PSInSAR Data Research Articles

Estimation of small surface displacements in the Upper Rhine Graben area from a combined analysis of PS-InSAR, levelling and GNSS data

The intra-plate deformation of the Upper Rhine Graben (URG) located in Central Europe is investigated using geodetic measurement techniques. We present a new approach to calculate a combined velocity field from InSAR, levelling and GNSS measurements. As the expected tectonic movements in the URG area are small (less than 1mma−1), the best possible solutions for linear velocity rates from single-technique analyses are estimated in a first step. Second, we combine the velocity rates obtained from InSAR (line of sight velocity rates in ascending and descending image geometries), levelling (vertical velocity rates) and GNSS (horizontal velocity rates) using least-squares adjustment (LSA). Focusing on the Northern URG area, we analyse SAR data on four different image stacks (ERS ascending, ERS descending, Envisat ascending, Envisat descending) using the Persistent Scatterer (PS) approach. The linear velocity rates in ascending and descending image geometries, respectively, are estimated in an LSA from joint time-series analysis of ERS and Envisat data. Vertical velocity rates from levelling are obtained from a consistent adjustment of more than 40 000 measured height differences using a kinematic displacement model. Horizontal velocity rates in east and north direction are calculated from a time-series analysis of daily coordinate estimates at 76 permanently operating GNSS sites in the URG region. As the locations, at which the measurement data of PS-InSAR, levelling and GNSS reside, do not coincide, spatial interpolation is needed during several steps of the rigorous processing. We use Ordinary Kriging to interpolate from a given set of data points to the locations of interest with a special focus on the modeling and propagation of errors. The final 3-D velocity field is calculated at a 200 m grid, which carries values only close to the location of PS points, resulting in a mean horizontal and vertical precision of 0.30 and 0.13 mm a−1, respectively. The vertical component of the combined velocity field shows a significant subsidence of about 0.5 mm a−1 in the northern part of the graben coinciding with a well-known quaternary basin structure. Horizontal displacement rates of up to 0.8 mm a−1 in southeast direction are observed outside the graben, in reasonable alignment with the average direction of maximum horizontal stress. Within the graben, the velocity directions rotate toward east in the non-subsiding part, while an opposite trend is observed in the subsiding part of the graben. The complexities of the observed velocity field are compatible to the geomechanical situation in our investigation area which is characterized by a transition from a restraining to a releasing bend setting. Glacial isostatic adjustment is another potential source influencing the observed velocity field, as well as anthropogenic signals due to mining, oil exploration and groundwater usage that have been identified in some places.

Inter-comparison and time series fusion of ascending and descending PSInSAR data for land subsidence monitoring

Inter-comparison and time series fusion of ascending and descending PSInSAR data for land subsidence monitoring

Analysis of building deformation in landslide area using multisensor PSInSAR™ technique

Buildings are sensitive to movements caused by ground deformation. The mapping both of spatial and temporal distribution, and of the degree of building damages represents a useful tool in order to understand the landslide evolution, magnitude and stress distribution. The high spatial resolution of space-borne SAR interferometry can be used to monitor displacements related to building deformations. In particular, PSInSAR technique is used to map and monitor ground deformation with millimeter accuracy. The usefulness of the above mentioned methods was evaluated in San Fratello municipality (Sicily, Italy), which was historically affected by landslides: the most recent one occurred on 14th February 2010. PSInSAR data collected by ERS 1/2, ENVISAT, RADARSAT-1 were used to study the building deformation velocities before the 2010 landslide. The X-band sensors COSMO-SkyMed and TerraSAR-X were used in order to monitor the building deformation after this event. During 2013, after accurate field inspection on buildings and structures, damage assessment map of San Fratello were created and then compared to the building deformation velocity maps. The most interesting results were obtained by the comparison between the building deformation velocity map obtained through COSMO-SkyMed and the damage assessment map. This approach can be profitably used by local and Civil Protection Authorities to manage the post-event phase and evaluate the residual risks.

On the prediction of settlement from high-resolution shear-wave reflection seismic data: The Trondheim harbour case study, mid Norway

This paper presents a novel approach to predict long-term settlement in the Trondheim harbour, mid Norway, from high-resolution shear-wave seismic reflection data, complemented with cone penetration test results (CPTU) and index soil properties from nearby boreholes in this reclaimed coastal area. The data enables sub-surface geo-characterisation in high-resolution, down to the basement at a depth of about 175m. Correlations between shear-wave velocity and Janbu's classical 1D consolidation parameters (m, M0, M1, σ′c and OCR) are used for settlement analysis. Both the magnitude and rate of time-settlement predictions compare well with the measured settlements from GPS levelling and PSInSAR data acquired since the late 1980s and the early 1990s in the area, respectively. The shear-wave reflection data further provide important input to understand the spatial patterns of land-subsidence in the Trondheim harbour. The highest settlement rates occur in areas where depth to bedrock is greatest and where thicker deposits with low stiffness are found. In summary, the data and workflow presented here are useful tools for predicting settlements based on correlations with shear-wave velocity measurements.

