The Anomaly of Outgoing Longwave Radiation before Earthquakes by the wavelet analysis in Sichuan-Yunnan area

摘要

In this paper mid-term infrared (IR) emission anomalies related to medium or large earthquake using wavelet time-frequency analysis method have been detected using OLR(Outgoing Longwave Radiation) daily grid data (2.5°) for Sichuan-Yunnan area. Our analysis of OLR mean value(25 points totally) about Sichuan-Yunnan study area from 2000 to 2008 using wavelet time-frequency analysis shows obvious peaks in the scale of 0-0.2 years. The peaks appearedin the latter half of 2002 and 2007. It can be found that nine earthquakes (Ms > 6.0)had happened in Sichuan-Yunnanregion during this period, and these earthquakes mainly concentrated in 2003 and 2008. The OLR anomalies in 2002 and 2007 can be thought as precursors for earthquakes in 2003 and 2008, respectively. The anomalies are mainly occurred on half a year to one year before earthquakes. And the anomalous points in twenty-five studied points are near the epicenters. It indicates that there are relationship between earthquakes and OLR anomalies which can be detected by this method. It is possible to identify some mid-scale anomalies before occurrences of medium to large earthquakes by using this method. The result of this study will provide reference to mid-term earthquake prediction.