Transcript Crustral structure across the Southern Japanese Alps segment of

Crustral structure across the
Southern Japanese Alps segment
of the Itoigawa-Shizuoka
Tectonic Line
Speaker: Yannis Panayotopoulos
North : Northern Fossa
Magna sedimentary
units and old
Japanese accretionary
prism rocks boundary.
South : Izu-Bonin units and
present Japanese
accretionary prism
rocks boundary.
I.S.T.L
Mt. Fuji 
A 5 year project aiming to investigate the tectonic
setting along ISTL.
Derive a 3d velocity model for the entire ISTL
region and correlate it with the geologic structures
in the area.
Correlate the regional seismicity with movement of
the different segments of the ISTL fault system.
2005 research: The south central part of ISTL in
the Southern Japanese
Alps and Kofu
basin area.
• 2 station arrays with
26 and 30 stations
each with 1-1.5 km
spacing.
• 6 stations (+ 8 AIST)
distributed in the area.
• 100 telemetric stations
(JMA, NAID, UNI)
• 3 component 1 Hz
seismometers and
removable HD
recorders.
• Recording period
from 2005/09/16 to
2005/12/22
• Reprocessed 610 JMA
catalog data from
2005/09/01 to 2005/12/31
• 83,053 P and S phase
arrivals (31,147 JMA)
• 348 events and 11 shots
(100~300 kg) selected for
tomography inversion
Vp (km/sec)
4
5
6
7
8
9
0
5
Depth (km)
10
15
20
25
30
35
40
ERI
ERI average
Method：
Double-difference
tomography
(Zhang and Thurber 2003)
Grid points：
x: 5km spacing for the
central 60km、１５ｋｍ
or ２０ｋｍ in the
perimeter.
y: 9 lines at -54, -32, 16, -8, 0, 8, 16, 32, 54
km.
At depth:
0、3, 6, 9, 12,16, 20,
30, 35, 100, 200 km
Checkerboard resolution test for
the grid lines located at 8, 0, -8 km.
SW
NE
SW
NE
SW
NE
Vp cross sections for the grid lines
located at 8, 0, -8 km.
SW
NE
SW
NE
SW
NE
Major geological units in the area.
Yatsugatake Volcano
Chichibu Belt
Ryoke belt: Granitic rocks. Simanto belt:
flysch, shale and chert.
ISTL
Chichibu belt: pillow basalt, reef limestone
radiolarian chert.
Ryoke Belt
MTL
Active Fault
ISTL Mt. Fuji
Shimanto Belt
Izu-Bonin
Estimated 450 rotation angle of the
Japanese ark in Kii area after the
Sea of Japan clockwise movement
(kano 1990).
Izu-Bonin ark tip prevented the
clockwise rotation in the area.
Apparent maximum 120 km
counterclockwise movement of MTL.
Yatsugatake volcano: Volcanic tuffs.
Izu-Bonin: Volcanic rocks
Kano et al (2002,1990)
MTL
SW
G.ISTL
ChichibuShimanto
SW
MTL
NE
Yatsugatake
Volcano?
G.ISTL
Geological ISTL dipping to the west at
450 ~ 550.
Seismicity may be related to ISTL
movement at the northern cross
section (8 km).
SW
MTL
NE
Kofu Basin
ChichibuShimanto
Apparent 10~15 km shortening of the
Chichibu-Shimanto units.
A.ISTL
G.ISTL
A.ISTL
NE
Kofu Basin
ChichibuShimanto
?
The ISTL seems to be the boundary between
the accretionary prism units and the IzuBonin arc sequences.
It forms a thrust fault that deeps approximately
500 towards the west.
The seismicity at the northern profile may be
connected to the deeper part of the ISTL.