Anomalies of middle infrared brightness before 2008 Yutian M_S7.3 and 2010 Yushu M_S7.1 earthquakes

This paper use middle infrared brightness data from geostationary satellite to research the 2008 Yutian M_S7.3 and the 2010 Yushu M_S7.1 earthquakes by estimating relative variance rate of power spectrum. The results show that the power spectrum amplitude of middle infrared brightness increased at different degrees before the two earthquakes. The characteristic periods were about 64 days and 13 days respectively. Before the two earthquakes, characteristic power spectrum amplitudes reached relatively the maximum or extreme in recent years, which were over six times of their average. The duration of power spectrum amplitude over twice of average were 80 days. The extreme areas of power spectrum amplitude over six times of average reached about 120000 and 40000 square kilometers respectively. These results are basically consistent with the previous results from outgoing long-wave radiation and thermal infrared brightness temperature data, which can be used as reference for realizing multi-wave band monitoring of heat radiation so as to predict earthquake in the future.