Monitor the microwave thermal emission anomaly around the Yushu earthquake fault zone by using AMSR-E data

Earthquake is caused by collision and compression of lithosphere plates. It has been found that during rock failure under lithosphere plate compression, some anomalies of thermal emission at certain frequencies, e.g. 300MHz, 2GHz and 22GHz, might be observed. Satellite-borne AMSR-E (Advanced Microwave Scanning Radiometer-EOS) has dual-polarized 12 channels (6.925, 10.65, 18.7, 23.8, 36.5 and 89GHz), where two channels, 18.7 and 23.8GHz, are close to the sensitive frequency, i.e. 22GHz. In this paper, the brightness temperature (Tb) at the channel 18.7GHz is especially analyzed to see if the emission anomaly is correlated with the earthquake in Yushu area, Qinghai province (32°N-34°N, 96°E-98°E), China on April 14, 2010. An anomaly index (RAI, radiation anomaly index) is defined for monitoring the Tb change and RAI during prior- and post-earthquake, and another channels, i.e. 23.8 and 10.6 GHz, as the assistance to exclude the influences most likely from atmospheric water vapor and terrain surface temperature on RAI. The AMSR-E Tb data during 2003-2010 were collected, and RAI of Yushu area indicated plausible anomaly on April 12, 2010, which is the date that two days before the Yushu earthquake. Thus, the analysis of RAI might provide a feasible tool for earthquake forecast from multi-year observations of AMSR-E data.