From high temporal resolution to synthetically enhanced radiometric resolution: insights from Night Thermal Gradient results.

Electromagnetic emissions in thermal infrared bands are an important research topic on pre-earthquake studies. Satellite thermal data have been investigated by many independent research groups looking for their anomalous behaviour before main earthquakes occurrences. Among them, geosynchronous satellite data are reported as less prone to artefacts during data processing. In this work, the Night Thermal Gradient (NTG) algorithm is presented, which has been specifically proposed for geostationary thermal infrared data processing. NTG method relies on the exploitation of high temporal resolution data to find coherent low frequency components of a hypothetical precursory signal of seismic activity. In this paper, the method is presented by giving details about the applied procedures, steps, theoretical assumptions and results obtained during the studies of L’Aquila 2009 earthquake and the seismic activity of Central Italy and Sardinia.