Distribution of the Metropolitan Seismic Observation network

 Bull. Earthq. Res. Inst.
Univ. Tokyo
Vol. 2. ,**3 pp. /1῏03
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Distribution of the Metropolitan Seismic Observation
network
Shin’ichi Sakai* and Naoshi Hirata
Earthquake Research Institute, the University of Tokyo
Abstract
The Special Project for Earthquake Disaster Mitigation in the Tokyo Metropolitan Area has
been ongoing (,**1῏,*+,). Under this project, the Metropolitan Seismic Observation network
(MeSO-net), which consists of about .** observation sites, has been constructed. This network
consists of five dense linearly arrayed stations and evenly spaced stations. This five liner arrays
focus on observing highly active seismicity, many repeating earthquakes, slow slip area, and
historical large earthquakes. The correlations of waveform from local and teleseismic events are
high because observation points are deployed at about , or --km intervals. In addition, identification of any stations of the later phase is easy even if artificial noise is very intense. These widely
developed stations have been used e#ectively for the seismic tomography method. These dense
intervals of MeSO-net will induce a more highly resolved structure than previous studies. MeSO-net
has observed earthquakes of more than M ,.*. Low-frequency waveforms of less than *.+ Hz have
been observed by MeSO-net. The distribution of amplitudes observed at each station show
heterogeneous amplification of shaking motions.
Our study will lead to improved quality of plate structure, and contribute to a new assessment
of seismic hazards in the Tokyo Metropolitan Area, Japan.
Key words : MeSO-net, dense seismic observation, seismic sensitivity, heterogeneous amplification
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58 Fig. +. Distribution of seismic stations of MeSO-net.
Color indicates year station was established. Dots indicate stations under development.
Large square and small squares indicate area of estimated Northern Tokyo-Bay
Earthquake and stations still to be developed within it.
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59 ῌ Fig. ,. Distribution of earthquakes of more than M ,.* are shown with MeSO-net.
Color indicates focal depth. Earthquakes were determined by MeSO-net (,**2. .. +ῌ,**3. 3. -*).
Fig. -. Waveforms of earthquake (M ,./, depth-* km) occurring at northern Tokyo-bay on +1 Oct.,
,**3 observed by the Tsukuba-Fujisawa line. Top is northern station and bottom is southern station.
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61 ῌ Fig. .. Waveforms of earthquake (M ,.-, Depth,0 km) occurring in Setagaya-ku, Tokyo on 0 Jul.,
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Fig. /. Distribution of magnitude of amplitude of MeSO-net.
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List of the seismic stations of the MeSO-net that started in ,**1.
65 ῏῍ῐ῎ῌΐῒ ῑ
Table ,.
List of the seismic stations of the MeSO-net that started in ,**2.
ῌ 66 ῌ
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67 ῏῍ῐ῎ῌΐῒ ῑ
Table -.
List of the seismic stations of the MeSO-net that started in ,**3.
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Igarashi, T., ,**3, Seismic velocity discontinuities in the
crust and uppermost mantle beneath the Kanto district,
central Japan, identified from receiver function imaging and repeating earthquake activity, Gondwana Research, +0, -῍., .3+῍/*-.
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Kimura, H., K. Kasahara, T. Igarashi and N. Hirata, ,**0,
Repeating earthquake activities associated with the
Philippine Sea plate subduction in the Kanto district,
central Japan : A new plate configuration revealed by
interplate aseismic slips, Tectonophysics, .+1, +῍,, +*+῍
++2.
Matsubara, M., K. Obara, and K. Kasahara, ,**2, Three-
dimensional P- and S-wave velocity structures beneath
the Japan Islands obtained by high-density seismic
stations by seismic tomography, Tectonophysics, ./.,
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E#ect of slab-slab contact and overlap on seismicity, J.
Geophys. Res., ++., B*2-*3, doi : +*.+*,3/,**2JB**0+*+.
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