利用IGS数据分析伊朗、巴基斯坦两次强震前的TEC异常

Analysis of the TEC Anomaly prior to Two Earthquakes in Pakistan and Iran by Adopting Statistics of IGS

摘要:

利用IGS发布的总电子含量（TEC）数据，采用从点到面的滑动标准差法，分析了伊朗和巴基斯坦两次强震前的TEC变化，发现两次强震前都出现TEC异常，表现为：(1)4月16日震前14日和16日出现TEC减少异常；(2)9月24日震前的19日、20日和21日出现TEC增大异常；(3)从平面分析上看两次地震前都出现了一定区域的TEC异常，异常程度从异常中心到外逐渐减弱，但异常中心不一定在震中位置。

Abstract:

Exploring and detecting the portents of earthquakes are common puzzles for experts and scholars at home and abroad.While studying earthquake in Alaska，Leonard and Barnes determined that the ionosphere changes prior to earthquakes，and they first recognized the causal nexus between them.In recent years，the Global Positioning System （GPS）has expanded rapidly to offer a new and more effective method for observing Turkish earthquake code （Total Electron Content (TEC)）values and detecting portents of earthquakes.In 1998，the International GPS Service（IGS）began to release global ionosphere service products.Due to the broader covering range of IGS，its statistics have been adopted by an increasing number of scholars to investigate TEC values and their anomalies，aiming at detecting portents of earthquakes.On April 16 and September 24，2013，two earthquakes，both at a scale of 7.7，struck Iran and Pakistan.At such a high scale，the two quakes showed the traits of narrow space，time occurrence，and high casualties and losses；therefore，we used them as study targets.Existing research proves that when the sun cycles and geomagnetic activity show a relatively equal period，the TEC does not exhibit strong fluctuation unless there are other strong disturbance sources.Accordingly，in seismically active zones，excessive TEC fluctuation is much more likely to indicate impending earthquakes. We chose the core of the two earthquakes as our study targets，and we developed two wave figures of TEC variation with statistics of 20 days prior to earthquake occurrence.We determined that TEC varies periodically.The statistics generally showed steady movement，with substantial rising or reduction only on some days.To make our study more precise and logical，we enlarged our TEC study from the quake cores to the affected areas.We made a sliding comparison of the TEC variation in the entire area and obtained its distribution figure.To provide clarity，we illustrated these waves with various colors.After accounting，we noticed that the anomaly presented itself in the quake cores in addition to the surrounding areas.From the angle of anomaly degree，we noticed a decrease from the cores to the outer regions.With the TEC statistics issued by IGS and adoption of the sliding standard deviation from the cores to the impacting area of the quakes，we analyzed the TEC variations prior to the two earthquakes and detected the TEC anomalies.The TEC reduced unconventionally on April 14 and 16 and increased unconventionally on September 19，20，and 21.Moreover，with a plane survey，we detected TEC anomalies in some regions prior to both earthquakes，which decreased from the cores of the anomalies to their periphery regions；however，these anomaly cores did not all correspond with the cores of the two earthquakes.After analyzing the statistics form the cores of the earthquakes to affected areas，we determined the degree and increase area of these TEC anomalies.However，due to length of the thesis and our research facilities，additional work is required to determine the causes of these anomalies.Factors leading to these anomalies vary widely and include macula，geomagnetic index，cycling tracks of the Sun and the Earth，and weather anomalies，which are worth of our further study.