Criticality Analysis of the Lower Ionosphere Perturbations Prior to the 2016 Kumamoto (Japan) Earthquakes as Based on VLF Electromagnetic Wave Propagation Data Observed at Multiple Stations

Abstract

Abstract:The perturbations of the ionosphere which are observed prior to significant earthquakes (EQs) have long been investigated and could be considered promising for short-term EQ prediction. One way to monitor ionospheric perturbations is by studying VLF/LF electromagnetic wave propagation through the lower ionosphere between specific transmitters and receivers. For this purpose, a network of eight receivers has been deployed throughout Japan which receive subionospheric signals from different transmitters located both in the same and other countries. In this study we analyze, in terms of the recently proposed natural time analysis, the data recorded by the above-mentioned network prior to the catastrophic 2016 Kumamoto fault-type EQs, which were as huge as the former 1995 Kobe EQ. These EQs occurred within a two-day period (14 April: M W = 6.2 and M W = 6.0, 15 April: M W = 7.0) at shallow depths (~10 km), while their epicenters were adjacent. Our results show that lower ionospheric perturbations present critical dynamics from two weeks up to two days before the main shock occurrence. The results are compared to those by the conventional nighttime fluctuation method obtained for the same dataset and exhibit consistency. Finally, the temporal evolutions of criticality in ionospheric parameters and those in the lithosphere as seen from the ULF electromagnetic emissions are discussed in the context of the lithosphere-atmosphere-ionosphere coupling.

Study in Natural Time of Geoelectric Field and Seismicity Changes Preceding the Mw6.8 Earthquake on 25 October 2018 in Greece

“…In Table 8.1 of Reference [ 6 ], one can find a compilation of 14 cases including a variety of dynamical models in which the condition = 0.070 has been ascertained (cf. this has been also later confirmed in the analyses of very recent experimental results in Japan by Hayakawa and coworkers [ 55 , 56 , 57 ]). Especially for the case of SES activities, it has been found that, when they are analyzed in natural time, we find values close to 0.070 ([ 35 , 36 , 38 , 39 ], e.g., see Table 4.6 on p. 227 of Reference [ 6 ]), i.e., when analyzing in natural time the small EQs with magnitudes greater than or equal to a threshold magnitude that occur after the initiation of an SES activity within the selectivity map of the measuring station that recorded the SES activity, the condition is found to hold for a variety of a few days up to one week before the strong EQ occurrence [ 6 , 30 , 40 , 41 , 44 , 45 , 46 , 47 , 54 , 58 ] .…”

Tsallis Entropy Index q and the Complexity Measure of Seismicity in Natural Time under Time Reversal before the M9 Tohoku Earthquake in 2011

“…[ 11 ], one can find a compilation of 14 cases in which the condition = 0.070 has been ascertained. (This was also later confirmed in the analyses of very recent experimental results in Japan by Hayakawa and coworkers [ 45 , 46 ].) In addition, natural time has been recently employed by Turcotte and coworkers [ 47 , 48 , 49 , 50 ] as a basis for a new method to estimate the current level of seismic risk.…”

On the Statistical Significance of the Variability Minima of the Order Parameter of Seismicity by Means of Event Coincidence Analysis

“…NTA has found applications in a wide variety of fields ranging from cardiology (see, e.g., [12][13][14][15]) to statistical physics (see, e.g., [16][17][18][19][20][21]), and atmospheric science (see, e.g., [22][23][24]). One of the main applications of NTA, however, is the study of the physics of EQs (see, e.g., [25][26][27][28][29][30][31][32][33][34][35][36][37]). In addition, natural time is considered as the basis of the "nowcasting earthquakes" methodology that has been introduced recently [38][39][40][41][42][43][44][45][46].…”