurements. The best-fitting model shows that a thrust faulting on a reverse fault and left-lateral strike-slip faulting on a nearly vertical fault with the centroid depths of 9.3±0.6 and 8.4±0.7 km, respectively, are most likely responsible for the earthquake doublet. The eastern Denali fault (EDF) and Duke River fault are major active faults in the region and the earthquake doublet could be due to reactivation of the part of the two faults system.

The increasing amount of SAR data available opens new challenges in terms of data storage management and processing load. Fully exploit those large databases requires the developement of automatic processing chains. The InSAR Mass processing Toolbox for Multidimensional time series (MasTer) is able to combine any type of SAR data to produce automatic unsupervised 2D ground deformation time series, from data download up to updated displaying of 2D time series results on a web page, updated incrementally as soon as a new image is available. We present our last methodological improvement based on the computation of a coherence proxy to guide a pair selection optimization, balancing the use of each image as master and slave. Whereas this new tool reduces the number of DInSAR interferograms computed by up to 75%, it also increases the signal to noise ratio of the time series by reducing the influence of DEM errors and atmospheric noise.

Recently, a large number of synthetic aperture radar (SAR) images has been introduced into landslide investigations with the growing launch of new SAR satellites, such as ALOS/PALSAR-2 and Sentinel-1. Therefore, it is appropriate to develop new approaches to retrieve three-dimensional (3D) displacements and long-term (> 10 years) displacement time series to investigate the spatio-temporal evolution and creep behavior of landslides. In this study, a new approach for the estimation of 3D and long-term displacement time series of landslides, based on the fusion of C- and L-band SAR observations, is presented. This method is applied to map 3D and long-term displacements (nearly 12 years) of the landslides in Gongjue County, Tibet in China; four sets of SAR images from different platforms (i.e., L-band ascending ALOS/PALSAR-1, C-band descending ENVISAT, and C-band ascending and descending Sentinel-1 SAR datasets) covering the period of January 2007 to November 2018 were collected and exploited. First, the assumption that the landslide moves parallel to its ground surface is used to produce 3D displacement rates and time series by fusing ascending and descending Sentinel-1 SAR images, from which the optimal sliding direction for each pixel of the slope is well estimated. Then, the long-term displacement time-series of the landslide between January 2007 and October 2018 in the estimated sliding direction is recovered by fusing L-band ALOS/PALSAR-1 and C-band Sentinel-1 SAR images. In order to fill the time gap of nearly four years between ALOS/PALSAR-1 and Sentinel-1 SAR images, the Tikhonov regularization (TR) method is developed to establish the observational equation. Moreover, to solve the problem arising from ALOS/PALSAR-1 and Sentinel-1 images with different wavelengths, incidence angles and flight directions, the measurements from ALOS/PALSAR-1 and Sentinel-1 images are both projected to the estimated optimal sliding direction to achieve a unified displacement datum. Our results from ascending and descending Sentinel-1 images suggest that the maximum displacement rates of the study area in the vertical and east-west directions from December 2016 to October 2018 were greater than 70 and 80 mm/year, respectively, and 2D displacement results reveal that the displacement patterns and movement characteristics of all the detected landslides are not identical in the study area. Specifically, the 3D displacement results successfully revealed the spatiotemporal displacement patterns and movement direction of each block of the Shadong landslide, and long-term displacement time series showed for the first time that the maximum cumulative displacement exceeds 1.3 m from January 2007 to October 2018. Moreover, the kinematic evolution and possible driving factors of landslides were investigated using 2D and 3D and long-term displacement results, coupled with hydrological factors and unidimensional constitutive models of the rocks. This research was financially funded by the Natural Science Foundation of China (Grant Nos. 41874005, 41929001, 41731066), the Fundamental Research Funds for the Central University (Grant Nos. 300102269712 and 300102269303), and China Geological Survey Project (DD20190637 and DD20190647). This research was also supported by a Chinese Scholarship Council studentship awarded to Xiaojie Liu (Ref. 202006560031). Roberto Tomás was supported by the Spanish Ministry of Economy, Industry and Competitiveness (MINECO), the State Agency of Research (AEI) and European Funds for Regional Development (FEDER) under project TEMUSA (TEC2017-85244-C2-1-P).

The Frank Slide in 1903 caused the deaths of more than 70 people, and there remains a risk of a second rock avalanche. Since then, many different methods have been used to monitor the slope for signs of movement. On April 8, 2020, the Alberta Energy Regulator (AER) contacted the Canada Centre for Mapping and Earth Observation (CCMEO) with a request for emergency assistance to monitor Turtle Mountain for deformation using interferometric synthetic aperture radar following the hardware failure of their ground-based monitoring system. This report describes at a high level the communication, planning, setup, operation, and reporting for this emergency request. Each deformation monitoring program presents a unique challenge, but this methodology can be broadly adapted to similar InSAR monitoring requests in the future. The purpose of this report is to provide a record of the services provided to help guide future geohazards monitoring requests, which may become more frequent with increased landslide risk due to climate change and greater satellite data availability. Between April 8 and June 30, 2020, 40 images were collected by RADARSAT-2 and RADARSAT Constellation Mission satellites over Turtle Mountain. These images were processed quickly after acquisition and no significant deformation was observed during the monitoring period. Historical deformation of up to 5 cm in the line-of-sight was observed between 2014 and 2020.

Space-borne Differential Interferometric Synthetic Aperture Radar (DInSAR) has been extensively used in the last two decades to measure ground surface deformation, providing key information for the characterization and understanding of many natural and anthropogenic processes. However, conventional DInSAR technique measures only one component of the surface deformation (i.e. the satellite's line-of-sight (LOS)), causing the interpretation of DInSAR measurements to be challenging and potentially narrowing the understanding of the mechanisms and dynamics of the deformation processes at work. Presently available methods that estimate 3D surface deformation from DInSAR generally operate on individual interferograms and therefore do not produce 3D surface deformation time series. However, the availability of time series is essential for studying surface deformation processes, bringing information on, e.g., temporally and spatially-variable external forcing conditions and characteristics of future deformation patterns. The Multidimensional Small Baseline Subset (MSBAS) method was already able to produce 2D (east and vertical) surface deformation time series from multi-tracks and multi-sensors DInSAR data. Here we propose a novel version of the MSBAS (MSBAS-3D) method that can produce 3D (north, east, and vertical) surface deformation time series from ascending and descending DInSAR data. This new method proposes measuring the surface deformation for processes producing motion parallel to the surface, such as landslides and glacier flows, while conserving the DInSAR accuracy. The ability of MSBAS-3D to capture the full 3D deformation pattern of processes with a surface signature is illustrated for a large, slow-moving, deep-seated landslide, for which long DInSAR and dGNSS time series, as well as ground truth data, are available. Surface deformation is measured over a four-year period using 1D (LOS), 2D and 3D MSBAS methods, and the advantages and limitations of each approach are described. In this case, the novel MSBAS-3D technique produces superior results that greatly simplify interpretation of the processes at work. The MSBAS-3D software can be downloaded from http://insar.ca/ .

