Remote Sensing Study On The Characteristics Of Methane Emission Before Typical Earthquakes In Qinghai Tibet Plateau

China is an earthquake- prone region with the strongest inland earthquakes in the global, the high intensity and wide distribution made it essential for disaster prevention and reduction to strengthen the research of earthquake monitoring and prediction. In recent years, the extraction of anomalous information before earthquake based on satellite remote sensing has attracted wide attention at home and abroad. Amount of research work has proved that abnormal earth degassing is an extremely important precursor information of earthquakes.In order to study the relationship between seismic activity and evolution of methane concentration, cases of 7 earthquakes with magnitudes above7 in Qinghai Tibet Plateau, the spatial-temporal evolution characteristics of CH4 before and after the earthquake are studied using CH4 data of atmospheric infrared sounder (AIRS)instrument on Aqua satellite. Total volume of CH4, vertical CH4 profiles, Surface methane concentration and CH4 concentration gradient before and after the earthquake were analyzed by the difference method with the background by the mean of 5-years data.Methane concentration increased in the 7 earthquakes. The evolution trend of CH4 appeared as following: initially rose ? increased abruptly and diffused ?accumulated and reached to maximum ? attenuated ?returned to normal after earthquake. The anomalies of CH4 appeared mostly in 2 months before the earthquakes,the abnormal information distribution related to epicenter and faults. The abnormal methane concentration before earthquake has obvious vertical structure characteristics of ground source methane emission, which shows that the near surface layer is abnormal high value center. The anomalies of three intermediate-focus earthquakes are relatively lower than the 4 shallow earthquakes.All the achievements in this study can provide reference material for the study of abnormal degassing information extraction and mechanism of earth degassing,enhance the capabilities of seismic anomalies monitoring,and increase the accuracy of seismic comprehensive prediction.