The Nankai Trough Tectonic Compilation Map Project- an example of using the Frontier Database systemYukari Kido
Institute of Frontier Research for Earth Evolution (IFREE)
Japan Marine Science and Technology Center (JAMSTEC)
2-15 Natsushima-cho, Yokosuka, 237-0061, Japane-mail: kidoy@jamstec.go.jp

Abstract
Institute of Frontier Research for Earth Evolution (IFREE,
recently re-modified from FRPSD) have been cooperative
experiment with the explosive seismology group on land
Shikoku and the northern Shikoku Basin using the R/V Kairei
in 1997 through 2000 (Fig. 1). Along totally 5000km lines,
300 OBSs are deploying to reveal extensive crustal structure
off Nankai trough to the underneath Shikoku. Figure 1 shows
seafloor topography, bathymetry, and physiographic featuresof the Nankai Trough margin off Shikoku Island, SW Japan.
We can combine all together and compile available data ofmultichannel seismic (MCS) reflection obtained by
JAMSTEC, JAPEX, and JNOC. The purposes of thesestudies within a multi-purpose Frontier Database framework
are: (1) to obtain geophysical and geological observations ofsubduction zones at the Nankai Trough and the northern
Shikoku Basin region known as one of the most focus-on
seismogenic zone around Japan; (2) to interpret for variations
in sub-bottom topography, gravity, magnetics, thermalstructure; (3) to reveal a fine scale shape of subductedseamounts and its vicinity area; (4) to identify geophysicalfeatures across the trough axis with intensity variations, heat
flux and shape of decollement zone, accretionary prism, andoceanic layers, and deformational characteristics at a large
earthquake; (5) to understand the northern edge of thePhilippine plate
kinematically. Figure 2 shows
three-dimensional display obtained by 44 multi-channel
seismic (MCS) profiles. Upon constructing crustal structure
models by R/V Kairei, JNOC, and Japex from shallower todeeper part, baseline and mapping projection are defined as
WGS84. Clear reflecting surfaces shown on several tracklines were digitized to define the ocean bottom, BSR(bottom-simulating reflector), and the top of oceanic layer.
The approach of three-dimensional view has been helpful tounderstand each layers horizontal distribution. There arealmost same characteristic features with ocean bottom andBSR distribution. Figure 3 is an example of site judgement todecide exact drilling sites. We compiled whole track lines
with each survey name, top of subducting slab depth,bathymetry (with thick line at 2,500 m), coseismic slip
distribution from the inversion of tsunami waveforms by
Tanioka and Satake (2001) and possible drilling target areas(red zones). Drilling target zone of Nankai trough are the areawith shallower than 2,500 m of oceanic floor and up to 5,000m depth of subducting slab from the ocean bottom. Redzones are available drilling sites. These kind of maps areuseful to discuss and collaborate in between scientists,engineers, and crews to decide operating sites.

accumulated recently by JAMSTEC and other institutions for
all the marine region. A universal marine geophysicalDatabase system and interactive compilations and analyses
system are constructed within the IFREE framework.
Geophysical data sets obtained during cruises are entered into
the main server of the JAMSTEC Database, which ismaintained by JAMSTEC Computer and Information Office(JCIO). They are selected, edited and formatted to fit to theFrontier Database. Using two-and three-dimensional forward
modeling of gravity and magnetic profiles, with seismic
structural data in the Frontier Database, a qualitativeinterpretation of the geometry, densities and magnetization ofsubducting plates, marginal basins, and island arcs are
discussed (after Kido et al., 1999).

Frontier Database

Future prospect

This study is supported by Database system of Intitute of
Frontier Research for Earth Evolution (IFREE) in JAMSTEC.
Marine geophysical data of bathymetry, gravity,
geomagnetics, heat flow measurements, crustal structure,
seismicity, fault and bio-marker distribution have been

Outline
The Frontier geophysical database project is one componentof the 1997 and subsequent fiscal years' Frontier Research
Program and is designed specifically to help clarify theseismogenic mechanism of great subduction zone
earthquakes and construct long-term earthquake recurrence
models. It contains reflection and refraction seismic data,
bathymetry and ship track locations, gravity, earth magnetism,
heat flow and fluid seep distribution data acquired bydeep-sea research vessels. In designing the Frontier database,it has been necessary to consider several operationalrequirements. In particular, the database must be capable ofbeing added to in the future as new data are obtained. The
data are used as input for crustal deformation models. Using
the integrated datasets with inversion and forward modelingsoftware, we are also able to perform verification of themodels' results.

