68 2005 9
175
1.1.1
1980 COCORP Brown, 1991 Lithoprobe Cook et al., 1992
laminate
Improved Mapping Method for Deep Crustal Imaging - Application to Wide-angle Refl ectionData in the Southwest Japan Arc and its Interpretation -
Tetsuya TAKEDA
Solid Earth Research Group,National Research Institute for Earth Science and Disaster Prevention, Japan
Abstract
Wide-angle refl ection data often show remarkable refl ections from the deep crust. In order to obtain new images of crustal inhomogeneity beneath the southwest Japan arc, I propose an improved mapping method designed for sparsewide-angle refl ection data. The method, an improved form of the Common Scatter-Point (CSP) stacking method, has theadvantages of both the Common Mid-Point (CMP) and CSP stacking methods, which means that it can add a migrationeffect to the CMP method, and has less of the ghost curves that results from the CSP method. When applied to twosets of wide-angle reflection data (the 1988 Kawachinagano-Kiwa profile and the 1989 Fujihashi-Kamigori profile),the method provided clear images of the subducting Philippine Sea plate and the island-arc’s lower crust. The mainresults are as follows: (1) Intra-plate seismic activity is concentrated within the oceanic mantle, which suggests that theoceanic mantle may be subject to dehydration embrittlement; and (2) The lower crust beneath the southwest Japan archas strong inhomogeneity, with a wavelength ranging from several to a dozen kilometers, which may result from crustalreconstruction due to igneous activity that has occurred since the Cretaceous.
Key words : Common Scatter-Point (CSP) stacking method, Wide-angle refl ection, The 1988 Kawachinagano-Kiwa profi le, The 1989 Fujihashi-Kamigori profi le, The Philippine Sea plate
Allmendinger et al., 1986Moho
MohoMoho 3-5km
Hale and Thompson, 1982
1.2
1985,
68 2005 9
176
1999km
Ikami et al., 1986, Takeda et al., 2004, 1997
PnMoho
32-35km27km
Iwasaki et al., 2001P S
Moho
TASP Sato et al.,1998Iwasaki et al., 1999
Vibroseis®
Lithoprobe
pop-up1999
Vibroseis®
Moho
1.3
Chang et al. 1989Zelt et al. 1998 Chang et al.
1989
Zelt et al. 1998 syntheticOBH Ocean-Bottom Hydrophone
OBH 2km4%
1991 Matsu’ura et al. 19911991
CMP
CMP
100m
1999
S/N
S/N1 100m
1.4
1.1Moho
1.11989 S-1
6km/sec reduceFig. 1.1 Example of the record section of the refraction survey
the 1989 Fujihashi-Kamigori profi le conducted by the Research Group for Explosion Seismology RGES . The reduction velocity is 6km/sec. Wide-angle refl ections from the crustal lower part are identifi ed in the area enclosed by the trapezoid.
177
2
Moho
2.2.1
LithoprobeLithoprobe
Cook et al., 1992
1995 2.1
1/30 1/500
1.5km
150-200km
CMP
2
2.2 CMP2.2.1 CMP
2.1 a2
CMP Common MidPoint
2.1 b
NMO NMO
CMP
CMPP S
multiple NMO
n S/N n1/2
CMP
2.1 Lithoprobe Southern Canadian CordelleraCook et al., 1992
1995Table 2.1 Specification comparison between a continental deep
seismic survey of the Southern Canadian Cordellera Cook et al., 1992 from the Lithoprobe project, and
a wide-angle reflection/refraction survey from the 1989 Fujihashi-Kamigori profile Research Group for Explosion Seismology, 1995 .
68 2005 9
178
2.2.2 CMPCMP 1 2
CMP
CMP
CMP S/NCMP
2.32.3.1
2.2
t=0t=t0
t=t0
3t=t0
2.4.3
2.2
Fig. 2.2 Scheme of the Common Scatter-Point CSP stacking method. Amplitudes are allocated on the isochrone of the scatter traveltime left . The scatter point is emphasized after the allocated amplitudes are stacked right .
2.1 CMP a 2 b NMOc NMO d CMP
Fig. 2.1 Scheme of the Common Mid-Point CMP stacking method. a Simple model with a singlehorizontal refl ector triangles and squares indicate shot points and receivers, respectively b BeforeNMO correction c After NMO correction d CMP stacking after NMO correction.
