On the Origin of ULF Magnetic Waves Before the Taiwan Chi-Chi 1999 Earthquake (original) (raw)
Related papers
2011
From the results of monitoring carried out in Italy, analyses were made of radio wave anomaly data in frequencies lower than 10 Hz and peaks between 55 microGauss and 0.3milliGauss which had preceded the M9.0 Japanese earthquake on 11 March 2011. From the 1 March onwards, the trains of interferences had already markedly increased -a good 179 radio wave anomalies were measured, in comparison to 109 during the previous month, February 2011. This series of data remained on the high side until plummeting to only 66 on the day of the earthquake, then rising sharply again to 246 on the following day (12 th March 2011). The magnetic field observed by satellite, both before and during the earthquake, showed a pattern analogous to the number of radio wave anomalies measured on the ground. Here too there was a dramatic fall when the earthquake occurred, followed by an abrupt rise. In Italy, just a few minutes after the mainshock, the gravimeter registered a substantial reduction in the grav...
Terrestrial, Atmospheric and Oceanic Sciences, 2008
On 24 March 1991, global ultra-low-frequency (ULF) pulsations (1.1-3.3 mHz) observed in the magnetosphere as well as on the ground were studied via analyzing magnetic field data obtained from a global network, comprising ground-based observatories and geosynchronous satellites. In the magnetosphere, the compressional and transverse components of the magnetic fields recorded at two satellites, GOES 6 and GOES 7, showed dominant fluctuations when they were in the vicinity of the noon sector, whereas the transverse fluctuations became dominant when they were at the dawn side. Similarly, on the ground, the H and D components had major fluctuations along with an increase in amplitude from low to high geomagnetic latitudes. In addition, the amplitude of the ULF pulsation was enhanced at the dawn and dusk sides. The geomagnetic pulsations propagated anti-sunward and were of counterclockwise and clockwise elliptical polarizations at the dawn and dusk sides respectively. The counterclockwise elliptical polarization reversed to a clockwise elliptical polarization at geomagnetic local noon and linear polarization was observed during the reversal. It appears that the analysis of the global network data not only provided us with a study of the characteristics of the waves in the magnetosphere and on the ground but also provided us with correlations between the geosynchronous and ground observations, which should be essential to the determination of possible mechanisms of this storm-related wave event.
Space weather and earthquakes: possible triggering of seismic activity by strong solar flares
ANNALS OF GEOPHYSICS, 2020
The studies completed to-date on a relation of the Earth's seismicity and solar processes provided the fuzzy and contradictory results. The main problem of this research is a lack of physical explanation of a mechanism of earthquake triggering by strong variations of space weather conditions. Based on results obtained in the field and laboratory experiments on earthquake triggering by DC pulses injection into the Earth crust we may assume that the similar triggering phenomena may occur after the strong electromagnetic impact to the earthquake source due to solar flares or geomagnetic storms. Numerical estimations demonstrated that telluric currents induced by geomagnetic pulsations generated by solar flare have the similar density at the depth of earthquake source location (10-6 A/m 2) in comparison with the current density generated by artificial power sources (10-7-10-8 A/m 2) resulted in observed spatiotemporal redistribution of seismic activity in the regions of Pamirs and Northern Tien Shan. For supporting the idea of a possible earthquake triggering by solar flares we carried out a statistical analysis of global and regional (Greece) seismicity behavior during the solar flare of X9.3 class occurred on September 6, 2017 (the strongest flare over the past thirteen years). We have discovered a new evidence of earthquake triggering due to the Sun-Earth interaction by simple comparison of a number of earthquakes before and after the strong solar flare. The global number of earthquakes (USGS catalog, M ≥ 4) for time window of ±11 days after the solar flare has increased by 68%, and the regional seismicity (Greece, EMSC catalog, M ≥ 3) has increased by 120%.
