Present-Day Surface Deformation in North-East Italy Using InSAR and GNSS Data

Geodetic data can detect and estimate deformation signals and rates due to natural and anthropogenic phenomena. In the present study, we focus on northeastern Italy, an area characterized by similar to 1.5-3 mm/yr of convergence rates due to the collision of Adria-Eurasia plates and active subsidence along the coasts. To define the rates and trends of tectonic and subsidence signals, we use a Multi-Temporal InSAR (MT-InSAR) approach called the Stanford Method for Persistent Scatterers (StaMPS), which is based on the detection of coherent and temporally stable pixels in a stack of single-master differential interferograms. We use Sentinel-1 SAR images along ascending and descending orbits spanning the 2015-2019 temporal interval as inputs for Persistent Scatterers InSAR (PSI) processing. We apply spatial-temporal filters and post-processing steps to reduce unrealistic results. Finally, we calibrate InSAR measurements using GNSS velocities derived from permanent stations available in the study area. Our results consist of mean ground velocity maps showing the displacement rates along the radar Line-Of-Sight for each satellite track, from which we estimate the east-west and vertical velocity components. Our results provide a detailed and original view of active vertical and horizontal displacement rates over the whole region, allowing the detection of spatial velocity gradients, which are particularly relevant to a better understanding of the seismogenic potential of the area. As regards the subsidence along the coasts, our measurements confirm the correlation between subsidence and the geological setting of the study area, with rates of similar to 2-4 mm/yr between the Venezia and Marano lagoons, and lower than 1 mm/yr near Grado

Coseismic deformation and source modeling of the May 2012 Emilia (Northern Italy) earthquakes

On May 20th, 2012, an ML 5.9 earthquake (Table 1) occurred near the town of Finale Emilia, in the Central Po Plain, Northern Italy (Figure 1). The mainshock caused 7 casualties and the collapse of several historical buildings and industrial sheds. The earthquake sequence continued with diminishing aftershock magnitudes until May 29th, when an ML 5.8 earthquake occurred near the town of Mirandola, ~12 km WSW of the mainshock (Scognamiglio et al., 2012). This second mainshock started a new aftershock sequence in this area, and increased structural damage and collapses, causing 19 more casualties and increasing to 15.000 the number of evacuees. Shortly after the first mainshock, the Department of Civil Protection (DPC) activated the Italian Space Agency (ASI), which provided post-seismic SAR Interferometry data coverage with all 4 COSMO-SkyMed SAR satellites. Within the next two weeks, several SAR Interferometry (InSAR) image pairs were processed by the INGV-SIGRIS system (Salvi et al., 2012), to generate displacement maps and preliminary source models for the emergency management. These results included continuous GPS site displacement data, from private and public sources, located in and around the epicentral area. In this paper we present the results of the geodetic data modeling, identifying two main fault planes for the Emilia seismic sequence and computing the corresponding slip distributions. We discuss the implication of this seismic sequence on the activity of the frontal part of the Northern Apennine accretionary wedge by comparing the co-seismic data with the long term (geological) and present day (GPS) velocity fields.Published645-6551.1. TTC - Monitoraggio sismico del territorio nazionale1.9. Rete GPS nazionale1.10. TTC - Telerilevamento3.2. Tettonica attivaJCR Journalrestricte

Activation of the SIGRIS monitoring system for ground deformation mapping during the Emilia 2012 seismic sequence, using COSMO-SkyMed InSAR data

On May 20, 2012, at 02:03 UTC, a moderate earthquake of local magnitude, ML 5.9 started a seismic sequence in the central Po Plain of northern Italy (Figure 1) [Scognamiglio et al. 2012, this volume]. The mainshock occurred in an area where seismicity of comparable magnitude has neither been recorded nor reported in the historical record over the last 1,000 years [Rovida et al. 2011]. The aftershock sequence evolved rapidly near the epicenter, with diminishing magnitudes until May 29, 2012, when at 07:00 UTC a large earthquake of ML 5.8 occurred 12 km WSW of the mainshock, starting a new seismic sequence in the western area (Figure 1); a total of seven earthquakes with ML >5 occurred in the area between May 20 and June 3, 2012 (Figure 1). The details of the seismic sequence can be found in the report by Scognamiglio et al. [2012]. Immediately after the mainshock, the Italian Department of Civil Protection (Dipartimento di Protezione Civile; DPC) requested the Italian Space Agency (Agenzia Spaziale Italiana; ASI) to activate the Constellation of Small Satellites for Mediterranean Basin Observation (COSMOSkyMed) to provide Interferometric Synthetic Aperture Radar (InSAR) coverage of the area. COSMO-SkyMed consists of four satellites in a 16-day repeat-pass cycle, with each carrying the same SAR payload [Italian Space Agency 2007]. In the current orbital configuration, within each 16- day cycle, image pairs with temporal baselines of 1, 3, 4 and 8 days can be formed from the images acquired by the four different sensors. Combined with the availability of a wide range of electronically steered antenna beams with incidence angles ranging from about 16° to 50° at near-range [E-geos 2012], this capability allows trade-offs between temporal and spatial coverage to be exploited during acquisition planning. A joint team involving the Istituto Nazionale di Geofisica e Vulcanologia (INGV; National Institute of Geophysics and Volcanology) and the Istituto per il Rilevamento Elettromagnetico dell'Ambiente (IREA-CNR; Institute for the Electromagnetic Sensing of the Environment) was activated to generate InSAR-based scientific products to support the emergency management. In this framework, the ASI and DPC requested that INGV activated the Spacebased Monitoring System for Seismic Risk Management (SIGRIS) [Salvi et al. 2010]. SIGRIS consists of a hardware/ software infrastructure that is designed to provide the DPC with value-added information products in the different phases of the seismic cycle. During earthquake emergencies, its goal is to rapidly provide decision-support products, such as validated ground-displacement maps and seismic source models. This study reports the details of the activation of the SIGRIS system in the case of the Emilia sequence. It provides a description of the COSMO-SkyMed datasets and processing procedures, as well as selected interferometric results for the coseismic and post-seismic ground deformation. Fault modeling results for the seismic sources of the largest earthquakes, and a more detailed discussion of the observed ground deformations are reported in Pezzo et al. [2012]