179
2.3.2
0.5-2km
2.42.4.1
2 2.2
CMP
CMP
2.4.2
2.3t=t0
1
0A t=t0 θ
G L t=t0
dl0 F control factor
θcontrol factor θ
θ
| θ F | > π/2 0
control factorθ 0 | θ |θ π/2 control
factor θcontrol factor
| θ |θ F| θ |θ
control factor F2.4 F→FF θ
θ =0θF→0FF 0 | θ |θ
π/2control factor F→FFCMP CMP
F→0FF
control factor CMP
control factor
2.2 CMPTable 2.2 Comparison between Common Mid-Point CMP and
Common Scatter-Point CSP stacking methods.
2.3 I
Fig. 2.3 Scheme of the improved mapping method. Amplitudes areallocated on the isochrone of the scatter traveltime using aweighting function.
68 2005 9
180
CMP
θ θ2
2.5 AB
SPA RPB 2
φ
θ φφ 3
F θ φ
φφ
control factor CMP
control factor
2.4.3
2.6TSPRTT
TSPRTT TSPTT + TPRTT 4
2.5 P 2
θ P ABφ
Fig. 2.5 Geometry of the angles θ andθ φ . θ is an angle between θthe normal line and the bisector of the scatter angle at the scatter point P. φ is an angle between the horizontal line φand the tangent at P.
2.62
Fig. 2.6 Scheme of making a scatter traveltime map. Maps of traveltime from a shot point upper left and from areceiver point lower left . A scatter traveltime map ismade from a summation of both the traveltime maps
right .
2.4 II control factorcontrol factor
CMP
Fig. 2.4 Schematic diagrams of the control factor’s effect. The improved mapping method comes close to the CMP stacking method as the control factor increases, and it comes close to the CSP stacking method as the control factor decreases.
181
TSP
TPR
2
1 1
Hole and Zelt 1995
TRPTT
TRTT P TPRTT 5
TSPRTT
TSPRTT TSPTT + TRPTT P 6
2.4.4
2λ
rvr
7
Rayleigh 1/4
1 23 control factor
1 rz
8
2s
in
9
3 control factorcontrol factor
control factor θ θ max
z d
10
3
2.4.5control factor
CMPcontrol
factor
3.3.1
1 23 control factor 4
control factor 41
NMO
CMP
2
3 control factor
68 2005 9
182
control factorCMP
4
250m 2
Hole and Zelt 1995synthetic Zelt and Smith 1992
convolutionsynthetic 100Hz
8.3Hz 1
3.2NMO
3.1a CMP
NMO 4NMO
b
NMONMO
100% c d NMO150% 200%
b
150%
200% 150%
4
3.270km
3.1 NMO aNMO b
c150% d 200%
Yilmaz 2001Fig. 3.1 Stretching effect caused by NMO correction Yilmaz,
2001 . a A synthetic CMP gather before NMO correction, b after NMO correction without stretch limits, c after muting using a stretch upper limit of 150 percent, and d after muting using a stretch upper limit of 200 percent.
3.270km
140km140km
Fig. 3.2 Schematic diagrams of the stretching effect caused by theimproved mapping method. Scatter traveltime maps showthe cases in which the source-receiver offsets were 70km
left and 140km right . The case of 140km has anisochrone contour with a wider interval.
3.3Fig. 3.3 Synthetic horizontal multi-layered model.
183
140km
1secNMO
NMO1
2 3
180km×50km 3.3
15km 25km 35km 45km6.1→6.4km/sec 6.4
→6.9km/sec 6.9→7.6km/sec 7.6→8.0km/sec1 1km 179
1990
3.44
3.5150% 170%
180% 190% 200% 210% 250%
3.4 synthetic 6km/sec reduce
Fig. 3.4 Synthetic seismograms reduced by a velocity of 6km/sec.
3.5 150%, 170%, 180%, 190%, 200%, 210%, 250%
Fig. 3.5 Effects of stretch upper limits in the improved mapping method. The stretch upper limits are 150, 170, 180, 190, 200, 210, and 250% as well as no limit.
68 2005 9
184
8
15km30km
45km 60km
150%
35km 40km 250%150%
35km70km
190%190%
190%3.3
3.62
3.6
43.7
21 I
1 23
1 2 II
III IVII 1 2
III 2
3.6
Fig. 3.6 Traveltime of head waves calculated using a finite difference method. In case of a large offset, head waves propagating in the lower layer at a high velocity are faster than direct waves.
3.7 4
Fig. 3.7 Calculation of traveltime map without head waves in a four-horizontal-layered model.
185
I IV I 1II 2
V
3.2
70 km3.8
1.5sec3.9
2sec140km 3.10
70km
10km 3.11
control factor F=1FF3.12
080km
80km
2.1L
3.8 70km
Fig. 3.8 Scatter traveltime map for a case with a source-receiver offset of 70km with left , and without right head waves.