Natural Hazards and Earth System Science, 2011
Lithospheric ultra low frequency (ULF) magnetic activity is recently considered as a very promising candidate for application to short-time earthquake forecasting. However the intensity of the ULF lithospheric magnetic field is very weak and often masked by much stronger ionospheric and magnetospheric signals. The study of pre-earthquake magnetic activity before the occurrence of a strong earthquake is a very hard problem which consists of the identification and localization of the weak signal sources in earthquake hazardous areas of the Earth's crust.
Open Journal of Earthquake Research, 2015
The ultra-low frequency (ULF) magnetic field data at a station very close to the 2008 Sichuan earthquake (EQ) (on 12 May, 2008; M = 8.0) are extensively studied on the basis of combined statistical and natural time analyses. Two effects in ULF are treated: one is the well-known ULF radiation from the lithosphere, and the other is the non-conventional depression of ULF horizontal magnetic field. The simple statistical analysis has yielded: 1) no clear evidence of the presence of precursory ULF radiation, and 2) a significant effect of depression of ULF horizontal field a few days before the EQ (as a signature of ionospheric perturbations). The recently introduced natural time analysis has also been performed in order to study the critical features of the lithosphere and essentially new information has been brought about. The parameter "polarization", as the ratio of vertical to horizontal components, showed critical features in the time period of 17-27 April, about one month to two weeks before the EQ as a signature of lithospheric radiation. Then, the natural time analysis has reconfirmed the presence of ionospheric perturbations a few days before the EQ, together with an additional time window found on 19-23 April, about one month before the EQ, exhibiting critical features in the ULF depression.
Anomaly disturbances of the magnetic fields before the strong earthquake in Japan on March 11, 2011
Annals of geophysics = Annali di geofisica
One of the strongest earthquakes, with magnitude M 8.9, occurred at the sea bottom near to the east coast of Japan on March 11, 2011. This study is devoted to the investigation of anomaly disturbances in the main magnetic field of the Earth and in ultra-low frequency magnetic variations (F <10 Hz) observed before this earthquake. Secular variations of the main geomagnetic field were investigated using three-component 1-h data from three magnetic observatories over the 11-year period of January 1, 2000, to January 31, 2011. The Esashi and Mizusawa magnetic stations are situated northwest of the earthquake epicenter, at distances of around 170 km to 200 km, and the Kakioka observatory is situated southwest of the earthquake epicenter, at a distance of about 300 km. During this period, there were four local anomalies in the secular variations. The last anomaly was the biggest, which began around 3 years prior to the earthquake moment. All of the anomalies can be most distinctly recognized, in the form of differences in the corresponding magnetic components at these remote magnetic stations. For investigations of the ultra-low frequency magnetic field disturbances, three-component 1-s data at two magnetic stations (Kakioka and Uchiura) were used. The Uchiura station is situated 119 km south of Kakioka, at a distance of about 420 km from the earthquake epicenter. Data from the time interval of February 18, 2011 to March 10, 2011 (only at night-time: 01:00 to 04:00 local time) were investigated in a wide frequency range. In the frequency range of 0.033 Hz to 0.01 Hz, there was the clearest anomaly, seen as a decrease in the correlation coefficients of the corresponding magnetic components at these two stations, from February 22, 2011. Differences in the Z components showed an increase, and became positive after this date. This might suggest that the ultra-low frequency lithospheric source appeared north of the Kakioka station. Outside this specified frequency range, the anomalies were not well defined.