Developments in Interferometric Synthetic Aperture Radar (InSAR) and GNSS (Global Navigation Satellite System) during the past decades have promoted significant advances in geosciences, providing high-resolution ground deformation data with dense spatio-temporal coverage. This large dataset can be exploited to produce accurate assessments of the primary processes occurring in geologically active areas. We present a new, original methodology to carry out a multi-source inversion of ground deformation data to better understand the subsurface causative processes. A nonlinear approach permits the determination of location, size and three-dimensional configuration, without any a priori assumption as to the number, nature or shape of the potential sources. The proposed method identifies a combination of pressure bodies and different types of dislocation sources (dip-slip, strike-slip and tensile) that represent magmatic sources and other processes such as earthquakes, landslides or groundwater-induced subsidence through the aggregation of elemental cells. This approach has the following features: (1) simultaneous inversion of the deformation components and/or line-of-sight (LOS) data; (2) simultaneous determination of diverse structures such as pressure bodies or dislocation sources, representing local and regional effects; (3) a fully 3D context; and (4) no initial hypothesis about the number, geometry or types of the causative sources is necessary. This methodology is applied to Mt. Etna (Southern Italy). We analyze the ground deformation field derived from a large InSAR dataset acquired during the January 2009 – June 2013 time period. The application of the inversion approach models several interesting buried structures as well as processes related to the volcano magmatic plumbing system, local subsidence within the Valle del Bove and seaward motion of eastern flank of the volcano., This research has been primarily supported by the Spanish Ministerio de Ciencia, Innovación and Universidades research project DEEP-MAPS (RTI2018-093874-B-I00) and partially by the Spanish Ministry of Economy and Competitiveness research projects AQUARISK (ESP2013-47780-557-C2-1-R) and Thematic Network EPOS Spain (CGL2016-81965-REDT), and the EU 7th Framework Programme EPOS IP (676564-EPOS IP). Research by KFT is funded by CIRES, University of Colorado Boulder. We thank M. Polcari and J. Escayo for providing the 3D coseismic deformation data for the 2014 Napa Valley earthquake. This is a contribution to the Moncloa Campus of International Excellence and part of the CSIC-PTIs TELEDETEC and POLARCSIC activities.

We reveal transient surface deformation following the 2017 Mw7.3 Sarpol Zahab (Iran) earthquake using Interferometric Synthetic Aperture Radar (InSAR) measurements. Based on the coseismic interferograms derived from the Advanced Land Observing Satellite‐2 (ALOS‐2) data, the preferred slip model of the earthquake has a centroid depth of 14.5 ± 4 km and suggests that a basement fault is most likely responsible for the 2017 earthquake in the northwest Zagros fold‐thrust belt zone. Two slip asperities with a maximum slip of 6 m separated by 16 km are observed in the best fitting slip model. The accumulated afterslip in the first month after the mainshock determined from the Sentinel‐1 postseismic interferograms reveals a slip distribution that lies immediately updip of the coseismic slip, implying that frictional properties of the fault vary along the rupture patch. The Bamo Mount in the earthquake area was uplifted by approximately 1 m during the earthquake. We suggest that local topographic growth from both seismic and aseismic faulting behaviors is common within the Zagros fold‐thrust belt zone based on our findings regarding the 2017 earthquake and other significant events in the region. Published version

Landslides are the most common natural hazard in British Columbia. The province has recorded the largest number of historical landslide fatalities in Canada, and damage to infrastructure comes at a great cost. In order to understand the potential impacts of landslides, radar remote sensing has become a cost-effective method for detecting downslope movements. This study investigates downslope movements in the Southern Interior of British Columbia, Canada, with Sentinel-1 and RADARSAT Constellation Mission (RCM) interferometric synthetic aperture radar (InSAR) data. The 2-dimensional time-series analysis with Sentinel-1 ascending and descending InSAR pairs from October 2017 to June 2021 observed distinct earthflow movements of up to ~15 cm/year in the east–west direction. The Grinder Creek, Red Mountain, Yalakom River, and Retaskit Creek earthflows previously documented are still active, with east–west movements of ~30 cm over the past four years. New RCM data acquired from June 2020 to September 2020 with a 4-day revisit capability were compared to 12-day Sentinel-1 InSAR pairs. The 4-day RCM InSAR pairs at higher spatial resolution showed better performance by detecting relatively small-sized slope movements within a few hundred meters, which were not clearly observed by Sentinel-1. The temporal variabilities observed from the RCM InSAR showed great potential for observing detailed slope movements within a narrower time window.

International audience; On April 25th 2015, the Mw 7.8 Gorkha (Nepal) earthquake ruptured a portion of the Main Himalayan Thrust underlying Kathmandu and surrounding regions. We develop kinematic slip models of the Gorkha earthquake using both a regularized multi-time-window (MTW) approach and an unsmoothed Bayesian formulation, constrained by static and high rate GPS observations, synthetic aperture radar (SAR) offset images, interferometric SAR (InSAR), and teleseismic body wave records. These models indicate that Kathmandu is located near the updip limit of fault slip and approximately 20 km south of the centroid of fault slip. Fault slip propagated unilaterally along-strike in an ESE direction for approximately 140 km with a 60 km cross-strike extent. The deeper portions of the fault are characterized by a larger ratio of high frequency (0.03–0.2 Hz) to low frequency slip than the shallower portions. From both the MTW and Bayesian results, we can resolve depth variations in slip characteristics, with higher slip roughness, higher rupture velocity, longer rise time and higher complexity of subfault source time functions in the deeper extents of the rupture. The depth varying nature of rupture characteristics suggests that the up-dip portions are characterized by relatively continuous rupture, while the down-dip portions may be better characterized by a cascaded rupture. The rupture behavior and the tectonic setting indicate that the earthquake may have ruptured both fully seismically locked and a deeper transitional portions of the collision interface, analogous to what has been seen in major subduction zone earthquakes.

