Giuseppe Solaro

Deformation and eruptions at Mt. Etna (Italy): A lesson from 15 years of observations

This work was partly funded by INGV and the Italian DPC and was supported by ASI, the Preview Project and CRdC-AMRA. DPC-INGV Flank project providing the funds for the publication fees.

Ground deformation and source geometry of the 24 August 2016 Amatrice earthquake (Central Italy) investigated through analytical and numerical modeling of DInSAR measurements and structural-geological data

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.

Detachment depth revealed by rollover deformation: An integrated approach at Mount Etna

This work was partially funded by INGV and the DPC‐INGV project “Flank”, and partially by the ASI (SRV project).

Stress transfer in the Lazufre volcanic area, central Andes

eruptive centers situated in an area larger than 1800 km 2 and (2) a small-scale uplift located at Lastarria volcano, which is the only volcano to show strong fumarolic activity in decades, with most of the clear deformation apparently not observed before 2000. Both the large and small uplift signals can be explained by magmatic or hydrothermal sources located at about 13 km and 1 km deep, respectively. To test a possible relationship, we use numerical modeling and estimate that the depth inflating source increased the tensile stress close to the shallow source. We discuss how the deep inflating source may have disturbed the shallow one and triggered the observed deformation at Lastarria. Citation: Ruch, J., A. Manconi, G. Zeni, G. Solaro, A. Pepe, M. Shirzaei, T. R. Walter, and R. Lanari (2009), Stress transfer in the Lazufre volcanic area, central Andes, Geophys. Res. Lett., 36, L22303, doi:10.1029/2009GL041276.

Capturing the fingerprint of Etna volcano activity in gravity and satellite radar data

Long-term and high temporal resolution gravity and deformation data move us toward a better understanding of the behavior of Mt Etna during the June 1995 – December 2011 period in which the volcano exhibited magma charging phases, flank eruptions and summit crater activity. Monthly repeated gravity measurements were coupled with deformation time series using the Differential Synthetic Aperture Radar Interferometry (DInSAR) technique on two sequences of interferograms from ERS/ENVISAT and COSMO-SkyMed satellites. Combining spatiotemporal gravity and DInSAR observations provides the signature of three underlying processes at Etna: (i) magma accumulation in intermediate storage zones, (ii) magmatic intrusions at shallow depth in the South Rift area, and (iii) the seaward sliding of the volcanos eastern flank. Here we demonstrate the strength of the complementary gravity and DInSAR analysis in discerning among different processes and, thus, in detecting deep magma uprising in months to years before the onset of a new Etna eruption.

Coseismic Fault Model of Mw 8.3 2015 Illapel Earthquake (Chile) Retrieved from Multi-Orbit Sentinel1-A DInSAR Measurements

On 16 September 2015, a Mw 8.3 interplate thrust earthquake ruptured offshore the Illapel region (Chile). Here, we perform coseismic slip fault modeling based on multi-orbit Sentinel 1-A (S1A) data. To do this, we generate ascending and descending S1A interferograms, whose combination allows us to retrieve the EW and vertical components of deformation. In particular, the EW displacement map highlights a westward displacement of about 210 cm, while the vertical map shows an uplift of about 25 cm along the coast, surrounded by a subsidence of about 20 cm. Following this analysis, we jointly invert the multi-orbit S1A interferograms by using an analytical approach to search for the coseismic fault parameters and related slip values. Most of the slip occurs northwest of the epicenter, with a maximum located in the shallowest 20 km. Finally, we refine our modeling approach by exploiting the Finite Element method, which allows us to take geological and structural complexities into account to simulate the slip along the slab curvature, the von Mises stress distribution, and the principal stress axes orientation. The von Mises stress distribution shows a close similarity to the depth distribution of the aftershock hypocenters. Likewise, the maximum principal stress orientation highlights a compressive regime in correspondence of the deeper portion of the slab and an extensional regime at its shallower segment; these findings are supported by seismological data.

