In this paper, an extension of the minimum cost flow (MCF) algorithm dealing with a sparse data grid, which allows the unwrapping of multitemporal differential synthetic aperture radar (SAR) ...interferograms for the generation of deformation time series, is presented. The proposed approach exploits both the spatial characteristics and the temporal relationships among multiple interferograms relevant to a properly chosen sequence. In particular, the presented solution involves two main steps: first of all, for each arc connecting neighboring pixels on the interferometric azimuth/range grid, the unwrapped phase gradients are estimated via the MCF technique applied in the temporal/perpendicular baseline plane. Following this step, these estimates are used as a starting point for the spatial-unwrapping operation implemented again via the MCF approach but carried out in the azimuth/range plane. The presented results, achieved on simulated and real European Remote Sensing satellite SAR data, confirm the effectiveness of the extended MCF unwrapping algorithm
We investigate the 19 September 2021 eruption of the Cumbre Vieja volcano (La Palma, Canary Islands, Spain). In particular, we analyze the Differential Interferometric Synthetic Aperture Radar ...(DInSAR) measurements obtained by processing Sentinel‐1 images acquired from both ascending and descending orbits. First, we show the importance, for oceanic islands like La Palma, of investigating DInSAR products retrieved from time series, instead of single interferograms, to effectively remove possible atmospheric artifacts within the displacement measurements. Subsequently, we invert the retrieved data through analytical modeling. Our results highlight that a sill–like source was active in the pre–eruptive phase (8–16 September), whereas the action of two dikes prevailed during the co‐eruptive phase (17–22 September). This evolution suggests a process of magma rising through a network of interconnected sills and dikes. The seismicity, that preceded and accompanied the onset of the eruption, is consistent with our findings.
Plain Language Summary
Since 19 September 2021, an intense eruptive activity has begun at Cumbre Vieja volcano (La Palma, Canary archipelago, Spain), causing huge social and economic damage. The eruption was preceded and accompanied by numerous phenomena, such as gas emissions and seismic activity. In this work, we exploit the Differential Interferometric Synthetic Aperture Radar (DInSAR) measurements, obtained by processing Sentinel‐1 images, to quantify the retrieved pre‐ and co‐eruptive deformation patterns. In particular, this eruption provided us the opportunity to show the importance, for oceanic islands like La Palma, of investigating DInSAR products retrieved from time series, instead of conventional single interferograms, to effectively remove possible atmospheric artifacts within the displacement measurements. Subsequently, we invert the retrieved surface deformation measurements to investigate the geometries of the volcanic sources responsible for the observed deformations. Our results show the evolution of this eruptive phenomenon from the pre‐to the co‐eruptive phases, suggesting that a complex network of sills and dikes has allowed the magma rising. Moreover, our findings are in good agreement with the recorded seismicity and several geophysical evidence.
Key Points
We retrieve the pre‐ and co‐eruptive deformation patterns of Cumbre Vieja volcano through an advanced processing of Sentinel‐1 radar data
We show that a sill‐like source was active in the pre‐eruptive phase, whereas the action of two dikes prevailed in the co‐eruptive one
The retrieved sources are consistent with magma rising through a network of interconnected sills and dikes, and the seismicity evolution
We investigate in this work the performance of the Small BAseline Subset (SBAS) approach that is a Differential Synthetic Aperture Radar Interferometry (DInSAR) algorithm allowing the generation of ...mean deformation velocity maps and displacement time series from a data set of subsequently acquired SAR images. In particular, we have carried out a quantitative assessment of the SBAS procedure performance by processing SAR data acquired by the European Remote Sensing Satellite (ERS) sensors and comparing the achieved results with geodetic measurements that are assumed as reference. The analysis has been focused on the Napoli bay (Italy) and Los Angeles (California) test areas where different deformation phenomena are present and, at the same time, a large amount of ERS SAR data is available as well as geometric leveling (in the Napoli zone) and continuous GPS (in the Los Angeles zone) measurements, to be used for our performance analysis. Moreover, due to the presence of large urbanized zones, the selected test sites are also characterized by extended, highly coherent areas in the DInSAR maps.
The presented study shows that the SBAS technique provides an estimate of the mean deformation velocity with a standard deviation of about 1 mm/year for a typical ERS data set including between 40 and 60 images. Moreover, the single displacement measurements, computed with respect to a reference point of known motion, show a sub-centimetric accuracy with a standard deviation of about 5 mm, consistently in both the SAR/leveling and SAR/GPS comparisons; we also show that there is an increase of this standard deviation value as we move away from the reference SAR pixel, with an estimated spatial variation value of about 0.05 mm/km.
