Ground Deformation Field Research Articles

Study of the influence of spatial effects on the ground surface and buildings in a two-lane tunnel boring

There are a series of engineering risks, such as ground subsidence, building tilt and cracking, in the process of shield tunnel driving through buildings, which have many adverse effects on urban residents and engineers. In particular, the differences in the effects of the interaction of two-lane tunnels on the building structure and ground deformation field are less often considered under different spatial effects such as construction sequences and tunnel spacings. As well as the problem of analyzing the building as a whole out of reality. To solve these problems, the spatial effect of the shield tunnel underpassing the shallow foundation building is simulated by Plaxis3D software to study the sensitivity analysis of surface settlement and the internal forces and deformation law of the building above in the process of tunneling underpassing with different depths of burial H and horizontal distance D of the double line tunnel. The engineering impact zoning method can investigate the safety of tunnels and buildings under different spatial effects when tunnels pass through buildings. The splitting of the building into plates and columns can reveal the forces and deformation laws of different structural parts. The results show that during the construction process of the double-line tunnel, the tunnel constructed first has a “blocking effect” on the tunnel constructed later, which affects the distribution of the disturbance area to a certain extent and changes the curve shape of the settlement trough. When the “blocking effect” occurs, the surface settlement and building deformation will be significantly reduced. In the internal forces of the building, the plate structure is mainly subjected to changes in axial forces, while the column structure is mainly affected by shear forces and bending moments. The factor of safety of tunnels decreases as the tunnel spacing decreases and as the building loads above increase.

Geomorphological evidence for volcano-tectonic deformation along the unstable western flank of Cumbre Vieja Volcano (La Palma)

In 2021, La Palma's southern volcanic complex Cumbre Vieja erupted for its longest period in historic times. Although the geological record shows no evidence for a collapse of Cumbre Vieja, ground deformation studies and field observations suggest that its western flank is moving seawards, following the direction of previous collapses of the island. To better estimate the hazard of a potential flank collapse of Cumbre Vieja, it is important to identify the lateral extent and depth of the mobile sector. Here, we analyse the volcano-tectonic deformation along Cumbre Vieja's western flank, based on geomorphological analysis of combined topographic and new ship-born bathymetric data as well as the analysis of shallow seismicity records associated with the 2021 eruption. In our interpretation, the shoreline-crossing Puerto Naos Ridge results from tectonic uplift accompanying transpressional deformation along the northern boundary of Cumbre Vieja's moving flank, therefore decoupling a stable sector in the north from the mobile sector farther south. The proposed moving sector is consistent in scale with previous ground deformation studies and documented flank collapses of structurally similar volcanoes. We present a workflow for semi-automatically detecting boundaries of unstable volcanic flanks based on morphological changes captured in digital elevation data. The method correctly delineated the known boundaries of the unstable flanks of Mt. Etna and Kilauea volcanoes. The ability to constrain potential boundaries of unstable volcanic flanks should inform the planning of future geophysical and geodetic campaigns aiming to identify precursory signals of potential flank failures.

On the seafloor horizontal displacement from cGPS and compass data in the Campi Flegrei caldera