Geoscience Letters, 2024
The China Seismo-Electromagnetic Satellite (CSES), with a sun-synchronous orbit at 507 km altitude, was launched on 2 February 2018 to investigate pre-earthquake ionospheric anomalies (PEIAs) and ionospheric space weather. The CSES probes manifest longitudinal features of four-peak plasma density and three plasma depletions in the equatorial/low-latitudes as well as mid-latitude troughs. CSES plasma and the total electron content (TEC) of the global ionosphere map (GIM) are used to study PEIAs associated with a destructive M7.0 earthquake and its followed M6.5 and M6.3/M6.9 earthquakes in Lombok, Indonesia, on 5, 17, and 19 August 2018, respectively, as well as to examine ionospheric disturbances induced by an intense storm with the Dst index of − 175 nT on 26 August 2018. Anomalous increases (decreases) in the GIM TEC and CSES plasma density (temperature) frequently appear specifically over the epicenter days 1-5 before the M7.0 earthquake and followed earthquakes, when the geomagnetic conditions of these PEIA periods are relatively quiet, Dst: − 37 to 19 nT. In contrast, TEC and CSES plasma parameter anomalies occur globally in the southern hemisphere during the storm days of 26-28 August 2018. The CSES ion velocity shows that the electric fields of PEIAs associated with the M7.0 earthquake are 0.21/0.06 mV/m eastward and 0.11/0.10 mV/m downward at post-midnight/post-noon on 1-3 August 2018, while the penetration electric fields during the storm periods of 26-28 August 2018 are 0.17/0.45 mV/m westward/downward at post-midnight of 02:00 LT and 0.26/0.26 mV/m eastward/upward at post-noon of 14:00 LT. Spatial analyses on CSES plasma discriminate PEIAs from global effects and locate the epicenter of possible forthcoming large earthquakes. CSES ion velocities are useful to derive PEIA-and storm-related electric fields in the ionosphere. Key points 1. Spatial analyses are essential to find pre-earthquake ionospheric anomalies (PEIAs). 2. PEIA-related electric fields can be estimated by using the ion velocity in the ionosphere. 3. China seismo-electromagnetic satellite is used to detect PEIAs and study ionospheric space weather.
Geomagnetism and Aeronomy, 2007
A very strong magnetic storm of May 15, 2005, was caused by an interplanetary magnetic cloud that approached the Earths' orbit. The sheath region of this cloud was characterized by a high solar wind density (~25-30 cm -3 ) and velocity (~850 km/s) and strong variations (to ~20 nT) in the interplanetary magnetic field (IMF). It has been indicated that an atypical bay-like geomagnetic disturbance was observed during the initial phase of this storm in a large longitudinal region at high latitudes: from the morning to evening sectors of the geomagnetic local time. Increasing in amplitude, the magnetic bay rapidly propagated to the polar cap latitudes up to the geomagnetic pole. An analysis of the global space-temporal dynamics of geomagnetic pulsations in the frequency band 1-6 mHz indicated that most intense oscillations were observed in the morning sector in the region of the equivalent ionospheric current at latitudes of about 72 ° -76 ° . The wavelet structure of magnetic pulsations in the polar cap and fluctuations in IMF was generally similar to the maximum at frequencies lower than 4 mHz. This can indicate that waves directly penetrated into the polar cap from the solar wind. PACS numbers: 94.30.Lr; 94.30.Ms
Variations in the ULF index of daytime geomagnetic pulsations during recurrent magnetic storms
Geomagnetism and Aeronomy, 2010
A new index of wave activity (ULF index) is applied to analyze daytime magnetic pulsations in the Pc5 range (f = 2-7 mHz) during ten successive recurrent magnetic storms (CIR (corotating interaction region) storms) of 2006. The most intense daytime geomagnetic Pc5 pulsations on the Earth's surface in all phases of CIR storms are predominantly observed in the pre noon sector at latitudes higher than 70°, while those in CME storms (storms initiated by coronal mass ejection (CME)) are observed at latitudes lower than 70°. A comparison of wave activity during CIR and CME storms has shown that the amplitude of Pc5 pulsa tions in CIR storms is much smaller than that in CME storms and the spectrum maximum is observed at lower frequencies and higher latitudes. At the same time, the mechanism of ULF wave generation during both types of magnetic storms seems to be similar, namely, resonance of magnetic field lines due to the develop ment of the Kelvin-Helmholtz instability caused by an approach of a high velocity solar wind stream to the Earth's magnetosphere. Since resonance oscillations are excited only in the closed magnetosphere, the higher latitude position of the Pc5 pulsation intensity maximum in CIR storms points to larger dimensions of the daytime magnetosphere during CIR storms as compared to CME storms.