玉树Mw7．1地震前电离层异常扰动初步分析

为了研究地震电离层效应，采用CODE提供的全球电离层地图（GIM）数据分析了2010年4月14日玉树7．1级地震．通过插值提取了震中区域震前的TEC时间序列，利用滑动四分位距法排除太阳（SSN、F10．7）和地磁活动（Dst、Kp）的干扰，发现电离层在震前26天和13天存在明显异常．全球电离层异常分布结果显示，震前26天的电离层异常幅度小于震前13天的异常幅度，这可能与临震时间有关．此外，两次异常的峰值点与震中区域并不严格对应，而是靠近震中偏向赤道的一侧，同时磁共轭区也有异常出现，但范围和幅度较小，这两次电离层异常有可能是地震前兆．

Preliminary analysis of ionospheric anomaly preceding the Yushu earthquake

To investigate the seismic ionospheric effect, pre-earthquake ionospheric anomalies of Yushu MwT. 1 earthquake on April 14th 2010 was analyzed by CODErs Global Ionosphere Maps （GIM） which were estimated from GPS data, and the pre-earthquake TEC time series over epicenter was extracted by interpolation. Before detecting ionospheric TEC anomalies, the solar （SSN, F10.7 index） and geomagnetic activities（Dst index, Kp index） had been examined in detail by the sliding inter quartile range, the results showed that abnormal signals of TEC variation were detected in 13th day and 26th day prior to Yushu earthquake. The global disturbance maps represent that the amplitude of ionospheric anomalies in 26th day prior to earthquake was smaller than that in 13th day before earthquake, these may be related to the number of days prior to earthquake. The anomalous peaks were not concide with vertical projection of epicenter, but on the side that was closer to the equator. Besides, the anomalies were also observed in the magnetically conjugated region, but those scopes and amplitudes were smaller. The TEC anomalies are suggested to be the precursors of Yushu earthquake.