GNGTS 2014 - Atti del 33° Convegno Nazionale

GNGTS 2014 S essione 2.1 95 The 2 nd year of the project, instead to the search of pre-seismic short-term ”anomalies” was focused to monitoring large-scale/medium-short term (months to weeks) variations of the strain field (see, e.g., Rydelek and Sacks, 1999) by direct and indirect observations. To this aim TIR satellite images were analysed no more looking for the occurrence of TIR anomalies in possible relation with earthquakes but, instead, to understand if the variations of the TIR signals observed at wider space-time scales could give information about the evolution of the above mentioned process involving medium-short term variations of the strain field which can hesitate (but even not) in large earthquakes. Like for the 1 st year of the DPC-INGV-S3 Project, nine years (from 2004 to 2012) of midnight TIR MSG-SEVIRI image acquired at the UNIBAS-SI station were analysed to generate reference fields μ Δ T ( r ) and σ Δ T ( r ) at each location r . RETIRA index was then computed Fig. 1 – �� ��� ����� ���� �� ����� ��� ������ ����������� ���� ���� �� ��������� ��� ������� ������� In the upper part is shown the RETIRA computation area used to calculate the spatial average T(t’) which enters in the computation of the considered signal ΔT( r ,t’)=T( r ,t’)-T(t’) and corresponding reference fields μ ΔT ( r ) (temporal mean) and σ ΔT ( r ) (temporal standard deviation). The red boxes represent the two study areas (respectively the Po Plain and Pollino area) object of the 1 st year of the DPC-INGV-S3 Project. In the bottom two examples of products provided for the two areas are reported, where different colors represent different value of RETIRA index (yellow 3≤RETIRA<3.5; orange 3.5≤RETIRA<4; red RETIRA≥4) and cloudy pixels (gray).