Seafloor deformation monitoring is now routinely performed in the marine sector of the Campi Flegrei volcanic area (Southern Italy). The MEDUSA infrastructure is formed by four buoys deployed at a water depth ranging from 40 to 96 m, and equipped with cGPS receivers, accelerometers and magnetic compasses to monitor the buoy status and a seafloor module with a bottom pressure recorder and other onboard instruments. The analysis of the time series data acquired by the MEDUSA monitoring infrastructure system allows to study the seafloor deformation in the Campi Flegrei caldera with geodetic accuracy. In a previous work, we show that the time series acquired by the Campi Flegrei cGPS onland network and MEDUSA over the period 2017–2020 are in good agreement with the ground deformation field predicted by a Mogi model which is widely used to describe the observed deformation of an active volcano in terms of magma intrusion. Only for one of the buoys, CFBA (A), the data differ significantly from the model prediction, at a level of simeq 6.9 sigma and of simeq 23.7 sigma for the seafloor horizontal speed and direction, respectively. For this reason, we devised a new method to reconstruct the horizontal sea bottom displacement considering in the analysis both cGPS and compass data. The method, applied to the CFBA buoy measurements and validated also on the CFBC (C) buoy, uses compass data to correct cGPS positions accounting for the pole inclination. Including also systematic errors, the internal consistency, always within sim 3 sigma for the speed and sim 2 sigma for the angle, between the results derived for different maximum inclinations of the buoy pole (up to 3.5^{circ }) indicates that the method allows to significantly reduce the impact of the pole inclination which, if not properly taken into account, can alter the estimation of the horizontal seafloor deformation. In particular, we find a good convergence of the retrieved velocity and deformation angle as we include in the analysis data from increasing values of the buoy pole inclination. Taking the result derived assuming the maximum allowed cutoff and accounting for statistical and systematic errors, we found a speed v = (3.521 ± 0.039 (stat) ± 0.352 (syst)) cm/yr and a deformation direction angle alpha = (-115.159 ± 0.670 (stat) ± 7.630 (syst))^{circ } (statistical errors at 1 sigma quoted from the rms of their values, main systematic errors added linearly). The relative impact of the main potential systematic (statistical) effects increases (decreases) with the cutoff. Our analysis provides a horizontal speed consistent with the model at a level of simeq 5.2 sigma (stat only) or of simeq 0.5 sigma (stat and syst added linearly), and a deformation angle consistent with the model at simeq 4.3 sigma level (stat only) or at simeq 0.3 sigma level (stat and syst added linearly). Correspondingly, the module of the vectorial difference between the velocity retrieved from the data and the velocity of the adopted Mogi model diminishes by a factor of simeq 7.65 ± 1.23 (stat) or ± 5.78 (stat + syst) with respect to the previous work. A list of potential improvements to be implemented in the system and instruments is also discussed.

Modeling the Deformation Sources in Volcanic Environments Through Multi-Scale Analysis of DInSAR Measurements

In this work, we propose a multi-scale approach for modeling the ground deformation field of volcanic sources. The methodology is based on the use of Multiridge and ScalFun methods to analyze the elastic deformation fields by providing source information, such as the depth, the horizontal position, and its morphological features. This strategy is alternative with respect to the classical inverse approaches since it allows overcoming some aspects of the ambiguities related to the interpretation of DInSAR measurements. Indeed, the multi-scale method does not need a priori constraints on the model parameters to achieve an unambiguous solution. First, we argue on the general physical conditions so that the deformation field, generally represented by biharmonic functions, also satisfies Laplace’s equation and the law of homogeneity. This occurs in the case of sources with hydrostatic pressure-change embedded in an elastic half-space. In these conditions, the properties of harmonic and homogeneous functions can be employed to model the ground deformation fields using multi-scale procedures. Then, we demonstrate the soundness of the proposed approach through the application of Multiridge and ScalFun methods to synthetic tests. We analyze the fields generated by spherical, pipes- and sills-like sources and consider different model settings, as the layered half-space, the noisy, and the multi-source scenarios. For all these simulations, we achieve unconstrained information related to the source geometry with satisfying accuracy. Finally, in order to show the flexibility of the multi-scale approach in different volcanic environments, we use Multiridge and ScalFun methods for analyzing DInSAR measurements relevant to Uturuncu, Okmok, and Fernandina volcanoes, retrieving information about their volcanic systems. In the first case, we point out a transient source at a depth of 4.5 km b.s.l., which is activated during 2006–2007 together with the stable and well-known Altiplano Puna Magma Body (APMB); in the second one, we retrieve a concentrated body at a depth of 3.1 km b.s.l. during 2003–2004; and in the last case, we interpret the 2013 unrest episode as caused by a pipe-like source located at a depth of 1.7 km b.s.l.

Machine‐Learning Characterization of Tectonic, Hydrological and Anthropogenic Sources of Active Ground Deformation in California

AbstractTectonic, hydrological and industrial processes coexist in the dynamic natural environments. However, our knowledge of ground deformation associated with tectonic, hydrological and anthropogenic processes and their interactions remains limited. California represents a natural laboratory that hosts the San Andreas fault system, Central Valley and other aquifer systems, and extensive human extraction of natural resources. The attendant multi‐scale ground deformation that has been mapped using Copernicus Sentinel‐1 Synthetic Aperture Radar (SAR)‐satellite constellation from four ascending and five descending tracks during 2015–2019. We consider the secular horizontal surface velocities and strain rates, constrained from GNSS measurements and tectonic models, as proxies for tectonic processes, and seasonal displacement amplitudes from interferometric SAR (InSAR) time series as proxies for hydrological processes. We synergize 23 types of multidisciplinary datasets, including ground deformation, sedimentary basins, precipitation, soil moisture, topography, and hydrocarbon production fields, using a machine learning algorithm–random forest, and we succeed in predicting 86%–95% of the representative data sets. High strain rates along the SAF system mainly occur in areas with a low‐to‐moderate vegetation fraction (∼0.3), suggesting a correlation of rough/high‐relief coastal range morphology and topography with the active faulting, seasonal and orographic rainfall, and vegetation growth. Linear discontinuities in the long‐term, seasonal amplitude and phase of the surface displacement fields coincide with some fault strands, the boundary zone between the sediment‐fill Central Valley and bedrock‐dominated Sierra Nevada, and the margins of the inelastically deforming aquifer in the San Joaquin Valley, suggesting groundwater flow interruptions, contrasting elastic properties, and heterogeneous hydrological units.

