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1.
We consider data obtained when the parameters of the ionospheric Es and F2 layers and the vertical gradient of the electric potential in the surface atmosphere were simultaneously measured during the preparatory period of crustal earthquakes with M = 5.0–6.2 in the Kamchatka region. The appearance of anomalously high Es, accompanied by an increase in frequency parameters of the sporadic layer and the regular F2 layer, was detected on days when possible earthquake precursors, as determined earlier, occurred in atmospheric electric fields. The presumed earthquake precursors in the ionosphere are divided into two groups with different earthquake lead times ranging from several hours to two weeks. Empirical dependences are presented that connect the lead time of an earthquake (from the moment of the appropriate anomaly’s occurrence in the ionosphere or in the atmospheric electric field to the moment of the shock) and the epicentral distance to the observation point with the earthquake magnitude. These dependences are different for the two groups of presumed earthquake precursors, but they are close inside each group of possible precursors selected on the basis of quasistatic electric field measurements and revealed in ionospheric parameter variations.  相似文献   

2.
We have studied changes in the ionosphere prior to strong crustal earthquakes with magnitudes of М ≥ 6.5 based on the data from the ground-based stations of vertical ionospheric sounding Kokobunji, Akita, and Wakkanai for the period 1968–2004. The data are analyzed based on hourly measurements of the virtual height and frequency parameters of the sporadic E layer and critical frequency of the regular F2 layer over the course of three days prior to the earthquakes. In the studied intervals of time before all earthquakes, anomalous changes were discovered both in the frequency parameters of the Es and F2 ionospheric layers and in the virtual height of the sporadic E layer; the changes were observed on the same day at stations spaced apart by several hundred kilometers. A high degree of correlation is found between the lead-time of these ionospheric anomalies preceding the seismic impact and the magnitude of the subsequent earthquakes. It is concluded that such ionospheric disturbances can be short-term ionospheric precursors of earthquakes.  相似文献   

3.
We have analyzed variations in the near-surface atmospheric electric field (Ez) normalized to their daily averages that were simultaneously observed in different high-latitude regions at moderate geomagnetic activity (Kp ∼ 3). The Ez data were measured under fair weather conditions at the Vostok Antarctic research station (Φ′ = −83.5°) in the southern polar cap and at the Hornsund Arctic observatory (Φ′ = 74.0°) on Svalbard close to the polar boundary of the auroral oval in the Northern Hemisphere. It is established that variations in the atmospheric electric field in the polar cap region at the Vostok station are controlled (the correlation coefficient R ∼ 0.7–0.9) by variations in the overhead ionospheric potential. The situation at the Hornsund observatory is more complicated. During intervals when Hornsund occurred below the westward electrojet, the correlation was typically positive with R ∼ 0.60–0.85; however, while this observatory was in the region of the eastern electrojet, the correlation could be negative with R ∼ 0.7–0.8. Normally, during such periods, the westward electrojet was detected polarwards of Hornsund while, according to the SuperDARN radar data, the observatory was located below the negative vortex of the polar ionospheric convection.  相似文献   

4.
The 15-min data of vertical ionosphere sounding and 10-min data from measurements of the vertical component (Ez) of the near-surface quasistatic atmospheric electrical field and the respective values of electrical conductance of near-surface air at the Paratunka complex geophysical observatory in the period from January 28 to January 30, 2016 have been analyzed to reveal the possible anomalies preceding the M = 7.2 earthquake that occurred on January 30, 2016, at 0325 UT. The distance between the observatory and epicenter was 117 km. These anomalies have been revealed, and the majority of them, in our opinion, may be related to the processes of earthquake preparation.  相似文献   

5.
Data from 15-minute measurements at the vertical ionospheric sounding station in Irkutsk during the summer months of 2008–2011 are analyzed in order to detect in the ionosphere effects of preparation of weak earthquakes of the K = 10–12 energy class. The method of revealing disturbances in ionospheric parameters by simultaneous observations of the sporadic E layer and regular F2 layer, which was previously applied by the authors in the case of stronger earthquakes, was used. The efficiency of using this method to detect ionospheric disturbances preceding earthquakes also in the case of weak earthquakes is demonstrated. Possible ionospheric precursors of the selected series of earthquakes are identified. For them, an empirical dependence relating the time of advance of the shock moment by the probable ionospheric precursor on the energy class of the earthquake and the epicenter distance to the observation point is found.  相似文献   

