Masashi Kamogawa

Natural time analysis of critical phenomena

A quantity exists by which one can identify the approach of a dynamical system to the state of criticality, which is hard to identify otherwise. This quantity is the variance of natural time χ, where and pk is the normalized energy released during the kth event of which the natural time is defined as χk = k/N and N stands for the total number of events. Then we show that κ1 becomes equal to 0.070 at the critical state for a variety of dynamical systems. This holds for criticality models such as 2D Ising and the Bak–Tang–Wiesenfeld sandpile, which is the standard example of self-organized criticality. This condition of κ1 = 0.070 holds for experimental results of critical phenomena such as growth of rice piles, seismic electric signals, and the subsequent seismicity before the associated main shock.

Atmospheric anomalies observed during earthquake occurrences

[1] Appearance of anomalies in the atmosphere before earthquakes (EQs) has been verified, through observation of anomalous transmission of VHF electromagnetic (EM) waves beyond line-of-sight. Anomalous increase of the received intensity for a few minutes - several hours on a day was identified by the previous 15-day running median and its inter-quartile range. The cross-correlation between the EQ occurrences and the anomalies shows that the appearance of anomalies was significantly enhanced within 5 days before M � 4.8 EQs. The one-day average number of the anomaly appearance within 5 days was found 2.4 times larger than that of other days. Through the polarization measurement of the received EM waves, the anomalies were found to occur in the atmosphere. INDEX TERMS: 6904 Radio Science: Atmospheric propagation; 6964 Radio Science: Radio wave propagation; 7223 Seismology: Seismic hazard assessment and prediction.Citation: Fujiwara, H., M. Kamogawa, M. Ikeda, J. Y. Liu, H. Sakata, Y. I. Chen, H. Ofuruton, S. Muramatsu, Y. J. Chuo, and Y. H. Ohtsuki (2004), Atmospheric anomalies observed during earthquake occurrences, Geophys. Res. Lett., 31, L17110,

Minimum of the order parameter fluctuations of seismicity before major earthquakes in Japan

It has been shown that some dynamic features hidden in the time series of complex systems can be uncovered if we analyze them in a time domain called natural time χ. The order parameter of seismicity introduced in this time domain is the variance of χ weighted for normalized energy of each earthquake. Here, we analyze the Japan seismic catalog in natural time from January 1, 1984 to March 11, 2011, the day of the M9 Tohoku earthquake, by considering a sliding natural time window of fixed length comprised of the number of events that would occur in a few months. We find that the fluctuations of the order parameter of seismicity exhibit distinct minima a few months before all of the shallow earthquakes of magnitude 7.6 or larger that occurred during this 27-y period in the Japanese area. Among the minima, the minimum before the M9 Tohoku earthquake was the deepest. It appears that there are two kinds of minima, namely precursory and nonprecursory, to large earthquakes.

Preseismic lithosphere‐atmosphere‐ionosphere coupling

Preseismic anomalous states in the atmosphere and ionosphere as well as those in the near-Earth (telluric) currents and ultralowfrequency electromagnetic variations have been, since the 1970s, reported as occurring prior to earthquakes. These preseismic phenomena have not yet been universally accepted, partly because the low occurrence frequency of large earthquakes has hindered establishing their statistical significance. Recent achievements in this respect, however, seem to be highly encouraging for promoting further studies on preseismic lithosphere-atmosphere-ionosphere (LAI) coupling.

Preseismic anomalous telluric current signals observed in Kozu-shima Island, Japan

Monitoring of telluric current, which is practically a synonym for geoelectric potential difference, was conducted on Kozu-shima Island about 170 km south of Tokyo from May 14, 1997 to June 25, 2000. During the monitoring period, 19 anomalous telluric current changes (ATCs) were observed. Their possible correlation with nearby earthquakes was statistically examined by assuming various lead times for different ranges of magnitude and focal distance. The best correlation may be obtained for earthquakes with a magnitude greater than 3.0 occurring within 20 km of focal distance. There were 23 such earthquakes, of which 11 were preceded by ATCs within 30 d. Of these 11 earthquakes, preceding ATCs of 5 and 6 were positive and negative polarities of telluric current, respectively. Their epicenters were spatially well clustered in the east and west of the island. These facts were clearly beyond those expected by chance and led to a simple speculative model.

