Decomposing DInSAR Time-Series into 3-D in Combination with GPS in the Case of Low Strain Rates: An Application to the Hyblean Plateau, Sicily, Italy

Differential Interferometric SAR (DInSAR) time-series techniques can be used to derive surface displacement rates with accuracies of 1 mm/year, by measuring the one-dimensional distance change between a satellite and the surface over time. However, the slanted direction of the measurements complicates interpretation of the signal, especially in regions that are subject to multiple deformation processes. The Simultaneous and Integrated Strain Tensor Estimation from Geodetic and Satellite Deformation Measurements (SISTEM) algorithm enables decomposition into a three-dimensional velocity field through joint inversion with GNSS measurements, but has never been applied to interseismic deformation where strain rates are low. Here, we apply SISTEM for the first time to detect tectonic deformation on the Hyblean Foreland Plateau in South-East Sicily. In order to increase the signal-to-noise ratio of the DInSAR data beforehand, we reduce atmospheric InSAR noise using a weather model and combine it with a multi-directional spatial filtering technique. The resultant three-dimensional velocity field allows identification of anthropogenic, as well as tectonic deformation, with sub-centimeter accuracies in areas of sufficient GPS coverage. Our enhanced method allows for a more detailed view of ongoing deformation processes as compared to the single use of either GNSS or DInSAR only and thus is suited to improve assessments of regional seismic hazard

Surface deformation analysis in Northeast Italy by using PS-InSAR and GNSS data

In the present study, we exploited the potential of satellite-based geodetic data for detecting and measuring surface displacement in Northeast Italy. In this contest, we focused mainly on 1) the estimation of the interseismic deformation during the satellites’ observation period, 2) the detection and analysis of the main deformation patterns, and 3) the correlation of the signals to the active tectonic structures. Despite the low convergence rates (~ 1.5-3 mm/yr), Northeast Italy is an active tectonic area, as testified by the instrumental and historical seismicity. The Adria-Eurasia convergence is mainly accommodated by the thrusts and strike-slip faults of the Southeastern Alps and the External Dinarides, located in the northern and northeastern sectors of the study area. The Venetian-Friulian plain and the Adriatic coasts, affected by active subsidence, dominate the southern region. We used the Stanford Method for Persistent Scatterers (StaMPS) applied to Sentinel-1 SAR images acquired along the ascending and descending orbit tracks between 2015 and 2019. Based on a stack of single-master differential interferograms, we detected coherent and temporally stable pixels based on amplitude and phase noise analysis. After applying spatial-temporal filters and additional post-processing operations to refine the measurements, we used Adria-fixed GNSS velocities derived by permanent stations in the study area to calibrate the InSAR velocities. The outcome consists of Line-OF-Sight (LOS) mean ground velocity maps derived by displacement time series along the radar directions for each satellite track. The combination of the LOS datasets yields vertical and east-west velocity maps, which are mostly in agreement with GNSS data and previous geodetic studies. Based on our measurements, we observe a significant positive velocity gradient of 1 mm/yr across the westernmost sector of the Alpine system, suggesting an aseismic motion of the root of the Bassano-Valdobbiadene thrust. The positive vertical gradients (~1 and up to 2 mm/yr) across the Alpine-Dinaric systems in the central and eastern sectors and the eastward motion that increases northeastward (1-2 mm/yr) may be related to the active Alpine-Dinaric thrusts and strike-slip faults. We also suggest that the detected westward motion of the Friulian plain (around Udine) might be attributed to the presence of tectonic structures characterized by transcurrent-transpressive kinematics. Finally, we detect other signals, such as the significant subsidence (2-4 mm/yr) along the coasts and on the southern Venetian-Friulian plain, confirming the correlation between subsidence and the geological setting of the study area. In conclusion, our study confirms the potential of MT-InSAR and GNSS data for the estimation of the surface deformations in response to active tectonics, even in areas characterized by low deformation rates, such as Northeast Italy.In the present study, we exploited the potential of satellite-based geodetic data for detecting and measuring surface displacement in Northeast Italy. In this contest, we focused mainly on 1) the estimation of the interseismic deformation during the satellites’ observation period, 2) the detection and analysis of the main deformation patterns, and 3) the correlation of the signals to the active tectonic structures. Despite the low convergence rates (~ 1.5-3 mm/yr), Northeast Italy is an active tectonic area, as testified by the instrumental and historical seismicity. The Adria-Eurasia convergence is mainly accommodated by the thrusts and strike-slip faults of the Southeastern Alps and the External Dinarides, located in the northern and northeastern sectors of the study area. The Venetian-Friulian plain and the Adriatic coasts, affected by active subsidence, dominate the southern region. We used the Stanford Method for Persistent Scatterers (StaMPS) applied to Sentinel-1 SAR images acquired along the ascending and descending orbit tracks between 2015 and 2019. Based on a stack of single-master differential interferograms, we detected coherent and temporally stable pixels based on amplitude and phase noise analysis. After applying spatial-temporal filters and additional post-processing operations to refine the measurements, we used Adria-fixed GNSS velocities derived by permanent stations in the study area to calibrate the InSAR velocities. The outcome consists of Line-OF-Sight (LOS) mean ground velocity maps derived by displacement time series along the radar directions for each satellite track. The combination of the LOS datasets yields vertical and east-west velocity maps, which are mostly in agreement with GNSS data and previous geodetic studies. Based on our measurements, we observe a significant positive velocity gradient of 1 mm/yr across the westernmost sector of the Alpine system, suggesting an aseismic motion of the root of the Bassano-Valdobbiadene thrust. The positive vertical gradients (~1 and up to 2 mm/yr) across the Alpine-Dinaric systems in the central and eastern sectors and the eastward motion that increases northeastward (1-2 mm/yr) may be related to the active Alpine-Dinaric thrusts and strike-slip faults. We also suggest that the detected westward motion of the Friulian plain (around Udine) might be attributed to the presence of tectonic structures characterized by transcurrent-transpressive kinematics. Finally, we detect other signals, such as the significant subsidence (2-4 mm/yr) along the coasts and on the southern Venetian-Friulian plain, confirming the correlation between subsidence and the geological setting of the study area. In conclusion, our study confirms the potential of MT-InSAR and GNSS data for the estimation of the surface deformations in response to active tectonics, even in areas characterized by low deformation rates, such as Northeast Italy

