Satellite thermal infrared anomalies associated with strong earthquakes in the Vrancea area of Romania

Thermal anomalies which are known to be significant precursors of strong earthquakes can be evidenced by spectral thermal infrared (TIR) bands recorded by sensors on board of NOAA-AVHRR and Terra/Aqua-MODIS satellite. In order to locate relevant thermal anomalous variations prior to some strong even moderate earthquakes recorded in Vrancea tectonic active zone in Romania, satellite derived geophysical parameters have been used: land surface temperature (LST), outgoing long-wave radiation (OLR) and mean air temperature (AT). Spatio-temporal variations of LST, OLR, and AT before and after three strong earthquakes in Vrancea area (M-w = 7.4, 4 March 1977; M-w = 7.1, 30 August 1986; M-w = 6.9, 30 May 1990) and a moderate earthquake (M-w = 5.9, 27 October 2004) have been analyzed. Anomalous spatio-temporal patterns of these parameters developed a few days up to few weeks before the earthquakes disappeared after the main shocks. Significant increases in land surface temperature, outgoing long-wave radiation, and mean air temperature can be assigned to energy exchange mechanism during earthquake preparatory events. Such preseismic anomalies can be considered to be associated with the thermodynamic, degassing and ionization geochemical processes which seem to be activated due to the increased stress in the ground, and microfracturing of the rocks especially along area's active faults.