共查询到19条相似文献，搜索用时 140 毫秒
1.
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. 相似文献
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利用赤道异常北驼峰区深圳站2011年1月到2012年12月监测到的GPS-TEC数据,统计分析了华南地区电离层TEC耗空的时间和空间分布特征.结果表明:TEC耗空随时间、地理经纬度位置等变化呈现出不同的特征.前半夜和在赤道异常北驼峰区域,深度在20 TECU左右的耗空明显和强闪烁(S4≥0.5)相关,在后半夜或在赤道异常北驼峰外边缘区域,存在一些深度小于10 TECU的耗空对应着无闪烁现象发生.统计结果还表明:TEC耗空呈现出季节变化规律,2011和2012年TEC耗空主要出现在春秋分期间,TEC耗空深度主要分布为1~20TECU,持续时间集中在16~30 min,出现的时间主要集中在12:30-15:30UT(20:30-23:30LT),午夜之后TEC耗空活动呈逐渐减弱趋势. 相似文献
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基于GPS TEC数据, 以2016年4月13日发生在缅甸的M7.2地震为例, 通过限定上、 下阈值的扰动提取方法分析了地震电离层效应在中国区域的时空分布。 结果显示, 该地震前2~4天, 中国区域的TEC扰动为地震电离层前兆; 其中4月11日(震前2天)电离层扰动受地震的影响最大, 扰动范围可达2816 km; 同时还发现4月11日异常最明显的区域在震中偏北方向(中国南部), 单独提取该区域经度链上的JPL TEC数据, 发现异常区域内北驼峰北移的现象, 并用静电场理论对异常区域向北偏移的物理机制做了分析解释。 相似文献
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基于中国陆态网络地基GPS-TEC观测，针对2008～2019年发生在中国区域的7个MS≥6.0地震，采用滑动四分位距法分析了地震前后的电离层扰动时空分布特征。结果显示，5个地震的震前2～6天，GPS-TEC值出现负异常扰动，地震发生期间及震后电离层TEC出现正异常扰动，主要集中在震后2～7天；GPS观测站距离震中越近，垂直上空的TEC扰动越明显，扰动空间最大范围可达2000km。随着震级的增加，震前电离层TEC异常扰动的发生率有所增加，且异常覆盖的范围也有所扩大。因此，认为震前一周内的电离层TEC变化可能提供揭示电离层扰动与地震活动之间关系的线索。 相似文献
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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. 相似文献
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基于GPS TEC数据,对1998年11月1日-2010年12月31日中国大陆MS≥6.0地震临震电离层扰动进行了研究.分析发现,震中上空及周围的东、南、西、北4个方向震前15天到地震当天时序变化趋势较相似,5个方向都观测到了震前3-5天负异常稍高于正异常的现象.按震中±10°、±20°、±30°不同空间尺度分析震前0-15天TEC变化,研究表明临震电离层异常最明显的区域并不位于震中的正上空,而是向磁赤道方向偏移,空间影响尺度大约为±15°左右;正异常在震前14天、10天震中西南方向出现不同程度的高值区,负异常在震前5天震中东南方向较明显.最后,应用静电场假设对这些现象进行了解释. 相似文献
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《地球物理学报》2017,(3月磁暴)
2015年3月17日爆发了本太阳活动周最大的地磁暴,Dst指数达到-233 nT.本文利用电离层测高仪f_。F_2和h_mF_2、北斗同步卫星(BDSGEO)TEC以及GPS电离层闪烁S4指数对此次磁暴期间中国中低纬地区(北京、武汉、邵阳和三亚)的电离层变化进行分析,并对此次磁暴所引发电离层暴的可能机制进行了探讨.磁暴期间,中低纬电离层暴整体表现为正相暴之后长时间强的负相暴.3月17日白天中纬正相暴为风场抬升电离层所致,而驼峰区及低纬地区正相暴由东向穿透电场所引起;3月18日白天长时间的强负相暴为西向扰动发电机电场和成分扰动所引起;3月17和18日夜间的负相暴可能是日落东向电场受到抑制以及赤道向风场对扩散的抑制导致驼峰向赤道压缩所致,同时被抑制的日落东向电场强度不足以触发产生赤道扩展F,导致低纬三亚和邵阳夜间电离层闪烁在磁暴期间受到完全抑制.这是我们首次基于北斗同步卫星TEC组网观测开展的电离层暴研究. 相似文献
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2015年3月17日爆发了本太阳活动周最大的地磁暴,Dst指数达到-233 nT.本文利用电离层测高仪f_。F_2和h_mF_2、北斗同步卫星(BDSGEO)TEC以及GPS电离层闪烁S4指数对此次磁暴期间中国中低纬地区(北京、武汉、邵阳和三亚)的电离层变化进行分析,并对此次磁暴所引发电离层暴的可能机制进行了探讨.磁暴期间,中低纬电离层暴整体表现为正相暴之后长时间强的负相暴.3月17日白天中纬正相暴为风场抬升电离层所致,而驼峰区及低纬地区正相暴由东向穿透电场所引起;3月18日白天长时间的强负相暴为西向扰动发电机电场和成分扰动所引起;3月17和18日夜间的负相暴可能是日落东向电场受到抑制以及赤道向风场对扩散的抑制导致驼峰向赤道压缩所致,同时被抑制的日落东向电场强度不足以触发产生赤道扩展F,导致低纬三亚和邵阳夜间电离层闪烁在磁暴期间受到完全抑制.这是我们首次基于北斗同步卫星TEC组网观测开展的电离层暴研究. 相似文献
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I. E. Zakharenkova I. I. Shagimuratov A. Krankowski A. F. Lagovsky 《Studia Geophysica et Geodaetica》2007,51(2):267-278
In this paper the analysis of the ionospheric total electron content (TEC) variations obtained with using GPS measurements
before the Hokkaido earthquake (M = 8.3) is presented. Anomalous behavior of TEC was detected within several days before the
main event. Anomaly appeared as the local TEC enhancement situated in the vicinity of the forthcoming earthquake epicenter.
These structures occurred during 5 days prior to the shock at the same interval of local time. At the process of the earthquake