Combined Geodetic and Seismological Study of the December 2020 Mw = 4.6 Thiva (Central Greece) Shallow Earthquake

On 2 December 2020, a moderate and shallow Mw = 4.6 earthquake occurred in Boeotia (Central Greece) near the city of Thiva. Despite its magnitude, the co-seismic ground deformation field was detectable and measurable by Sentinel-1, ascending and descending, synthetic aperture interferometry radar (InSAR) acquisitions. The closest available GNSS station to the epicenter, located 11 km west, measured no deformation, as expected. We proceeded to the inversion of the deformation source. Moreover, we reassessed seismological data to identify the activated zone, associated with the mainshock and the aftershock sequence. Additionally, we used the rupture plane information from InSAR to better determine the focal mechanism and the centroid location of the mainshock. We observed that the mainshock occurred at a shallower depth and the rupture then expanded downdip, as revealed by the aftershock distribution. Our geodetic inversion modelling indicated the activation of a normal fault with a small left-lateral component, length of 2.0 km, width of 1.7 km, average slip of 0.2 m, a low dip angle of 33°, and a SW dip-direction. The inferred fault top was buried at a depth of ~0.5 km, rooted at a depth of ~1.4 km, with its geodetic centroid buried at 1.0 km. It was aligned with the Kallithea fault. In addition, the dip-up projection of the modeled fault to the surface was located very close (~0.4 km SW) to the mapped (by existing geological observations) trace of the Kallithea fault. The ruptured area was settled in a transition zone. We suggest the installation of at least one GNSS and seismological station near Kallithea; as the activated zone (inferred by the aftershock sequence and InSAR results) could yield events with M ≥ 5.0, according to empirical laws relating to rupture zone dimensions and earthquake magnitude.

Mapping InSAR deformation of low and moderate earthquakes

Abstract Low-to-moderate magnitude earthquakes often induce small ground displacement. For such events, ground deformation fields detected by SAR interferometry can be masked or not clearly discernible from the fringes distribution because of the presence of error sources, such as atmospheric artifacts and topographic residuals. We show two examples of low-moderate magnitude earthquakes, for which we adopted a new automatic tool for calculating the fringe pattern stemming from seismological data. The tool estimates the extent and the geographic position of the deformation by running a forward model of the seismic source, thus identifying the best SAR frame to be collected and the expected surface effects to better figure-out the outcomes of InSAR processing. We present the Mw 5.7 occurred in Greece and the Mw 5.4 occurred in Zagreb on 21 and 22 March 2020, respectively. For the Greek earthquake, the tool predicted a deformation close to the InSAR product, and gave evidences of atmospheric disturbances, thus providing information for inverse source modelling. The tool in the Zagreb event was used to infer the extent and location of the ground motion, that were used to identify the best SAR pair to be processed, being the SAR frames edge very close to the epicenter.

Application of SBAS Technique Combined with BP Neural Network in the Settlement of the Yinxi Industrial Park in Baiyin

In recent years, due to the obvious ground settlement and other phenomena of the Yinxi Industrial Park in Baiyin, it has brought many hidden dangers to the local development, it is of great practical significance to monitor the deformation of the area for a long time series. The ground deformation field of Yinxi Industrial Park from June 2018 to April 2021 was obtained by processing Sentinel-1A data using SBAS technology, and the high coherence point D1 was predicted and analyzed by BP neural network. The results show that subsidence occurs in several places in the Yinxi Industrial Park, and the average annual subsidence rate ranges from -19.28 mm to 5.08 mm, the areas of severe settlement have a clear geographical distribution, mainly concentrated in road and building areas, other areas have a more stable ground base; the mean square error in the BP neural network prediction result is 2.56 mm, and the average relative error is 6.06%, which is a high prediction accuracy. The predicted cumulative settlement value at point D1 in 2023 is 45 mm, and there is a tendency for the settlement to intensify. The prediction results are of great significance for the early identification and prevention of ground settlement in the study area.

