Investigation of ULF magnetic disturbances in Japan during seismic active period

Abstract

Results of investigation of ULF electromagnetic disturbances recorded in Japan during a seismic active period are discussed. Observations were carried out at two magnetic stations located at a distance ~4 km along a geomagnetic meridian. A central zone of the seismic activity was situated ~35 km East of the magnetic stations at the depth ~3 km under sea bottom. Methodological aspects of data processing are considered in connection with large industrial noise observed in the territory of Japan. A digital filtration and spectral method were used to calculate RMS values of H, D, and Z components of magnetic variations. The data were filtered in 4 frequency ranges f 1 =0.2-2.5 Hz, f 2 =0.05-0.2 Hz, f 3 =0.01-0.05 Hz, and f 4 =0.002-0.0l Hz for 2, 4 and 8-hours nighttime intervals of each day during the period 21.03-02.06.1998. It is found that RMS values of raw data increase during the bursts of the seismic activity. Ratios of RMS values of Z component to the horizontal ones (Z/H, Z/D, ZIG) increase ~ 15 days before a start of the seismic active period, then the they decrease and reach their minimum at the moment of an earthquake (strongest shock Ms=5. 7), followed by a smooth relaxation of these ratio values. The availability of two magnetic stations gives an opportunity to define gradients of the electromagnetic disturbances. The RMS values of the gradients and the ratios of Z component gradients to the horizontal ones are found to exhibit the same temporal evolutions as the raw data.

A Closer Cooperation between Space and Seismology Communities – a Way to Avoid Errors in Hunting for Earthquake Precursors

“…The phase shift ∆φ corresponds to an apparent phase velocity U = ω(∂φ/∂x) −1 . The measurements in [Ismaguilov et al, 2003;Kopytenko et al, 2002] were made for Pc3 frequency band (0.05 Hz). For the reasonable values Γ ~0.1, a~10 3 km, the apparent phase velocity in the resonant region is to be U~25 km/s.…”

“…To identify anomalies, the parameter ∆S was used, which is the reciprocal value of the Figure 6. The gradients and phase velocities of anomalous ULF signals in Pc3 frequency band (0.05 Hz) detected before EQ by gradient method in [Ismaguilov et al, 2003;Kopytenko et al, 2002].…”

“…The observational results indicated that it is promising to study such phenomena in the ultra-low-frequency (ULF) range (10 mHz-10 Hz) [Petraki et al, 2015]. The signatures of anomalous electromagnetic ULF activity near the epicenter hoursdays before EQs were reported (see numerous articles in monographs [Hayakawa, 2009[Hayakawa, , 2013Hayakawa and Molchanov, 2002]). Several types of ULF geomagnetic anomalies were noticed: the appearance of broadband electromagnetic noise [Molchanov et al, 1992]; a change in the spectral composition [Hayakawa et al, 1999]; changes in the polarization structure [Hayakawa et al, 1996].…”

Аномалия Геомагнитного Поля, Предшествующая Возникновению Землетрясений На Территории Республики Армения И Сопредельных Районов

“…Как известно, землетрясения часто сопровождаются аномальными электромагнитными возмущениями. За последние годы некоторые авторы занимались установлением и изучением этих связей, и результаты их исследований не оставляют сомнения в том, что подобная связь существует [9][10][11][12][13][14][15][16][17][18][19][20][21].…”

Влияние Звуковой Волны Нарадиальный Температурный Градиент Газа Положительного Столба

“…К ним относятся, например, влияние на такие параметры плазмы, как напряженность электрического поля внутри плазмы, распределение концентрации заряженных частиц, которое тесно связано с температурой газа [1,2]. Акустические волны также могут воздействовать на совокупность заряженных частиц и вызывать излучение электромагнитных волн в различных диапазонах -от УНЧ до светового [3][4][5]. Второе направление -влияние плазмы на параметры акустических волн, например, усиление звука и нестабильности в плазме [6].…”