Microwave radiation anomaly of Yushu earthquake and its mechanism

A violent earthquake (Ms 7.1) occurred in Yushu county of China on April 14, 2010, and the epicenter was (33.1°N, 96.7°E). It caused 2689 people death. We use the AMER-E satellite remote sensing data to analyze the variation of microwave radiation around the epicenter. It was found 45 days before the earthquake a high microwave radiation strip appeared in the southwest of the epicenter, and gradually became longer and wider. The largest increment of microwave brightness temperature was up to 12K. 9 days before earthquake another high microwave radiation strip appeared in the northwest of the epicenter and the epicenter was just in the intersection of the two the high microwave radiation strips. 4 days before the earthquake the strength of the microwave anomaly became weak, but one day before the earthquake the strength became increase again. After the main shock the anomaly still existed for about 20days and was finally disappeared. To explore the cause of microwave radiation anomaly the microwave polarization difference index (MPDI) and the air temperature variation was investigated. The final result indicated the microwave anomaly was caused by the temperature increase, i.e. the anomaly should belong to thermal anomaly.