3.9 70km
Fig. 3.9 Difference between scatter traveltime maps with and without head waves for an offset of 70km.
3.10 140km
Fig. 3.10 Scatter traveltime map for a case with a source-receiver offset of 140km with left , and without head waves
right .
3.11 140km
Fig. 3.11 Difference between scatter traveltime maps with and without head waves for an offset of 140km.
68 2005 9
186
190% F=10FF3.13
190%3.14 70km
190%20km
190
140km
40km 70km
3.15 2θ θ
control factor | θ | controlfactor | θ |
control factor
3.4 control factorcontrol
factor controlfactor CMP
2
10° 20° 3.1620km 40km
3.13
190% control factor 10
Fig. 3.13 Seismic sections applied with the improved mapping method using a stretch upper limit of 190% and a control factor of 10. With left and without right head waves.
3.14 190%70km
140kmFig. 3.14 Mapped area using a stretch upper limit of 190% for
offsets of 70km left , and 140km right .
3.15 70km 140km
θFig. 3.15 Distributions of θ for offsets of 70kmθ left and 140km
right .
3.12
control factor 1Fig. 3.12 Seismic sections applied with the improved mapping
method using no stretch upper limit and a control factor of 1. With left and without right head waves.
187
60km 3 2km 4590km× 50km synthetic
3.17 29 control factorF
1, 2.5, 5, 10, 20, 40, 80, 160, 320 93.18 2
F=1FFF=320FF CMP
F=1FF2 10° 20°
F=320FF CMP
120° 18°
10°control factor
F=20FF2
F=80FFcontrol factor
20°
F=2.5FF 20°F=5FF 20°
F=10FF 18°control factor
18° 10°10°
control factor
3 control factor
F=1FFF=320FF
3F=80FF
F
3.5 control factor
3.4control factor
9synthetic
0.15sec3.19
synthetic 3.20
3.16 210° 20°
Fig. 3.16 Synthetic velocity model. The two left dipping refl ectors have dip angles of 10° and 20°, respectively.
3.17 synthetic 20km6km/sec reduce
Fig. 3.17 Example of synthetic wave forms without noise. The shot point is located at an offset of 20km. The reduction velocity is 6km/sec.
68 2005 9
188
control factorF=1FF
F=5FF F=10FFF=20FF
40 S/NF
F=160FFF=320FFF=40FF
CMP
control factor
control factorcontrol factor
3.19 synthetic20km 5-10Hz
6km/sec reduceFig. 3.19 Example of synthetic wave forms with noise. The shot
point is located at an offset of 20km. The reduction velocity is 6km/sec.
3.18 synthetic control factor control factor 1, 2.5, 5, 10, 20, 40, 80, 160, 320
Fig. 3.18 Effect of the control factor of the improved mapping method, which is applied to synthetic data without noise. The control factor range is from 1 to 320. A white dashed line indicates a refl ector of the synthetic velocity model.
189
F=10FF 80control factor
3.6
control factor
control factorCMP
control factor
control factor
4.4.1
19881992 1989
1995 21988
1991CMP
1989 -
200kmPn Moho
3.20 synthetic control factor control factor 1, 2.5, 5, 10, 20, 40, 80, 160, 320
Fig. 3.20 Effect of the control factor of the improved mapping method, which is applied to synthetic data with noise. The control factor range is from 1 to 320. A white dashed line indicates a refl ector of the velocity model used.
68 2005 9
190
4.24.1 fl ow chart
2
8HzBandpass
S
S
P SVS P
S PBandpass
F-K
aliasingVp/Vs 1.73 S
S4.2 S
AGC Automatic Gain Control
S
DeconvolutionDeconvolution
DeconvolutionWiener Robinson and
Treitel, 1980 Wiener
4.3
4.1 fl ow chartFig. 4.1 Flow chart to process wide-angle reflection data in this
study.
4.2 SS
Fig. 4.2 Example of observed wave forms before left and after right the S-wave removal. First arrivals with large
amplitudes are also removed.
4.3 Deconvolution
0.6sec 0.07secFig. 4.3 Application of deconvolution. Before left and after
right deconvolution using an operator length of 0.6sec and a prediction lag of 0.07 sec.