Newly Acquired Data
In JAMSTEC, 5 research vessels have been in operation for
200 days a year. A large amount of various data sets areaccumulated every day by day. A list of data newly obtainedby JAMSTEC is shown in Table. All cruise data have beenstocked and registered in the JCIO database system. In theFrontier database, only inventory information list of thenavigation data has been renewed after each cruise. The
necessary data from the JCIO database is chosen andprocessed to grid data using whole data obtained so far.
Finally, geophysical data (location, topography, gravity,geomagnetism, seismic, heat flow data) are registered in
JCIO database and Frontier database.

In order to facilitate the study of past, contemporary
and future changes in the deep sea environment
Pan-pacific regions, we aim for an object-oriented
approach to the collection of data from a variety ofsources. The construction of a database containing

datasets of seismicity and potential field data, crustal
and thermal structures, and other data will make itpossible to carry out multi-faceted studies of thegeophysical properties of particular oceanic regions.
One of goals of such database system will be widelyused and spread for not only geophysicists andgeologists but public users, such as GEODAS(GEOphysical DAta System) developed by NGDC andJANUS providing from ODP (Ocean Drilling Program)office. JANUS includes huge volumes of dataset; e.g.
paleontology, lithostratigraphy, chemistry, physics,
sedimentology, and geophysical data for ocean
sediments and hard rocks. We expect the flow of
information through such a database to bebi-directional. That is, while data from the database areused as the basis for numerical simulation of plate
behavior or seismic activity, the results of such analysis
should be fed back into the database so that future
geophysical surveys can be more reliably planned andexecuted. This iterative approach will enable us tofirmly establish the reliability of the database and its

associated models.

References
Kido, Y., T. Tsuru, J-O. Park, T. Higashikata, Y. Kaneda, andY. Kono (1999) Development of Frontier Database Systemand Its Application, Geoinformatics, vol. 10, no. 3, pp.
155-167.
Kido, Y., T. Tsuru, J-O Park, T. Higashikata, Y. Kaneda, Y.
Kono (2000) Three Dimensional Overview of the Japan
Trench -an example of Utilization of the Frontier Database
System-, Computers & Geosciences, vol. 27, pp. 43-57.
Tanioka, Y. and K. Satake (2001) Detailed coseismic slip
distribution of the 1944 Tonankai earthquake estimated fromtsunami waveforms, Geophys. Res. Lett., vol. 28, no. 6, pp.
1075-1078.
Tanioka, Y. and K. Satake, Coseismic slip distribution of the1946 Nankai earthquake and aseismic slips caused by theearthquake. Earth Planets Space, in press.

No.
Items.
Data description and management application
1. Marine Geophys. Logging data obtained by R/Vs Kairei, Kaiyo, Yokosuka, Natsushima, Mirai; Project
Data
name, Time, Time zone, Location, Temperature, Salinity, Water sounding profile, Ship
Speed, Climate, etc.
2. Bathymetry Data Seabeam 2000, HS10, Gridded data through SeaView tool3.

Gravity Data

Gravity data by KSS-31 Bodenseewer, S-63 LaCoste & Romberg

4.

Magnetic Data5.

Total magnetic field by Proton magnetometer, Three component magnetic data by
Fluxgate magnetometer, Ship’s roll, pitch and yaw data, Shipboard magnetization
effects
Multi-channel reflection data, OBS (Ocean Bottom Seismograph) refraction data

Reflection/
Refraction Data
Jamstec
marine Terrestrial Heat Flow Data, Seismicity observed by array OBSs,
geophys. data
Cold seep distribution data

6.