Source Model of the 2014 Mw 6.9 Yutian Earthquake at the Southwestern End of the Altyn Tagh Fault in Tibet Estimated from Satellite Images

AbstractMultiple fault segments ruptured during the 2014 Yutian earthquake, but the detailed source parameters and the mechanism of rupture complexity remain poorly understood. Here, we use high-resolution TanDEM-X satellite data and Satellite Pour l’Observation de la Terre-6/7 images to map the coseismic ground deformation field of the event. We find that the majority of coseismic slip occurred in the upper 10 km with the maximum left-lateral fault slip of ∼2.5 m at ∼6 km depth. The fault ruptured across a large 4.5 km extensional stepover from one left-lateral fault segment to another, with some right-lateral relay faulting in between. We find that the earthquake was followed by shallow afterslip concentrating at the southwestern end of coseismic rupture, in an area of many aftershocks and positive Coulomb failure stress change. Our findings demonstrate the power of satellite remote sensing technology in constraining source geometry and slip model of complex earthquakes when ground measurements are limited.

3D multi-source model of elastic volcanic ground deformation

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.

Contribution to knowledge regarding the sources of earthquakes on the island of Ischia (Southern Italy)

This paper analyses data regarding the seismicity and ground deformations of the island of Ischia. The goal is to describe these phenomena as a space–time process, exploring the mechanism as a whole in order to answer questions concerning why and how historical earthquakes occurred and the geological constrains at the time of the earthquake of 21 August 2017. According to our analysis, the genesis of earthquakes in the island may be due either to regional tensile tectonics or to increased pressure in a shallow magma source. The eruptive rest following the 1302 Arso lava flow, the seismic silence from 1883 and the ground sinking recorded at least from the end of the nineteenth century suggest a decline of pressure in the shallow magma source and in the action of the stress field generated by the spreading of the Tyrrhenian Basin. The mechanism that can generate the observed ground deformation field and seismicity is the gravitational and thermal loading of the island, because the load of the massif of Mt. Epomeo onto its hot substratum may induce the gravitational spreading that would have produced its sliding southwards and its rotation northwards. The surface of detachment plunges towards the south and emerges at a high angle at the northern edge of Mt. Epomeo, where coseismic ground effects and the greatest damage have been observed. This mechanism that generated the 21 August 2017 earthquake could be extended to historical seismicity.

Magmatic and tectonic sources at Vulcano (Aeolian Islands, Southern Italy): A geodetic model based on two decades of GPS observations

An update of the surface ground deformation field over the Lipari-Vulcano complex has been provided by analyzing all the available GPS observations collected in the last two decades. The geodetic velocity field, referred to a fixed Eurasian frame, shows a remarkable negative velocity gradient between the southernmost stations (velocity values of ∼9.0mm/yr) and the northernmost ones, resulting in a N–S contraction of ∼4.5mm/yr. In addition, all the GPS stations show subsidence with rates decreasing from the northernmost stations (∼ -10.0mm/yr) to the southernmost ones (∼ -4.8mm/yr). Modelling of geodetic data demonstrates that the observed surface deformation field results from the joint contribution of regional (tectonic) and local (magmatic) sources. Such a dataset is unable to uniquely constrain the magmatic source. Indeed, the three performed models (M1, M2 and M3) produce statistically equivalent deformation sources. The source modeled in M1 is spatially coincident with that of M3, and both are located beneath the Vulcanello cone at depth of ∼4km bsl. Conversely, the source modeled in M2 is placed at depth of 0.76km bsl beneath the northern rim of the La Fossa crater. Integration of these results with geochemical and petrological data already available from literature suggests, however, that the M1≡M3 source placed beneath the Vulcanello cone should be the preferred model.