Interseismic ground velocities in Central Apennines from GPS and InSAR measurements: new contributions for seismic hazard models by preliminary results of ESA CHARMING project

The contribution of space geodetic techniques to interseismic velocity estimation, and thus seismic hazard modelling, has been recognized since two decades and made possible in more recent years by the increased availability and accuracy of geodetic measurements. We present the preliminary results of a feasibility study performed within the CHARMING project (Constraining Seismic Hazard Models with InSAR and GPS), funded by the European Space Agency (ESA). For a 200 km x 200 km study area, covering the Abruzzi region (central Italy) we measure the mean surface deformation rates from Synthetic Aperture Radar and GPS, finding several local to regional deformation gradients consistent with the tectonic context. We then use a kinematic finite element model to derive the long-term strain rates, as well as earthquake recurrence relations. In turn these are input to state-of-the-art probabilistic seismic hazard models, the output of which is validated statistically using data from the Italian national accelerometric and macroseismic intensity databases.Published373-3773T. Pericolosità sismica e contributo alla definizione del rischioN/A or not JCRope

Mid-term review results of the ESA STSE Pathfinder CHARMING project (Constraining Seismic Hazard Models with InSAR and GPS)

We probe the feasibility of integrating GPS and Synthetic Aperture Radar deformation rates within the seismic hazard models of the central Apennines (Italy), exploiting data from over 100 GPS stations and the ~20- year long ERS and ENVISAT SAR image archive. We then use a kinematic finite element model to derive the long-term strain rates, as well as earthquake recurrence relations. In turn these are input to state-of-the-art probabilistic seismic hazard models, the output of which is validated statistically using data from the Italian national accelerometric and macroseismic intensity databases.Published23-273T. Pericolosità sismica e contributo alla definizione del rischioN/A or not JCRrestricte

Measuring the north-south coseismic displacement component with high-resolution multi aperture InSAR

Earthquake source inversions based on space-borne Synthetic Aperture Radar interferometry (InSAR) are used extensively. Typically, however, only the line-of-sight (LoS) surface displacement component is measured, which is mainly sensitive to the vertical and E–W deformations, although well-established methods also exist to estimate the flight-path component, which is highly sensitive to the N–S displacement. With high-resolution sensors, these techniques are particularly appealing, because accuracies in the order of 3 cm can be achieved, while retaining spatial resolutions between 45 m and a few km, depending on the required level of filtering. We discuss the application to COSMO-SkyMed SAR imagery of the Spectral Diversity or Multi Aperture Interferometry technique, presenting the first SAR flight-path displacement field associated with the Mw 6.3, 2009 L’Aquila event (central Apennines). Finally, we observe and characterize a previously unknown misregistration pattern.Published28-352T. Tettonica attivaJCR Journalrestricte

Measuring the north-south coseismic displacement component with high-resolution multi aperture InSAR

Earthquake source inversions based on space-borne Synthetic Aperture Radar interferometry (InSAR) are used extensively. Typically, however, only the line-of-sight (LoS) surface displacement component is measured, which is mainly sensitive to the vertical and E–W deformations, although well-established methods also exist to estimate the flight-path component, which is highly sensitive to the N–S displacement. With high-resolution sensors, these techniques are particularly appealing, because accuracies in the order of 3 cm can be achieved, while retaining spatial resolutions between 45 m and a few km, depending on the required level of filtering. We discuss the application to COSMO-SkyMed SAR imagery of the Spectral Diversity or Multi Aperture Interferometry technique, presenting the first SAR flight-path displacement field associated with the Mw 6.3, 2009 L’Aquila event (central Apennines). Finally, we observe and characterize a previously unknown misregistration pattern

Deformation of the western Indian plate boundary: insights from differential and multi-aperture InSAR data inversion of the 2008, Baluchistan (Western Pakistan) seismic sequence

In this study,we use Differential Synthetic Aperture Radar Interferometry (DInSAR) and multiaperture interferometry (MAI) to constrain the sources of the three largest events of the 2008 Baluchistan (western Pakistan) seismic sequence, namely two Mw 6.4 events only 12 hr apart and an Mw 5.7 event that occurred 40 d later. The sequence took place in the Quetta Syntaxis, the most seismically active region of Baluchistan, tectonically located between the colliding Indian Plate and the Afghan Block of the Eurasian Plate. Surface displacements estimated from ascending and descending ENVISAT ASAR acquisitions were used to derive elastic dislocation models for the sources of the two main events. The estimated slip distributions have peak values of 120 and 130 cm on a pair of almost parallel and near-vertical faults striking NW–SE, and of 50 cm and 60 cm on two high-angle faults striking NE–SW. Values up to 50 cm were found for the largest aftershock on an NE–SW fault located between the sources of the main shocks. The MAI measurements, with their high sensitivity to the north–south motion component, are crucial in this area to accurately describe the coseismic displacement field. Our results provide insight into the deformation style of the Quetta Syntaxis, suggesting that right-lateral slip released at shallow depths on large NW fault planes is compatible with left-lateral activation on smaller NE–SW faults.Published25-392T. Tettonica attivaJCR Journalrestricte