191
Zelt and Smith 1992
8km8km 2
31
0.1sec
3
0.1sec2
4.3 19884.3.1
5 1988 11
19881992
4.4
5Ichikawa,
1980 km
30-40Ito et al., 1996
4cm/yearSeno et al., 1993
1944 M7.91946 M8.0
684 176Ando, 1975 Ando 1975 19441946
65km 8615km
S-1 S-6 64.5
100Hz AD
4.4 1988 1989 - 1995Fig. 4.4 Geological map of the Kinki district including the 1988 Kawachinagano-Kiwa and the 1989 Fujihashi-Kamigori profi les, after
the Geological Survey of Japan 1995 .
68 2005 9
192
4.5 19881995 5 2001
41997
Fig. 4.5 Location map of the 1988 Kawachinagano-Kiwa profi le. Stars and open circles indicate shot and receiver points, respectively. Hypocenters of micro-earthquakes from May 1995 to April 2001 Nakamura et al., 1997 are superposed.
4.6 1988 S-1 5-8Hz6km/sec reduce
Fig. 4.6 Record section S-1 for the 1988 Kawachinagano-Kiwaprofile using a bandpass filter of 5-8Hz. The reductionvelocity is 6km/sec.
4.7 1988 S-6 5-8Hz6km/sec reduce
Fig. 4.7 Record section S-6 for the 1988 Kawachinagano-Kiwa profile using a bandpass filter of 5-8Hz. The reduction velocity is 6km/sec.
4.8 19888km
Fig. 4.8 Upper crustal velocity model for the 1988 Kawachinagano-Kiwa profi le after traveltime inversion.
4.9 1988
Fig. 4.9 Model parameters used for the traveltime inversion of the upper crustal velocity model for the 1988 Kawachinagano-Kiwa profile. The boundary and velocity nodes are indicated by squares and circles, respectively.
193
, 1992 S-14.6 15km 30km
24.6 a 35km
4.6 b S-6 4.74.7 c
5-7sec 50km-20-0km 24.7 d
P SS
4.3.28km
4304.8
4.94.1
4.10
95 4.10.2km
0.05km/sec 30.02km/sec
65km Pn
Sasaki et al., 197022km 6.4km/sec
35km 6.8km/sec 35km 7.6km/sec4.11
4.83.1-4.5km/sec
4.1 1988
Table 4.1 Resolutions and standard deviations of the model parameters used to invert the upper crustal velocity model for the 1988 Kawachinagano-Kiwa profi le.
4.10 1988
Fig. 4.10 Ray path diagram used for the inversion of upper the crustal velocity model for the 1988 Kawachinagano-Kiwa profi le.
4.11 1988
Fig. 4.11 Lower crustal velocity model for the 1988 Kawachinagano-Kiwa profi le. The velocity of the lower crust is assumed to refer to the 1989 Fujihashi-Kamigori this study and Kurayoshi-Hanafusa Yoshii et al., 1974 profi les.
68 2005 9
194
500m
1km 5.6km/sec
4.3.3control factor 1, 2.5, 5, 10, 20,
40, 80, 160, 320 94.12 3.5
3.19F=1FF
FF=20FF 40
F=80FFF
F=20FF 80
F=40FF 4.1330km
S-1 2
10° 15° 25kmS-6
33km 235km
20° 30°50km
Moho
4.12 1988 control factor 1, 2.5, 5, 10, 20, 40, 80, 160, 320
Fig. 4.12 Seismic sections of the 1988 Kawachinagano-Kiwa profi le. The range of the control factor FF is from 1 upper left to 320 lower right .
195
35km5
4.3.41991 CMP
4.14
1991
20-30kmS-6
4.7 21991 1
4.14 a1991
40km 14.14 b CMP
125km
35km
19914.14 c CMP
4.13 1988F=40FF
Fig. 4.13 Seismic section of the 1988 Kawachinagano-Kiwa profi le and its interpretation F=40FF .
4.14 1991 a2 b c
Fig. 4.14 Comparison between this study and the previous study. Cross-sections for this study left and for Yoshii 1991 right . a Undetectable double refl ectors, b undetectable multi refl ectors, c undetectable
change of the dip angle.
4.15 19891985 1 1994 12
1997Fig. 4.15 Location map of the 1989 Fujihashi-Kamigori profile. Stars and open
circles indicate shot and receiver points, respectively. Hypocenters of micro-earthquakes from May 1995 to April 2001 Nakamura et al., 1997are superposed.
68 2005 9
196
4.4 19894.4.1
19891995 4.15
4.4S-3
1987
Yoshii et al., 1974 1
2 30-40km 3 Pn7.8km/sec
4cm/yearSeno et al., 1993
Watanabe et al. 1990 1997
50km
198860-70km
210km
4.16 1989 S-1 3-8Hz6km/sec reduce
Fig. 4.16 Record section S-1 of the 1989 Fujihashi-Kamigori profile using a bandpass filter of 3-8Hz. The reduction velocity is 6km/sec.
