International Workshop
Cutting Edge Technology for Understanding the Earth2023 January 12th, Tohoku University, Sendai

Scientific and Technological Achievementsof the D/V Chikyu
In the Plate Subduction Zone Drilling

Asahiko Taira

Advisor, JAMSTEC
Director, Institute of Ocean Research and Development, Tokai Univ.

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The Deep-sea Scientific Drilling Vessel Chikyu
The Flagship of IODP since 2007

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IODP=Integrated Ocean Drilling Program
Integrated＝Integrated Technology
Integrated Technology=Core：Geological Sampling
Logging：Physical Property Measurements
Seismic：Seismic Profiling of Geological Structure
Observatory：Borehole Observatory＆Cable Network
Experiment：Active Experiment using Borehole
e.g.: Controlled Hydrothermal Mineral
Precipitation at the Okinawa Trough3R/V Tanseimaru ‒ R/V Fred Moore
Two-ship Seismic Experiment at the Nankai TroughJuly 1987 (Univ. Tokyo-UTAustin-Univ.Hawaii)
R/VFred Moore&R/VTanseimaru

Prof. Greg Moore& Dr. A. Nishizawa

A.Taira on R/V Tanseimaru
By A.4TairaTwo-ship Seismic Profiling:
High-quality Velocity Structure Determination

by A. TairaCorrelation of Seismic Profile and Lithology
Site 808, Leg 190 Nankai TroughReverseFault
Turbidites

Decollement

Oceanic CrustFrom Taira et al. EPSL (1990)

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ODP Nankai Downhole Observatory: ONDO ProjectLeg 190, 1990
Taira, A. et al. Proc.ODP (1990)
⾳響データ
通信装置
再⼊⽤
コーン

Acoustic
Transmitter
すえつけ⽤バネ

Date Recorder
Thermistor Cable

データ記録
装置

Landing Device

The First Trial ofDownhole
Observatory
But, Failed ! 残念！
Acoustic Data Transmitter

ケーシング
温度センサー付きケーブル（500m）
圧⼒計
おもり

Schematics of ONDO 7

Chikyu Project Proposal:

Not Just For Geological Sampling But Monitoring of Earth Interior
Repeated Air-gun Shooting

Repeated Mapping and Measurements

Observatory Network
Acoustic GeodesyenoZcineSeismog）（地震発⽣帯Plate

Borehole Observatory

onitcu2001年の財務省への説明資料より
Subd

From Presentation by A. Taira at the Ministry of Finance, 2001

Topography of Japan Islands and Plate Boundaries
North AmericanPlate
Japan Trench
EurasianPlate

10cm/year
Pacific Plate
4cm/yearPhilippine Sea
Plate
Nankai Troughby A. Taira10

J-FAST
Japan Trench Mega-earthquake
Fast-Response Drilling
Exp.343 and Exp.343T
201211

Tsunami washed the Sendai Airport,
March 11, 2011

Photo by JiJi press (2011) 12

Huge Tsunami Observed by Ocean-floor Sensors
The offshore pressure sensors detected the huge tsunami
20 minutes prior to the arrival at the City of Kamaishi. Kamaishi
Wave Kamaishi
Height Ground Motion 20 minutes
14:47

Tsunami

15:21

Land sideKamaishi

1618m
1013m

Cable Observation Point: TM1 & TM2
Off the coast of Kamaishi
Earthquake Research Institute(ERI), Univ. ofTokyo. (2011),
Maeda et al., Earth Planets Space (2011)

Observed waveform

TimeData were not used for theofficial warning system
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Huge Eastward Motion of Landward Slope and Trench Axis
Slide made by S.Kuramoto
based on National Geographic Inst. Home Page,
Fujiwara et al., Science (2011),
Kodaira et al., Nat. Geosci. (2012)

JapanTrench

深度Japan Trench

Exp. 343: Fault Zone Core from 817mbsf
For the first time in the history of Scientific Ocean Drilling,M9-earthquake fault zone was drilled, logged and sampled.

by IODP/JAMSTEC

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Installation and Recovery of
Thermistor String, Exp. 343T

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Fault at 817mbsf and Thermal Anomaly
Resistivity (Hole Image)

Mean Resistivity

Gamma Ray

Fulton et al., Science (2013)
Mori et al.,Oceanography (2014)
Kirkpatrick et al., Tectonics (2015)

Residual Temperature

Fault Zone
Fault Zone

Friction Coefficient less than 0.1

Resistivity = Water Content

Gamma Ray=Clay Content18

IODPNankai TroughSeismogenic Zone Experiments(NantroSEIZE)
Multiple Expeditions
2007-201819

！ 3D Seismic Profile of the Nankai TroughAccretionary Prism & Forearc Basin( JAMSTEC - Univ. Hawaii Collaboration )Forearc Basin

Accretionary Prism

Mega-Splay Fault
Oceanic Crust

三次元地殻構造探査

From Moore et al. Science,(2007)