We investigate a large geodetic data set of interferometric synthetic aperture radar (InSAR) and GPS measurements to determine the source parameters for the three main shocks of the 2016 Central ...Italy earthquake sequence on 24 August and 26 and 30 October (Mw 6.1, 5.9, and 6.5, respectively). Our preferred model is consistent with the activation of four main coseismic asperities belonging to the SW dipping normal fault system associated with the Mount Gorzano‐Mount Vettore‐Mount Bove alignment. Additional slip, equivalent to a Mw ~ 6.1–6.2 earthquake, on a secondary (1) NE dipping antithetic fault and/or (2) on a WNW dipping low‐angle fault in the hanging wall of the main system is required to better reproduce the complex deformation pattern associated with the greatest seismic event (the Mw 6.5 earthquake). The recognition of ancillary faults involved in the sequence suggests a complex interaction in the activated crustal volume between the main normal faults and the secondary structures and a partitioning of strain release.
Key Points
Coseismic ground deformation of the 2016 Central Italy earthquake sequence measured with InSAR and GPS data
At least four main normal fault segments played an active role in the sequence
Antithetic faults and/or preexisting compressional structures may have been reactivated during the sequence with extensional kinematics
We present a new differential synthetic aperture radar (SAR) interferometry algorithm for monitoring the temporal evolution of surface deformations. The presented technique is based on an appropriate ...combination of differential interferograms produced by data pairs characterized by a small orbital separation (baseline) in order to limit the spatial decorrelation phenomena. The application of the singular value decomposition method allows us to easily "link" independent SAR acquisition datasets, separated by large baselines, thus increasing the observation temporal sampling rate. The availability of both spatial and temporal information in the processed data is used to identify and filter out atmospheric phase artifacts. We present results obtained on the data acquired from 1992 to 2000 by the European Remote Sensing satellites and relative to the Campi Flegrei caldera and to the city of Naples, Italy, that demonstrate the capability of the proposed approach to follow the dynamics of the detected deformations.
We investigate the ground deformation and source geometry of the 2016 Amatrice earthquake (Central Italy) by exploiting ALOS2 and Sentinel‐1 coseismic differential interferometric synthetic aperture ...radar (DInSAR) measurements. They reveal two NNW‐SSE striking surface deformation lobes, which could be the effect of two distinct faults or the rupture propagation of a single fault. We examine both cases through a single and a double dislocation planar source. Subsequently, we extend our analysis by applying a 3‐D finite elements approach jointly exploiting DInSAR measurements and an independent, structurally constrained, 3‐D fault model. This model is based on a double fault system including the two northern Gorzano and Redentore‐Vettoretto faults (NGF and RVF) which merge into a single WSW dipping fault surface at the hypocentral depth (8 km). The retrieved best fit coseismic surface deformation pattern well supports the exploited structural model. The maximum displacements occur at 5–7 km depth, reaching 90 cm on the RVF footwall and 80 cm on the NGF hanging wall. The von Mises stress field confirms the retrieved seismogenic scenario.
Key Points
Investigation of the ground deformation and source geometry of the 2016 Amatrice earthquake (Central Italy)
Coseismic displacements modeling through a 3‐D finite elements approach jointly exploiting DInSAR measurements and a 3‐D fault model
Evidence of a bilateral rupture propagating along two en echelon normal faults conjoined at the hypocenter
This paper presents a differential synthetic aperture radar (SAR) interferometry (DIFSAR) approach for investigating deformation phenomena on full-resolution DIFSAR interferograms. In particular, our ...algorithm extends the capability of the small-baseline subset (SBAS) technique that relies on small-baseline DIFSAR interferograms only and is mainly focused on investigating large-scale deformations with spatial resolutions of about 100/spl times/100 m. The proposed technique is implemented by using two different sets of data generated at low (multilook data) and full (single-look data) spatial resolution, respectively. The former is used to identify and estimate, via the conventional SBAS technique, large spatial scale deformation patterns, topographic errors in the available digital elevation model, and possible atmospheric phase artifacts; the latter allows us to detect, on the full-resolution residual phase components, structures highly coherent over time (buildings, rocks, lava, structures, etc.), as well as their height and displacements. In particular, the estimation of the temporal evolution of these local deformations is easily implemented by applying the singular value decomposition technique. The proposed algorithm has been tested with data acquired by the European Remote Sensing satellites relative to the Campania area (Italy) and validated by using geodetic measurements.