4.17 1989 S-4 3-8Hz6km/sec reduce
Fig. 4.17 Record section S-4 of the 1989 Fujihashi-Kamigori profile using a bandpass filter of 3-8Hz. The reduction velocity is 6km/sec.
4.18 19898km
Fig. 4.18 Upper crustal velocity model for the 1989 Fujihashi-Kamigori profi le after traveltime inversion.
4.19 1989
Fig. 4.19 Model parameters used for traveltime inversion of theupper crustal velocity model for the 1989 Fujihashi-Kamigori profi le. The boundary and velocity nodes areindicated by squares and circles, respectively.
197
1371.5km
S-1 S-44 500-800kg
70km
S-1 S-4180km 7km/sec
Pn 4.16 4.17S-1
reverberation2sec
S30km
S-1S/N S-4
4.4.28km
3104.18
4.194.2 4
70km4.20
90%3 99
4.290% 0.2km
0.1km/sec
Pn
40km
8km148
Pn 234.21
4.224.3
4.23 530% 4.3
690% 60%
0.05km/sec 0.6km8km 4.18
1km
S-1 S-31km
S-2 S-3 3.4km/secS-1 S-2 2.9km/sec
S-3S-4 5.3km/sec
Moho34km
7.6km/sec 25km 6.3km/sec 6.6km/sec
4.4.3F 1, 2.5,
5, 10, 20, 40, 80, 160, 320 94.24
70km 4 S/N
control factorcontrol factor
F=1FF CMP F=320FF
F 1 2.515-35km
F
F
F=20FF 80 S/N
CMP
F=40FF4.25
km25km 35km
10km refl ective zone
S-4refl ective zone
Moho33km
68 2005 9
198
4.2 1989
Table 4.2 Resolutions and standard deviations of the modelparameters used to invert the upper crustal velocitymodel for the 1989 Fujihashi-Kamigori profi le.
4.20 1989
Fig. 4.20 Ray path diagram used for the inversion of the upper crustal velocity model for the 1989 Fujihashi-Kamigoriprofi le.
4.21 1989 -
Fig. 4.21 Lower crustal velocity model for the 1989 Fujihashi-Kamigori profi le after traveltime inversion.
4.22 1989
Fig. 4.22 Model parameters used for the traveltime inversion of the lower crustal velocity model for the 1989 Fujihashi-Kamigori profi le. The boundary and velocity nodes areindicated by squares and circles, respectively.
4.3 1989
Table 4.3 Resolutions and standard deviations of the modelparameters used to invert the lower crustal velocitymodel for the 1989 Fujihashi-Kamigori profi le.
199
4.24 1989 control factor 1, 2.5, 5, 10, 20, 40, 80, 160, 320
Fig. 4.24 Seismic sections of the 1989 Fujihashi-Kamigori profi le. The range of the control factor FF is from 1 upper left to 320 lower right .
4.23 1989
Fig. 4.23 Ray path diagram used for the inversion of the lower crustal velocity model for the 1989 Fujihashi-Kamigori profi le.
4.25 1989F=40FF
Fig. 4.25 Seismic section of the 1989 Fujihashi-Kamigori profi le and its interpretation F=40FF .
68 2005 9
200
50km140-160km
refl ective zoneMoho
5
5.5.1 19885.1.1
4.13 25km50km
35km 20° 30°33km
2
1999
5.1Kodaira et al. 2001 2002
165km185km
150km2002
5.2 6°
12°2
2002 4km /sec1km
225km 2002
24km/sec
1.5km2002
1994160km
1997 5.3
19973°→5°→10°
5.4 1997
19971997
10°20° 2
10° 20°15° 3 10°
20km 15°24km 20° 38km
5.1 1999
2002Fig. 5.1 Location map of the seismic survey line conducted in
1999 solid line Kurashimo et al., 2002 . The lineintersects with the Nankai trough, in the eastern part of Shikoku Island and the Chugoku District.
5.2
2002Fig. 5.2 Geometry of the subducting Philippine Sea plate and the
crustal velocity structure Kurashimo et al., 2002 . Thehypocenters are also superimposed.
