Teleseismic magnetic effects (TMDs) of 2011 Tohoku earthquake

Abstract

[1] Anomalous magnetic variations were observed by ground magnetometers in East Asia area after the 2011 Tohoku earthquake. Some earlier reports showed that the seismo-magnetic variations have obvious amplitude around the epicenter, we emphasis here that the variations can still be notable at stations 2000-4000 km away from epicenter, and we define it as teleseismic magnetic disturbances (TMDs). TMDs appear about 8 min later after the arrival of seismic Rayleigh waves at teleseismic distances and propagate at a horizontal velocity of 3.9 AE 0.1 km/s. The wave-like TMDs last for no longer than 10 min and have a main period of 2.1-3.3 min. TMDs are not generated by direct effects of processes in focal area crust or tsunami waves, instead, their properties consist with the Rayleigh wave model of seismo-ionospheric disturbances. Hence, we conclude that the TMDs are the magnetic manifestation of seismotraveling ionospheric disturbances (STIDs) generated by the interaction between the ionosphere and atmosphere through acoustic waves launched by traveling Rayleigh waves. Our findings contribute to the knowledge of seismo-electromagnetic effects in the atmosphere-ionosphere system and further our understanding of couplings between various spheres of the Earth.

Latitude and Longitude Dependence of Ionospheric TEC and Magnetic Perturbations From Infrasonic‐Acoustic Waves Generated by Strong Seismic Events

“…Figures 4b, 4d, 4f, and 4h show the geomagnetic field perturbations at ground level due to the AW-generated dynamo currents (e.g., Figure 3). The magnetic field perturbations maximize at ∼1.5-2 nT PTP which is roughly consistent with reported observations of magnetic fluctuations following the 2011 Tohoku EQ (Hao et al, 2013;Utada et al, 2011). Fields produced by ionospheric dynamo effects initially have very complicated nondipolar structure (see also rotation of features in the field components in Movies S9-S11)-consistent with the complicated field-aligned current structures shown in Figure 3.…”

“…Recent interest has focused on piezomagnetic effects associated with stress buildup and release in a fault before and during large EQs (e.g., Utada et al, 2011, and references therein). Although the M 9.1 11 March 2011 Tohoku EQ (Hao et al, 2012(Hao et al, , 2013Utada et al, 2011) apparently generated magnetic field fluctuations, there was additional evidence for coseismic magnetic perturbations. Although the M 9.1 11 March 2011 Tohoku EQ (Hao et al, 2012(Hao et al, , 2013Utada et al, 2011) apparently generated magnetic field fluctuations, there was additional evidence for coseismic magnetic perturbations.…”

Weak ionization of the global ionosphere in solar cycle 24

“…An ultra weak solar cycle or grand solar minimum will also provide a suitable moment for researchers to continue with the investigation of non-solar forcing made during the declining phase and minimum of SC23, which have greatly improved our understanding of energy coupling between the lower and upper atmospheres (see the review articles by Laštovička, 2009 andPancheva andMukhtarov, 2012). Various sources of energy from below have been found effectively to disturb the ionosphere, such as the modulation of the ionosphere by planetary waves , spread F triggered by gravity waves from cyclones in the troposphere (Xiao et al, 2009;Xiao et al, 2012), and ionospheric disturbances caused by upward propagation of atmospheric infrasonic waves (Hao et al, , 2013.…”

Co-seismic signatures in magnetometer, geophone, and infrasound data during the Meinong Earthquake

“…Nevertheless, the long lasting co-seismic pulsations appearing at the CC station might be due to the ground water and underground structure around Meishan fault being complex (Yen et al 2008;Ching et al 2011;Wilcox et al 2011). By contrast, researchers (Iyemori et al 2005;Hao et al 2013;Yen et al 2015;Liu et al 2016a) observe that seismo-magnetic pulsations with much longer period (low frequency) constantly lag seismic wave pulses by about 200+ minutes, suggesting that ionospheric conductivity affects magnetic fields. Since there is almost no time lag between magnetic pulsations and seismic waves at each co-located station, the co-seismo magnetic pulsation is unlikely related to the ionospheric conductivity.…”

“…Traditionally, seismometers (also geophones) record seismic waves monitoring the Earth's surface motion (Shearer 1999), and infrasound systems measure atmospheric pressure changes induced by the Earth's surface motion and/or seismic waves, mainly Rayleigh waves, on the ground (Mutschlecner and Whitaker 2005;Liu et al 2006Liu et al , 2010Liu et al , 2016a. Meanwhile, scientists report magnetic pulsations triggered by seismic waves (Iyemori et al 1996(Iyemori et al , 2005Honkura et al 2002;Abdul Azeez et al 2009;Widarto et al 2009;Hao et al 2013;Gao et al 2014;Yen et al 2015;Liu et al 2016a). However, in previous co-seismic geomagnetic variations observed in time scale of seconds were rare, because the amplitude is rather small.…”