Sentinel 1 SAR interferometry applications: The outlook for sub millimeter measurements

Optical leveling campaigns, tiltmeters, GPS and InSAR are geodetic techniques used to detect and monitor surface deformation phenomena. In particular, InSAR data from satellite radar sensors are gaining increasing attention for their cost-effectiveness and unique technical features, making possible the monitoring of large areas, even revisiting the past. Moreover, more advanced InSAR techniques (PSInSAR™, SqueeSAR™) developed in the last decade are capable of providing millimeter precision, comparable to optical leveling, and a high spatial density of displacement measurements, over long periods of time without need of installing equipment or otherwise accessing the study area.Thanks to the high density and quality of the measurements the PSInSAR data can be successfully used in geophysical inversion, to measure the permeability of oil reservoirs and/or to evaluate the possibilities and risks due to seismic faulting in the sequestration of CO2. In these cases, the precision, the sub weekly frequency of the measurements and the time required for the data to be available are the most important aspects, more relevant than the spatial resolution.Until recently, the main limitation to the application of InSAR was the relatively long revisiting time (24 or 35days) and the quite long waiting period for the delivery of the acquired data. The new Sentinel-1 mission, based on a constellation of two satellites, is expected to reduce such limitations guaranteeing a revisit cycle of 6days on a global scale and in particular over Europe and Canada and providing a high level of service reliability with near-real-time delivery of data within 24h, important for risk management applications. The new X band satellite SAR constellations like Cosmo Skymed and TerraSAR X have also a short revisiting time, from 4 to 11days. However, their coverage is limited to well definite areas, and an expensive decision has to be made if to initiate the observations on any target. Sentinel 1, instead, yields global and costless observations and thus, after the end of the commissioning phase, will always produce present and past ground motion for any target.It's important to underline that the millimeter accuracy, applying the InSAR analysis with Sentinel-1, will be achieved within a shorter observation time frame, thanks to the increased number of acquired images per year (Attema et al. 2010, De Zan et al., 2008). Results from ground based radar show that this improved precision is indeed achievable from C to Ku band, provided that an accurate model of the delay due to atmospheric water vapor is available or that precise reference points are close by.

Iso-Kinematic Maps from statistical analysis of PS-InSAR data of Piemonte, NW Italy: Comparison with geological kinematic trends

SAR interferometry based on Permanent Scatterers (PS-InSAR™) is used here to study the present crustal mobility of a large area of NW Italy, in the Piemonte region. Thirty-eight satellite scenes (ERS SAR), taken from May 1992 to January 2001, were analysed for detecting more than 2 million PS on the study area. Continuous velocity surface maps (Iso-Kinematic Maps: IKM) were obtained from geo-statistical and spatial cluster techniques (Hot Spot analysis) of PS “short-period” data, to identify relative ground motions and to compare them with “long-period” tectonic mobility trends, i.e. those inferred at regional scale over geological times (some million years). The comparison was made by individuation of homogeneous kinematic areas, represented in the IKM, and characterization of the boundaries between them (Iso-Kinematic Boundaries: IKB). The IKB were used as tools to asses if the PS-InSAR data on present-day crustal mobility could fit with the distribution of real tectonic structures or field geological elements. IKM were drawn for uplifting geological sectors of Piemonte (Maritime Alps, Gran Paradiso, Langhe) where moderate to very low seismicity is recorded, and gravitational instabilities of rock mass on mountain slopes are widespread. The land sectors have been chosen in order to test the suitability of IKM in very different geo-morphological conditions. Different types of correspondence between the IKM and the geological kinematic trend were found: - a first type in which the kinematic trend of short-period (a decade of years, i.e. the PS-InSAR detection time span) is in agreement with a long-period tectonic trend (some million years) and seem to be driven by well known faults subparallel to the IKB. These kinematic trends can be hidden by the slope movement due to gravitational instabilities; - a second type in which the kinematic trend of short-period does not strictly correspond to the long-period trend, but can be considered as minor-order, uplifting-subsidence cycles, even if in contrast with the long-period kinematic trend. Alternatively, the short-period kinematic trends could reflect the action of deep-seated geological forces or structures, not yet known or inferable (at least with the recorded PS-InSAR velocities) on the basis of the available geological data and models.