Volcanic structures investigation through SAR and seismic interferometric methods: The 2011–2013 Campi Flegrei unrest episode

Observations from satellites provide high-resolution images of ground deformation allowing to infer deformation sources by developing advanced modeling of magma ascent and intrusion processes. Nevertheless, such models can be strongly biased without a precise model of the internal structure of the volcano. In this study, we jointly exploited two interferometric techniques to interpret the 2011–2013 unrest at Campi Flegrei caldera (CFc). The first is the Interferometric Synthetic Aperture Radar (InSAR) technique, which provides highly-resolved spatial and temporal images of ground deformation. The second is the Ambient Noise Tomography (ANT), which images subsurface structures, providing the constraints necessary to infer the depth of the shallow source at CFc (between 0.8 and 1.2 km). We applied for the first time a tool to delineate the deformation source boundaries from the observed deformation maps: the Total Horizontal Derivative (THD) technique. The THD processes the vertical component of the ground deformation field detected through InSAR applied to COSMO-SkyMed data. The patterns retrieved by applying the THD technique show consistent spatial correlations with (1) the seismic group-velocity maps achieved through the ANT and (2) the distribution of the earthquakes nucleated during the unrest at ~1 km. High-velocity anomalies, the retrieved geometrical features of the deformation field, and the spatial distribution of seismicity coincide with extinct volcanic vents in the eastern part of the caldera (Solfatara/Pisciarelli and Astroni). Such a coincidence hints at a significant role of the extinct plumbing system in either constraining or channeling the eastward propagation of magmatic fluids. Here, we demonstrated that a joint analysis of the InSAR patterns, seismic structures, and seismicity allows us to model in space and time the characteristics and nature of the shallow deformation source at CFc. Using published literature, we show that the effects of structural heterogeneities at shallow depths may have a more significant early-stage impact on the evolution of the surface displacement signals than deeper magmatic sources: these secondary structural effects may produce local amplification in the deformation records which can be mistakenly interpreted as early signals of impending eruptions. The achieved results are particularly relevant for the understanding of the origin of deformation signal at volcanoes where magma propagation within sills is expected, as at CFc.

Systematic preparation and processing of interferometric synthetic aperture radar data for monitoring linear transportation infrastructure

We propose a methodology for the systematic preparation and processing of interferometric synthetic aperture radar (InSAR) data for monitoring linear transportation infrastructure subject to geohazards. The methodology is applied to two RADARSAT-2 Spotlight synthetic aperture radar datasets, and three case studies in Cornwall, Eastern Ontario, Canada, are examined. An InSAR processing sequence was established and 19 SLA24 and 15 SLA74 images were used to create time-series deformation maps spanning from March 2015 to September 2016. The noise floors were ±1.5 and ±1.0 cm, for the SLA24 and SLA74 datasets, respectively. Phase unwrapping errors, atmospheric path delay, and the limited number of images were identified as the largest contributors to measurement uncertainty, which was of the same order as the ground deformation field. To improve coherence and utility of the radar images for monitoring the effects of geohazards on infrastructure, it is recommended that imagery acquisitions consider the use of small incidence angles with moderate image resolution and 6- to 12-day revisit periods.

Correlation Between Seismic Damages of Tawarayama Tunnel and Ground Deformation Under the 2016 Kumamoto Earthquake

The spatial correlation of the ground deformation at Mt. Tawarayama in Kumamoto City in Japan with the seismic damages of Tawarayama tunnel was developed to explore whether the seismic damages of underground structures are related to the ground deformation. A pair of digital elevation model data sets were captured from the high-density airborne light detection and ranging data before and after the 2016 Kumamoto earthquake. A new variant of iteratively closest point (ICP) algorithm named combination and classification ICP was introduced to detect the three-dimensional ground deformation field. The seismic damages of Tawarayama tunnel caused by the earthquake were studied via site investigation. The results indicated that the strong ground deformation can reflect the seismic performance of the tunnel to some extent. Furthermore, the results of the ground deformation direction validated the assumption of seismic wave propagation along the tunnel. It gives a clear explanation for the mechanism of the seismic damages under the earthquake force, especially lining cracks, pavement damage, and construction joint damage.

Multiridge Method for Studying Ground-Deformation Sources: Application to Volcanic Environments

Volcanic phenomena are currently monitored by the detection of physical and chemical observations. Generally, the ground deformation field is the most relevant shallow expression of the geometric and physical parameters variations in the magmatic reservoir. In this study, we propose a novel method for the direct estimation of the geometric parameters of sources responsible for volcanic ground deformation detected via the DInSAR technique. Starting with the biharmonic properties of the deformation field, we define an approach based on the Multiridge and ScalFun methods to achieve relevant information about both the positions and shapes of active sources, such as the Mogi source. Our methodology is definitely different from the methods currently used for modeling ground-deformation sources, mainly based on forward or inverse techniques. In fact, (i) it does not require any assumptions about the source type, and (ii) it is not influenced by the distribution of medium elastic parameters or (iii) the presence of high-frequency noise in the dataset. For synthetic cases, we accurately estimate the depth to the source within a 3% error. Finally, we study the real case of the Okmok volcano ground-deformation field and achieve results compatible with those in previous works.

