Report on the International Workshop for Large-scale Research Cruises

1. General information

Cruise Title:

East/central Pacific International Campaign (EPIC)-I: Understanding the budget, dynamics and the role of

fluid in subducting lithosphere -

Moderator’s Name： Masa Kinoshita / Hikaru Iwamori

Moderator’s Department：JAMSTEC

Required cruise days (round-trip)：

Year 1: 141 days

Year 2: 111 days

(244 days for EPIC-II Expedition)

Major Survey Area：Eastern / Northern Pacific Ocean

Brief description of the scientific objectives and survey plan of the cruise(s) (up to 200 words)

The sea water which is absorbed into the oceanic lithosphere, subducted along the seismogenic

zone, and eventually dehydrated back to the crust, plays an essential role on the earth’s activities such as

seismogenesis, arc volcanism and the deep life hosted by mantle serpentine. It is the Earth science’s

primary question where and how the fluid is absorbed, and how much in total before it is subducted. To

address this question, we select the fast-spreading ocean lithosphere of the northern Cocos Plate as our

primary site. We collect seismic reflection and refraction data along a long-enough transect across the

trench axis in order to depict the hydrated region in the oceanic lithosphere in terms of Vs anomalies. As of

today, we believe that JASMTEC vessel is equipped with the best seismic tool.

The influence of subducted fluid on the seismogenic characteristics will also be partially

investigated in other subduction zones (Cascadia, Mexico and Costa Rica). We also take the advantage of

the transit time with operations (bathymetry, etc.) of relatively a small additional shiptime.

We propose our expedition for 140 days including a transit time. It can be significantly saved if

this expedition is combined with other expeditions.

Keywords (up to 5):

Water in the oceanic crust and upper mantle

Serpentinization

Outer rise bend fault

Subduction zone earthquake

Deep Life

Relationships to the JAMSTEC Mid-term program: 1) Submarine resources R&D Investigation into processes and spatial and temporal variation of flux between solid earth and

hydrosphere 3) Oceanic seismogenic zone R&D Research with the goal constructing a new conceptual model of a seismogenic zone through a

comparative study in subduction zones. We will discuss future plans for big geophysical cruises including large-scale, high resolution, seismic seafloor imaging, sediment sampling, monitoring of crustal activity and integration with bore hole data

4) Marine biosciences R&D Exploration of Limits and Biosphere in Deep Earth 5) Development and utilization of advanced research technologies Simulation and the physics, chemistry and geological exploration of mantle and core

2. Co-proponents

Name Organization Country Remarks

1 Jason Morgan Department of Earth Sciences, Royal Holloway, University of London Egham

UK #03 lead Cocos Bend-fault

2

B. Ildefonse, I. Grevemeyer, T. Henstock, D. Teagle, P. Vannucchi, H. Villinger

#03

3 Go Fujie JAMSTEC Japan #03,17,

4 Shuichi Kodaira JAMSTEC Japan #03,17,27,29, 40

5 Cesar R. Ranero Barcelona Center for Subsurface Imaging, ICREA at CSIC

Spain #17 lead CRISP seismogenesis

6

V. Sallares, I. Grevemeyer, D. Klaeschen, T. Minshull

#17

7 Yoshihiro Ito DPRI, Kyoto Univ, Japan #27 lead Mexico seismic gap

8

Toshiya Kanamatsu, Victor M. Cruz Atienza, Carlos Mortera Gutierrez, Allen

#27

Husker, Vladimir Kostglodov, Bill Bandy, Masanao Shinohara, Ryota Hino

9 Michael Riedel Natural Resources Canada, Geological Survey of Canada

Canada #29 lead Cascadia seismogenesis

10

K. Wang M. Nedimovic, H. Kao, V. Barrie, M. Bostock, A. Calvert, S. Dosso, K. Obana, R.D. Hyndman, G.D. Spence, E. Davis, J. Cassidy, J. Henton, K. Becker

