汶川Ms8.0地震前电离层VTEC的异常变化

利用地基GPS观测资料反演的垂直电子总含量（VTEC）,本文考察了2008年5月12日汶川Ms8.0地震期间的电离层变化.在考察过程中,以前10天的VTEC均值和伴随的2倍标准偏差作为参考来识别电离层异常.最终的考察分析结果表明：（1）VTEC的异常增加出现在5月3日和5月9日,而VTEC的异常减小出现在4月29日和5月6日;（2）所有这4天的电离层VTEC异常持续时间均超过了4 h,且异常自东向西漂移;（3）相对于电离层的非扰动状态,在5次电离层异常的峰值时刻,震中附近VTEC增加或减小超过30％的空间区域沿经、纬向分别超过了4000 km和1500 km.鉴于地震期间的日－地空间环境和电离层VTEC异常特征,我们认为,5月3日下午和5月9日的VTEC正异常可能是本次汶川地震的电离层前兆.     

华南地区电离层在汶川地震前VTEC异常的研究

基于华南地区GPS监测网数据．解算出华南地区电离层VTEC在汶川地震前出现的异常。从时间序列和空间等值线分布两方面分析了VTEC的变化．时间序列分析表明5月4日至5月12日电离层VTEC负异常扰动明显．5月4日至5月13日的空间分布也表明了同样的结论,并同时指出负异常有向低纬度区域漂移的趋势。并对异常判断依据和机理作了初步的讨论．     

2017年九寨沟M7.0地震前临震电离层异常研究

为研究2017年8月8日四川九寨沟M7.0地震前电离层异常,利用地基GNSS(Global Navigation Satellite System)垂直电子总含量(Vertical Total Electron Content, VTEC)和电离层测高仪F2层临界频率(foF2)观测数据,考察了震前20日内电离层变化,发现震前第4日(8月4日)及地震发生前5小时,震中附近上空出现显著电离层正异常。结合异常对应的日地空间环境分析,认为震前第4日出现的异常由磁暴引起,而发震当日出现的临震电离层异常可能与孕震活动有关。本文表明电离层测高仪具有同GNSS VTEC一致的异常检测结果。相比公布时间滞后的GNSS数据及其产品,测高仪数据的获取更加及时,将两种电离层观测手段结合起来,能实现两种技术优势互补,提高地震电离层监测能力。     

汶川地震前电离层VTEC的异常响应

2008年5月12日我国四川省汶川县发生了8.0级大地震,基于中国地壳运动观测网(CMONOC)的GPS观测数据,解算得到了震中上空附近的电离层VTEC;以VTEC的滑动均值为背景参考值,以2倍均方差作为误差限值,对临震一个月的VTEC 资料进行了处理分析．结果显示,在震前多次出现VTEC的异常扰动,其中4月29日、5月6——7日为异常减少,5月9日为异常增加,而且电离层VTEC的异常驼峰有向磁赤道漂移的趋势．由于距离发震时刻较近,排除其它因素后可能源于此次地震引起的电离层效应．      

2019年长宁M_S 6.0地震前后电离层垂直电子总含量（VTEC）异常扰动分析

2019长宁发生M_S 6.0地震,利用CODE全球电离层格网数据、中国地壳运动观测网络GPS数据、震中区域GPS数据,分别计算全球、中国区域垂直电子总含量(VTEC)异常分布及震中区域站点VTEC时间序列,揭示此次地震发生前后不同空间尺度电离层异常扰动变化。结果表明:地震发生前3天(6月14日),长宁震区上空出现连续电离层异常扰动现象,异常空间分布呈现向磁赤道偏移趋势。VTEC结果的时、空尺度变化反映,本次电离层扰动可能与长宁地震孕震过程有关,可为川滇区域临震电离层异常扰动监测及地震分析预报提供震例依据。     

汶川大地震前后电离层电子含量的扰动分析

为了分析地震前后电离层电子含量的变化,本文选取四川汶川发生8.0级地震前后10天电离层中的电子含量作为研究对象,使用IGS网站提供的VTEC数据,采取统计学分析方法,结合太阳和地磁活动信息,对此次地震前后电离层VTEC资料进行了详细的统计分析和讨论,数据分析结果表明大地震前电离层电子含量会出现明显扰动,电离层中电子含量的异常变化有可能是地震发生的前兆信息.     

日本M_S9.0地震前VTEC异常扰动分析

基于GPS观测资料获取的电离层VTEC数据,采用kalman滤波法针对2011年3月11日日本本州海域附近MS9.0地震前后的电离层VTEC变化进行了异常检测。检测结果表明,震前第3天和第6天的VTEC均存在异常增大现象,异常区域在震中以南且偏向于赤道方向,并伴随自东向西漂移的过程。综合考虑太阳和地磁活动水平认为,震前第3天与第6天的电离层异常可能与本次地震活动有关。     

利用GPS和DEMETER数据分析汶川地震前电离层变化

利用GPS TEC和法国DEMETER卫星ISL探测器的观测数据,分析了汶川地震前电离层变化.结果表明,电离层TEC在5月6-10日地方时下午有连续的负异常现象,5月9日地方时下午有明显的正异常现象.电离层TEC异常的范围主要位于震中南部区域,EW方向上1 100 ～1 670km,SN方向上1 600 ～3 700km.5月6日的负异常偏震中东南,5月7日的负异常偏震中西南,5月9日的正异常偏震中东南.震中西南和南部地区负异常较东南地区明显,震中南部和东南地区正异常程度较西南地区偏高,震中位置所对应南半球磁力线共轭区都出现了一定程度的正或负扰动.DEMETER卫星观测的电子密度Ne和离子密度N.在5月6-10日也出现了明显的负异常,异常分布与电离层TEC异常分布较为一致,主要集中在震中南部.震中所在的经度带上存在2个负异常峰值,且在纬度上关于地磁赤道对称.最后在上述异常的基础上,对基于岩石圈-大气层-电离层耦合的地震电离层异常机理开展了初步讨论.     

