Marine Ecosystems Research Department - jamstec japan agency ...

JAMSTEC 2002 Annual Report
Deep Sea Research Department
(System #) and south off Hokkaido over the forearc
of the Kuril Trench (System #). System # is laid out
km long over the Nankai Earthquake fault.
System # is laid out km long over the
Tokachi-oki Earthquake fault.
Both these M-class events are historically known
to recur. The data from these observatories are telemetered
to Japan Meteorological Agency and to
Yokohama branch institute of JAMSTEC (www.jamstec.go.jp/scdc/top_e.html).
We are currently planning
to establish the third cabled system near the
Tonankai Earthquake fault area off the Kii Peninsula.
The data from System # are contributing to the
improvement of hypocenters of offshore events
(Figure ). Also, the signal quality improved after
burying the seismographs (Figure ).
Depth (km)
Depth (km)
0
100
200
0
100
200
S30E
44˚
43˚
42˚
41˚
40˚141˚ 142˚ 143˚ 144˚ 145˚ 146˚ 147˚
N30W
0 100 200 300
Distance (km)
Depth (km)
A
0
100
200
0
100
200
0
100
B
S30E
C
B
N30W
A
C
b) Data transfer system upgrade
A significant change was made to the existing data
transfer system for improved data management and
data access. Data from all the cabled observatory
systems operated by JAMSTEC (#, # and
Hatsushima System off Hatsushima Island, Sagami
Bay) were transformed to comply with the IP (internet
protocol) network. The seismic data are now also
telemetered to the Hi-Net system (nationwide seismic
network) operated by NIED (National Institute for
Earth Science and Disaster Prevention). Our cabled
systems include video image data and they are now
sent via a HTTPD (hypertext transfer protocol daemon)
video server. These upgrades after tests will
become routine in .
200
0 100 200 300
Distance (km)
Fig. 5 Hypocenter distribution using both off-Kushiro–Tokachi
OBS's (denoted as KOBS's hereafter) and land-based
observations during the period from 20 April 2001 to 11
March 2003. Top: Epicenters and seismic station distribution.
Square and triangular symbols respectively denote locations
of KOBS's and land-based stations used in this study. Black
line is for the route of the off-Kushiro–Tokachi cabled system
(System #2). The two left figures show vertical cross sections
of hypocentral distribution in boxed area in the top figure:
The middle left figure is for an along-trench cross section,
and bottom left for a cross-trench. Three right figures
from the top to the bottom are all cross-trench vertical sections
denoted respectively as A, B and C in the top figure.
Microseismic activity in each area differs from those in the
other areas, from a point view of the hypocenter distribution.
22