Satellite thermal infrared anomalies associatedwith strong earthquakes in the Vrancea area ofRomania

Abstract

Thermal anomalies which are known to be significantprecursors of strong earthquakes can be evidencedby spectral thermal infrared (TIR) bands recordedby sensors on board of NOAA-AVHRR and Terra/Aqua-MODIS satellite. In order to locate relevant thermal anomalousvariations prior to some strong even moderate earthquakesrecorded in Vrancea tectonic active zone in Romania,satellite derived geophysical parameters have beenused: land surface temperature (LST), outgoing long-waveradiation (OLR) and mean air temperature (AT). Spatiotemporalvariations of LST, OLR, and AT before and afterthree strong earthquakes in Vrancea area (M_w = 7.4, 4March 1977; M_w = 7.1, 30 August 1986; M_w = 6.9, 30 May1990) and a moderate earthquake (M_w = 5.9, 27 October2004) have been analyzed. Anomalous spatio-temporalpatterns of these parameters developed a few days up tofew weeks before the earthquakes disappeared after themain shocks. Significant increases in land surface temperature,outgoing long-wave radiation, and mean air temperaturecan be assigned to energy exchange mechanismduring earthquake preparatory events. Such preseismicanomalies can be considered to be associated with thethermodynamic, degassing and ionization geochemicalprocesses which seem to be activated due to the increasedstress in the ground, and microfracturing of the rocks especiallyalong area’s active faults.