Space-borne Synthetic Aperture Radar (SAR) provides an opportunity for monitoring ground deformation at active volcanoes with high temporal and spatial resolutions. Modern SAR satellites acquire very large volumes of data that no longer can be effectively and efficiently processed and interpreted manually. The development of novel automatic processing methodologies is warranted in order to fully utilize big data. The Multidimensional Small Baseline Subset (MSBAS) methodology is an example of the semi-automatic processing system for computing temporally dense two-dimensional, horizontal east-west and vertical time series of ground deformation from ascending and descending SAR imagery acquired by various satellites. Here MSBAS is used for mapping ground deformation at the Piton de la Fournaise volcano (La Reunion Island, France) during the February 2012–April 2016 period from RADARSAT-2 data. Five volcanic eruptions occurred during the June 2014–October 2015 period, producing over 60cm of horizontal and over 30cm of vertical ground deformation, well-resolved in the MSBAS-derived time series. Validation of DInSAR results by comparison with GNSS observations and modeling of the two last and largest eruptions was performed. Validation showed good overall agreement between DInSAR and GNSS observations while revealing the benefits and limitations of both techniques. Modeling of fault and dike geometries attempted to explain the dis-proportionally large eastward motion of the eastern flank of the Piton de la Fournaise volcano that occurred during these eruptions. We demonstrated that the simple elastic model consisting of two dikes and a sliding surface can account for the observed ground deformation.

Copahue volcano straddling the edge of the Agrio-Caviahue caldera along the Chile-Argentina border in the southern Andes has been in unrest since inflation began in late 2011. We constrain Copahue's source models with satellite and airborne interferometric synthetic aperture radar (InSAR) deformation observations. InSAR time series from descending track RADARSAT-2 and COSMO-SkyMed data span the entire inflation period from 2011 to 2016, with their initially high rates of 12 and 15 cm/yr, respectively, slowing only slightly despite ongoing small eruptions through 2016. InSAR ascending and descending track time series for the 2013–2016 time period constrain a two-source compound dislocation model, with a rate of volume increase of 13 × 106 m3/yr. They consist of a shallow, near-vertical, elongated source centered at 2.5 km beneath the summit and a deeper, shallowly plunging source centered at 7 km depth connecting the shallow source to the deeper caldera. The deeper source is located directly beneath the volcano tectonic seismicity with the lower bounds of the seismicity parallel to the plunge of the deep source. InSAR time series also show normal fault offsets on the NE flank Copahue faults. Coulomb stress change calculations for right-lateral strike slip (RLSS), thrust, and normal receiver faults show positive values in the north caldera for both RLSS and normal faults, suggesting that northward trending seismicity and Copahue fault motion within the caldera are caused by the modeled sources. Together, the InSAR-constrained source model and the seismicity suggest a deep conduit or transfer zone where magma moves from the central caldera to Copahue's upper edifice.

We present RADARSAT-2 Differential Interferometric Synthetic Aperture Radar (DInSAR) observations of deformation due to fluid extraction at the Cerro Prieto Geothermal Field (CPGF) and afterslip on the 2010 M7.2 El Mayor-Cucapah (EMC) earthquake rupture during 2011–2016. Advanced multidimensional time series analysis reveals subsidence at the CPGF with the maximum rate greater than 100 mm/yr accompanied by horizontal motion (radial contraction) at a rate greater than 30 mm/yr. During the same time period, more than 30 mm of surface creep occurred on the Indiviso fault ruptured by the EMC earthquake. We performed inversions of DInSAR data to estimate the rate of volume changes at depth due to the geothermal production at the CPGF and the distribution of afterslip on the Indiviso fault. The maximum coseismic slip due to the EMC earthquake correlates with the Coulomb stress changes on the Indiviso fault due to fluid extraction at the CPGF. Afterslip occurs on the periphery of maximum coseismic slip areas. Time series analysis indicates that afterslip still occurs 6 years after the earthquake.

Short- and long-term ground deformation at the cyclic steam stimulation (CSS) enhanced oil recovery sites in the Cold Lake region of Alberta, Canada, was measured with RADARSAT-2 differential interferometric synthetic aperture radar (DInSAR) during 2011–2016. The interferometric processing of 84 high-resolution spotlight images revealed extensive short-term ground uplift and subsidence greater than 15 cm over the 24-day satellite revisit cycle. Time-series analysis based on the multidimensional small baseline subset (MSBAS) methodology demonstrated that while the predominant deformation signal is cyclical in nature, a long-term subsidence and uplift with maximum deformation rates greater than 5 cm/year is also present. These measurements suggest that CSS injection and production operations result in the long-term semipermanent deformation in the area of reservoir operations, and that the response to injection and extraction can differ from the previous cycles.

Abrupt change in the long term displacement trend was observed in the downtown of Seattle (Washington, USA) with the satellite Differential Interferometric Synthetic Aperture Radar (DInSAR). The forty nine ascending and forty six descending RADARSAT-2 Spotlight SAR images with range-azimuth resolution of 1.6×0.8 m and ground coverage of 18×8 km were collected during June 6, 2012–August 16, 2015. The vertical deformation time series were computed from the ascending and descending data sets with the advanced Multidimensional Small Baseline Subset (MSBAS) software. During June 6, 2012–August 31, 2014 subsidence occurred along the two transportation routes, running north-south parallel to the coast line, reaching 2.5 cm. The long term deformation rate did not exceed 1.2 cm/year and was nearly constant during that time. After August 31, 2014, rapid subsidence appeared in the downtown of Seattle, in a region where it previously was not observed. Over the next four months during August 31, 2014–December 29, 2014 cumulative subsidence reached approximately 2.5 cm, which corresponds to an annual rate of 10 cm/year, about eight times faster than during the previous two years. The rate of subsidence remained high for an additional few months before converging to its secular value. The cause of subsidence was linked to the recent anthropogenic activities related to tunnel boring for Alaskan Way Viaduct replacement project. The elliptical model for subsidence due to groundwater pumping proposed by Tiampo et al. (2012) was used to invert for the physical parameters of the associated groundwater pumping. The results are in good accordance with the location of pumping operations and the groundwater bearing strata in the region. Over a long period of time such fast subsidence will cause additional strain on urban infrastructure, particularly older, historic structures and high-rise buildings. This work provides an excellent example of the importance and applicability of rapid, accurate monitoring of ongoing, large infrastructure projects using DInSAR techniques in order to make optimal use of limited resources and perform early intervention and mitigation strategies.

