2012年彝良M_S5.7和M_S5.6级地震热辐射亮温异常分析

Study of brightness temperature anomalies of Yiliang (China) M_S5.7 and M_S5.6 earthquakes on 7 Sep.,2012

为分析与2012年彝良地震前有关的热红外异常现象,我们选取了99°E-109°E、23°N-33°N范围内从2010年11月1日至2012年10月31日为期两年由中国静止气象卫星FY-2E观测的热红外遥感亮温资料,对亮温资料进行阈值去云影响预处理,而后应用小波能谱分析方法对预处理后的资料进行分析,获得了亮温小波相对能谱信息.分析结果表明从2012年7月下旬开始在彝良MS5.7、MS5.6地震震中周围开始出现亮温相对能谱异常,之后异常区域逐渐扩大并向震中区域集中,并于8月中下旬在震中附近形成NE向沿活动断层条带状分布的异常区域,相对能谱最大异常幅度达8倍,随后异常区域和幅度逐渐减小,地震发生后数天异常消失.从像元(105.3°E,28.3°N)异常时间进程上可以看出此次异常是两年时间里亮温相对能谱最为突出的异常变化,因此认为这次沿彝良地震发震断裂带分布的亮温相对能谱增大现象可能是彝良地震引起的.

In order to analyze brightness temperature anomalies that might be associated with Yiliang（Ms-5.7 and Ms =5. 6） double earthquake occurred in Yiliang county （in Yunnan province, China） on 7 Sep. , 2012, Daily infared data from the Chinese Geostationary Meteorological Satellite FY-2E were collected for the period from 1 Nov. 2010 to 31 Oct. 2012 and the spatial region of 99°E-109°E by 23°N-33°N. Preprocessing was taken on the brightness temperature data using a 1. 5 times mean variance threshold to eliminate the effect from clouds. Then wavelet power spectrum method was applied to the data after preprocessing. Analyzed results clearly show that relative wavelet power spectrum （RWPS for short） anomalies appeared since late July around the epicenter. The abnormal areas gradually extended and amassed towards to the epieenter. In middle and late August, a striped abnormal area of NE direction was formed along with the seismogenic fault where Yiliang earthquake occurred, and the RWPS reached its highest magnitude of 8. The abnormal area and RWPS magnitude dwindled afterward and anomalies disappeared several days after the earthquakes. Time-spatial evolution of one pixel （5 km X 5 km resolution, located at 105. 3°E and 28. 3°N） showed that anomaly presented in this manuscript was the most conspicuous one within the two years. Therefore, the abnormal change of RWPS along the seismogenic fault during this time period was possibly associated with Yiliang earthquake.