6.
We analyze ionospheric oblique sounding data on three high-latitude and one high-latitude–midlatitude HF radio paths for February 15 and 16, 2014, when two substorms and one magnetic storm occurred. We investigate cases of anomalous propagation of signals: their reflection from sporadic layer Es, lateral reflections, type “M” or “N” modes, the presence of traveling ionospheric disturbances, and the diffusivity of signals and triplets. The most significant results are the following. In geomagnetically undisturbed times, sporadic Es-layers with reduced maximum observed frequencies (MOFEs) on three high-latitude paths were observed in both days. The values of MOFEs during disturbances are large, which leads to the screening of other oblique sounding signals reflected from the ionosphere. On all four paths, the most frequently traveling ionospheric disturbances due to the terminator were observed in quiet hours from 03:00 to 15:00 UT on the first day and from 06:00 to 13:00 UT on the second day of the experiment. In addition, both the sunset terminator and the magnetic storm on the high-latitude–mid-latitude path were found to generate traveling ionospheric disturbances jointly. No such phenomenon was found on high-latitude paths.  相似文献   

7.
The existence of anomalous ionospheric reflections was shown on the basis of vertical soundings at the Moskow station. They are observed at heights of 100–200 km. These anomalous reflections are not related to the main Ne(h) ionospheric profile. Morphological characteristics of such reflections are presented: the daily, seasonal, and cyclic dependences of their appearance.  相似文献   

8.
The possible seismic ionospheric effects before two strong earthquakes in Italy, which took place near Rome station (January 7, 1962, M = 6.0; April 5, 1998, M = 5.3), have been studied using the data of several European stations for ground-based vertical sounding of the ionosphere. An analysis of the behavior of the foF2 critical frequencies for the earthquake that occurred on January 7, 1962, made it possible to simultaneously consider the effects, originating during earthquake preparation under quiet geomagnetic conditions and caused by the magnetic strom that began on January 10, 1962, using a unified technique. It has been indicated that the distinguished precursor effects of two considered earthquakes with magnitudes not more than 6.0 are localized in the region with an epicentral distance of about 400 km, whereas the disturbances caused by the magnetic storm are of a planetary character. The amplitude of foF2 seismic ionospheric disturbances is much smaller than the maximal variations caused by the magnetic storm; however, the absolute value of this amplitude is a factor of 1.5 as large as the standard deivation from the monthly median.  相似文献   

9.
Seismoionospheric disturbances in the parameters of the ionospheric F 2 and sporadic E layers at the chain of the Japanese stations for vertical sounding of the ionosphere before strong crustal earthquakes with M>6.5 during the period from 1968 to 1992 have been considered. The dependence of the disturbance time of appearance in the ionospheric parameters on the earthquake magnitude and epicentral distance, obtained for each specific earthquake using the selected series of ionospheric stations, made it possible to consider these disturbances among medium-term precursors of earthquakes. The velocity of the disturbance front apparent motion has been determined based on the model of horizontal radially-isotropic disturbance propagation from the projection of the impending earthquake epicenter to the ionospheric altitudes. The conclusion has been made that the distinguished seismoionospheric disturbances follow the boundary of the earthquake preparation region, expanding on the Earth’s surface.  相似文献   

10.
We have studied the influence of daytime polar substorms (geomagnetic bays under the IMF Bz > 0) on variations of the vertical gradient of the atmospheric electric field potential (Ez) observed at the Polish Hornsund Station (Svalbard, Norway). Only the observations of Ez under “fair weather” conditions were used, i.e. in the absence of strong wind, precipitations, low cloud cover, etc. We studied more than 20 events of daytime polar substorms registered by the Scandinavian chain of IMAGE magnetometers in 2010–2014 during the “fair weather” periods at the Hornsund Station. Analysis of the observations showed that Ez significantly deviates from the its background variations during daytime, as a rule, when the Hornsund Station is in the region of projection of the daytime auroral oval, the position of which was determined from OVATION data. It was shown that the development of a daytime polar substorm leads to fluctuating enhance of Ez values. It was found that Ez surges are accompanied by intensification of field-aligned electric currents outflowing from the ionosphere, which were calculated from the data of low-orbit communication satellites of the AMPERE project.  相似文献   