A Minimum Acceleration Approach for the Retrieval of Multiplatform InSAR Deformation Time Series

We present in this paper a technique for the generation of 3-D (2-D) displacement time series of the earths surface, based on the combination of multiplatform SAR data. The algorithm assumes the availability of two (or more) archives of SAR images acquired from complementary (i.e., ascending/descending) tracks over the same area on the ground. SAR data are preprocessed through one of the currently available multitemporal differential interferometry synthetic aperture radar (DInSAR) toolboxes in order to recover, in correspondence to a set of very coherent points, the line-of-sight (LOS) displacement time series. The latter are then geocoded to a common grid and jointly inverted (pixel-by-pixel) to estimate the (unknown) time series of the 3-D (East-West, North-South, Up-Down) displacement components. To this aim, an underdetermined system of linear equations has to be solved. Previous works have proposed to solve similar ill-posed problems by applying the (truncated) singular-value-decomposition method and/or by regularizing the germane system of linear equations by adding further constraints, which impose conditions on the minimum-norm velocity of the solution. On the contrary, in this study, we adopt a different strategy, which is based on imposing that the 3-D deformation time series have minimum acceleration. The developed combination technique is a postprocessing tool that can be easily implemented. Indeed, it does not require the simultaneous processing of very large sequences of DInSAR interferograms. As a matter of fact, the retrieval of preliminary LOS-projected DInSAR time series can be independently carried out by using one (or more) of the currently available multitemporal DInSAR toolboxes, with no restrictions at all on the class to which they belong (small-baseline- and/or permanent-scatterers-oriented). Experiments carried out on simulated and real data prove the validity of the proposed combination algorithm in retrieving 2-D (East-West, Up-Down) surface displacement time series with subcentimeter accuracy, and the North-South components with an accuracy of some centimeters.

Analysis of ground deformation using SBAS-DInSAR technique applied to COSMO-SkyMed images, the test case of Roma urban area

Differential Synthetic Aperture Radar Interferometry (DInSAR) represents a well-established remote sensing technique for the investigation of ground deformation phenomena.Among the DInSAR techniques, the Small BAseline Subset (SBAS) approach exploits ground surface at two mapping scales, low and high resolution, and allows the detection and monitoring of local deformation processes that may affect single buildings or man-made structures in urban areas. This work investigates the capability improvement of the SBAS-DInSAR technique to analyse deformation processes in urban areas by exploiting SAR data acquired by the Cosmo-SkyMed (CSM) constellation in comparison with the results obtained from data of first generation ERS/ENVISAT radar systems of he European Space Agency. In particular, we extracted mean deformation velocity maps as seen by the three different radar systems and, for each coherent pixel, we retrieved the corresponding displacement time series. Our analysis was focused on the Torrino area where independent studies had already revealed significant deformation signals testified by the serious damages on many buildings in the area. Moreover, in order to understand the causes of the CSM observed displacement rates, reaching few cm per year, we also performed a comparative analysis between DInSAR products and independent information derived from electrical resistivity tomography data and geological maps.

Satellite Monitoring of Hazards: A Focus on Istanbul, Turkey

Satellite remote sensing data can provide important information on ground displacement, which can help scientists better understand and monitor geohazards such as earthquakes, volcano unrest, or landslides. However, access to such data and their results often has been difficult or has occurred with significant delay. As a result, a remotely sensed assessment of ground displacements is often not available until months or years after the occurrence of a natural disaster.

Aftershocks, groundwater changes and postseismic ground displacements related to pore pressure gradients: Insights from the 2012 Emilia-Romagna earthquake

During the 2012 Emilia-Romagna (Italy) seismic sequence, several time-dependent phenomena occurred, such as changes in the groundwater regime and chemistry, liquefaction, and postseismic ground displacements. Because time-dependent phenomena require time-dependent physical mechanisms, we interpreted such events as the result of the poroelastic response of the crust after the mainshock. In our study, we performed a two-dimensional poroelastic numerical analysis calibrated with Cosmo-SkyMed interferometric data and measured piezometric levels in water wells. The simulation results are consistent with the observed postseismic ground displacement and water level changes. The simulations show that crustal volumetric changes induced by poroelastic relaxation and the afterslip along the mainshock fault are both required to reproduce the amplitude (approximately 4 cm) and temporal evolution of the observed postseismic uplift. Poroelastic relaxation also affects the aftershock distribution. In fact, the aftershocks are correlated with the postseismic Coulomb stress evolution. In particular, a considerably higher fraction of aftershocks occurs when the evolving poroelastic Coulomb stress is positive. These findings highlight the need to perform calculations that adequately consider the time-dependent poroelastic effect when modeling postseismic scenarios, especially for forecasting the temporal and spatial evolution of stresses after a large earthquake. Failing to do so results in an overestimation of the afterslip and an inaccurate definition of stress and strain in the postseismic phase.