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We present an improved picture of the ongoing crustal deformation field for the Zagros Foldand- Thrust Belt continental collision zone by using an extensive combination of both novel and published GPS observations. The main results define the significant amount of oblique Arabia-Eurasia convergence currently being absorbed within the Zagros: right-lateral shear along theNWtrending Main Recent fault inNWZagros and accommodated between fold-andthrust structures and NS right-lateral strike-slip faults on Southern Zagros. In addition, taking into account the 1909-2016 instrumental seismic catalogue, we provide a statistical evaluation of the seismic/geodetic deformation-rate ratio for the area. On Northern Zagros and on the Turkish--Iranian Plateau, a moderate to large fraction (~49 and >60 per cent, respectively) of the crustal deformation occurs seismically. On the Sanandaj--Sirjan zone, the seismic/geodetic deformation-rate ratio suggests that a small to moderate fraction (<40 per cent) of crustal deformation occurs seismically; locally, the occurrence of large historic earthquakes (M ≥ 6) coupled with the high geodetic deformation, could indicate overdue M ≥ 6 earthquakes. On Southern Zagros, aseismic strain dominates crustal deformation (the ratio ranges in the 15-33 per cent interval). Such aseismic deformation is probably related to the presence of the weak evaporitic Hormuz Formation which allows the occurrence of large aseismic motion on both subhorizontal faults and surfaces of décollement. These results, framed into the seismotectonic framework of the investigated region, confirm that the fold-and-thrust-dominated deformation is driven by buoyancy forces; by contrast, the shear-dominated deformation is primary driven by plate stresses. [ABSTRACT FROM AUTHOR]

We present an up-to-date high resolution picture of the ongoing crustal deformation field of Italy, based on an extensive combination of permanent and non-permanent GPS observations carried out since 1994. In addition, we present an updated map of contemporary SHmax orientations computed by a multidisciplinary data set of well-constrained stress indicators, including both published results and novel analyses. The comparison of stress and geodetic strain-rates directions reveals that both patterns are near-parallel over a large part of the investigated area, highlighting that crustal stress and surface deformation are driven by the same mechanism. The comparison of the azimuthal patterns of surface strain and mantle deformation shows a modest correlation on the Alps and a low correlation along the Apennines chain and the Calabro-Peloritan Arc. Along the Apennines chain, this feature suggests the occurrence of significant strain partitioning and crust-mantle mechanical decoupling. Along the Calabro- Peloritan Arc, the apparent low correlation reflects a different mantle-crust mechanism of deformation to the ongoing subduction and rollback of the Ionian slab. In addition, the superposition of regional/local effects related to second-order sources (crustal lateral density changes, strength contrasts), which at regional/local scale modulate the crustal stress/strainrate pattern, cannot be ruled out. [ABSTRACT FROM AUTHOR]

In this work, we study the subsidence of Dallol, an explosive crater and hydrothermal area along the spreading Erta Ale ridge of Afar (Ethiopia). No volcanic products exist at the surface. However, a diking episode in 2004, accompanied by dike-induced faulting, indicates that Dallol is an active volcanic area. The 2004 diking episode was followed by quiescence until subsidence started in 2008. We use InSAR to measure the deformation, and inverse, thermoelastic and poroelastic modelling to understand the possible causes of the subsidence. Analysis of InSAR data from 2004–2010 shows that subsidence, centered at Dallol, initiated in October 2008, and continued at least until February 2010 at an approximately regular rate of up to 10 cm/year. The inversion of InSAR average velocities finds that the source causing the subsidence is shallow (depth between 0.5 and 1.5 km), located under Dallol and with a volume decrease between −0.63 and −0.26 × 106 km3/year. The most likely explanation for the subsidence of Dallol volcano is a combination of outgassing (depressurization), cooling and contraction of the roof of a shallow crustal magma chamber or of the hydrothermal system. [ABSTRACT FROM AUTHOR]

