Anomaly disturbances of the magnetic fields before the strong earthquake in Japan on March 11, 2011

Abstract

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 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.

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

“…The amplitude-phase gradient method assumes that ULF wave horizontal propagation velocity is determined by crust conductivity as follows U = λ/T = 10ρ/T , where the relation of the wavelength with resistivity was used λ = 10ρT . The gradient method enabled to seemingly successfully retrieve seismogenic signals several months before nearby EQs with M = 5-6 in Japan at a distance <100 km [Kopytenko et al, 2012]. The measured amplitude gradient in the band 0.03-0.1 Hz (Pc2-3 band) was typically around G ≈ 0.1-1 pT/km, and phase velocity U ≈ 20-100 km/s.…”

“…To choose a proper frequency range not contaminated by the resonant effect, the theoretically calculated latitudinal profile of fundamental Alfven period T A (Φ) can be used [Menk and Waters, 2013]. Notice, the results presented in [Ismaguilov et al, 2003;Kopytenko et al, 2012] were obtained at low latitudes for geomagnetic signals with periods around the resonant periods. Thus, the gradient method of seismic-related signal detection must be supported by the examination of reso- nant effects, and can be performed only in a frequency-space domain far from the resonant region.…”

Seismo Electromagnetics and Earthquake Prediction: History and New directions

“…(a) Lithospheric effects. Kopytenko et al (2012) investigated the magnetic field variations at three observatories (Esashi, Mizusawa, and Kakioka) over the 11-year period of 1 January 2000 through 31 January 2011. They found a medium-term anomaly around 3 years before the EQ, and also a short-term precursor in the ULF frequency range of 0.0033-0.01 Hz was observed starting 22 February 2011.…”

Criticality features in ultra-low frequency magnetic fields prior to the 2013 M6.3 Kobe earthquake

“…Based on extensive studies during the last few decades it is recently plausible that electromagnetic (EM) phenomena do appear prior to an earthquake (EQ) [Hayakawa and Molchanov 2002, Pulinets and Boyarchuk 2004, Molchanov and Hayakawa 2008, Hayakawa 2009, Hayakawa 2012, Hayakawa 2013. Such possible EQ precursors include lithospheric phenomena such as DC geoelectric field, ultra-low-frequency (ULF) radiation, fracto-EM MHz -kHz emissions, and seismoatmospheric and -ionospheric perturbations.…”

“…Then, ULF emissions in possible association with the 1993 Guam EQ (M=8.0) were found [Hayakawa et al 1996, Kawate et al 1998]. A number of other studies reporting lithospheric ULF electromagnetic emissions have also been published [e.g., Kopytenko et al 1994, Molchanov and Hayakawa 1998, Kopytenko et al 2001, Ismaguilov et al 2001, Ismaguilov et al 2002, Kopytenko et al 2003, Kopytenko et al 2007, Molchanov 2011, Kopytenko et al 2012. Though there have recently been published a few papers casting a doubt that those ULF emissions were not seismogenic, but just an effect of geomagnetic storms [e.g., Campbell 2009], their arguments were not adequate to deny the presence of seismogenic ULF emissions.…”