Annales Geophysicae, 23, 1335–1346, 2005
SRef-ID: 1432-0576/ag/2005-23-1335
© European Geosciences Union 2005
Annales Geophysicae
Anomalous effect in Schumann resonance phenomena observed in
Japan, possibly associated with the Chi-chi earthquake in Taiwan
M. Hayakawa1, K. Ohta2, A. P. Nickolaenko1,3, and Y. Ando1
1 The University of Electro-Communications, Department of Electronic Engineering,
1-5-1 Chofugaoka, Chofu Tokyo 182-8585, Japan
2 Chubu University, Department of Electronics Engineering, 1200
Matsumoto-cho Kasugai, Aichi, 487-8501, Japan
3 Institute of Radiophysics and Electronics, Academy of Sciences of Ukraine, Kharkov, Ukraine
Received: 6 December 2004 – Revised: 14 February 2005 – Accepted: 22 February 2005 – Published: 3 June 2005
Abstract.
[expand]The Schumann resonance phenomenon has been
monitored at Nakatsugawa (near Nagoya) in Japan since the
beginning of 1999, and due to the occurance of a severe
earthquake (so-called Chi-chi earthquake) on 21 September
1999 in Taiwan we have examined our Schumann resonance
data at Nakatsugawa during the entire year of 1999. We have
found a very anomalous effect in the Schumann resonance,
possibly associated with two large land earthquakes (one is
the Chi-chi earthquake and another one on 2 November 1999
(Chia-yi earthquake) with a magnitude again greater than
6.0). Conspicuous effects are observed for the larger Chi-chi
earthquake, so that we summarize the characteristics for this
event.
The anomaly is characterized mainly by the unusual
increase in amplitude of the fourth Schumann resonance
mode [see below - arc-us]and a significant frequency shift of its peak frequency
(1.0 Hz) from the conventional value on the By magnetic
field component which is sensitive to the waves propagating
in the NS meridian plane. Anomalous Schumann resonance signals
appeared from about one week to a few days
before the main shock. Secondly, the goniometric estimation
of the arrival angle of the anomalous signal is found to
coincide with the Taiwan azimuth (the unresolved dual direction
indicates toward South America). Also, the pulsed
signals, such as the Q-bursts, were simultaneously observed
with the “carrier” frequency around the peak frequency of
the fourth Schumann resonance mode. The anomaly for the
second event for the Chia-yi earthquake on 2 November had
much in common. But, most likely due to a small magnitude, the
anomaly appears one day before and lasts until
one day after the main shock, with the enhancement at the
fourth Schumann resonance mode being smaller in amplitude than
the case of the Chi-chi earthquake. Yet, the other
characteristics, including the goniometric direction finding
result, frequency shift, etc., are nearly the same. Although
the emphasis of the present study is made on experimental
aspects, a possible generation mechanism for this anomaly
s discussed in terms of the ELF radio wave scattered by a
conducting disturbance, which is likely to take place in the
middle atmosphere over Taiwan.
Model computations show
that the South American thunderstorms (Amazon basin) play
the leading role in maintaining radio signals, leading to the
anomaly in the Schumann resonance.
Keywords. Ionosphere (Ionospheric disturbances) – Electromagnetics
(Wave propagation) – Meteorology and atmospheric dynamics (Lightning)
Abstract here:
http://www.ann-geophys.net/23/1335/2005 ... -2005.html
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