Anomaly of thermal infrared brightness temperature and basin effect before Jiuzhaigou M_S7.0 earthquake in 2017

In this paper, wavelet transform and power spectrum estimation methods are used for processing and analyzing the brightness temperature data from China’s geostationary meteoro-logical satellite. Then the obtained time-frequency data is scanned by time and space scanning method. The results show that: ① Before the Jiuzhaigou M_S7.0 earthquake on August 8, 2017, there was a thermal infrared radiation warming zone along the Longmenshan fault zone. The thermal radiation anomaly is mainly distributed on the edge of the Sichuan basin, with an anomalous area of 6×10⁴ km². The Jiuzhaigou earthquake occurred at the edge of the warming area. ② The time series evolution characteristics of relative power spectrum of the Jiuzhaigou earthquake show that after the relative power spectrum amplitude increases rapidly in early July 2017, there is a long-term continuous high amplitude state, which is more prominent than the data of the past ten years. It did not recover until some time after the earthquake. ③ The anomalous distribution of the Jiuzhaigou earthquake is similar to that of the Wenchuan earthquake. The comprehensive analysis of other earthquakes occurring at the edge of the petroliferous basin suggests that the thermal radiation anomalies are similar to the basin morphology. The corresponding rate of this basin-like anomaly is 75% compared with the M_S≥6.5 earthquake. ④ The earthquake basin effect is the main reason for the similar thermal radiation spatial distribution of earthquakes with different seismogenic structures located at the edge of the basin, which is consistent with the theoretical explanation of the earth deflation theory.