Exploring deformation scenarios in Timanfaya volcanic area (Lanzarote, Canary Islands) from GNSS and ground based geodetic observations

We report on a detailed geodetic continuous monitoring in Timanfaya volcanic area (TVA), where the most intense geothermal anomalies of Lanzarote Island are located. We analyze about three years of GNSS data collected on a small network of five permanent stations, one of which at TVA, deployed on the island, and nearly 20years of tiltmeter and strainmeter records acquired at Los Camelleros site settled in the facilities of the Geodynamics Laboratory of Lanzarote within TVA.This study is intended to contribute to understanding the active tectonics on Lanzarote Island and its origin, mainly in TVA. After characterizing and filtering out the seasonal periodicities related to “non-tectonic” sources from the geodetic records, a tentative ground deformation field is reconstructed through the analysis of both tilt, strain records and the time evolution of the baselines ranging the GNSS stations. The joint interpretation of the collected geodetic data show that the area of the strongest geothermal anomaly in TVA is currently undergoing a SE trending relative displacement at a rate of about 3mm/year. This area even experiences a significant subsidence with a maximum rate of about 6mm/year. Moreover, we examine the possible relation between the observed deformations and atmospheric effects by modelling the response functions of temperature and rain recorded in the laboratory. Finally, from the retrieval of the deformation patterns and the joint analysis of geodetic and environmental observations, we propose a qualitative model of the interplaying role between the hydrological systems and the geothermal anomalies. Namely, we explain the detected time correlation between rainfall and ground deformation because of the enhancement of the thermal transfer from the underground heat source driven by the infiltration of meteoric water.

An improved data integration algorithm to constrain the 3D displacement field induced by fast deformation phenomena tested on the Napa Valley earthquake

In this work, we propose an improved algorithm to constrain the 3D ground displacement field induced by fast surface deformations due to earthquakes or landslides. Based on the integration of different data, we estimate the three displacement components by solving a function minimization problem from the Bayes theory. We exploit the outcomes from SAR Interferometry (InSAR), Global Positioning System (GNSS) and Multiple Aperture Interferometry (MAI) to retrieve the 3D surface displacement field. Any other source of information can be added to the processing chain in a simple way, being the algorithm computationally efficient. Furthermore, we use the intensity Pixel Offset Tracking (POT) to locate the discontinuity produced on the surface by a sudden deformation phenomenon and then improve the GNSS data interpolation. This approach allows to be independent from other information such as in-situ investigations, tectonic studies or knowledge of the data covariance matrix. We applied such a method to investigate the ground deformation field related to the 2014 Mw 6.0 Napa Valley earthquake, occurred few kilometers from the San Andreas fault system.

3D displacement field retrieved by integrating Sentinel-1 InSAR and GPS data: the 2014 South Napa earthquake

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.

Annual rates of ground deformation (1993–2010) at Campi Flegrei, Italy, revealed by Persistent Scatterer Pair (PSP) – SAR interferometry

Campi Flegrei is an active volcanic district located along the Eastern Tyrrhenian continental margin, Italy, and is worldwide known for dramatic ground deformation phenomena (bradyseism) recorded over the last centuries. The purpose of this article is to present the annual rates of ground deformation fields (average velocity, average acceleration, and combined annual velocity/acceleration) at Campi Flegrei, during almost two decades (years 1993–2010). The research work was conducted based on a temporal analysis and advanced mapping of Persistent Scatterer Pair (PSP) data, obtained from interferometric processing of radar satellite European Remote Sensing-1/2 and Environmental Satellite (ENVISAT) scenes of the study area. Patterns and trends of annual PSP velocity have provided a reconstruction of the spatial and temporal variability of ground deformation in terms of uplift and/or subsidence along the satellite line of sight (LOS). The analysis of annual PSP velocity and acceleration has revealed an intense dynamics of the Campi Flegrei caldera collapse-resurgence system, testified by the high PSP velocity and acceleration values, as well as the significant changes in the rates of ground deformation through time. The main results of this research indicate that the largest ground deformation is localized within and around the structural border of the Campi Flegrei caldera and suggest a systematic recurrence of opposite trends (uplift vs. subsidence) in the ground deformation of the inner caldera region with respect to the surrounding areas throughout the analysed time period.