Abstract: Using relative power spectrum method to deal with thermal infrared brightness temperature data from the Fengyun satellite, we found that there were obvious precursory anomalies before the occurrence of the 2016 Litang M_S5.1 and Zaduo M_S6.2 earthquakes. The characteristic of abnormal temporal and spatial evolution was that high-value aggregation of the brightness temperature power spectrum at the Jiali-Zayu fault, Nu River fault and Lancang River fault on August 12th, 2016. Further, the amplitude and area increased gradually until September 1 reaching its maximum, later gradually decreased and returned to normal on September 21, 2016. The anomaly lasted nearly 40 days. After the occurrence of anomaly, Litang M_S5.1 and Zaduo M_S6.2 earthquakes occurred in the anomaly area on September 23 and October 17 respectively. The average power spectrum time series of the two epicentral region are similar to the temporal evolution of the anomaly region, and the earthquakes occurred after the average relative power spectral values return to normal backgrounds.

Key words: Thermal infrared brightness temperature anomaly, Earthquake precursor, The 2016 Litang M_S5.1 and Zaduo M_S6.2 earthquakes