Table

Newly acquired data list132˚133˚134˚135˚136˚34˚EPANJAP

Kii
Peninsuland35˚slaku I

-10o00

ShikPP
30˚PSP
135˚

140˚-2000

00

0145˚

1946 Nankaido
Coseismic

-2000

00

-100-300-4000-1000

Cape
Ashizuri-100004-30
00

-4000

1MS-1

KR

-2000

-04

1098

583
582

298
00

0a00

ront00r/yShikoku Basin

Defo

rm

atio

-30cm

Na

4

nk

-2

nF

ghour
iT

-40

10-0
98-30100

KR

808

5-2

32˚

N5-1000

RC258-1
N55

RC248-4000

130˚

Kyushu-1-200033˚

Cape
Muroto

031˚

km

50

Fig. 1Bathymetry and physiographic features of the Nankai Trough margin off Shikoku, SW Japan. Positions ofmultichannel seismic reflection lines are shown. The bold lines indicate the positions of profiles N55-1, MS104, N55-2-1,KR9810-01, and KR9810-04 displayed in Figures 2, 3, 4, 5, and 6, respectively. Site 808 of Ocean Drilling Program (ODP)
Leg 131 is indicated as a circle. The thin-solid rectangle is the coseismic rupture area of the 1946 Nankai earthquake(Aida, 1981; Ando, 1982). The convergence rate of the Philippine Sea Plate under the Eurasia Plate is approximately4 cm/yr (Seno et al., 1993). Water depth contours are in meters. EP=Eurasia Plate. PSP=Philippine Sea Plate. PP=Pacific Plate.

Nankai Trough MCS 3D compilation

BSR distribution around Nankai trough off Shikoku

Ocean Bottom
SW JapanShikoku

Nankai trough

BSR
4km

KyushuOceanic layer

4km

N ESW
NE
W S

Ocean Bottom
BSRFig. 2 (a) Upon constructing crustal structure models by R/V Kairei,
4km
baseline and mapping projection are defined as WGS84. Clear reflecting
surfaces shown on several track lines were digitized to define the ocean
4kmbottom and BSR (bottom-simulating reflector). The approach of three
dimensional view has been helpful to understand each layers horizontaldistribution.
N ES(b) (c)Three layers, ocean bottom, BSR (bottom-simulatingWreflector), and the top of oceanic layer are displayed as
three-dimensional view from the western direction.

Oceanic layer130˚36˚

131˚

132˚133˚134˚135˚136˚137˚138˚139˚35˚-1000

35˚140˚
36˚

t83-3-1

0-10009 75-200

t83-1
t74-1-7

nt96_nt103
t83-3
t74-i
t83-1-1
t83-1-2
k90-1
t83-i-1

k90-2

m78-f-1
t83-3-3
t83-i
k90-4
t83-2-2
t83-j

t74-11
k90-3
t74-h-1
t74-g-1

33˚

t74-1-4
N55-3-1-1000
t74-1-1

kr9702_nt201
m78-e
nt96_nt1t2
kr9806_12
nt96_nt203

t74-1-6

nt96_nt101
00
-40

k90-f
t74-2-4
k90-e

N55-A

kr9806_01-250

t74-f-20

t74-2-1

32˚

N55-1
kr9904_07
kr9904_08

t74-3
m78-n-1
t74-4

k90-c-1000

kr9704_mt301

75

t74-7

m78-i-1

03

t74-8

31˚

32˚

0

900kr9704_mt302

-400

t74-6

-2000

t74-b-2-20

kr9806_06
kr9806_07

kr9806_10
kr9704_mt303

kr9904_06

000-3
t74-5-1

33˚

kr9702_nt1t2
k90-n

N55-2
t74-a-2

3

t83-e
t83-f

s83-2
t74-g-2

t74-f-1

34˚

t83-b
t83-d

-3
00
034˚

-400

-300

0m78-lt74-9

31˚

kr9810_1

000

-4
-200

m78-120t74-b-1
t74-10-1-4000

m78-m-2

t74-a-1

30˚

-40

130˚

131˚132˚133˚

134˚

50

30˚

00

km
0-2

00

0m78-n-3

100

135˚

136˚137˚138˚139˚140˚

Fig.3 Nankai trough drilling site working map
0-0.5 0.5-1 1-1.5 1.5-2 2-2.5 2.5-3 3 <Fig.3slip, mNankai trough drilling site working map. We compiled whole track lines with each survey name, top ofsubducting slab depth, bathymetry (with thick line at 2,500 m), coseismic slip distribution from the inversion of tsunami
waveforms by Tanioka and Satake (2001) and possible drilling target areas (red zones). Drilling target zone of Nankai trough arethe area with shallower than 2,500 m of oceanic floor and up to 5,000 m depth of subducting slab from the ocean bottom. Redzones are available drilling sites.