201
25km15°
1997
19972 4.2-4.6km/sec 5.3-5.9km/
sec 21.8km
2 2
5km/sec1.9km 1997 2
1.8km 223
1997
3°→5°→10° 20°
35km 30°2
33km2002
12°
19884.13 5.5
1995 7 2001 6
20°45km
30°
5.3 19941997
Fig. 5.3 Location map of the seismic line off of the Kii Peninsula in 1994 the easternmost north-south line in the figure
Nishisaka, 1997 .
5.41997
Fig.5.4 Geometry of the subducting Philippine Sea plate and the crustal velocity structure off of the Kii Peninsula
Nishisaka, 1997 .
5.5 1988
Fig. 5.5 Seismic section for the 1988 Kawachinagano-Kiwa profi le superimposed with hypocenters, which were provided by the Earthquake Observation Center of the Earthquake Research Institute at the University of Tokyo.
68 2005 9
202
10km
5.61.5km
5.7
5.85.5 1km
210±2.5km
7km1997
19975.2
5.6 5.5 1988 -
Fig. 5.6 Errors of the hypocenters shown in Fig. 5.5.
5.71997
Fig. 5.7 Velocity structure used for hypocentral determination leftmost Nakamura et al., 1997 .
5.8 1988
Fig. 5.8 Seismic section for the 1988 Kawachinagano-Kiwa profi le based on the same velocity structure used for the hypocentral determination.
203
10km
Seno et al. 2001
2000
40-60km 640-690Ulmer and Trommsdorff, 1995 Peacock and Wang
19995.9
40-60km14km 5.8
5.1.24.13 20km 25km
10 15°
underplating2 Matsuda and Isozaki 1991
5.10
underplating
25km
19972
33km
5.9 Peacock and Wang 1999
Peacock and Wang 1999Fig. 5.9 Thermal structure of the subducting Philippine Sea plate
from off of Shikoku Island Peacock and Wang, 1999 .
5.10 Matsuda and Isozaki 1991
Fig. 5.10 Schematic section of accretionary prism Matsuda and Isozaki, 1991 .
68 2005 9
204
Moho
Moho
Moho 1Moho
2 Moho
3 Moho
MohoMoho
5.2 19895.2.1
4.2525-35km refl ective
zonekm 10km
4.13
refl ectivesill
Mooney and Meissner, 1992
ductile fl owlaminate
sill
MohoMoho 34km
10km
Moho
Mooney and Meissner 1992Moho
3-5km
Braile and Chang 1986Moho
5.11
Moho
5.11 Braile and Chang 1986 Moho
Fig. 5.11 Moho transition zone model Braile and Chang, 1986 . The transition zone consists of random, thick-variable, high- and low-velocity lamellae.
205
MohoMoho
Moho
sill
Moho
5.2.2 50km
50km4.25
PS S-1
P S6km/sec reduce 5.12 a
3.46km/sec reduce 5.12 b5.12 b
1/1.73 2P
S50km S P
50kmP S
SP 1.2-3.0
Vp/VsS
5.12 1989 S-1 a 3-8Hz6km/sec
reduce b S2-5Hz 3.46km/sec reduce
Fig. 5.12 Record sections S-1 of the 1989 Fujihashi-Kamigoriprofile using a a bandpass filter of 3-8Hz and areduction velocity of 6km/sec, and b a bandpass fi lter of 2-5Hz and a reduction velocity of 3.46km/sec toclarify the S-wave refl ections.
5.13
Furukawa et al. 1998
Fig. 5.13 upper Distribution of heat fl ow data. The contour lines show estimated heat flow. lower Heat flow profile in the cross-arc direction using heat fl ow data from the rectangle in the upper fi gure Furukawa et al., 1998 .
68 2005 9
206
Furukawaet al., 1998 60-70mW/m2
5.13
50km
4cm/year Seno et al., 1993
Watanabe et al., 1990 ,1997 1997
1985-1994 10 13
5.14
50km
Seno
et al. 1993
5.1470km 5.1.1
14km
55km
50km
Seno et al. 2001
50km
6.Moho
control factorcontrol factor
CMP
synthetic
190%
control factorsynthetic
control factorcontrol factor 1 320
CMP
CMP
control factor
syntheticcontrol factor
5.14 1984 19941997
Seno et al. 1993
Fig. 5.14 Depth contours of the subcrustal earthquakes1984~1994 in southwestern Japan Nakamura et al.,
1997 . The solid triangles indicate the leading edgewhere the seismicity disappears. The solid line indicatesthe depths of the subcrustal earthquakes extrapolated along the plate motion as shown by Seno et al. 1993 .