Advancements in radar technology are increasing our ability to detect Earth surface deformation in permafrost environments. In this paper we use satellite Differential Interferometric Synthetic Aperture Radar (DInSAR) to describe the growth of a large, relatively young pingo in the Tuktoyaktuk Coastlands. High-resolution RADARSAT-2 imagery (2011–2014) analyzed with the Multidimensional Small Baseline Subset (MSBAS) DInSAR revealed a maximum 2.7 cm yr−1 of domed uplift located in a drained lake basin. Satellite measurements suggest that this feature is one of the largest diameter pingos in the region that is presently growing. Observed changes in elevation were modeled as a 348 × 290 m uniformly loaded elliptical plate with clamped edge. Analysis of historical aerial photographs suggested that ground uplift at this location initiated sometime between 1935 and 1951 following drainage of the residual pond. Uplift is largely due to the growth of intrusive ice, because the 9 % expansion of pore water associated with permafrost aggradation into saturated sands is not sufficient to explain the observed short- and long-term deformation rates. The modeled thickness of ice-rich permafrost using the Northern Ecosystem Soil Temperature (NEST) was consistent with the maximum height of this feature. Modeled permafrost aggradation from 1972 to 2014 approximated elevation changes estimated from aerial photographs for that time period. Taken together, these lines of evidence indicate that uplift is at least in part a result of freezing of the sub-pingo water lens. Seasonal variations in the uplift rate seen in the DInSAR data closely match the modeled seasonal pattern in the deepening rate of freezing front. This study demonstrates that interferometric satellite radar can detect and contribute to understanding the dynamics of terrain uplift in response to permafrost aggradation and ground ice development in remote polar environments. The present-day growth rate is smaller than predicted by the modeling and no clear growth is observed at other smaller pingos in contrast with field studies performed mainly before the 1990s. Investigation of this apparent discrepancy provides an opportunity to further develop observation methods and models.

A large dike intrusion and fissure eruption lasting 9 months began on November 27, 2013, beneath the south flank of Tolbachik Volcano, Kamchatka, Russia. The eruption was the most recent at Tolbachik since the Great Tolbachik Eruption from 1975 to 1976. The 2012 eruption was preceded by more than 6 months of seismicity that clustered beneath the east flank of the volcano along a NW–SE trend. Seismicity increased dramatically before the eruption, with propagation of the seismicity from the central volcano conduit in the final hours. We use interferometric synthetic aperture radar (InSAR) to compute relative displacement images (interferograms) for {SAR} data pairs spanning the eruption. We use satellite {SAR} data from the Canadian Space Agency's RADARSAT-2 and from the Italian Space Agency's COSMO-SkyMed missions. Data are modeled first through a Markov Chain Monte Carlo solution for a single tensile dislocation (dike). We then use a boundary element method that includes topography to model a distributed dike-opening model. We find the best-fitting dike dips 80° to the {WNW} with maximum opening of 6–8 m, localized in the near surface and more broadly distributed in distinct regions up to 3 km beneath the surface, which varies from 1 to 2 km elevation for the eruptive fissures. The distribution of dike opening and its correspondence with co-diking seismicity suggests that the dike propagated radially from Tolbachik's central conduit.

At the Aquistore CCS site, located in the southeastern Saskatchewan, Canada, carbon dioxide (CO 2 ) is to be injected at variable rates of up to 1500 tonne/day. The storage reservoir consists of a dominantly clastic, brine-filled interval (Deadwood and Winnipeg formations) which reside at 3150–3350 m depth. Ground deformation at this site is being monitored to track pressure-induced uplift and potential upward migration of CO 2 through faults and fractures. Deformation monitoring is conducted using space-borne Differential Interferometric Synthetic Aperture Radar (DInSAR), capable of achieving millimeter precision and meter spatial resolution over the entire monitored area. During June 2012–October 2014, prior to CO 2 injection, two ascending and two descending high-resolution RADARSAT-2 data sets were acquired and simultaneously processed with the advanced Multidimensional Small Baseline (MSBAS) DInSAR producing vertical and horizontal East-West deformation time series with six days temporal sampling, four times more frequent than the repeat cycle of each individual data set. Two years of monitoring prior to the onset of (CO 2 ) injection allowed measurement of the deformation field of the background natural and anthropogenic processes. Vertical and horizontal ground deformation was detected with the rates of ±1.0 and ±0.5 cm/year and with precision of 0.3 and 0.2 cm/year (2 σ ) correspondingly. Background motion (shape and magnitude) may resemble deformation signals due to potential upward migration of CO 2 through faults and fractures. Analytic elastic and poroelastic modeling was performed to estimate the ground deformation that will be produced when injection begins. For this purpose, rock properties determined from geophysical well logs and in situ temperature and pressure were used. For the elastic model it was determined that a maximum of vertical deformation of 1.6 cm/year will be located around the injection well, whereas the maximum of horizontal deformation of 0.6 cm/year will be located about 3 km away from the injection well. For a more realistic poroelastic model, it was determined that maximum vertical deformation will not exceed 1.6 cm and maximum horizontal deformation will not exceed 0.1 cm/year during the entire 25 year injection cycle. According to this model, the established monitoring network cannot detect predicted horizontal motion since it is below its sensitivity, whereas for detection of vertical motion ground-based monitoring sites need to be installed near and also at distance from the injection well. Six day temporal sampling allows determination of the transient uplift phase. A proposed MSBAS strategy overcomes limitations of the classical DInSAR, such as sparse temporal resolution and the lack of ability to extract individual deformation components from the line-of-sight retrievals, and can be implemented at other onshore CCS sites for operational monitoring, using readily available SAR data.

In this study we used RADARSAT-2 and Sentinel-1 Synthetic Aperture Radar data for measuring subsidence above a flooded potash mine, which is almost entirely located within the city of Berezniki (Perm Krai, Russia), population 150,000. This area has experienced very fast subsidence since October 2006 when the integrity of the Berezniki-1 mine was compromised, resulting in water intrusion, subsequent flooding and closure of the mine. Due to the ongoing dissolution of carnallite, subsidence in this region is expected to continue in the foreseeable future. In addition to rapid subsidence, at least five sinkholes have formed in the region, with the largest being 440 × 320 m. We observed ground subsidence during the period October 2011–April 2014 (RADARSAT-2) with a vertical rate up to 14 cm/year and horizontal rate up to 10 cm/year; during the period July 2016–June 2020 (Sentinel-1) with a vertical rate up to 17 cm/year. Our results were validated by precise leveling, with a coefficient of correlation of 0.75. Subsidence faster than 17 cm/year observed by precise leveling was not resolvable with Differential Interferometric Synthetic Aperture Radar (DInSAR). Our results show the complementary nature of ground-based and space-borne measurement techniques. The precise leveling captures subsidence along profile lines with high precision but lower temporal resolution, while DInSAR captures subsidence with high spatial and temporal resolutions but with lower precision. DInSAR is also significantly affected by decorrelation outside of urban areas. An important advantage of our methodology is the ability to measure the horizontal east component of the ground deformation when both, ascending and descending, data are available. This measurement directly characterizes the level of anthropogenic load on buildings and infrastructure. We recommend continuing monitoring subsidence using both measurement techniques, which can also be complemented by continuous Global Navigation Satellite System (GNSS).