#29

11 Jerome Dyment Marine Geoscience Team, Institut de Physique du Globe de Paris, CNRS

France #35 lead Cretaceous superchron

12

Yves Gallet, Nobuaki Fuji, Roi Granot, Nobukazu Seama, Yoshifumi Nogi, Toshitsugu Yamazaki, Chie Honsho, Kyoko Okino, Taichi Sato

#35

13 Shigeaki Ono ODS-JAMSTEC Japan #40 lead M2M

14 Tomoaki Morishita Kanazawa University Japan #40

15

Umino, S., Seama, N., Michibayashi, K., Ildefonse, Moore. G., B., Kelemen, P., Teagle, D., Ono, S., Abe, N. and M2M proponents

$40

16 Masa Kinoshita KOCHI-JAMSTEC Japan #55 lead, #29, #60 lead

17

Toshiya Kanamatsu, Weiren Lin, Tsuyoshi Ishikawa, Natsue Abe

#55

18 Katz Suzuki JAMSTEC Japan #58 lead

19 Hide Kumagai JAMSTEC Japan #58

20

M. Yamano, E. Davis, H. Villinger, R. Harris, X. Gao, W. Lin, T. Hirose, A. Yamaguchi, K. Wang

3. Scientific Objectives of the cruises

Formation, evolution, and recycling into the mantle of oceanic lithosphere is the most

fundamental part of the plate tectonic cycle, and a primary mechanism for thermal and chemical exchanges

between the solid Earth and the hydrosphere. The sea water which is absorbed into the oceanic lithosphere,

subducted along the seismogenic zone, and eventually dehydrated back to the crust, plays an essential role

on the earth’s activities such as seismogenesis, arc volcanism and the deep life hosted by mantle serpentine.

Recent studies have demonstrated that the hydrothermal circulation at the mid-oceanic ridges

cannot supply an adequate fluid to generate serpentine in the upper mantle, which is being revealed as the

low Vs anomaly through seismic surveys. If this is the case, the oceanic lithosphere should migrate from

ridges to the trench without being serpentinized (i.e. keeping its ’fresh’ condition). Thus, it is the Earth

science’s primary question to know where and how the fluid is absorbed, and how much in total before it is

subducted.

Among various subduction zones, we select, as the primary site for EPIC-I expedition, the

fast-spreading ocean lithosphere of the northern Cocos Plate from its formation at the East Pacific Rise to

subduction in the Mid-America Trench (Morgan et al; Proposal #03). We propose to collect seismic

reflection and refraction data along a linear transect with grids in some focus areas in the passively cooling

oceanic plate and the transition into the subduction zone where faults that form as the plate bends allow

seawater to penetrate through the crust and into the upper mantle. Based on this information, fluid flow

associated with these plate bending faults will be extensively investigated using near-seabed bathymetry

and water sampling, and detailed ROV heat flow and vent sampling.

This proposal will deliver key information on the evolution of oceanic lithosphere and provide

essential site survey information for two IODP potential proposals: the MoHole to Mantle initiative (M2M;

IODP-805MDP[1]) (Umino et al; Proposal #40) and the new Bend Fault Serpentinization experiments in

the outer rise.

The influence of subducted fluid on the seismogenic characteristics will also be partially

investigated in other subduction zones (Cascadia, Mexico and Costa Rica) through seismic and other

geophsycal & geological surveys (Riedel et al; Proposal #29; Ranero et al., Proposal #17; Ito et al.,

Proposal #27). The Cascadia subduction zone has an end-member warm, smooth, and sediment-rich

megathrust that generates great earthquakes and tsunamis, having important comparisons with SW Japan.

The objectives to study the potential of “slip to trench” rupture in a sediment-rich environment and to study

how the plate boundary transitions from normal to extremely oblique subduction and eventually to

strike-slip faulting. In the Mid-America Trench, Ranero et al. (#29) propose a regional-scale, unprecedented

high-resolution 3D survey with the trevel-time and the full-waveform inversions for Vp and its anisotropy.

