On the possible origin of thermal infrared radiation (TIR) anomalies in earthquake-prone areas observed using robust satellite techniques (RST)

• Published in: Chemical geology 2013-02, Vol.339, p.157-168
• Main Authors: Tramutoli, Valerio, Aliano, Carolina, Corrado, Rosita, Filizzola, Carolina, Genzano, Nicola, Lisi, Mariano, Martinelli, Giovanni, Pergola, Nicola
• Format: Article
• Language: English
• Subjects: air; Bozdag–Guzdak; carbon dioxide; Degassing; Earthquake precursors; earthquakes; greenhouse gases; infrared radiation; lakes; Meteosat TIR anomalies; methane; molecular weight; rivers; RST; turbulent flow; wind
• ISSN: 0009-2541; 1872-6836
• DOI: 10.1016/j.chemgeo.2012.10.042

Several studies performed in the past 30years suggested the existence of anomalous space-time transients, in the thermal infrared (TIR) radiation emitted by the Earth, possibly related to earthquake preparatory phenomena. Among various theories about their origin, the abrupt increase in greenhouse gas (such as CO2, CH4, etc.) emission rates was also proposed to explain the appearance of anomalous TIR signal transients in some relation with the place and the time of earthquake occurrence. As, under stable atmospheric conditions, the accumulation/dispersion of gases in the air depends on their molecular weight, CO2 tends to collect near the ground and layer forming “rivers” and/or “lakes” following terrain morphology close to its sources. On the contrary, the dispersion pattern of CH4, whose mass is smaller than that of CO2, is less affected by the terrain morphology so that the gas tends to be dispersed very readily, basically governed by the wind and normal atmospheric turbulence. If TIR anomalies are effectively related to exceptional degassing events, such differences should produce very different spatial/temporal patterns in the TIR anomalies observed, depending on the greenhouse gas emanated. In this paper, this hypothesis has been tested from different viewpoints and the results show that:a)an increase of only 2–3 times the normal CO2 mixing ratio level is sufficient to justify the excesses observed in TIR signal.b)areas dominated by diffusing gases which are heavier than the air (like CO2) show (as expected) anomalous TIR patterns which follow morphological lineaments (e.g. tectonic faults); in areas dominated by diffusing gases which are lighter than the air (like CH4) the TIR patterns observed spread over wide zones, following prevailing winds and diffusing around with less marked correlation with morphological lineaments.c)anomalous TIR patterns were observed over the Azerbaijan region during the Bozdag–Guzdak mud volcano eruption (May 1995), showing exactly the same spatial/temporal behavior expected for methane-dominated degassing areas. ► CO2–CH4 escaping as possible origin of pre-seismic TIR anomalies is investigated. ► Comparison of TIR anomalies observed in different degassing regimes by using RST ► Radiative transfer: 3 times of CO2 level sufficient to justify observed TIR anomalies ► CH4 test case was in May 1995: the mud-volcano Bozdag–Guzdak eruption. ► Different TIR anomaly patterns observed in CO2 or CH4 dominated degassing areas.