207
2
CMP
30km 20° 30°
25-35kmkm- 10km refl ective zone
Moho10km
MohoBraile and Chang 1986
Moho50km
S P
Moho 19881989
1 Allmendinger, R., Farmer, H., Hauser, E., Sharp, J., Tish, D. V., Oliver, J., and Kaufman, S. 1986 : Phanerozoic tectonics of the Basin and Range-Colorado Plateau transition from COCORP data and geologic data: a review. in Reflection Seismology: The Continental Crust, edited by Barazangi, M. and Brown, L. D., Am. Geophys. Union, Geodyn. Ser. 14, 257-267.
2 Ando, M. 1975 : Source Mechanisms and Tectonic Significance of Historical Earthquakes along the Nankai Trough, Japan. Tectonophysics, 27, 119-140.
3 1985
60, 615-637.4 1992
67, 303-323. 5 1995
70, 9-31. 6 1999
74, 63-122.
7 Braile, L. and Chang, C. S. 1986 : The continental Mohorovicic discontinuity; Results from near-vertical and wide-angle seismic refraction studies. in Reflection Seismology: A gloval perspective, edited by Barazangi, M. and Brown, L. D., Am. Geophys. Union, Geodyn. Ser. 13, 257-272.
8 Brown, L. D. 1991 : A new map of crustal ‘terranes' in the United States from COCORP deep seismic reflection profi ling. Geophys. J. Int., 105, 3-13.
9 Chang, W. F., McMechan, G. A., and Keller, G. R. 1989: Wave Field Processing of Data From a Large-Aperture Seismic Experiment in Southwestern Oklahoma. J. Geophys. Res., 94, 1803-1816.
10 1995 100 1 3CD-ROM G-1:
11 Cook, F. A., Varsek, J. L., Clowes, R. M., Kanasewich, E.
68 2005 9
208
R., Spencer, C. S., Parrish, R. R., Brown, R. L., Carr, S.D., Johnson, B. J., and Price, R. A. 1992 : Lithoprobecrustal reflection cross section of the southern CanadianCordellera, 1, Foreland thrust and fold belt to Fraser river fault. Tectonics, 11, 12-35.
12 Furukawa, Y., Shinjoe, H., and Nishimura, S. 1998 :Heat flow in the southwest Japan arc and its implicationfor thermal processes under arcs. J. Geophys. Res., 25,1087-1090.
13 Hale, L. D. and Thompson, G.A. 1982 : The SeismicReflection Character of the Continental MohorovicicDiscontinuity. J. Geophys. Res., 87, 4625-4635.
14 1999
27, 39-43.15 Hole, J. A. and Zelt, B. C. 1995 : 3-D fi nite-difference
refl ection traveltimes. Geophys. J. Int., 121, 427-434.16 Ichikawa, K. 1980 : Geohistory of the Median Tectonic
Line of Southwest Japan. Mim. Geol. Soc. Japan, 18,187-212.
17 Ikami, A., Yoshii, T., Kubota, S., Sasaki, Y., Hasemi, A.,Moriya, T., Miyamachi, H., Matsu'ura, R. S., and Wada, K.
1986 : A seismic-refraction profi le in and around Naganoprefecture, central Japan. J. Phys. Earth, 34, 457-474.
18 Ito, T., Ikawa, T., Adachi, I., Isezaki, N., Hirata, N.,Asanuma, T., Miyauchi, T., Matsumoto, M., Takahashi,M., Matsuzawa, S., Suzuki, M., Ishida, K., Okuike, S.,Kimura, G., Kunitomo, T., Goto, T., Sawada, S., Takeshita,T., Nakaya, H., Hasegawa, S., Maeda, T., Murata, A.,Yamakita, S., Yamaguchi, K., and Yamaguchi 1996 : S.,Geophysical exploration of the subsurface structure of theMedian Tectonic Line, East Shikoku, Japan. Jour. Geol.Soc. Japan, 102, 346-360.
19 Iwasaki, T., Kato, A., Abe, S., Ichinose, Y., Umino, N.,Okada, T., Koshiya, S., Kosuga, M., Saka, M., Sato, H.,Shimizu, N., Takeda, T., Tsumura, N., Noda, K., Hasegawa,A., Hirata, N., Watanabe, K., Ikawa, T., and Ohguchi, T.
1999 : Seismic Refraction Observation at the Sen'yaFault Zone, Northern Honshu, Japan, Bull. Earthq. Res.Inst., 74, 49-62.
