( 1 ) Anomalous pre-seismic transmission of FM radio waves resulting from
large earthquakes, and its statistical relationship to magnitude of impending
earthquakes
( 2 ) Recent anomaly of Eq echoes observed at Hokaido, Honshu and Kyushu stations
Takeo Moriya
2012, Dec. 19.
Institute for Seismology and Volcanology, Graduate school of Science, Hokkaido University
( 1 )
To confirm the
relationship between anomalous transmission of VHF-band radio waves and
impending earthquakes, we designed a new data-collection system and have
documented the anomalous VHF-band radio-wave propagation beyond the line of
sight prior to earthquakes since December 2002 in Hokkaido, northern Japan.
Anomalous VHF-band radio waves were recorded before two large earthquakes, the
Tokachi-oki earthquake (Mj=8.0, Mj: magnitude defined by the Japan
Meteorological Agency) on 26 September 2003 and the southern Rumoi
sub-prefecture earthquake (Mj=6.1) on 14 December 2004.
Radio waves transmitted from a given FM radio station are considered to
be scattered, such that they could be received by an observation station beyond
the line of sight.
A linear relationship
was established between the logarithm of the total duration time of anomalous
transmissions (Te) and the magnitude
(M) or maximum seismic intensity (I) of the impending earthquake, for
M4-M5 class earthquakes that occurred at depths of 48 to 54 km beneath the
Hidaka Mountains in Hokkaido in June 2004 and
August 2005. Similar linear relationships are also valid for earthquakes that
occurred at different depths. The relationship was shifted to longer Te for shallower earthquakes and to
shorter Te for deeper ones. Numerous
parameters seem to affect Te,
including hypocenter depths and surface conditions of epicentral area (i.e.,
sea or land). This relationship is important because it means that pre-seismic
anomalous transmission of VHF-band waves may be useful in predicting the size of
an impending earthquake. It is suggested that movement of positive hole from
source region when stress is increasing, proposed by Freund (2000), is deeply
related to the creation of the EQ echo.
Figure 1. Plane schema for propagation of EQ echoes, which maybe
created on the epicenter of impending earthquake in the service area of FM
station.
Figure 2. Many kind of abnormal propagation of VHF waves. EQ echo is
created near the surface, and independent from ionosphere disturbance.
Figure 3. Time chart of EQ echoes and earthquake.
Te, total duration time, is very important information,
M and maximum intensity about
impeding earthquake.
Figure 4. Location of observing (○) and transmitting (△:
FM broadcasting, ▲: 64 MHz transmitting
)stations in the Hokkaido Island, Japan.
Figure 5. Example records of scattering waves associated by sporadic E
layer disturbance. On the record of ERM, EQ echo
from HOO can be seen on the blue colored trace. This suggests
EQ echo is quite local phenomena and independent from ionosphere disturbance.
Figure 6. Example records of EQ echoes observed at ERM station before Hidaka Mountains earthquake. Usually FM wave
from HOO is interrupted by summit of Hidaka Mountains and cannot reach to ERM.
Variation pattern of the EQ echo is quite differ from other anomalous propagations, and easily can be distinguished.
Figure 7. Log (Te) versus Imax. Te is total duration times of EQ
echoes observed before an earthquake.
Linear relation between Log (Te) and Imax
can be seen. A quantitative
relation between Imax and Te seems to establish.
This is evidence that Te is earthquake
precursor.
Figure 8. Distribution of epicenter (○) before which EQ echoes from HOO (△) were observed (X, not observed) at ERM (●).
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( 2 )
Recent anomaly of Eq echoes observed at Hokaido, Honshu and Kyushu stations