日本9级地震前的电离层变化

The ionospheric anomalies prior to the MW9.0 Japan earthquake

利用全球电离层数据分析了2011年3月11日日本MW9.0级地震前的电离层变化,选取了震中网格震前70天的电离层数据,采用移动平均值法计算得到TEC数据的平均值、标准差、上限和下限,超出上下限阈值的认为是异常,然后利用DST指数排除掉由地磁活动引起的电离层异常,认为震前3天即3月8日的电离层异常增强有可能和地震相关.通过分析3月8日与7日06时的电离层空间变化,发现电离层增强区域主要集中在震中南部几千千米范围内.而后计算了震中周边10个网格的电离层变化值,发现在震中周边几千千米范围内,只有震中网格的变幅最大,为推测发震地点提供了可能.

Total Electron Content （TEC） data is used to analyze the ionosphere change before Japan MW9.0 earthquake occurred on March 11, 2011. TEC data is from January 1 to March 11, 2011, and 7 days running average method is used to calculate the mean value, standard deviation, the upper threshold and the lower threshold. The TEC data is considered as anomaly when it is bigger than the upper threshold or smaller than the lower threshold. Next, DST index is used to exclude the anomaly which is related with the solar activity. Finally Then a strong TEC anomaly is found on March 8 which is located in a large area about thousands kilometers south of the epicenter. Then the 10 grids around the epicenter are calculated and it is find that only the epicenter grid shows the maximum value, which provides a possible method to estimate the epicenter location.