approach the amplitude of modification was increased, and it has reached the 85–90% level relative to the non-disturbed conditions
18 hours before the earthquake. The area of strong positive disturbance has extended over 1500 km in latitudes and 4000 km
in longitudes. The analysis have shown that according to the series of characteristics (its locality, affinity with the epicenter,
dome-shaped zone of manifestation, characteristic time of existence) the detected ionospheric anomaly may be associated to
the precursors of seismic activity. 相似文献
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Anamolous ionospheric TEC variations prior to the Indonesian earthquake (M 7.1) of November 15, 2014
Salih Alcay 《Geomagnetism and Aeronomy》2017,57(3):301-307
This paper investigates preearthquake ionospheric variations with the use of TEC of Global Ionospheric Maps (GIMs) and regional maps based on Precise Point Positioning (PPP) during the 7.1-M Indonesian earthquake that occurred on November 15, 2014. TEC maps corresponding to 10 days before to 4 days after the event were examined. In addition, a time series of TEC values according to the PPP maps were also evaluated. In addition to GIMs, it was possible to detect TEC variations with PPP maps. The results showed that ionospheric TEC decreased strikingly 4 days prior to the earthquake. This TEC variation was highly likely related to seismic activity. 相似文献
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《Journal of Atmospheric and Solar》2008,70(15):1919-1928
This paper investigates the features of pre-earthquake ionospheric anomalies in the total electron content (TEC) data obtained on the basis of regular GPS observations from the International GNSS Service (IGS) network. For the analysis of the ionospheric effects of the 26 September 2005 Peru earthquake, Global Ionospheric Maps (GIMs) of TEC were used. The possible influence of the earthquake preparation processes on the main low-latitude ionosphere peculiarity—the equatorial anomaly—is discussed. Analysis of the TEC maps has shown that modification of the equatorial anomaly occurred a few days before the earthquake. In previous days, during the evening and night hours (local time—LT), a specific transformation of the TEC distribution had taken place. This modification took the shape of a double-crest structure with a trough near the epicenter, though usually in this time the restored normal latitudinal distribution with a maximum near the magnetic equator is observed. Additional measurements (CHAMP satellite) have also confirmed the presence of this structure. To compare the vertical TEC measurements obtained with GPS satellite signals (GPS TEC), the International Reference Ionosphere, IRI-2001, was used for calculating the IRI TEC. 相似文献
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Weiping Jiang Yifang Ma Xiaohui Zhou Zhao Li Xiangdong An Kaihua Wang 《Journal of Seismology》2017,21(6):1599-1612
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. 相似文献
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Investigation of ionospheric TEC changes related to the 2008 Wenchuan earthquake based on statistic analysis and signal detection 
