Sven Borgstrom

From ERS-1/2 to Sentinel-1: two decades of subsidence monitored through A-DInSAR techniques in the Ravenna area (Italy)

Land subsidence due to underground resources exploitation is a well-known problem that affects many cities in the world, especially the ones located along the coastal areas where the combined effect of subsidence and sea level rise increases the flooding risk. In this study, 25 years of land subsidence affecting the Municipality of Ravenna (Italy) are monitored using Advanced Differential Interferometric Synthetic Aperture Radar (A-DInSAR) techniques. In particular, the exploitation of the new Sentinel-1A SAR data allowed us to extend the monitoring period till 2016, giving a better understanding of the temporal evolution of the phenomenon in the area. Two statistical approaches are applied to fully exploit the informative potential of the A-DInSAR results in a fast and systematic way. Thanks to the applied analyses, we described the behavior of the subsidence during the monitored period along with the relationship between the occurrence of the displacement and its main driving factors.

Sentinel-1 assessment of the interferometric wide-swath mode

This contribution reports on the performance investigations of the interferometric wide swath (IW) mode of Sentinel-1, which is implemented using the terrain observation by progressive scans (TOPS) mode. The key aspects of the TOPS mode that need to be considered for accurate interferometric processing will be presented, and first analyses with Sentinel-1 time series will be shown. The results focus on the pilot sites of Campi Flegrei/Vesuvius and Mexico City, as well as Greenland glaciers. Other aspects related to the interferometric performance are also presented, like the burst synchronization, the pointing accuracy, or the considerations when evaluating non-stationary scenes.

Steady subsidence of a repeatedly erupting caldera through InSAR observations: Aso, Japan

The relation between unrest and eruption at calderas is still poorly understood. Aso caldera, Japan, shows minor episodic phreatomagmatic eruptions associated with steady subsidence. We analyse the deformation of Aso using SAR images from 1993 to 2011 and compare it with the eruptive activity. Although the dataset suffers from limitations (e.g. atmospheric effects, coherence loss, low signal-to-noise ratio), we observe a steady subsidence signal from 1996 to 1998, which suggests an overall contraction of a magmatic source below the caldera centre, from 4 to 5 km depth. We propose that the observed contraction may have been induced by the release of the magmatic fluids feeding the eruptions. If confirmed by further data, this hypothesis suggests that degassing processes play a crucial role in triggering minor eruptions within open conduit calderas, such as at Aso. Our study underlines the importance of defining any eruptive potential also from deflating magmatic systems with open conduit.

Sentinel-1 tops interferometric time series results and validation

This paper presents results of the Sentinel-1 sensor in the interferometric wide-swath (IW) mode encompassing the first two years of operation of the mission. The paper focuses on persistent scatterer interferometric results and their validation. Further applications and investigations are also addressed, e.g., earthquakes, volcanoes and tomography.

Volcanic risk system (SRV): ASI pilot project to support the monitoring of volcanic risk in Italy by means of EO data

The ASI-SRV(Sistema Rischio Vulcanico) project started at the beginning of the 2007 is funded by the Italian Space Agency (ASI) in the frame of the National Space Plan 2003-2005 under the Earth Observations section for natural risks management. Coordinated by the Istituto Nazionale di Geofisica e Vulcanologia (INGV), which is responsible at national level for the volcanic monitoring, the project has as main objective to develop a pre-operative system based on EO data and ground measurements integration to support the volcanic risk monitoring of the Italian Civil Protection Department. The project philosophy is to implement specific modules which allow to process, store and visualize through Web GIS tools EO derived parameters considering three activity phases: (1) knowledge and prevention; (2) crisis; (3) post crisis. In order to combine effectively the EO data and the ground networks measurements the system will implement a multi-parametric analysis tool, which represents and unique tool to analyze contemporaneously a large data set of data in ¿near real time¿. The SRV project will be tested his operational capabilities on three Italian volcanoes: Etna, Vesuvio and Campi Flegrei.

Interferometric investigations with the Sentinel-1 constellation

The contribution focuses on the current status of the ESA study entitled “InSARAP Sentinel-1 Constellation Study”, which investigates the interferometric performance of the S1A/S1B units. General aspects like the interferometric compatibility in terms of common range and Doppler bandwidth and the burst synchronization are addressed. Besides the first interferometric results with both units, time series results over the pilot sites combining both satellites are also shown, as well as some investigations with fast moving (i.e., glaciers) scenarios.

Joint inversion of the 2011 Tohoku (Japan) earthquake from dinsar and GPS data

On March 11, 2011 a Mw 9.0 earthquake hit Honsu island in Japan. The so called “Tohoku-Oki” giant earthquake occurred near the northeast coast resulting from thrust faulting on or near the subduction zone plate boundary between the Pacific and North America plates. The rupture zone is roughly centered on the earthquake epicenter alongstrike, while peak slips were up-dip of the hypocenter, towards the Japan Trench axis. The rupture was also responsible of a big tsunami that struck a large portion of the coastal area of Tohoku-Oki region. Soon after the earthquake numerous space remote sensing sensors were tasked to acquire as much as possible information about the situation on ground. In particular, a large numbers of SAR images were collected from the ENVISAT and ERS-2 satellite. For this event, a group of researchers from the Istituto Nazionale di Geofisica e Vulcanologia (INGV), named Tohoku-Oki INGV Team, decided to apply a multidisciplinary approach to carry on some analysis addressed to achieve added value outcomes. In this work we present part of the work done by the Team concerning DInSAR data analysis and the methodology to retrieve the seismic source of this extraordinary and disastrous event.