In this work the long-term DInSAR deformation time series have been jointly exploited with the geological information and the structural characteristics of the buildings, in order to study the ...interactions between the soils and the man-made structures and to investigate the response of different buildings to the settlements.
The presented analysis has been carried out by applying the advanced multi-temporal DInSAR technique referred to as Small BAseline Subset (SBAS) approach to an ERS/ENVISAT SAR dataset, collected over the town of Roma (Italy) in the 1992–2010 time interval.
Our study has been performed first at the large spatial scale, and then at the local scale, focusing on some buildings located within the city centre on the eastern side of the Tevere River.
The obtained SBAS-DInSAR measurements, analysed in light of the geological setting and the spatial distribution of the settlements, indicate that the observed displacements are mainly linked to a residual consolidation process, correlated with the urbanization and hydrometric level of the Tevere River. The local variation in the deformation rates can be related to the intrinsic variability of the soils filling the alluvial valley and to time since loading application.
•Extensive use of long-term SBAS DInSAR data for back-analysis of large urban areas•Non-invasive displacement measurements for monitoring single buildings•Joint analysis of SBAS-DInSAR differential settlements and detailed stratigraphic profiles•Correlation between residual consolidation process, urbanization and hydrometric level of Tevere River
We investigate the surface deformation of the eastern California area that includes Long Valley caldera and Mono Basin. We apply the SAR Interferometry (InSAR) algorithm referred to as Small BAseline ...Subset (SBAS) approach that allows us to generate mean deformation velocity maps and displacement time series for the investigated area. The results presented in this work represent an advancement of previous InSAR studies of the area that are mostly focused on the deformation affecting the caldera. In particular, the proposed analysis is based on 21 SAR data acquired by the ERS-1/2 sensors during the 1992–2000 time interval, and demonstrates the capability of the SBAS procedure to identify and analyze displacement patterns at different spatial scales for the overall area spanning approximately 5000 km
2. Two previously unreported localized deformation effects have been detected at Paoha Island, located within the Mono Lake, and in the McGee Creek area within the Sierra Nevada mountains, a zone to the south of the Long Valley caldera. In addition a spatially extended uplift effect, which strongly affects the caldera, has been identified and analyzed in detail. The InSAR results clearly show that the displacement phenomena affecting the Long Valley caldera have a maximum in correspondence of the resurgent dome and are characterized by the sequence of three different effects: a 1992–1997 uplift background, a 1997–1998 unrest phenomenon and a 1998–2000 subsidence phase. Moreover, the analysis of the retrieved displacement time series allows us to map the extent of the zone with a temporal deformation behavior highly correlated with the detected three-phases deformation pattern: background uplift-unrest-subsidence. We show that the mapped area clearly extends outside the northern part of the caldera slopes; accordingly, we suggest that future inversion models take this new evidence into account. The final discussion is dedicated to a comparison between the retrieved InSAR measurements and a set of GPS and leveling data, confirming the validity of the results achieved through the SBAS-InSAR analysis.
We investigate the co-seismic effects of the Mw 7.8 Gorkha earthquake through a Finite Element modelling approach that jointly exploits space-borne DInSAR deformation measurements and ...geologic-structural information. Our model permits to retrieve the coseismic displacements with a very good accuracy and to confirm the finding of earlier studies suggesting that the slip reaches a maximum value of about 7m at a depth of 7–15km along the Main Himalayan Thrust (MHT) and occurs in an area about 30km northern of Kathmandu. In particular, the main-shock ruptured the deep part of the seismogenic zone of MHT, with rather small displacement values retrieved along the splay faults (Main Frontal Thrust – MFT; Main Boundary Thrust – MBT) in the southern region. A relevant aspect of our results is the imaging of about 3m of displacement in correspondence to the shallow portion of the Main Central Thrust (MCT) to the north and of the Munsiari/Mahabharat Thrust (MT) to the south; this finding may be associated to a possible mechanism for accommodating the MHT-sourced deformation on the adjacent thrusts, highlighting a passive role of the hinterland structures as receiver faults of the displacements transferred from earthquakes originating on the MHT. In addition, the proposed model allow us to map the stress field distribution (evaluated through von Mises failure criteria) associated to the main seismic event; this result is in good agreement with the hypocentral distribution and mechanism of the investigated aftershocks.
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.
Key PointsDetection of active seismogenic structures responsible for ground deformationEvaluate the role of tectonic constrain on the modulation of ground deformationProvide a detailed characterization of the rock failure mechanisms
We present an automatic pipeline implemented within the Amazon Web Services (AWS) Cloud Computing platform for the interferometric processing of large Sentinel-1 (S1) multi-temporal SAR datasets, ...aimed at analyzing Earth surface deformation phenomena at wide spatial scale. The developed processing chain is based on the advanced DInSAR approach referred to as Small BAseline Subset (SBAS) technique, which allows producing, with centimeter to millimeter accuracy, surface deformation time series and the corresponding mean velocity maps from a temporal sequence of SAR images. The implemented solution addresses the aspects relevant to i) S1 input data archiving; ii) interferometric processing of S1 data sequences, performed in parallel on the AWS computing nodes through both multi-node and multi-core programming techniques; iii) storage of the generated interferometric products. The experimental results are focused on a national scale DInSAR analysis performed over the whole Italian territory by processing 18 S1 slices acquired from descending orbits between March 2015 and April 2017, corresponding to 2612 S1 acquisitions. Our analysis clearly shows that an effective integration of advanced remote sensing methods and new ICT technologies can successfully contribute to deeply investigate the Earth System processes and to address new challenges within the Big Data EO scenario.