11.
I suggest that earthquake precursors can be divided into two major categories, physical and tectonic. I define physical precursor to be a direct or indirect indication of initiation or progression of an irreversible rupture-generating physical process within the preparation zone of a forthcoming earthquake. Tectonic precursor is defined as a manifestation of tectonic movement which takes place outside the preparation zone of an impending earthquake as a link in a chain of particular local tectonism in each individual area preceding the earthquake.Most intermediate-term, short-term and immediate precursors of various disciplines within the source regions of main shocks are considered physical ones. Some precursory crustal deformations around the source regions are, however, possibly tectonic precursors, because they may be caused by episodic plate motions or resultant block movements in the neighboring regions of the fault segments that will break. A possible example of this phenomena is the anomalous crustal uplift in the Izu Peninsula, Japan, before the 1978 Izu-Oshima earthquake ofM s 6.8. Some precursory changes in seismicity patterns in wide areas surrounding source regions also seem to be tectonic precursors, because they were probably caused by the particular tectonic setting of each region. A typical example is a so-called doughnut pattern before the 1923 Kanto, Japan, earthquake ofM s 8.2.Although most studies on earthquake precursors so far seem to regard implicitly all precursory phenomena observed as physical ones, the two categories should be distinguished carefully when statistical analysis or physical modeling is carried out based on reported precursory phenomena. In active plate boundary zones, where a practical strategy for earthquake prediction may well be different from that in intraplate regions, tectonic precursors can be powerful additional tools for intermediate-term earthquake prediction.  相似文献   

12.
The paper presents the results of studying anomalous variations in the total electron content (TEC) of the ionosphere as probable precursors of strong seismic events. The vertical drift of the F2 layer’s ionospheric plasma under the effect of seismically generated zonal electric field is considered as a likely reason for the observed variations in the TEC. An estimation of this drift effects is made by mathematical simulation utilizing the global numerical model of the Earth’s upper atmosphere (UAM). Midlatitude ionospheric effects were simulated. Two types of seismogenerated electric fields (dipole and monopole) were used with various magnitudes and spatial configurations. The derived results were compared with the TEC data of GPS observations from the IGS for the Kitira earthquake in southern Greece (January 8, 2006; M 6.8). It was shown that variations generated by additional sources of the dipole type are consistent with the observed data; monopole-type sources did not reproduce some typical peculiarities of these observations and systematically underestimated the deviation value.  相似文献   

13.
刘江  徐锐  陈聪  饶太国  李兴泉 《地震学报》2021,43(5):605-614
介绍了川滇地区电离层多参量异常监测系统的设计思路与功能实现,并将该系统应用于2019年6月17日四川长宁MS6.0地震的监测试验。结果表明:该系统实现了全球和中国区域垂直总电子含量VTEC、站点VTEC和F2层临界频率foF2异常变化的实时监测,有助于开展示范性地震电离层异常监测工作,其图形及数据结果可为地震-电离层异常扰动判识提供佐证,为川滇地区地震监测预报提供电离层前兆信息支持。   相似文献   

14.
We performed an analysis of mean daily variations in the ΔEz atmospheric electric field at the Hornsund (located near the polar cap boundary) and Kakioka (located at near-equatorial latitudes) observatories under magnetically quiet and weakly disturbed conditions. At both observatories, the mean daily variations in ΔEz were found to be mainly controlled by the location of the observation point with respect to the focuses of the convective vortices of the DP 0 system. The substorm evolution in the nightside of the magnetosphere (a sharp burst in the AE index) was shown to lead to negative variations in ΔEz in the dayside sector at polar latitudes (the Hornsund observatory) and positive deviations in ΔEz at premidnight time at equatorial latitudes (the Kakioka observatory). It is concluded that variations in ΔEz at the Kakioka observatory are largely controlled by the equatorial electrojet, which is maximal during day-time hours, and at the Hornsund observatory these variations are controlled by the auroral electrojet, which is maximal at night-time and early morning hours of local time.  相似文献   

15.
The paper briefly reviews the recent advances and the main trend, as well as the major subjects for future study in the research on seismo-electromagnetic emissions. The preliminary results obtained show that the recently discovered electromagnetic emission phenomena prior to earthquake events are objective facts and may be prospective precursor applicable for short term earthquake prediction. Considering the complexity of the generation mechanisms, as well as the space coupling and the time variation processes of the seismo-electromagnetic emissions, we must deeply study the essential connection between the precursory emission phenomena and the seismogenic processes. Closely connect the field observations and theoretical research and try to comprehensively diagnose by correlating with other precursors. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 254–258, 1991.  相似文献   

