【摘要】 利用JPL提供的TEC地图数据和日本NICT提供的测高仪数据分析了2011年3月11日日本MW9.0级特大地震(Tohoku-oki Earthquake)前上空的电离层变化.GIM TEC地图数据分析发现,3月1～4日GPS TEC在赤道异常区域出现了不同程度的负扰动,其中3月1日和2日的扰动幅度和范围较大,以上很可能是由于3月1日爆发的9小时磁暴所致;此外,震前3天即3月8日04-14UT期间赤道异常区电离层TEC出现了明显的增强现象,异常最大幅度达30TECU,并伴随有南半球磁共轭区增强现象.日本境内的4个电离层测高仪数据分析显示,3月8日4个台站同时出现了foF2增强现象,其中Okinawa和Yamagawa两个站增幅明显.分析发现震前3天地震上空区域电离层参量异常增强,认为这可能与大气层和电离层垂直电场的变化有关,这种电场的变化有可能是地震产生的电磁信号传播所致.更多还原

【Abstract】 The 2011 March 11(05:46UT) Tohoku-Oki earthquake ruptured the plate boundary ~500 km in length and ~200 km in width along the Japan Trench where the Pacific Plate subducts beneath NE Japan and caused enormous lost to the country.The relationship between the behavior in atmosphere,ionosphere and the Tohoku-Oki earthquake was analyzed using the global ionosphere map(GIM) TEC data and ionosonde data.A time series of the GPS TEC right above the epicenter extracted from GIMs indicated that the daily variation of ionospheric TEC over the epicenter was not obvious.The latitude-time-TEC(LTT) of the GIM spatial variation showed a continuous negative disturbance in the northern crest of equatorial ionization(EIA) region during 1 March to 4 March.A larger range and scope of the disturbance could be found in 1 March and 2 March,which probably due to the nine hours magnetic storms in 1 March.In addition,it can be found from the GIM TEC maps that during 04-14UT on 8 March 2011,3 days before the earthquake,there is an enhancement of TEC with an amplitude peak of 30 TECU appearing in the EIA region,the west-south direction of the epicenter.Moreover,it could be seen that the perturbation in 8 March also is observed in the geomagnetic conjugate points of epicenter at the southern hemisphere.The region predominated by the enhancement on 8 March focuses on 20°~35°N in latitude with rounded shape which is usually controlled by the northern EIA,and the enhanced EIA region drifted westward.It was further found that the foF2 also recorded an unusual enhancement in 8 March by the four ionosonde stations in Japan,of which the increase is larger in Okinawa and Yamagawa.We had done other case studies including MW 7.9 Wenchuan,MW 9.1 Sumatra,MW 8.8 Chile earthquake and so on.For each case,a good agreement was found between the different parameters mentioned above.Preliminary study suggest that the enhancement of the ionospheric parameter on 8 March maybe related to the changes of the vertical electric field in the atmosphere and ionosphere,which probablely caused by the electromagnetic signal propagation from the earthquake preparation area.更多还原