Long-term monitoring of geodynamic surface deformation using SAR interferometry

Thesis (Ph.D.) University of Alaska Fairbanks, 2014Synthetic Aperture Radar Interferometry (InSAR) is a powerful tool to measure surface deformation and is well suited for surveying active volcanoes using historical and existing satellites. However, the value and applicability of InSAR for geodynamic monitoring problems is limited by the influence of temporal decorrelation and electromagnetic path delay variations in the atmosphere, both of which reduce the sensitivity and accuracy of the technique. The aim of this PhD thesis research is: how to optimize the quantity and quality of deformation signals extracted from InSAR stacks that contain only a low number of images in order to facilitate volcano monitoring and the study of their geophysical signatures. In particular, the focus is on methods of mitigating atmospheric artifacts in interferograms by combining time-series InSAR techniques and external atmospheric delay maps derived by Numerical Weather Prediction (NWP) models. In the first chapter of the thesis, the potential of the NWP Weather Research & Forecasting (WRF) model for InSAR data correction has been studied extensively. Forecasted atmospheric delays derived from operational High Resolution Rapid Refresh for the Alaska region (HRRRAK) products have been compared to radiosonding measurements in the first chapter. The result suggests that the HRRR-AK operational products are a good data source for correcting atmospheric delays in spaceborne geodetic radar observations, if the geophysical signal to be observed is larger than 20 mm. In the second chapter, an advanced method for integrating NWP products into the time series InSAR workflow is developed. The efficiency of the algorithm is tested via simulated data experiments, which demonstrate the method outperforms other more conventional methods. In Chapter 3, a geophysical case study is performed by applying the developed algorithm to the active volcanoes of Unimak Island Alaska (Westdahl, Fisher and Shishaldin) for long term volcano deformation monitoring. The volcano source location at Westdahl is determined to be approx. 7 km below sea level and approx. 3.5 km north of the Westdahl peak. This study demonstrates that Fisher caldera has had continuous subsidence over more than 10 years and there is no evident deformation signal around Shishaldin peak.Chapter 1. Performance of the High Resolution Atmospheric Model HRRR-AK for Correcting Geodetic Observations from Spaceborne Radars -- Chapter 2. Robust atmospheric filtering of InSAR data based on numerical weather prediction models -- Chapter 3. Subtle motion long term monitoring of Unimak Island from 2003 to 2010 by advanced time series SAR interferometry -- Chapter 4. Conclusion and future work

Secondary Fault Activity of the North Anatolian Fault near Avcilar, Southwest of Istanbul: Evidence from SAR Interferometry Observations