16.
Thedevelopmentandthevariationoftheearthquakeprocessisaverycomplicatedoneandaffectedandlimitedbymanyfactors.Thekeyoftheaccuratepredictionistosetupadynamiccomprehensivepredictionmodelbasedonthecomprehensionoftheprecursorcharacteristicandtheattentionofthevariationwithtimeofthesefactors.Inthispaper,wetrytoapplythefaultdiagnosistectonictoeanhquakeprediction.Thefaultdiagnosistectonicisanapplicableboundaryscience.Thebasicideaistojudgeifthefaultoccurinthesystemandtodeterminewhereandwhenthefaultoccuran…  相似文献   

17.
GPS observations of the European permanent network were used to identify seismo-ionospheric precursors of Baltic Sea earthquake of 21 September 2004. It is a very rare event for this region of Europe (magnitude of about 5.0). This value is the threshold for the occurrence of seismic effects in the ionosphere. In total electron content (TEC) data over the region of the earthquake, a specific ionospheric anomaly appeared one day before the earthquake was detected. The ionospheric variability had a positive sign with an enhancement of about 4–5 TECU (1 TECU = 1016 electrons/m2) relative to the non-disturbed state of the ionosphere. The anomaly had a duration of 4–5 hours in the day time. The special size of this anomaly was about 1000 km. The characteristic parameters of the anomaly show that it can be associated with ionospheric precursors of an earthquake.  相似文献   

18.
A great earthquake of M S=8.1 took place in the west of Kunlun Pass on November 14, 2001. The epicenter is located at 36.2°N and 90.9°E. The analysis shows that some main precursory seismic patterns appear before the great earthquake, e.g., seismic gap, seismic band, increased activity, seismicity quiet and swarm activity. The evolution of the seismic patterns before the earthquake of M S=8.1 exhibits a course very similar to that found for earthquake cases with M S≥7. The difference is that anomalous seismicity before the earthquake of M S=8.1 involves in the larger area coverage and higher seismic magnitude. This provides an evidence for recognizing precursor and forecasting of very large earthquake. Finally, we review the rough prediction of the great earthquake and discuss some problems related to the prediction of great earthquakes.  相似文献   

19.
A long-range correlation between earthquakes is indicated by some phenomena precursory to strong earthquakes. Most of the major earthquakes show prior seismic activity that in hindsight seems anomalous. The features include changes in regional activity rate and changes in the pattern of small earthquakes, including alignments on unmapped linear features near the (future) main shock. It has long been suggested that large earthquakes are preceded by observable variations in regional seismicity. Studies on seismic precursors preceding large to great earthquakes with M ≥ 7.5 were carried out in the northeast India region bounded by the area 20°–32°N and 88°–100°E using the earthquake database from 1853 to 1988. It is observed that all earthquakes of M ≥ 7.5, including the two great earthquakes of 1897 and 1950, were preceded by abnormally low anomalous seismicity phases some 11–27 years prior to their occurrence. On the other hand, precursory time periods ranged from 440 to 1,768 days for main shocks with M 5.6–6.5 for the period from 1963 to 1988. Furthermore, the 6 August, 1988 main shock of M 7.5 in the Arakan Yoma fold belt was preceded by well-defined patterns of anomalous seismicity that occurred during 1963–1964, about 25.2 years prior to its occurrence. The pattern of anomalous seismicity in the form of earthquake swarms preceding major earthquakes in the northeast India region can be regarded as one of the potential seismic precursors. Database constraints have been the main barrier to searching for this precursor preceding smaller earthquakes, which otherwise might have provided additional information on its existence. The entire exercise indicates that anomalous seismicity preceding major shocks is a common seismic pattern for the northeast India region, and can be employed for long-range earthquake prediction when better quality seismological data sets covering a wide range of magnitudes are available. Anomalous seismic activity is distinguished by a much higher annual frequency of earthquake occurrence than in the preceding normal and the following gap episodes.  相似文献   

20.
张北地震前、在中期阶段,多井水氡出现负异常变化;短期阶段出现区域水氡差分异常的月频次增加;短临阶段则出现怀来４井水汞的多次突跳。大同地震前多井出现水氡的趋势性正常,是张北地震水化前兆最显著的不同之处。本文分析了张北地震水化方法预报失误的原因。讨论认为,水氡负异常做为中期前兆的信度较低;为提高水化预报地震的效能,必须与其它前兆手段相结合。  相似文献   

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