In this study, coseismic and postseismic deformation following the October 31, 2013 M 6.4 earthquake in eastern Taiwan is investigated using InSAR and GPS measurements. The InSAR data includes a pair of ascending and descending SAR data from Radarsat-II satellite covering the mainshock. The GPS measurements span the earthquake and up to 340 days after the event. The geodetic measurements of coseismic deformation are inverted to determine fault geometry and slip distribution. GPS time series data are analyzed by Principal Component Analysis based Inversion Method (PCAIM) to derive space and time distribution of postseismic fault slip. The main coseismic slip in the best fitting oblique-thrust dislocation shows two clear asperities: a small asperity at a depth of about 5 km with a maximum slip of 0.6 m and a larger asperity between depths of 15–25 km with maximum slip of 1 m. There is little slip above 5 km, suggesting the presence of active subsurface (blind) faulting under the Central Range. The mainshock is followed by widespread frictional afterslip on one patch which is localized close to the deepest coseismic asperity.

The research objectives of the Aquistore CO2 storage project are to design, adapt, and test non-seismic monitoring methods for measurement, and verification of CO2 storage, and to integrate data to determine subsurface fluid distributions, pressure changes and associated surface deformation. Aquistore site is located near Estevan in Southern Saskatchewan on the South flank of the Souris River and west of the Boundary Dam Power Station and the historical part of Estevan coal mine in southeastern Saskatchewan, Canada. Several monitoring techniques were employed in the study area including advanced satellite Differential Interferometric Synthetic Aperture Radar (DInSAR) technique, GPS, tiltmeters and piezometers. The targeted CO2 injection zones are within the Winnipeg and Deadwood formations located at > 3000 m depth. An array of monitoring techniques was employed in the study area including advanced satellite Differential Interferometric Synthetic Aperture Radar (DInSAR) with established corner reflectors, GPS, tiltmeters and piezometers stations. We used airborne LIDAR data for topographic phase estimation, and DInSAR product geocoding. Ground deformation maps have been calculated using Multidimensional Small Baseline Subset (MSBAS) methodology from 134 RADARSAT-2 images, from five different beams, acquired during 20120612–20140706. We computed and interpreted nine time series for selected places. MSBAS results indicate slow ground deformation up to 1 cm/year not related to CO2 injection but caused by various natural and anthropogenic causes.

The Canadian RADARSAT Constellation Mission (RCM) will consist of three synthetic aperture radar (SAR) satellites to be launched in 2018. The Constellation 4-day revisit period will allow monitoring ground uplift and subsidence in Alberta’s oil sands, where the steam assisted gravity drainage (SAGD) and the cyclical steam stimulation (CSS)-enhanced oil recovery operations are employed for extracting viscous bitumen. Fast ground deformation occurring over a small area can only be captured by high-resolution, low-noise SAR. A large deformation gradient limits applicability of coarser resolution SAR, making accurate phase unwrapping impossible, especially in regions susceptible to significant temporal decorrelation. In this study we analyzed the suitability of RCM for monitoring ground deformation in Alberta’s oil sands using interferometric SAR (InSAR) methodology. RCM SAR sensor differs from RADARSAT-2 in resolution, coverage, polarimetric configuration options, and radiometry. Various RCM-simula...

We study land subsidence processes and the associated ground fissuring, affecting an active graben filled by thick unconsolidated deposits by means of InSAR techniques and fieldwork. On 21 September 2012, Ciudad Guzman (Jalisco, Mexico) was struck by ground fissures of about 1.5 km of length, causing the deformation of the roads and the propagation of fissures in adjacent buildings. The field survey showed that fissures alignment is coincident with the escarpments produced on 19 September 1985, when a strong earthquake with magnitude 8.1 struck central Mexico. In order to detect and map the spatio-temporal features of the processes that led to the 2012 ground fissures, we applied InSAR multi-temporal techniques to process ENVISAT-ASAR and RADARSAT-2 satellite SAR images acquired between 2003 and 2012. We detect up to 20 mm/year of subsidence of the northwestern part of Ciudad Guzman. These incremental movements are consistent with the ground fissures observed in 2012. Based on interferometric results, field data and 2D numerical model, we suggest that ground deformations and fissuring are due to the presence of areal subsidence correlated with variable sediment thickness and differential compaction, partly driven by the exploitation of the aquifers and controlled by the distribution and position of buried faults.

Nevado del Ruiz is part of a large volcano complex in the northern Andes of Colombia. Interferometric synthetic aperture radar observations from the RADARSAT-2 satellite since 2011 show steady inflation of the volcano since 2012 at 3–4 cm/yr. The broad (>20 km) deformation pattern from both ascending and descending track data constrain source models for either point or spheroidal sources, both located at >14 km beneath the surface (mean elevation 4.2 km) and 10 km SW of Nevado del Ruiz, below nearby Santa Isabel Volcano. Stress change computations for both sources in the context of a compressive regional stress indicate that dikes propagating from the source should become trapped in sills, possibly leading to a more complex pathway to the surface and explaining the significant lateral separation of the source and Nevado del Ruiz Volcano.

Because of its proximity to the city of Naples and with a population of nearly 1 million people within its caldera, Campi Flegrei is one of the highest risk volcanic areas in the world. Since the last major eruption in 1538, the caldera has undergone frequent episodes of ground subsidence and uplift accompanied by seismic activity that has been interpreted as the result of a stationary, deeper source below the caldera that feeds shallower eruptions. However, the location and depth of the deeper source is not well-characterized and its relationship to current activity is poorly understood. Recently, a significant increase in the uplift rate has occurred, resulting in almost 13 cm of uplift by 2013 (De Martino et al., 2014; Samsonov et al., 2014b; Di Vito et al., 2016). Here we apply a principal component decomposition to high resolution time series from the region produced by the advanced Multidimensional SBAS DInSAR technique in order to better delineate both the deeper source and the recent shallow activity. We analyzed both a period of substantial subsidence (1993–1999) and a second of significant uplift (2007–2013) and inverted the associated vertical surface displacement for the most likely source models. Results suggest that the underlying dynamics of the caldera changed in the late 1990s, from one in which the primary signal arises from a shallow deflating source above a deeper, expanding source to one dominated by a shallow inflating source. In general, the shallow source lies between 2700 and 3400 m below the caldera while the deeper source lies at 7600 m or more in depth. The combination of principal component analysis with high resolution MSBAS time series data allows for these new insights and confirms the applicability of both to areas at risk from dynamic natural hazards., The work of PG was supported by a Banting Postdoctoral Fellowship. This research was partially funded by the NERC project Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET, GA/13/M/031, http://comet.nerc.ac.uk). The work of KFT was supported by an NSERC Discovery Grant and CIRES, University of Colorado Boulder. This work also was supported by the AQUARISK Spanish project and the EU MED-SUV project.