A Model of Tsunami Generation by Mega-Splay Fault- 2007 Version Surface Propagation ofSeismic Rupture
through Mega-splay Fault:
The Cause of Tsunami
C0002

Weak Newly Formed
Accretionary Prism:
Non-Seismogenic

C0010

10cm/year
Pacific
Plate

4cm/yearPhilippine Sea
Plate
Plate Subduction
Observatory Site

Seismic Profile from Moore at al., Proc. IODP, (2009)21

Evidence for Trench Seismic Slip at the Nankai TroughA New Model for Tsunami Generation
Vitrinite reflectance (輝炭率）data(Coalification of Plant Debris) show
frictional heating
at the mega-splay fault
and the forefrontof the plate boundary.
輝炭率

輝炭率

Sakaguchi et al. Geology (2011)22

Revised Model of the Nankai TroughMega-earthquake& Tsunami Generation

Kuroshio-cho Town
1946 Nankai Earthquake T.H.=6m
Maximum Rupture and Tsunami Zone T.H.=34m(T.H.= Tsunami Height)

neoZsouivPre .0)9(MhetfoM

ummiaxBy JAMSTEC

reut
Rup

Add-on Tsunami Generation Zone
based on the IODP data
(M9.1 )
by Japan Cabinet Office (2012)（内閣府 中央防災会議）

DONET Technology Innovation

Connector Joint

Node for Extension

Termination Device

Seismometer

Pressure Gage (Tsunami Sensor)

By JAMSTEC

24Extension Cable

Borehole Observatory of C0002 SiteNankai Trough
The Observatory assembly
prepared for installation under thedrill-floor
Packer
Thermistor
Seismometer

JAMSTEC/CDEXより

Strain Gage
Pressure Gage

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JAMSTEC/CDEX

Detection of Slow-Slip Eventsby Pore Pressure Measurement

Comp. Comp.
(basinsite)

Ext. Comp.

From
Araki et al.
Science (2017)

Ext. Ext.

(splay faultsite)

1-4cm of slip at each event

Equal with 30-50% release of subduction strain

Proposed Full Coverage of the Nankai Troughby DONET-type Network & Real-time Warning System

GPS-Tsunami
AUV
Drilling/Coring Sites
GPS-Acoustic Geodesy

By JAMSTEC

Western Expansionof DONET-Type Cable Network: Under Construction

DONET1&2

次の南海トラフ沈み込み帯での巨大地震は、いつ、どこで、どのように発生するかは不明である。予測、予知することも現在の科学技術力ではできない。しかし発生に至る過程や、一部で地震が発生した後の追跡は可能である。
我々は即時モニタリングを最低限行うことによって、多くの生命・財産を守ることができるであろう。

Japan Trench and Nankai TroughProject Summary.

Technical innovation of core-log-seismicobservatory integration has completely revised ourunderstanding of the plate boundary megaearthquake and tsunami genesis.
◎

Combined borehole observatory and seafloor
cable network would provide real-time warning
system for the reduction of casualties.
(The system is now utilized at the national andlocal government levels and private organizations)◎28

Future Cutting-edge Technology
The Chikyu and IODP Beyond No.1
Further Development of Core-Log-SeismicObservatory-Experiment Integration
Key Technology: Fiber Optic Cable as Seismic &Crustal Motion Sensor◎Observation of High-Resolution

Plate-wide Seismicity andCrustal Deformation◎New Insight into Earth’s Interior

Dynamics and Geo-Hazard Science
Iceland crustal deformation
observed by fiber optic cable
Jousset, P. et al., Nature Comm. (2018) (green line)

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Future Cutting-edge Technology
The Chikyu and IODP Beyond: No.2

CrustMantle◎ Ultra-deep Drilling from theOceanic Crust to the Uppermost
Mantle◎ Drilling Transect of OceanicPlates ( Mantle Convection, PlateTectonics, Earthʼs Material Cycleand Evolution of Life )◎ Insights into Evolution andHabitability of Exoplanets◎ Borehole Experiments for DeepBiosphere (e.g. Role of Electromagnetic Energy)◎ Mantle Minerals as Paleo-detector
for Dark Matter and Neutrino
Baum, S. et al. et al,, arXiv:2106.06559 (2021)
Baum, s, et al., Looking for Dark Matter with Olivine,

After Inagaki, Kuramoto and Taira, Monthy Chikyu(in Japanese), (2021)Tohoku Univ. Frontier Symposium (2022)

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.

Acknowledgements

Providing this opportunity to me by Dr. Hiroko Watanabe,
Tohoku University and the organizing committee is greatlyappreciated.
I would like to thank my fellow co-workers for long-time
collaboration concerning the projects of Marine Geology& Geophysics, D/V Chikyu and IODP.
I am grateful for the information provided by Drs. Eiichiro
Araki and Keisuke Ariyoshi of JAMSTEC for the preparationof my talk.
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