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下载免费PDF全文 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 MS8.0 Wenchuan earthquake. 相似文献
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Earthquakes are among the most dangerous events that occur on earth and many scientists have been investigating the underlying processes that take place before earthquakes occur. These investigations are fueling efforts towards developing both single and multiple parameter earthquake forecasting methods based on earthquake precursors. One potential earthquake precursor parameter that has received significant attention within the last few years is the ionospheric total electron content (TEC). Despite its growing popularity as an earthquake precursor, TEC has been under great scrutiny because of the underlying biases associated with the process of acquiring and processing TEC data. Future work in the field will need to demonstrate our ability to acquire TEC data with the least amount of biases possible thereby preserving the integrity of the data. This paper describes a process for removing biases using raw TEC data from the standard Rinex files obtained from any global positioning satellites system. The process is based on developing an unbiased TEC (UTEC) data and model that can be more adaptable to serving as a precursor signal for earthquake forecasting. The model was used during the days and hours leading to the earthquake off the coast of Tohoku, Japan on March 11, 2011 with interesting results. The model takes advantage of the large amount of data available from the GPS Earth Observation Network of Japan to display near real-time UTEC data as the earthquake approaches and for a period of time after the earthquake occurred. 相似文献
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Ionospheric electromagnetic perturbations observed on DEMETER satellite before Chile M7.9 earthquake 下载免费PDF全文
下载免费PDF全文 Xuemin Zhang Jiadong Qian Xinyan Ouyang Xuhui Shen Jin&# an Cai Shufan Zhao 《地震科学（英文版）》2009,22(3):251-255
Based on the ionospheric electromagnetic data observed on DEMETER satellite of France, the ionospheric electromagnetic signals were analyzed within 10 days before Chile M7.9 earthquake on November 14, 2007. It is found that, low frequency electromagnetic disturbances began to increase in a large scale of latitude, and reached to a maximum one week prior to the earthquake, and at about three days before the quake, the peak values shifted to lower latitude. Taking three days as a group, spatial images of a few parameters were analyzed, from which it can be seen during the five days prior to this earthquake, the amplitude and scale of anomalies are enlarged, while the epicenter is located at the boundary of anomalous region. The anomalous tempo-spatial variation in electron density prior to the earthquake were also obtained in terms of tracing the data from revisited orbits in half a year prior to the quake. 相似文献
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使用相关方法和welch法计算功率谱密度研究汶川地震前后GPS TEC在时域和频域上的变化,并进一步分析NmF2空间分布变化.得出主要结论, 震前5月9日开始TEC平常具有良好的相关性被打破,24 h全日波、12 h半日波成分功率谱密度幅度值变化明显.5月12日至6月11日NmF2变化幅度明显增大.研究结果显示,TEC和NmF2时空分布变化存在电离层震前扰动和同震响应, 并且TEC震后的异常变化相比震前更加显著.表明使用的方法可以有效检测到地震发生前后电离层异常扰动信号. 相似文献