Vol. pp. 2. ,**3 +,1 +-3 ˘ˇˆ˙ MeSO-net Various Types of ... · (MeSO-net), which consists of...
Transcript of Vol. pp. 2. ,**3 +,1 +-3 ˘ˇˆ˙ MeSO-net Various Types of ... · (MeSO-net), which consists of...
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Bull. Earthq. Res. Inst.
Univ. Tokyo
Vol. pp.
* e-mail : [email protected]
M
Earthquake Research Institute, the University of Tokyo
The Special Project for Earthquake Disaster Mitigation in the Tokyo Metropolitan Area has
been ongoing ( ). Under this project, the Metropolitan Seismic Observation network
(MeSO-net), which consists of about observation sites, has been constructed. The correlations of
waveform from local and teleseismic events are high because observation sites are deployed at
about or -km intervals. In addition, the later phase is easily identified although artificial noise is
very intense. However, we are attempting to improve quality by characterizing the various types
of noise.
In the metropolitan area, various human activities are observed that generate noise such as
trains, automobiles, aircrafts, factories, and electrical power. These adversely a ect our observa-
tions. We recognize various types of noise from continuous records. A spectral graph and a
spectrogram in each station are useful for characterizing signals and noise. We also discovered a
form of system noise obtained from the relationship between sensor and electrical circuit. We
named it Aurora Noise. The strength of Aurora Noise was reduced by improving the electrical
circuit.
Our study will lead to improving the quality of observed data, and contribute to a new
assessment of seismic hazard in the Tokyo Metropolitan Area in Japan.
: Metropolitan Seismic Observation network, noise reduction, spectrogram
M
.
M .
M M
M M
Fig. M
M .
,
*
Yuuko Kawakita * and Shin’ichi Sakai
Abstract
Key words
MeSO-net
Various Types of Noise in MeSO-net
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Fig. . Large earthquakes (M . ) occurring in the
metropolitan area over about years.
Fig. . Map of observation points in MeSO-net.Colors indicate year of deployment. Large square indicates area
of estimated Northern Tokyo-bay earthquake. Small squares indicate the Hi-net’s station and JMA’s station.
MeSO-net
Metropolitan
Seismic Observation network : MeSO-net
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MeSO-net
Fig. . Time sequence of amplitude for each station Fig. . Time sequence of amplitude strength for each
from : to : on Oct., . station from : to : on Oct., .
(a) YYIM, W , Yayoi, Bunkyo-ku, Tokyo. (b) GSJM, (a) YYIM, W , Yayoi, Bunkyo-ku, Tokyo. (b) GSJM,
TF , Tsukuba, Ibaragi. (c) GNZM, TF , Ginza, Chuo- TF , Tsukuba, Ibaragi. (c) GNZM, TF , Ginza, Chuo-
ku, Tokyo. ku, Tokyo.
MeSO-net
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Fig. . Waveforms observed by Tukuba-Fujisawa line are shown for Sep.,
Top is northern station and bottom is southern station. (a) Not filtered, from : to : , (b) Not filtered, from
: to : , (c) Low-pass filtered ( sec.), from : to : , (d) Low-pass filtered ( sec.), from : to : .
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MeSO-net
Fig. . Spectrums of each station for hour. Fig. . Spectrums of each station for hour.
Blue line indicates spectrum from : to : on Blue line indicates spectrum from : to : on
Oct., , and red line indicates from : to : , Oct., , and red line indicates from : to : ,
(a) YYIM, (b) GSJM, (c) GNZM. (a) YYIM, (b) GSJM, (c) GNZM.
AD Hz Hz
Hz Fig. MeSO-net
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Fig. . Spectrogram of YYIM from : to : on Oct., .
Color indicates amplitude strength : blue is normal level and red is strong. For example, red signal at about
: indicates an earthquake (M . ) occurring in Tokyo (blue allow). Red allows and green allows indicate
weak signal and more weak signal, respectively. Pink allow indicates continuous noise around Hz.
Fig. . Spectrograms of earthquakes observed at YYIM.
(a) Earthquake (M . , km depth) occurring in eastern
Tokyo on Oct., . (b) Earthquake (M . , km
depth) occurring at Suruga Bay on Aug,, . (c)
Earthquake (M . , km depth) occurring at Samoa
Islands in southern Pacific on Sep,, .
a P S
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MeSO-net
Fig. . Spectrogram of JDJM from : to : on Oct., .
and red is strong.
Fig. . Spectrograms of JDJM on Oct., .
and red is strong. (a) Spectrogram from : to : .
(b) Spectrogram from : to : . (c) Spectrogram
from : to : .
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Fig. . Spectrograms of DSCM on Nov., .
Fig. . Relation between amplitude strength and
distance from train line. and red is strong. Red allows indicate noise from an
Solid and open circles indicate strength of ground automobile. (a) Spectrogram from : to : . (b)
shake and the atmospheric shake. Spectrogram from : to : .
Fig. b
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Jul., . (b) YKKM from : to : on Dec., .
MeSO-net
Fig. . Spectrograms of each station from : to
: on Nov., . Fig. . Spectrograms of each station.
Color indicates amplitude strength : blue is normal
level and red is strong. (a) GNZM, (b) SKPM, (c) and red is strong. (a) KH M from : to : on
HGCM.
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Fig. . Map of border between Chiba Prefecture and
Ibaragi Prefecture. Solid circle and open triangle
indicate the site that observed aircraft signal and
planned site, respectively. Shaded line indicates
estimated flight course.
Fig. . Relation between time of aircrat signal and
distance from NGSM.
Fig. . Spectrograms of each station from : to
: on Oct., .
Color indicates amplitude strength : blue is normal
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: on May, .
Color indicates amplitude strength : blue is normal
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Fig. . Spectrograms of each component at YYIM from Fig. . Spectrograms at YYIM.
: to : on Feb., .
Color indicates amplitude strength : blue is normal and red is strong. EW-component from : to :
level and red is strong. (a) UD, (b) NS, (c) EW. on Oct., .
Fig. . Spectrograms at YYIM.
and red is strong. NS-component from : to : on
Aug., .
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MeSO-net
MeSO-net
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MeSO-net
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(Received November , )
MeSO- (Accepted January , )
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