[Moment tensor solution]
〓 Question No.17 2008/06/10
Tell me about the velocity structure which you use for moment tensor calculation.
Answer
We use the horizontal multilayered velocity structure.
The structure is as follows.
Depth Thickness Pvelocity Svelocity Density Qp Qs
(km) (km) (km/s) (km/s) (kg/m^3)
0 3 5.50 3.14 2300 600 300
3 15 6.00 3.55 2400 600 300
18 15 6.70 3.83 2800 600 300
33 67 7.80 4.46 3200 600 300
100 125 8.00 4.57 3300 600 300
225 100 8.40 4.80 3400 600 300
325 100 8.60 4.91 3500 600 300
425  9.30 5.31 3700 600 300
You can find this model in
Kubo,A.,E.Fukuyama,H.Kawai,K.Nonomura,2002, NIED seismic moment tensor catalogue
for regional earthquakes around Japan: quality test and application,Tectonophysics, 356,2348
〓 Question No.11 2001/01/25
I have a couple of questions concerning the result of the moment tensoranalysis.
Above which magnitude does the catalog include all the events?
Do you have any references to quote about the results of the moment tensor analysis?
Answer
We have been analyzing the earthquakes whose magnitude is greater than 3.5 based on the
Emergent hypocenter information by JMA (Japan Meteorological Agency)
as well as on the Unifyed hypocenter catalog maintained by JMA.
However, we do not show all the result but the earthquakes whose variance reduction
(an index to measure the fit between observation and synthetics, 100% means perfect fit)
is greater than 50% are shown in the catalog.
Generally speaking, most of M4 earthquakes will be included.
But during the swarm activity or after the huge earthquake at teleseismic distance,
the waveforms are contaminated and it becomes difficult to analyse the waveforms.
Thus these earthquakes are dropped in the catalog. Unfortunately we did not conduct the statistical
analysis on this matter, so that we could only say the qualitative answer at this time.
As for the reference of the moment tensor analysis, please refer to the following paper:
Fukuyama, E., S. Ishida, D. S. Dreger and H. Kawai (1998) Automated
seismic moment tensor determination by using online broadband seismic waveforms,
Zisin (J. Seismol. Soc. Jpn) Ser. 2, 51, 149156
(in Japanese with English abstract).
[Miscellaneous]
〓 Question No.18 2008/06/10
I need any publications who specify the specifications of Fnet
Answer
We suppose this paper will provide all the information you need.
Okada, Y, Kasahara, K, Hori, S, Obara, K, Sekiguchi, S., Fujiwara, H., and Yamamoto, A.,
Recent progress of seismic observation networks in Japan Hinet, Fnet, KNET and KiKnet, Earth,
Planets and Space, Volume 56, p. xvxxviii, 2004

