Possible Anomalous Changes in Solar Quiet Daily Geomagnetic Variation (Sq) Related to the 2011 off the Pacific coast of Tohoku Earthquake (Mw 9.0)

Seasonal Variation Characteristics of Geomagnetic Sq External and Internal Equivalent Current Systems in East‐Asia and Oceania Regions

“…r = R 0 is assumed, because  0 0 « r R R (Matsushita & Maeda, 1965). The expansion series is truncated at M = 8, N = 60 (Liu et al, 2019;Xu & Li, 1994;Zhao et al, 2014) based on the two considerations:…”

“…S q variation significantly depends on LT and latitude. One can use observations from a meridian chain instead of a global station network to deduce S q currents (Liu et al., 2019; Xu, 2003), if there are enough geomagnetic stations spreading in latitudinal direction. In present study, as shown in Figure 1, we utilize 20 geomagnetic observatories distributed in East‐Asia and Oceania regions, which adequately cover the low‐middle geographic latitudinal zone from −60° to 60°.…”

A Critical Review of Ground Based Observations of Earthquake Precursors

“…Similar results have been obtained by De Santis et al ( 2020) that have applied a multi-parametric study to the 2019 M7.1 Ridgecrest earthquake, by analysing furthermore methane exhalations [as suggested by Cui et al (2019)], electron density fluctuations, and magnetic field measurements from Swarm satellites (Friis-Christensen et al, 2006;Zhu et al, 2019). The results can be summarized as follows: 1) precursor times would be much longer than those identified by other papers (especially about ionospheric precursors which seem to occur only a few hours to days before large seismic events) (see for example Heki, 2011;He and Heki, 2017;Yan R. et al, 2017); 2) the preparation phase would be much longer than few days [as also suggested by Liu et al (2020), Marchetti et al (2019), Marchetti et al (2020), Sugan et al (2014), Giovambattista and Tyupkin (2004)]; claimed precursors would follow the empirical Rikitake (1987) law, recently confirmed for ionospheric precursors from the satellite by De Santis et al (2019a). In any case, it is a complex task to monitor several or all atmospheric effects due to the LAIC mechanism that also include linear cloud structures (the "earthquake clouds" that would repeat the shape of the tectonic structure in the sky (Jones and Stewart, 1997;Nissen et al, 2012); OLR [Ongoing Longwave Radiation-infrared emission at 10-13 μm recorded above the clouds (Ouzounov et al, 2007)]; jet streams (Wu, 2007); etc.…”

“…More recently, Han et al (2016) have reported statistical significant anomalies in the geomagnetic diurnal variation (GDV) of the vertical component in a long-term observations from 17 Japanese stations about 2 months before the 2011 Tohoku earthquake (Mw 9.0) confirming results of Xu et al (2013) and Han et al (2015) on the same event. Liu et al (2020) extended the study of the geomagnetic solar quiet daily (Sq) for the same Tohoku event: by analysing data from 20 geomagnetic observatories in the period 2009-2012 pointing out a relevant perturbation about one month and half before the earthquake.…”

Continental Earthquakes: Physics, Simulation, and Data Science—Introduction

“…Meanwhile, the magnitude of the anomalies decreases with the distance from the epicenter, and becomes difficult to identify outside the 500-km radius. Liu et al (2019) investigated the observational data from 20 geomagnetic observatories at longitudes of 130°E to 150°E between 2009 and 2012 in order to detect possible anomalous changes in the geomagnetic solar quiet daily (Sq) variation related to the 2011 Tohoku earthquake (M w 9.0) that occurred on March 11, 2011, off the Pacific coast of Japan. They confirmed that about 1.5 months before the earthquake there were significant anomalous variations in the observation.…”