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

Abstract

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].