The Global Navigation Satellite System (GNSS) and Synthetic Aperture Radar Interferometry (InSAR) can be combined to achieve different goals, owing to their main principles. Both enable the collection of information about ground deformation due to the differences of two consequent acquisitions. Their variable applications, even if strictly related to ground deformation and water vapor determination, have encouraged the scientific community to combine GNSS and InSAR data and their derivable products. In this work, more than 190 scientific contributions were collected spanning the whole European continent. The spatial and temporal distribution of such studies, as well as the distinction in different fields of application, were analyzed. Research in Italy, as the most represented nation, with 47 scientific contributions, has been dedicated to the spatial and temporal distribution of its studied phenomena. The state-of-the-art of the various applications of these two combined techniques can improve the knowledge of the scientific community and help in the further development of new approaches or additional applications in different fields. The demonstrated usefulness and versability of the combination of GNSS and InSAR remote sensing techniques for different purposes, as well as the availability of free data, EUREF and GMS (Ground Motion Service), and the possibility of overcoming some limitations of these techniques through their combination suggest an increasingly widespread approach. [ABSTRACT FROM AUTHOR]

Modelling of combined Global Navigation Satellite System (GNSS) and Interferometric Synthetic Aperture Radar (InSAR) data was performed to characterize the source of the Mw6.9 earthquake that occurred to the north of Samos Island (Aegean Sea) on 30 October 2020. Pre-seismic analysis revealed an NNE–SSW extensional regime with normal faults along an E–W direction. Co-seismic analysis showed opening of the epicentral region with horizontal and vertical displacements of ~350 mm and ~90 mm, respectively. Line-of-sight (LOS) interferometric vectors were geodetically corrected using the GNSS data and decomposed into E–W and vertical displacement components. Compiled interferometric maps reveal that relatively large ground displacements had occurred in the western part of Samos but had attenuated towards the eastern and southern parts. Alternating motions occurred along and across the main geotectonic units of the island. The best-fit fault model has a two-segment listric fault plane (average slip 1.76 m) of normal type that lies adjacent to the northern coastline of Samos. This fault plane is 35 km long, extends to 15 km depth, and dips to the north at 60° and 40° angles for the upper and lower parts, respectively. A predominant dip-slip component and a substantial lateral one were modelled. [ABSTRACT FROM AUTHOR]

Evidences of flank instability has been documented at Mt. Etna volcano since the early 1980s. In particular, GPS and InSAR measurements as well as geostructural data have concurred in identifying a near continuous seaward motion of a large sector of Mt. Etna eastern flank (e.g. Palano, 2016). Such an unstable sector is delimited by the "NE Rift ‐ Pernicana fault" and by the "S Rift - Mascalucia-Tremestieri fault", respectively on its NW and SW half, while the presence of compressional structures (e.g. folds) has recently been observed at the toe of the continental margin, on the Etnean offshore (Gross et al., 2015). In addition, a prominent ESE lineament with prevailing right-lateral transpressive kinematics, located northward of Catania Canyon and considered as the off-shore prolongation of the Mascalucia-Tremestieri fault, has recently been discovered (Gross et al., 2015). The definition of the basal sliding surface is widely debated and a number of different models have been proposed in the last 3 decades: i) a shallow (~1.5 km) slip surface with a listric geometry located beneath the volcanic pile of Mt. Etna; ii) an approximately 5-km-deep sub-horizontal décollement occurring in quaternary sedimentary units; iii) alternating or contemporaneous movements on both shallow and deep slip surfaces; iv) a décollement surface located at a depth ranging from 1 to 4 km bsl.The establishment of continuous GPS networks (managed by different Institute and agencies as ISPRA, INGV, Topcon) has allowed detecting, since mid-2006, some aseismic slow slip events (SSE) from the daily-based time series of stations installed on the lower part of the unstable flank. At Mt. Etna, SSEs have probably been going on for a long time, but they have not been recognized because the campaign measurements carried out yearly since 2001 provide a broad snapshot that showed a fairly constant rate of motion of the flank. Here, taking advantage of the availability of a large dataset of continuous GPS observations, we provide a catalog of SSEs times as well as the spatial distribution of modelled slip on a décollement surface.References:Palano, M. (2016), Episodic slow slip events and seaward flank motion at Mt. Etna volcano (Italy), Journal of Volcanology and Geothermal Research, 324, 8-14, doi:10.1016/j.jvolgeores.2016.05.010.Gross, F., Krastel, S., Geersen, J., Behrmann, J.H., Ridente, D., Chiocci, F.L., Bialas, J.P., Papenberg, C., Cukur, D., Urlaub, M., and Micallef, A., 2015, The limits of seaward spreading and slope instability at the continental margin offshore Mt Etna, imaged by high resolution 2D seismic data. Tectonophysics, doi:10.1016/j.tecto.2015.11.011. [ABSTRACT FROM AUTHOR]