20 Iwasaki, T., Kato, W., Moriya, T., Hasemi, A., Umino, N.,Okada, T., Miyashita, K., Mizokami, T., Takeda, T., Sekine,S., Matsushima, T., Tashiro, K., and Miyamachi, H. 2001: Extensional structure in northern Honshu Arc as inferred from seismic refraction/wide-angle reflection profiling.Geophys. Res. Lett., 28, 2329-2332.
21 Kodaira, S., Kurashimo, E., Takahashi, N., Nakanishi,A., Miura, S., Park, J. O., Iwasaki, T., Hirata, N., Ito, K.,and Kaneda, Y. 2001 : Structural factors controlling therupture process of a megathrust earthquake at the Nankaitrough seismogenic zone. Geophys. J. Int., 149, 815-835.
22
2002
54-4 489-50523 Matsuda, T. and Isozaki, Y. 1991 : Well-Documented
Travel History of Mesozoic Pelagic Chert in Japan: From Remote Ocean to Subduction Zone. Tectonics, 10, 475-499.
24 1999
288pp.,
25 Matsu’ura, R., Yoshii, T., Moriya, T., Miyamachi, H., Sasaki, Y., Ikami, A., and Ishida, M. 1991 : Crustal Structure of a Seismic-Refraction Profi le across the Median and Akaishi Tectonic Lines, Central Japan. Bull. Earthq. Res. Inst. Univ. Tokyo, 66, 497-516.
26 Mooney, W. D. and Meissner, R. 1992 : Multi-genetic origin of crustal refl ectivity: a review of seismic refl ection profiling of the continental lower crust and Moho. in Continental Lower Crust, edited by Fountain, D. M., Arculus, R., and Kay, R, 45-79, ELSEVIER, Amsterdam.
271997
No.40, 1-20.28 1987
6 297pp., .29 1997
38pp.,
30 Peacock, S. M. and Wang, K. 1999 : Seismic Consequences of Warm Versus Cool Subduction Metamorphism: Examples from Southwest and Northeast Japan. Science, 286, 937-939.
31 Robinson, E. A. and Treitel, S. 1980 : Geophysical signal analysis: Prentice-Hall Book Co.
32 Sasaki, Y., Asano, S., Muramatu, I., Hashizume, M., and Asada, T. 1970 : Crustal Structure in the Western Part of Japan Derived from the Observation of the First and Second Kurayosi and the Hanabusa Explosions
Continued . Part 2. Crustal structure in the western part for Japan Continued . Bull. Earthq. Res. Inst. Univ. Tokyo, 48, 1129-1136.
33 Sato, H., Hirata, N., Ito, T., Tsumura, N., and Ikawa, T. 1998 : Seismic refl ection profi ling across the seismogenic
fault of the 1995 Kobe earthquake, southwestern Japan. Tectonophysics, 286, 19-30.
34 Seno, T., Stein, S., and Gripp, A. E. 1993 : A Model for Motion of the Philippine Sea Plate Consistent With NUVEL-1 and Geological Data. J. Geophys. Res., 98, 17941-17948.
35 Seno, T., Zhao, D., Kobayashi, Y., and Nakamura, M.
209
2001 : Dehydration in serpentinized slab mantle: Seismic evidence from southwest Japan, Earth Planets Space, 53, 861-871.
36 199726pp.
.37 Ulmer, P. and Trommsdorff, V. 1995 : Serpentine stability
to mantle depths and subduction-related magmatism. Science, 268, 858-861.
38 Watanabe, H. and Maeda, N. 1990 : Seismic Activity of Subcrustal Earthquakes and Associated Tectonic Properties in the Southeastern Part of the Kinki District, Southwestern Japan. J. Phys. Earth, 38, 325-345.
39 Yilmaz, Ö. 2001 : Seismic Data Analysis; Processing, Inversion, and Interpretation of Seismic Data, vol.1,
edited by Doherty, S. M., pp.1000, Society of Exploration Geophysicists, Tulsa.
40 Yoshii, T., Sasaki, Y., Tada, T., Okada, H., Asano, S., Muramatu, I., Hashizume, M., and Moriya, T. 1974 : The third Kurayosi explosion and the crustal structure in the western part of Japan. J. Phys. Earth, 22, 109-121.
41 199161, 570.
42 Zelt, C. A. and Smith, R. B. 1992 : Seismic travel inversion for 2-D crustal velocity structure. Geophys. J. Int., 108, 16-34.
43 Zelt, B. C., Talwani, M., and Zelt, C. A. 1998 : Prestack depth migration of dense wide-angle seismic data. Tectonophysics, 286, 193-208.
Accepted : April 20, 2005
68 2005 9
210
CMPCMP migration
2 1988 1989
1988 1989