Long-Term RST Analysis of Anomalous TIR Sequences in Relation with Earthquakes Occurred in Greece in the Period 2004-2013

Real-time integration of multi-parametric observationsis expected to accelerate the process toward improved, andoperationally more effective, systems for time-Dependent Assessmentof Seismic Hazard (t-DASH) and earthquake short-term (fromdays to weeks) forecast. However, a very preliminary step in thisdirection is the identification of those parameters (chemical, physical,biological, etc.) whose anomalous variations can be, to some extent,associated with the complex process of preparation for major earthquakes.In this paper one of these parameters (the Earth's emittedradiation in the Thermal InfraRed spectral region) is considered for itspossible correlation with M C 4 earthquakes occurred in Greece inbetween 2004 and 2013. The Robust Satellite Technique (RST) dataanalysis approach and Robust Estimator of TIR Anomalies(RETIRA) index were used to preliminarily define, and then toidentify, significant sequences of TIR anomalies (SSTAs) in 10 years(2004-2013) of daily TIR images acquired by the Spinning EnhancedVisible and Infrared Imager on board the Meteosat Second Generationsatellite. Taking into account the physical models proposed forjustifying the existence of a correlation among TIR anomalies andearthquake occurrences, specific validation rules (in line with theones used by the Collaboratory for the Study of Earthquake Predictability--CSEP--Project) have been defined to drive aretrospective correlation analysis process. The analysis shows thatmore than 93 % of all identified SSTAs occur in the prefixed space-time window around (M C 4) earthquake's time and location ofoccurrence with a false positive rate smaller than 7 %. Molchan errordiagram analysis shows that such a correlation is far to be achievableby chance notwithstanding the huge amount of missed events due tofrequent space/time data gaps produced by the presence of cloudsover the scene. Achieved results, and particularly the very low rate offalse positives registered on a so long testing period, seems alreadysufficient (at least) to qualify TIR anomalies (identified by RSTapproach and RETIRA index) among the parameters to be consideredin the framework of a multi-parametric approach to t-DASH.