Robust satellite techniques (RST) for seismically active areas monitoring: the case of 21st May, 2003 Boumerdes/Thenia (Algeria) earthquake

In the last decades, several authors have claimed a space-time correlation between increases of Earth's emitted Thermal Infra-Red (TIR) radiation and earthquake activity interpreting such TIR signals as seismic precursors. The main problems of such studies regard data analysis and interpretation, which are often done without a validation/confutation test. In this context, a robust data analysis technique (RST, i.e. Robust Satellite Techniques) was developed which permits a statistically based definition of an "anomaly" and uses a validation/confutation approach. This technique was already applied to satellite TIR surveys in seismic regions for tens of earthquakes occurred in Europe, Asia and America. In this work, the RST approach has been applied for the first time to the African region to assess its potentialities in different geographical and climatic conditions. Eight years of Meteosat TIR observations have been analyzed in order to characterize the TIR signal behaviour in absence of significant seismic activity. Boumerdes/Thenia (Algeria) earthquake (occurred on 21th May 2003, Mb= 6.8) has been considered as test case for validation purpose, while a relatively unperturbed period (no earthquakes with Mbges4) has been analyzed in the confutation phase. The results show in the area of interest positive space-time persistent TIR anomalies about one month before the main shock (validation). Such anomalies generally overlap the principal tectonic lineaments of the region, sometimes focusing in the vicinity of the earthquake epicentre. No significant (in terms of relative intensity and space-time pemstence) TIR anomalies were detected during less seismically perturbed periods (confutation).