Use of PSInSAR™ data to infer active tectonics: Clues on the differential uplift across the Giudicarie belt (Central-Eastern Alps, Italy)

The Permanent Scatterers Synthetic Aperture Radar INterferometry (PSInSAR™) methodology provides high-resolution assessment of surface deformations (precision ranging from 0.8 to 0.1 mm/year) over long periods of observation. Hence, it is particularly suitable to analyze surface motion over wide regions associated to a weak tectonic activity. For this reason we have adopted the PSInSAR technique to study regional movement across the Giudicarie belt, a NNE-trending trust belt oblique to the Southern Alpine chain and presently characterized by a low to moderate seismicity. Over 11,000 PS velocities along the satellite Line Of Sight (LOS) were calculated using images acquired in descending orbit during the 1992–1996 time span. The PSInSAR data show a differential uplift of around 1.4–1.7 mm/year across the most external WNW-dipping thrusts of the Giudicarie belt (Mt. Baldo, Mt. Stivo and Mt. Grattacul thrusts alignment). This corresponds to a horizontal contraction across the external part of the Giudicarie belt of about 1.3–1.5 mm/year.

Space-based Tectonic Modeling in Subduction Areas Using PSInSAR

While the application of InSAR (INterferometric Synthetic Aperture Radar) techniques to seismology has been well known since the mid-1990s (Massonnet et al. , 1993; Massonnet et al. , 1996), PSInSAR is generally unfamiliar to the Earth science community. The PS stands for “permanent scatterer”, and it is the use of these (along with the volume of scenes employed) that distinguishes the method from more familiar InSAR techniques. A permanent scatterer is any persistently reflective pre-existing ground feature, such as building roofs, metallic structures, and even large boulders. The use of these features offers the possibility of measurements of ground displacements to a degree of accuracy, and over periods of time, previously unobtainable from conventional interferometry. Furthermore, it is possible to construct histories of displacements over the full temporal extent of the SAR data archive (started in 1991) for any part of the globe with data coverage. PSInSAR therefore represents the equivalent of a newly discovered, superaccurate, extremely dense GPS network that has been in existence for the last twelve years. The high resolution of PSInSAR data, coupled with its being particularly suited to urbanized areas (numerous buildings, therefore many PS points), makes it an excellent tool for studying things such as urban subsidence (Ferretti et al., 2000; Mizuno and Kuzuoka, 2003; Dehls and Nordgulen, 2004). It also has applications in seismology: as a substitute for GPS data where these do not exist, and as an enhancement where they do. In this paper we report on a pilot project in Japan, the principal aim of which was to calibrate and test the PSInSAR measurements in an area where ground truth is very well established from GPS and leveling data. This work results from a European Space Agency (ESA) “Earth Observation Market Development” project entitled “Developing markets for EO-derived …

The modern movement in East Africa: The work of Amyas Connell (1900–1980) in Tanganyika and Kenya with reference to the crisis of decoration in modern African architecture

A multidisciplinary methodology, integrating stratigraphic, geomorphological and structural data, combined with GIS-aided analysis and PS-InSAR interferometric data, was applied to characterize the relationships between ground deformations and the stratigraphic and the morphostructural setting of the Venafro intermontane basin. This basin is a morphostructural depression related to NW-SE and NE-SW oriented high angle normal faults bordering and crossing it. In particular, a well-known active fault crossing the plain is the Aquae Juliae Fault, whose recent activity is evidenced by archeoseismological data. The approach applied here reveals new evidence of possible faulting, acting during the Lower to Upper Pleistocene, which has driven the morphotectonic and the environmental evolution of the basin. In particular, the tectonic setting emerging from this study highlights the influence of the NW-SE oriented extensional phase during the late Lower Pleistocene – early Middle Pleistocene, in the generation of NE-SW trending, SE dipping, high-angle faults and NW-SE trending, high-angle transtensive faults. This phase has been followed by a NE-SW extensional one, responsible for the formation of NW-SE trending, both NW and SE dipping, high-angle normal faults, and the reactivation of the oldest NE-SW oriented structures. These NW-SE trending normal faults include the Aquae Juliae Fault and a new one, unknown until now, crossing the plain between the Venafro village and the Colle Cupone Mt. (hereinafter named the Venafro-Colle Cupone Fault, VCCF). This fault has controlled deposition of the youngest sedimentary units (late Middle Pleistocene to late Upper Pleistocene) suggesting its recent activity and it is well constrained by PS-InSAR data, as testified by the increase of the subsidence rate in the hanging wall block.