Underground coal mining produces ground subsidence that adversely impacts the environment. Huainan coalfield, one of the largest coalfields in East China, experiences fast ground subsidence that restricts agricultural, urban and rural developments in this region. We used stacking and the small baseline subset interferometric synthetic aperture radar (InSAR) techniques to perform a spatio-temporal analysis of ground subsidence in Huainan coalfield caused by underground coal mining activities. Fourteen L-band ALOS PALSAR images acquired during 2007–2010 were used to retrieve high-resolution and high-precision time series of ground deformation and the mean deformation rate. The results show that subsidence with a rate of up to 15 cm/year is widely spread over the studied area in response to mining operation. In regions where mining lasted for many years, ground subsidence continues at a steady rate during the entire observation period. In regions of recent (i.e., since 2007–2009) mining activities, ground subsidence is rapidly accelerating. Accumulated subsidence already caused submerging of the agriculture lands, limiting further mining activities and farming. The InSAR results are consistent with the ground leveling measurements and observations. It is confirmed that the L-band InSAR can be successfully utilized for mapping long-term subsidence in Huainan coalfield in China caused by underground coal mining activities.

Applying the Multidimensional Small Baseline Subset interferometric synthetic aperture radar algorithm to about 1500 Envisat and RADARSAT-2 interferograms spanning 2003–2013, we computed time series of ground deformation over Naples Bay Area in Italy. Two active volcanoes, Vesuvius and Campi Flegrei, are located in this area in close proximity to the densely populated city of Naples. For the first time, and with remarkable clarity, we observed decade-long elevation-dependent seasonal oscillations of the vertical displacement component with a peak-to-peak amplitude of up to 3.0 cm, substantially larger than the long-term deformation rate (

Recent interferometric synthetic aperture radar observations over northern Alberta, Canada, show persistent surface heave occurring at rates of 1–4 cm/yr, localized at sites where the steam-assisted gravity drainage technique is currently used to extract bitumen from the Athabasca oil sands. We find that uplift rates above the horizontal injector wells are strongly correlated with rates of steam injection, even though there is a net fluid loss from the reservoir pore space as oil and water are withdrawn through the production wells. In combination with available steam injection and bitumen production data at four sites, we use reservoir flow models to explain how the thermal and geomechanical effects of steam injection on an oil sand reservoir can generate uplift at the surface. Results of our numerical experiments show that persistent surface heave consistent with observed rates can be driven by stress changes in the reservoir due to porous flow and thermal expansion. We also observe an unexpected localized uplift, of magnitude equal to or greater than the heave above the sites of steaming but located at clusters of wellheads which are outside the region of influence of the steam chambers. We show that this “wellhead” deformation can be explained by thermal expansion of rock near the injector wells.

River delta plains (deltas) are susceptible to subsidence producing undesirable environmental impact and affecting dense population. The City of Shanghai, located in the easternmost of Yangtze Delta in China, is one of the most developed regions in China that experiences the greatest land subsidence. Excessive groundwater withdrawal is thought to be the primary cause of the land subsidence, but rapid urbanization and economic development, mass construction of skyscrapers, metro lines and highways are also contributing factors. In this paper, a spatial–temporal analysis of the land subsidence in Shanghai was performed with the help of the Small Baseline Subset Interferometric Synthetic Aperture Radar. Twenty l-band ALOS PALSAR images acquired during 2007–2010 were used to produce a linear deformation rate map and to derive time series of ground deformation. The results show homogeneous subsidence within the research area, but exceptionally rapid subsidence around skyscrapers, along metro lines, elevated roads and highways was also observed. Because groundwater exploitation and rapid urbanization responsible for much of the subsidence in the Shanghai region are expected to continue, future subsidence monitoring is warranted.

We present a novel methodology for integration of multiple InSAR data sets for computation of two dimensional time series of ground deformation. The proposed approach allows combination of SAR data acquired with different acquisition parameters, temporal and spatial sampling and resolution, wavelength and polarization. Produced time series have combined coverage, improved temporal resolution and lower noise level. We apply this methodology for mapping coal mining related ground subsidence and uplift in the Greater Region of Luxembourg along the French–German border. For this we processed 167 Synthetic Aperture Radar ERS-1/2 and ENVISAT images acquired between 1995 and 2009 from one ascending (track 29) and one descending (track 337) tracks and created over five hundred interferograms that were used for time series analysis. Derived vertical and east–west linear deformation rates show with remarkable precision a region of localized ground deformation located above and caused by mining and post-mining activities. Time series of ground deformation display temporal variability: reversal from subsidence to uplift and acceleration of subsidence in the vertical component, and horizontal motion toward the center of the subsidence on the east–west component. InSAR results are validated by leveling measurements collected by the French Geological Survey (BRGM) during 2006–2008. We determined that deformation rate changes are mainly caused by water level variations in the mines. Due to higher temporal and spatial resolution the proposed space-borne method detected a larger number of subsidence and uplift areas in comparison to leveling measurements restricted to annual monitoring of benchmark points along roads. We also identified one deformation region that is not precisely located above the mining sites. Comparison of InSAR measurements with the water levels measured in the mining pits suggest that part of the water that filled the galleries after termination of the dewatering systems may come from this region. Providing that enough SAR data is available, this method opens new opportunities for detecting and locating man-made and natural ground deformation signals with high temporal resolution and precision.

[1] We provide new insights into the two main seismic events that occurred in 2012 in the Emilia region, Italy. We extend the results from previous studies based on analytical inversion modeling of GPS and RADARSAT-1 InSAR measurements by exploiting RADARSAT-2 data. Moreover, we benefit from the available large amount of geological and geophysical information through finite element method (FEM) modeling implemented in a structural-mechanical context to investigate the impact of known buried structures on the modulation of the ground deformation field. We find that the displacement pattern associated with the 20 May event is consistent with the activation of a single fault segment of the inner Ferrara thrust, in good agreement with the analytical solution. In contrast, the interpretation of the 29 May episode requires the activation of three different fault segments and a block roto-translation of the Mirandola anticline. The proposed FEM-based methodology is applicable to other seismic areas where the complexity of buried structures is known and plays a fundamental role in the modulation of the associated surface deformation pattern.