Natural-time analysis of critical phenomena: The case of seismicity

We first investigate in natural time the numerical simulations of a simple deterministic self-organized critical system introduced to describe avalanches in stick-slip phenomena. It is one-dimensional and belongs to the same universality class as the train model for earthquakes introduced by Burridge and Knopoff. We show that the variance κ1=χ2−χ2 of natural time χ, becomes approximately equal to 0.070 when the system approaches the critical state. Next, we analyze in natural time the small earthquakes subsequent to the low-frequency magnetic-field precursor observed near the epicenter of the Ms7.1 Loma Prieta earthquake in 1989. We find that almost five days before the mainshock, the condition κ1≈0.070 was reached.

Spatiotemporal variations of seismicity before major earthquakes in the Japanese area and their relation with the epicentral locations.

Significance It was recently found that a few months before major earthquakes, the seismicity in the entire Japanese region exhibits a characteristic change. This change, however, can be identified when seismic data are analyzed in a new time domain termed “natural time.” By dividing the Japanese region into small areas, we find that some small areas show the characteristic change almost simultaneously with the large area and such small areas are clustered within a few hundred kilometers from the actual epicenter of the related major earthquake. This phenomenon may serve for forecasting the epicenter of a future major earthquake. Using the Japan Meteorological Agency earthquake catalog, we investigate the seismicity variations before major earthquakes in the Japanese region. We apply natural time, the new time frame, for calculating the fluctuations, termed β, of a certain parameter of seismicity, termed κ1. In an earlier study, we found that β calculated for the entire Japanese region showed a minimum a few months before the shallow major earthquakes (magnitude larger than 7.6) that occurred in the region during the period from 1 January 1984 to 11 March 2011. In this study, by dividing the Japanese region into small areas, we carry out the β calculation on them. It was found that some small areas show β minimum almost simultaneously with the large area and such small areas clustered within a few hundred kilometers from the actual epicenter of the related main shocks. These results suggest that the present approach may help estimation of the epicentral location of forthcoming major earthquakes.

Reply to Comment on “The Prediction of Two Large Earthquakes in Greece”

We welcome the critical comments of Papadopoulos [2010]. We must point out, however, that most of them are incorrect. First, on 1 February 2008, P. A. Varotsos et al. (Seismic electric signals and 1/f “noise” in natural time, version 3, 2008; available at http://arxiv.org/abs/0711.3766v3) did document the seismic electric signal (SES) activity for the M 6—class earthquake, recorded at station PIR (one of the SES measuring stations located close to Pirgos city in western Greece) on 14 January 2008, and assigned the epicentral area (approximately 250 × 250 kilometers). Two weeks after the documentation, the Mw 6.9 Greek earthquake in question occurred, on 14 February 2008. As to the occurrence time of this earthquake, the newspaper Ethnos on 10 February 2008 (http://www.ethnos.gr/article.asp?catid=11424&subid2&tag=8777&pubid=444473) reported it as “imminent.” Second, we did not mention two relatively small Patras shocks on 4 February 2008 simply because VAN also documented them (P. A. Varotsos et al., 2008, version 3) based on separate SES activity recorded on 10 January 2008 at Patras.

Preseismic Changes of the Level and Temperature of Confined Groundwater related to the 2011 Tohoku Earthquake

Anomalous groundwater changes started three months before the 2011 M9.0 Off the Pacific coast of the Tohoku Earthquake (Tohoku EQ), Japan. Groundwater level and temperature decreased almost simultaneously in a 2000-m well at a spa, Goyo-onsen, in Iwate Prefecture, 155 km northwest of the epicenter. Since the source of Goyo-onsen, located above the edge of a coseismic rupture area of the Tohoku EQ fault, is probably confined, the observed anomalies were caused probably by preseismic crustal deformation. Preseismic groundwater anomalies have been observed prior to similar large subduction EQs such as the 1946 M8.1 Nankai EQ. Thus, monitoring confined groundwater may be useful to identify precursors of large subduction EQs.

Experimental conditions for ball lightning creation by using air gap discharge embedded in a microwave field

An experiment was carried out to reproduce ball lightning by using microwave radiation and electric discharge without a metal cavity. When the energy of the discharge was high, a plasma fireball was produced. When high-power microwave existed, a plasma fireball was produced even if the power of the discharge was low. We must pay more attention to places where high-power electromagnetic waves exist to see ball lightning.