Land subsidence represents the main response to deformations induced by multiple natural and anthropic phenomena (i.e., solid and fluid extraction, soil consolidation, aquifer compaction, load-induced compaction, etc.) which take place at different spatio-temporal scales (e.g. Bonì et al., 2017). The impacts of land subsidence can be infrastructural, economic, environmental, and social, and it enhances the risk of floods, affecting the human life and activities. Several localities are affected by land subsidence occurring at high rate (e.g., up to 11 cm/year as observed for instance on the Lorca basin, SE Spain; Fernandez et al., 2018).The Houston-Galveston region represents one of the largest subsidence areas in the USA. Here, land subsidence is caused by compaction of fine-grained aquifer sediments (silts and clays) below the surface due to groundwater withdrawal. Groundwater withdrawal from local aquifers has been the primary source of water for municipal supply, commercial and industrial use, and irrigation since the early 1900s. In order to regulate it (e.g., policy, groundwater regulation and permits) the Texas Legislature created the Harrise-Galveston Subsidence District in 1975 and the Fort Bend Subsidence District in 1989. A surveying network of permanent GPS stations was established in the early 1990 with the purpose of preventing future land subsidence and better securing the local infrastructure. In the last decade, additional networks have been established by international and local agencies, reaching as of 2017, the approximatively number of 200 permanent GPS stations.Here we updated the displacement field over the study area by analyzing an extensive GPS dataset covering the 2010.00-2019.00 time interval. Raw GPS observations have been processed by using the GAMIT/GLOBK software adopting the procedure described in Fernandez et al., (2018). Achieved results, referred to a local reference frame, are presented and discussed along with groundwater level information coming from well observations. ReferencesBonì, R., Meisina, C., Cigna, F., Herrera, G., Notti, D., Bricker, S.,... & Ezquerro, P. (2017). Exploitation of satellite A-DInSAR time series for detection, characterization and modelling of land subsidence. Geosciences, 7(2), 25.Fernandez, J., Prieto, J. F., Escayo, J., Camacho, A. G., Luzón, F., Tiampo, K. F.,... & Herrero, T. (2018). Modeling the two-and three-dimensional displacement field in Lorca, Spain, subsidence and the global implications. Scientific reports, 8. [ABSTRACT FROM AUTHOR]

Two small geodetic subnetworks were established in 2010 and in 2014, respectively, along the southeastern edge of the unstable eastern flank of Mt. Etna volcano. These networks have been monitored since late 2014 with GNSS techniques by the GEOmatic_laboratory of Earth Science Section of the University of Catania. The resulting horizontal velocity field allowed us to observe a westward decay of the rate and a different azimuthal pattern of motion between the two networks. We suggest that both features are due to active deformation of the Nizzeti faults. We also observed that the deforming region is not entirely confined by the Tremestieri-San Gregorio-Acitrezza fault zones, but it extends southwards. Areal upgrades of the networks as well as the scheduling of measurements at least on a monthly basis will improve our knowledge of the current deformation pattern of the investigated area. [ABSTRACT FROM AUTHOR]