In this study, we present coseismic and poseismic surface displacements caused by the 2015 M W 8.3 Illapel (Chile) earthquake with Sentinel-1A (S1A) and RADARSAT-2 (RS2) SAR imagery. The Central Chile, where the earthquake occurred, is a great place to apply InSAR techniques. All RS2 and S1A pairs have good coherence including one pair with a three-year long temporal baseline. However, topographically correlated atmospheric effects significantly influence most of InSAR results, particularly those postseismic interferograms. We use Global Atmospheric Models (GAM) simulation to mitigate the effects of stratified tropospheric delays before implementing InSAR deformation time series analysis. Two global atmospheric models, ERA-Interim and MERRA are compared for their performance to reduce the atmospheric effects. The results show that MERRA data can reduce atmospheric errors from 10% to 44%, which is slightly better than those derived from ERA-Interim. Both co- and post-seismic deformation patterns have been captured by RS2 and S1A interferograms.

The advanced processing methodology is presented for extracting information from earth observation data. Using imagery from various Synthetic Aperture Radar (SAR) satellites and Multidimensional Small Baseline Subset Differential Interferometric SAR (MSBAS-DInSAR) processing methodology we observed ground subsidence in Vancouver (British Columbia, Canada) and Seattle (Washington, USA). In Vancouver, subsidence with rate of up to 2 cm/year was detected during 1995–2012 over a broad area, including the Vancouver International Airport. In Seattle, subsidence with rate of up to 3 cm/ year was detected during 2012–2015. Between August 2014 and August 2015, unusually fast subsidence occurred beneath the city center. This subsidence is caused mainly by human activities, such as construction, urban infrastructure development and groundwater extraction, but also by natural processes, such as consolidation of sediments. Located in coastal areas, these cities may become affected by flooding if ground level subsides below the sea level or due to storm surge. The risk of flooding increases as the sea level continues to rise due to the climate change. The advanced image processing methodology of earth observation data described here allows near real-time monitoring of ground subsidence with high spatial resolution and high precision, therefore increasing level of preparedness and mitigating risk.

A new era of space-based surveillance for global changes has begun with newly launched Synthetic Aperture Radar (SAR) missions Sentinel-1A and ALOS-2 and the upcoming RADARSAT Constellation Mission (RMC) and NASAISRO (NISAR). Heavy loads of SAR data are expected to be acquired regularly in the near future. This no doubt, is good news for a wide range of research applications. However, it also remains challenging to effectively handle such large amounts of SAR data.

Human activities for extracting natural resources, may lead to subsequent gradual or abrupt surface deformation, with adverse effects in the local ecosystem and damage to man-made structures. Over the past two decades, interferometric SAR (InSAR) has been demonstrated as the optimal remote sensing technique to estimate surface deformation with high spatial coverage and vertical accuracy over traditional surveying methods. In this paper, the outcome of advanced differential InSAR processing to detect and analyze ground surface behavior due to man-made interactions are presented. An improvement was achieved in the temporal resolution and accuracy using a unique combination of both C-band and L-band SAR satellite acquisitions with different temporal and spatial baselines. The two alternate DInSAR methodologies were applied on the northeastern part of the Surat Basin, Australia for an area without long-term ground-based geodetic observations. The regions undergoing downward motion are located above coal seam gas (CSG) mining sites with rates up to 28 mm/year. Three scenarios were identified: (1) extensive groundwater extraction from shallow aquifers due to CSG mining, (2) CSG mining without direct impact on groundwater resources and (3) patchy uplift over an industrial forest adjacent to a CSG mining district. Contrary to a previous study conducted in this region using the PSInSAR™ technique which reported stability of the area with insignificant surface deformation, this study shows that there are considerable deformation signals consistent with resource extraction. Consequently, it is shown that the SBAS approach is superior to PSInSAR™ for deformation monitoring with focusing on naturally distributed scatterers.

In this study the integration of Sentinel-1 InSAR (Interferometric Synthetic Aperture Radar) and GPS (Global Positioning System) data was performed to estimate the three components of the ground deformation field due to the Mw 6.0 earthquake occurred on August 24th, 2014, in the Napa Valley, California, USA. The SAR data were acquired by the Sentinel-1 satellite on August 7th and 31st respectively. In addition, the GPS observations acquired during the whole month of August were analyzed. These data were obtained from the Bay Area Regional Deformation Network, the UNAVCO and the Crustal Dynamics Data Information System online archives. The data integration was realized by using a Bayesian statistical approach searching for the optimal estimation of the three deformation components. The experimental results show large displacements caused by the earthquake characterized by a predominantly NW-SE strike-slip fault mechanism., The research has been supported by the “Marco Polo” project by the University of Bologna (UNIBO), the Spanish Ministry of Economy and Competitiveness research project ESP2013-47780-557 C2-1-R and the EU 7th FP MED-SUV project (contract 308665).

On April 25, 2015, a destructive MW 7.8 earthquake struck the capital of Nepal, Kathmandu, killing more than 8800 people and destroying numerous historical structures. We analyze six coseismic interferograms from several satellites (ALOS-2, Sentinel-1 A, and RADARSAT-2), as well as three-dimensional displacements at six GPS stations to investigate fault structure and slip distribution of the Gorkha earthquake. Using a layered crustal structure, the best-fit slip model shows that the preferred dip angle of the mainshock fault is 6 ± 3.5° and the major slip is concentrated within depths of 8–15 km. The maximum slip of ~ 6.0 m occurs at a depth of 11 km, 70 km south east of the epicenter. The coseismic rupture extends ~ 150 km eastward of the epicentre with a cumulative geodetic moment of 7.8 × 1020 Nm, equivalent to an earthquake of MW 7.84. We also investigate the MW 7.2 aftershock on 12 May 2015 using another three postseismic interferograms from ALOS2, RADARSAT-2, and Sentinel-1 A. The InSAR-based best-fit slip model of the largest aftershock implies that its major slip is next to the eastern lower end of the mainshock rupture with a similar maximum slip of ~ 6 m at a depth of ~ 13 km. This study generates various coseismic geodetic measurements to determine the source parameters of the MW 7.8 Gorkha earthquake and 12 May MW 7.2 afershock, providing an additional chance to understand the local fault structure and slip extent. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore)

