Thermal infared brightness temperature anomaly evolution associated with Songyuan M_S5.7 earthquake on May 28, 2018

This paper analyzes relative wavelet power spectrum （RWPS） of thermal infrared brightness temperature in the vicinity of the epicenter of the Songyuan M_S5.7 earthquake on May 28, 2018 （40°N—50°N, 119°E—134°E） by using continuous wavelet transform method based on daily brightness temperature data from Chinese geostationary meteorological satellite FY-2E （FY-2G） during the period from 28 May 2016 to 2 May 2018. The characteristics of spatio-temporal evolution results showed that the thermal infrared bright temperature relative wavelet energy spectrum reached high value along the Second Songhuajiang fault with the NW direction since February of 2018, then anomalous areas gradually enlarged and gathered along the Qianguo segment of the Second Songhuajiang fault and Fuyu-Zhaodong fault. The anomaly amplitude reached maximum in March and attenuated quickly, and then shrinked into a narrow band along Fuyu-Zhaodong fault near the epicenter with anomaly amplitude decreasing gradually and disappeared till 40 days before the Songyuan M_S5.7 earthquake. The epicenter is on the edge of the anomaly area. Furthermore, we analyzed thermal infrared brightness anomalies and corresponding earthquakes in the studied area since 2013, and the statistical result showed that four of the seven groups of anomalies correspond to earthquakes which were all the shallow earthquakes occurred in the area during that period.