芦山M_S7.0地震前后电离层电子含量扰动分析

基于IGS提供的GIM数据和陆态网测站数据,采用统计学分析法对芦山MS7.0地震前后各10天的垂直总电子含量(VTEC)进行统计分析.结果显示,4月16—21日出现明显的VTEC异常减少.因此,在排除太阳活动因素后,认为电离层的异常变化有可能是地震发生的前兆信息.     

电离层VTEC异常分布产出系统设计与实现

基于C/S架构,采用C#、MySQL、ArcGIS等技术设计开发电离层VTEC异常分布产出系统,通过手动和自动模式快速产出全球VTEC、中国区域VTEC异常分布、空间环境参数及中国区域格网点VTEC时序曲线.系统实时监测全球VTEC、中国区域VTEC异常扰动变化,可测试地震—电离层监测在中国区域的应用效能,尝试为地震监...     

Ionospheric anomalies detected by ground-based GPS before the Mw7.9 Wenchuan earthquake of May 12, 2008, China

In this paper, we used the vertical total electron content (VTEC) derived from ground-based GPS observations to examine the ionospheric variations during the Mw7.9 Wenchuan earthquake which occurred on May 12, 2008, in China. The final results showed that the ionospheric VTEC around the epicenter increased obviously 9 days before the earthquake, decreased significantly 6 days before the earthquake, and increased strikingly 3 days before the earthquake. Relative to a normal non-perturbed state of the ionosphere, the maximum anomalies in the 3 days exceeded 40%, 40%, and 70%, respectively. The spatial sizes of the VTEC decrement and increment by more than 30% extended larger than 1500 km in latitude and 4000 km in longitude. Moreover, the maximum anomalies 6 days and 3 days before the earthquake moved towards the equator.     

Investigation of ionospheric TEC changes related to the 2008 Wenchuan earthquake based on statistic analysis and signal detection

Ionospheric TEC (total electron content) time series are derived from GPS measurements at 13 stations around the epicenter of the 2008 Wenchuan earthquake. Defining anomaly bounds for a sliding window by quartile and 2-standard deviation of TEC values, this paper analyzed the characteristics of ionospheric changes before and after the destructive event. The Neyman-Pearson signal detection method is employed to compute the probabilities of TEC abnormalities. Result shows that one week before the Wenchuan earthquake, ionospheric TEC over the epicenter and its vicinities displays obvious abnormal disturbances, most of which are positive anomalies. The largest TEC abnormal changes appeared on May 9, three days prior to the seismic event. Signal detection shows that the largest possibility of TEC abnormity on May 9 is 50.74%, indicating that ionospheric abnormities three days before the main shock are likely related to the preparation process of the M_S8.0 Wenchuan earthquake.     

Analysis of ionospheric vertical total electron content before the 1 April 2014 Mw 8.2 Chile earthquake

This paper studies ionospheric vertical total electron content (VTEC) variations before the 1 April 2014 Mw 8.2 Chile earthquake. VTEC derived from 14 global positioning system (GPS) stations and global ionospheric map (GIM) were used to analyze ionospheric variations before the earthquake using the sliding interquartile range method, and the results showed that significant positive VTEC anomalies occurred on 28 March. To explore possible causes of these anomalies, effects of solar and geomagnetic activities were examined, and VTEC variations during 17 March to 31 March in 2009–2013 were cross-compared. Also, VTEC for a full year before the earthquake was investigated. The results indicated that the anomalies were weakly associated with high solar activities and geomagnetic storms and that the anomalies were not normal seasonal and diurnal variations. An analysis of the spatial distribution of the observed anomalies was also presented, and it demonstrated that the anomalies specifically appeared around the epicenter on 28 March. We suggest that the observed anomalies may be associated with the subsequent Chile earthquake. Equatorial anomaly variations were analyzed to discuss the possible physical mechanism, and results showed that the equatorial anomaly unusually increased on 28 March, which indicates that anomalous electric fields generated in the earthquake preparation area and the meridional wind are possible causes of the observed ionospheric anomalies.     

Investigation of Lushan earthquake ionosphere VTEC anomalies based on GPS data

Vertical total electron content (VTEC) time series were obtained from 22 GPS stations near the epicenter of the Lushan earthquake. In this paper, we have adopted a sliding average method to detect and analyze anomalous VTEC associated with the earthquake. The results show that significant, negative ionosphere VTEC anomalies appeared over the 5 days before the earthquake, and on the day when earthquake occurred. The maximum value of VTEC anomalies that exceeded the lower bound reached 20 TECU. The spatial distribution of VTEC anomalies showed a conjugate structure, which shifted to the magnetic equator, and subsequently moved westwards.