We present source models for the August 2014 Murmuri (Dehloran) earthquake sequence in the Zagros Mountains of Iran. An Mw6.2 mainshock was followed by an aftershock sequence containing five events of Mw ≥ 5.4. Models of P and SH waveforms show that all events had dominantly thrust-faulting mechanisms, and had centroid depths that place them within the thick sedimentary sequence, above the crystalline basement. The combination of our estimated focal mechanisms, relative relocations of the event hypocentres and the surface displacement patterns observed using InSAR imply that the mainshock and largest aftershock ruptured different fault planes and both contributed to the surface deformation. The fault planes both slipped in horizontally elongated patches, possibly due to rheological layering limiting the updip and downdip extent of rupture. The slip vector of the Murmuri mainshock implies that the decollement beneath the Lorestan Arc is weaker than any such feature beneath the Dezful Embayment, providing an explanation for the plan-view sinuosity of the range-front of the Zagros Mountains.

We demonstrate here a computer code for calculation of time series and also mean and linear deformation rates from a set of coregistered unwrapped differential interferograms using a linear least-squares inversion technique based on the small baseline subset (SBAS) algorithm. The computer code is written in C and uses a singular value decomposition (SVD) routine from the LAPACK library and the fast Fourier transform for spatial filtering from the FFTW library. Various offset estimation and topographic correction algorithms are implemented, including simultaneous inversion for deformation rates and residual topographic error. This approach is particularly useful when applied to ALOS PALSAR interferograms that are coherent even at large perpendicular baselines and acquired with orbital parameters correlated with the time of acquisition. This methodology is applied to produce time series of ground deformation at Tauhara and Wairakei geothermal fields (Taupo Volcanic Zone, North Island, New Zealand) from 12 ALOS PALSAR images acquired between July 2007 and December 2009. We also present here a high-resolution deformation map of the ground subsidence caused by the extraction of geothermal groundwater for power generation, with maximum rates of subsidence of about 7cm/y.

In this letter, we propose a technique for selecting persistent scatterers (PSs) based on their polarization phase difference (PPD). We analyze a normalized PPD between HH and VV channels averaged over a temporal set of images and select pixels that demonstrate predominantly even or odd bounce scattering properties. We compare selected scatterers to PSs selected by applying an amplitude dispersion threshold as suggested by a standard PS interferometry (PSI) approach and show that both methods are complementary. However, the proposed approach can be potentially used on a small set of synthetic aperture radar (SAR) images, which can be beneficial in the early stage of data acquisition. We apply the proposed technique to produce a deformation map for the San Francisco region from six quad-pol RADARSAT-2 SAR images acquired during 2008-2009. The coverage and the precision of the produced deformation map are higher than if it was calculated with the standard PSI technique applied to the same data set.

L-band synthetic aperture radar (SAR) interferometry is very successful for mapping ground deformation in densely vegetated regions. However, due to its larger wavelength, the capacity to detect slow deformation over a short period of time is limited. Stacking and small baseline subset (SBAS) techniques are routinely used to produce time series of deformation and average deformation rates by reducing the contribution of topographic and atmospheric noise. For large sets of images that are presently available from C-band European Remote Sensing Satellites (ERS-1/2) and Environmental Satellite (ENVISAT), the standard stacking and SBAS algorithms are accurate. However, the same algorithms are often inaccurate when used for processing of interferograms from L-band Advanced Land Observing Satellite Phased Array type L-band SAR (ALOS PALSAR). This happens because only a limited number of interferograms is acquired and also because of large spatial baselines often correlated with the time of acquisition. In this paper two techniques are suggested that can be used for removing the residual topographic component from stacking and SBAS results, thereby increasing their accuracy.

We present here a methodology that allows the combination of GPS and Differential InSAR data for the calculation of continuous three-dimensional (3D) high-resolution velocity maps with corresponding errors. It is based on analytic minimization of the Gibbs energy function, which is possible in the case when neighborhood pixels of the velocity maps are considered independent. By joining scalar DInSAR data and vector GPS data, the technique allows us to achieve significant improvement in accuracy in the components of the velocity vector in comparison with the GPS data alone. In the accompanying example, the method is used for the investigation of the creep motion of the southern San Andreas fault around the Salton Sea region. The velocity maps are calculated for two time periods (1992-1998 and 1997-2001) and also for 3D and 2D cases. The preliminary analysis of the optimized data suggests that creep on the San Andreas fault in this region is time-dependent.

A method based on random field theory and Gibbs-Markov random fields equivalency within Bayesian statistical framework is used to derive 3-D surface motion maps from sparse global positioning system (GPS) measurements and differential interferometric synthetic aperture radar (DInSAR) interferogram in the southern California region. The minimization of the Gibbs energy function is performed analytically, which is possible in the case when neighboring pixels are considered independent. The problem is well posed and the solution is unique and stable and not biased by the continuity condition. The technique produces a 3-D field containing estimates of surface motion on the spatial scale of the DInSAR image, over a given time period, complete with error estimates. Significant improvement in the accuracy of the vertical component and moderate improvement in the accuracy of the horizontal components of velocity are achieved in comparison with the GPS data alone. The method can be expanded to account for other available data sets, such as additional interferograms, lidar, or leveling data, in order to achieve even higher accuracy.

In this study, we analyze 25 RADARSAT-2 images from ascending and descending geometries to study the creep rate on the Hayward fault and landslide motions near Berkeley, CA. We applied a coherence optimization technique from polarimetric synthetic aperture radar interferometry (PolInSAR) to increase the accuracy of the measurements. We resolve 3–5 mm/year of motion along the Hayward fault, in agreement with earlier creep estimates. We identify a potential motion on secondary fault, northeast and parallel to the Hayward fault, which is creeping at a lower rate of ~1.5 mm/year. In addition, we identify a number of landslides along the hills east of the fault that agree with earlier results from advanced interferometric synthetic aperture radar (SAR) analysis and field investigations. We investigate four particular slope instabilities, one of which was marked as moderately active, and three as highly active, by earlier field investigations. The resolved along-hill slope displacement is estimated at ~23 mm/year. Our results demonstrate that PolInSAR is an effective method to increase the interferometric coherence and provide improved resolution of deformation features associated with natural hazards., This research was funded by the NSERC and Aon Benfield/ICLR IRC in Earthquake Hazard Assessment, an NSERC Discovery Grant, and an Ontario Early Researcher Award. PJG also acknowledges support from a Banting postdoctoral fellowship (Government of Canada).