The authors present a new spotlight SAR data-focusing algorithm based on a two-step processing strategy that combines the advantages of two commonly adopted processing approaches: the efficiency of ...SPECAN algorithms and the precision of stripmap focusing techniques. The first step of the proposed algorithm implements a linear and space-invariant azimuth filtering that is carried out via a deramping-based technique representing a simplified version of the SPECAN approach. This operation allows the authors to perform a bulk azimuth raw data compression and to achieve a pixel spacing smaller than (or equal to) the expected azimuth resolution of the fully focused image. Thus, the azimuth spectral folding phenomenon, typically affecting the spotlight data, is overcome, and the space-variant characteristics of the stripmap system transfer function are preserved. Accordingly, the residual and precise focusing of the SAR data is achieved by applying a conventional stripmap processing procedure requiring a minor modification and implemented in the frequency domain. The extension of the proposed technique to the case of high bandwidth transmitted chirp signals is also discussed. Experiments carried out on real and simulated data confirm the validity of the presented approach, which is mainly focused on spaceborne systems.
Mount Etna underwent a cycle of eruptive activity over the past ten years. Here we compute ground displacement maps and deformation time series from more than 400 radar interferograms to reveal Mount ...Etna's average and time varying surface deformation from 1992 to 2001. We find that during this time interval it experienced magmatic inflation and radial spreading to the West, South, and East. Steady relative motion between the West and South flanks, and between the East and North flanks, during this time interval, suggests they are related to gravitational spreading of the volcanic edifice. Time series analysis shows that growth of a southeastern basal anticline began with the end of magma recharge in 1995, thus showing a direct link between deep‐seated magma intrusions and edifice spreading. These observations support a complex mode of radial gravitational collapse underlain by deeper magma driven basal spreading, although ultimately the two must be related.
The island of Ischia, located at the northwestern end of the Gulf of Napoli (Italy), is a volcanic area that is historically active (the Arso eruption, in 1302 and the Casamicciola earthquake, in ...1883) and has diffuse hydrothermal phenomena. We present in this work a study of the surface deformation occurring in the island, which is based on applying the Differential Synthetic Aperture Radar Interferometry (DInSAR) algorithm referred to as Small BAseline Subset (SBAS) technique. This study is focused on the 1992–2003 time interval and SAR data acquired by the European Remote Sensing (ERS) satellites from ascending and descending orbits have been used, thus allowing us to discriminate the vertical and east–west components of the displacements. A validation of the DInSAR results has been carried out first by comparing the vertical deformations estimated from the SAR data with those measured from the spirit leveling network that is present in the area. In particular, we computed the difference between the mean vertical deformation velocities estimated from the SAR and the corresponding geodetic measurements along three main leveling lines; the maximum value of the root mean square difference is of about 1 mm/yr. The final discussion is dedicated to the interpretation of the detected displacements, benefiting from the overall information extracted from the ascending and descending DInSAR measurements. In particular, DInSAR data relative to the vertical deformation component show that the present-day subsidence of Ischia mainly develops in areas characterized by active landsliding and along faults; moreover, the deflation of the island, which is recorded by the horizontal displacement component, is probably related to the de-pressurization of the hydrothermal system.
We investigate the surface displacements in the area affected by the April 2009 L'Aquila earthquake (Central Italy) through an advanced DInSAR analysis. In particular, we apply the SBAS approach to ...retrieve deformation maps and displacement time series from ENVISAT data acquired between February 2003 and October 2009 and from COSMO‐SkyMed data relevant to the six‐month interval following the earthquake. Our analysis shows no evidence of pre‐seismic surface deformation at the 35‐day temporal sampling of the ENVISAT sensor. On the other hand, by benefiting of the high spatial resolution and temporal sampling of the COSMO‐SkyMed satellites, we measure post‐seismic displacements at an unprecedented level of detail for a DInSAR analysis. This allows us to identify three main areas continuing to deform after the earthquake. In addition, our modeling shows that post‐seismic displacements are very likely related to the fault afterslip, since their decay times are on the order of 101–102 days.
We present an algorithm aimed at correcting satellite orbit information for the generation of differential SAR interferometry (DInSAR) deformation time-series. Our approach exploits small baseline ...differential interferograms, to preserve their spatial coherence, and is directly compatible with the Small BAseline Subset (SBAS) DInSAR technique. In particular, the algorithm investigates the differential phase gradient directly computed from the wrapped interferograms, and is focused on the estimation of the perpendicular baseline and of the parallel baseline azimuth rate components, separately performed along the range and azimuth directions, respectively. Starting from the estimations carried out on the interferograms, we then retrieve the orbit correction associated with each SAR acquisition of our time-series by solving a system of linear equations via the SVD method, extending the SBAS inversion concept also to the orbit estimation problem. Key application of this technique is the generation of deformation time-series from interferometric sequences of RADARSAT-1 SAR acquisitions which are available for several areas in the world, but are characterized by significantly low accuracy of the or bit information. The presented results, obtained by processing a data set consisting of 33 RADARSAT-1 images of Big Island at Hawaii, show that we may retrieve DInSAR time-series with sub centimeter accuracy, thus confirming the effectiveness of the pro posed technique.
PDF
