GNGTS 2015 - Atti del 34° Convegno Nazionale

22 GNGTS 2015 S essione 2.1 Deformation transient analysis in long term InSAR and GPS time series by means of the Principal Component Analysis (PCA): results from DPC-INGV S3 project G. Pezzo 1 , C. Tolomei 1 , E. Serpelloni 2 , A. Gualandi 2 , S. Salvi 1 , J.P. Merryman Boncori 3 , A. Lugari 1 1 Istituto Nazionale di Geofisica e Vulcanologia, CNT, Roma, Italy 2 Istituto Nazionale di Geofisica e Vulcanologia, CNT, Bologna, Italy 3 Sarmap SA, Purasca, Switzerland Introduction. The aim of the DPC-INGV S3 project “ Short term earthquake prediction and preparation ” (2014-15) was exploring the possibility that multiparametric monitoring of a number of observables potentially related to the crustal strain field could represent a tool for better constraining seismic hazard in Italy. The basic approach followed in the project considers seismogenic process as “ critical ” process in the frame of the “self-organized criticality” model (e.g., Kagan, 1994; Main, 1995, 1996). In this model, the seismogenic process is “critical” in nature (e.g. Kagan, 1992; Turcotte, 1992) having as a basic dynamical element the fault interaction (e.g., Sacks and Rydelek, 1995; Castellaro and Mulargia, 2001). This interaction is responsible for the observed phenomenology, that is characterized by irregularly distributed bursts of energy releases (time-space clustering of earthquakes) and scale relationships (e.g. the ‘Gutenberg-Richter law’). In this context, the basic goal of the project was the full exploitation of a huge amount of data to detect possible large scale/short term (months to weeks) transient strain field variations that could be the marker or the responsible of upcoming earthquakes. One of the key points is the space-time analysis of the surface deformations. Thus, our aim (Research Unit UR-01, Deformation transient analysis in long term InSAR and GPS time series ) was the analysis of the mean ground velocity and the relative displacement time series, obtained from both InSAR and Continuous GPS (CGPS) data. The use of radar satellite data and the differential interferometric technique allows to explore the processes and phenomena relative to the accumulation and subsequent release of crustal deformation during the seismic cycle at a high spatial resolution, while continuous GPS data guarantee high accuracies and precisions and higher temporal sampling with respect to InSAR observations. The integration of GPS and InSAR measurements, during both the SAR processing and post-processing steps, allows an overall improvement of InSAR accuracies, while allowing the exploration of systematic errors in InSAR data. The high temporal sampling of GPS and the wide area coverage of InSAR observations provide a solid observational space for monitoring both long-term crustal deformation and the occurrence of possible (shorter terms) deformation transients, for which we would expect some spatially coherent signals in the geodetic time-series. Finally, the GPS and InSAR displacement time-series will be the input of a multivariate statistical analysis, which will start from the use of a Principal Component Analysis (PCA) method. We focus our analysis on a study area of major concern located in the Po plain, in particular in the Emilia region, �������� �� � ������� �������� ������ ����� affected by a seismic sequence during 2012�. Seismotectonic context. The Emilia region is located in the Po Plain, representing the E-W continental collisional boundary between the subducting Adria plate to the north, and the overriding northern Apennines block to the south (e.g. Picotti and Pazzaglia, 2008). Seismic sections (e.g. Boccaletti and Martelli, 2004) reveal that central Po Plain is characterized by an arcuate blind thrust system, where the related growth folds are located below the Plio-Quaternary sedimentary cover (Pieri and Groppi, 1981; Pieri, 1983; Consiglio Nazionale delle Ricerche, 1992; Burrato et al. , 2003). The current tectonic activity of the frontal part of the northern Apennines accretionary wedge was proposed by many authors basing on geomorphological analysis, subsurface geology, seismicity, and present day stress field (Meletti et al. , 2000; Valensise and Pantosti, 2001; Burrato et al. 2003; Scrocca et al. , 2007; Boccaletti et al. , 2010). Burrato et al. (2003) described active fold growth in this area observing the northward