2015年阿拉善左旗5.8级地震前长波辐射异常研究*

通过涡度、距平、小波变换和时频分析等方法,研究了2015年4月15日阿拉善左旗5.8级地震前,震区(37.50°~43.50°N,103.50°~109.50°E)长波辐射(OLR)时空分布特征。结果显示:①2015年4月去除背景值之后的OLR涡度场在震中附近存在明显高值异常区;② 震中附近格点(39.50°N,105.50°E)和(40.50°N,107.50°E)OLR涡度日值超过二倍均方差频次在震前非线性增加;③ 基于自适应最优核的时频分析方法获得的上述两个格点OLR涡度时频分布图显示震前存在高能量密度区域;④ 本文获得的现象和汶川8.0级地震等震例结果相类似,值得深入研究。

Anomaly of Outgoing Long-wave Radiation before the 2015Alxazuoqi M5.8Earthquake

Temporal and spatial distribution characteristics of outgoing long-wave radiation (OLR)eddy of the 2015 M5.8Alxazuoqi earthquake epcentre region(104.50°~108.50°E, 37.50°~41.50°N)are analyzed in this paper,by using eddy,time-distance square method, wavelet transform,time-frequency analysis,and so on.Firstly,there exist significantly enhanced abnormal areas of OLR eddy field after removing background value before the M5.0Alxazuoqi earthquake.Secondly,there exists phenomenon of significantly nonlinear increase in OLR eddy monthly frequency histograms of greater than 2times mean square deviation at grid points(105.50°E,39.50°N)and(107.50°E,40.50°N)before the M5.8 earthquake.Thirdly,OLR eddy time-frequency analysis results at two grid points based on the adaptive optimal kernel method show that energy density enhance before the M5.8 earthquake.Fourthly,the epicenter of the M5.8Alxazuoqi earthquake locates in the edge of the abnormal enhancement area.