La Fossa Caldera at Vulcano (Italy) has been showing signs of unrest since September 2021. To investigate this phenomenon, we conducted an analysis of geodetic and seismological data from July to ...December 2021. In particular, we analyzed Multi Temporal Interferometric Synthetic Aperture Radar and Global Navigation Satellite System data, showing a pronounced elliptical uplift signal, which we elaborated using analytical source modeling. Additionally, seismic data were used to identify seismicity associated with hydrothermal system activity and assess its temporal evolution. The results indicate that the observed deformation is consistent with the expansion of the hydrothermal system within the La Fossa Caldera. These findings align with the analysis of seismic data, revealing signals indicative of hydrothermal activity, such as Very Long Period events. The results suggest that the ongoing phenomenon since 2021 represents a hydrothermal unrest, similar to the one observed during the late 1970s to early 1990s.
Plain Language Summary
La Fossa Caldera at Vulcano Island, part of the Aeolian Islands archipelago in Italy, has shown an increased volcanic activity since September 2021. This activity is characterized by an increase in fumarole temperatures, massive gas emissions, as well as a marked uplift of the crater area, accompanied by an increase in seismicity. To investigate the nature of these phenomena, an analysis of ground deformation data obtained from Multi Temporal Interferometric Synthetic Aperture Radar and Global Navigation Satellite System measurements is presented. Additionally, a detailed analysis of data recorded by the seismic network on Vulcano Island has been conducted. The results indicate that these anomalies can be attributed to the expansion of the hydrothermal system, a phenomenon previously observed in the late 1970s and early 1990s.
Key Points
Multi Temporal Interferometric Synthetic Aperture Radar enabled investigating localized ground deformation in the La Fossa Caldera
The analysis of local seismicity indicates it is associated with the injection of fluids into conduit‐like structures
The modeled source of ground deformation associated with the 2021 unrest is consistent with the pressurization of the hydrothermal system
We investigate the 24–27 December 2018 eruption of Mount Etna occurred from fissures located on the volcano eastern flank and accompanied by a seismic swarm, which was triggered by the magma ...intrusion and continued for weeks after the end of the eruption. Moreover, this swarm involved some of the shallow volcano‐tectonic structures located on the Mount Etna flanks and culminated on 26 December with the strongest event (ML 4.8), occurred along the Fiandaca Fault. In this work, we analyze seismological data and Sentinel‐1 Differential Interferometric Synthetic Aperture Radar (DInSAR) measurements, the latter inverted through analytical modeling. Our results suggest that a dike source intruded, promoting the opening of the eruptive fissures fed by a shallower dike. Moreover, our findings indicate that the activation of faults in different sectors of the volcano may be considered as a response to accommodate the deformations induced by the magma volumes injection.
Key Points
We investigate the ground displacements and the 3D source geometry of the December 2018 Mount Etna (Italy) volcano‐tectonic crisis
DInSAR data obtained from SAR data pairs collected by Sentinel‐1 have been inverted through analytical modeling
Our results suggest the presence of two volcanic sources: a shallow dike and a deeper one associated with a long‐term seismic swarm
The Atlas of Morocco: A Plume‐Assisted Orogeny Lanari, R.; Faccenna, C.; Natali, C. ...
Geochemistry, geophysics, geosystems : G3,
June 2023, 2023-06-00, 20230601, 2023-06-01, Letnik:
24, Številka:
6
Journal Article
Recenzirano
Odprti dostop
We explore the connections between crustal shortening, volcanism, and mantle dynamics in the Atlas of Morocco. In response to compressional forces and strain localization, this intraplate orogen has ...evolved far from convergent plate margins. Convective effects, such as lithospheric weakening and plume‐related volcanism, contributed in important ways to the building of high topography. We seek to better understand how crustal and mantle processes interacted during the Atlas' orogeny by combining multiple strands of observations, including new and published data. Constraints on crustal and thermal evolution are combined with new analyses of topographic evolution, petrological, and geochemical data from the Anti‐Atlas volcanic fields, and a simple numerical model of the interactions among crustal deformation, a mantle plume, and volcanism. Our findings substantiate that: (a) crustal deformation and exhumation accelerated during the middle/late Miocene, contemporaneous with the onset of volcanism; (b) volcanism has an anorogenic signature with a deep source; (c) a dynamic mantle upwelling supports the high topography. We propose that a mantle plume and the related volcanism weakened the lithosphere beneath the Atlas and that this favored the localization of crustal shortening along pre‐existing structures during plate convergence. This convective‐tectonic sequence may represent a general mechanism for the modification of continental plates throughout the thermo‐chemical evolution of the supercontinental cycle.
Key Points
Crustal thickening is limited and cannot account for the topography elevation of the Atlas system
Resumption of volcanism is contemporaneous with the acceleration of crustal deformation and topography growing
The erosion and weakening of the lower lithosphere, as a consequence of mantle plume, may enhance crustal deformation and exhumation
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