Strike-slip faults may be traced along thousands of kilometers, e.g., the San Andreas Fault (USA) or the North Anatolian Fault (Turkey). A closer look at such continental-scale strike faults reveals localized complexities in fault geometry, associated with fault segmentation, secondary faults and a change of related hazards. The North Anatolian Fault displays such complexities nearby the mega city Istanbul, which is a place where earthquake risks are high, but secondary processes are not well understood. In this paper, long-term persistent scatterer interferometry (PSI) analysis of synthetic aperture radar (SAR) data time series was used to precisely identify the surface deformation pattern associated with the faulting complexity at the prominent bend of the North Anatolian Fault near Istanbul city. We elaborate the relevance of local faulting activity and estimate the fault status (slip rate and locking depth) for the first time using satellite SAR interferometry (InSAR) technology. The studied NW-SE-oriented fault on land is subject to strike-slip movement at a mean slip rate of ~5.0 mm/year and a shallow locking depth of <1.0 km and thought to be directly interacting with the main fault branch, with important implications for tectonic coupling. Our results provide the first geodetic evidence on the segmentation of a major crustal fault with a structural complexity and associated multi-hazards near the inhabited regions of Istanbul, with similarities also to other major strike-slip faults that display changes in fault traces and mechanisms

Evaluation of InSAR monitoring data for post-tunnelling settlement damage assessment

The increasing demand for underground infrastructure should be supported by a rapid innovation in monitoring and damage assessment solutions to guarantee the safety of surface structures against ground settlements. This paper evaluates the use of Multi Temporal Synthetic Aperture Radar Interferometry (MT-InSAR) to calculate tunnelling-induced deformations of buildings. The paper introduces a step-by-step procedure to use InSAR displacements as an input to the structural damage assess- ment. After a comparison between traditional and InSAR monitoring data for the London area during the Crossrail excavation, the high resolution, high density InSAR based displacements were used to evaluate the building deformations for a number of case studies. Results demonstrate the quality of information provided by InSAR data on soil-structure interaction mechanisms. Such information, essential to evaluate current damage assessment procedures, is typically only collected for relatively few buildings due to the cost of traditional monitoring. A comparison between damage indicators derived from greenfield assumptions and building displacements quan- tifies the practical benefit of the proposed step-by-step procedure. This work aims at filling the gap between the most recent advances in remote sensing and the civil engineering practice, defining the first step of an automated damage assessment procedure which can impact large scale underground projects in urban areas

Unrest at Domuyo Volcano, Argentina, detected by geophysical and geodetic data and morphometric analysis

New volcanic unrest has been detected in the Domuyo Volcanic Center (DVC), to the east of the Andes Southern Volcanic Zone in Argentina. To better understand this activity, we investigated new seismic monitoring data, gravimetric and magnetic campaign data, and interferometric synthetic aperture radar (InSAR) deformation maps, and we derived an image of the magma plumbing system and the likely source of the unrest episode. Seismic events recorded during 2017-2018 nucleate beneath the southwestern flank of the DVC. Ground deformation maps derived from InSAR processing of Sentinel-1 data exhibit an inflation area exceeding 300 km2, from 2014 to at least March 2018, which can be explained by an inflating sill model located 7 km deep. The Bouguer anomaly reveals a negative density contrast of ~35 km wavelength, which is spatially coincident with the InSAR pattern. Our 3D density modeling suggests a body approximately 4-6 km deep with a density contrast of -550 kg/m3. Therefore, the geophysical and geodetic data allow identification of the plumbing system that is subject to inflation at these shallow crustal depths. We compared the presence and dimensions of the inferred doming area to the drainage patterns of the area, which support long-established incremental uplift according to morphometric analysis. Future studies will allow us to investigate further whether the new unrest is hydrothermal or magmatic in origin.Fil: Astort, Ana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Walter, Thomas R. German Research Centre for Geosciences; AlemaniaFil: Ruiz, Francisco. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; ArgentinaFil: Sagripanti, Lucía. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Nacif, Andres Antonio. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; ArgentinaFil: Acosta, Gemma. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Folguera Telichevsky, Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentin

Urban Deformation Monitoring using Persistent Scatterer Interferometry and SAR tomography

This book focuses on remote sensing for urban deformation monitoring. In particular, it highlights how deformation monitoring in urban areas can be carried out using Persistent Scatterer Interferometry (PSI) and Synthetic Aperture Radar (SAR) Tomography (TomoSAR). Several contributions show the capabilities of Interferometric SAR (InSAR) and PSI techniques for urban deformation monitoring. Some of them show the advantages of TomoSAR in un-mixing multiple scatterers for urban mapping and monitoring. This book is dedicated to the technical and scientific community interested in urban applications. It is useful for choosing the appropriate technique and gaining an assessment of the expected performance. The book will also be useful to researchers, as it provides information on the state-of-the-art and new trends in this fiel