Ultimately the 3D volume of physical properties should be used with CRISP riser drilling project with R/V

Chikyu to unravel plate boundary fault mechanics. The seismic potential of the Guerrero seismic gap off

Mexico will be investigated with a special reference to slow slip events (SSE) (Ito et al., #27), through

observation using ocean-bottom instruments and seismic reflection survey.

As the piggyback operations, we take the advantage of the transit from Japan to the eastern

Pacific region and back to Japan with relatively a small (or even no) additional shiptime. Jerome et al.

(#35) propose both the surface and near-bottom magnetic survey in the northern Pacific and the Indian

Ocean region in order to understand the mechanism for the long periods of constant magnetic polarity such

as the Cretaceous Normal Superchron. As the first step, we include only the surface magnetic and other

underway geophysics survey during the transit.

Other transit time is used for underway geophysics survey (multi-narrow beam bathymetry,

magnetic, gravity, subbottom profile), for most of these transit lines have not been surveyed with

high-resolution tools. Furthermore, some winch-based operations (CTD, piston-coring, heat flow, dredge)

may be conducted on the way to understand Mass and heat flux reference (Umino et al., #40; Kinoshita et

al., #55; Suzuki et al., #58).

Fig. 1 Schematic cross section of the Cocos plate from the East Pacific Rise to the Costa-Rica subduction zone,

illustrating the concept of studying the complete life cycle of an oceanic plate. 1: M2M, 2: outer rise deep drilling, going

through bent fault and reaching the serpentinized mantle, 3: CRISP (Chikyu +10 Report, 2013).

Why Eastern Pacific?

Main reason is that this environment, with its subduction of younger plates created at

fast-spreading ridge, provides unique examples where these basic processes occur at depths accessible to

current AUV and drilling technologies. For example, MoHole drilling is currently envisioned to be limited

to seafloor depths less than 4000m, and current AUVs are limited to 3500-4000m. The knowledge gained

here will be transferable to other subduction zones. This region also provides ‘young-plate’ end-members to

contrast with ‘old-plate’ end-members elsewhere.

Why we need JAMSTEC vessels?

These proposed projects are ambitious multinational collaborations that will push the frontiers of

our understanding of subduction systems. JAMSTEC will play a critical role in making this international

science possible. Deep-sea exploration technology will also be enhanced by the new experimental

methodologies that are proposed here.

JAMSTEC vessels offer rare seismic and ROV/AUV/Submersible capabilities required for this

research. We fully plan to augment JAMSTEC shiptime with complementary international ship-support.

4. Survey Plan of the cruises

Most of individual proposals in the eastern and central Pacific are focused on the regional seismic

reflection and refraction surveys. Some of them also propose detailed-scale investigation using ROV/AUV.

Since the number of ocean-bottom seismometers (OBSs) is limited, even with the cooperation from other

countries, we propose to focus on the primary site off Nicaragua in the Cocos plate to carry out an intensive

Multi-channel seismic (MCS) survey with OBSs. Other sites (Cascadia, off Mexico, off Osa) will be

conducted if the ship time of OBSs from other source is available. All the transit will be used for the survey

also, mainly as a bathymetry and shallow geological survey with some additional piston coring and heat

flow. The transit from Hawaii to Japan can be omitted if this expedition (EPIC-I) is continued to the

South-Pacific expedition, EPIC-II.

Operation for Year 2 should be planned based on the results from Year-1 expedition.

Table 1. Proposed expedition schedule for EPIC-I (Year 1)

Mission (proposal ##)

Operation Site DaysCollaboration

Transit/UG JAMSTEC to CNS-W 5

Cretaceous superchron (#35) HF

UG/PC CNS-W to CNS-E 11

ref.(#55) Transit/UG CNS-E to Cascadia 4

Cascadia Slip to trench/transition from normal to oblique subduction (#29)

MCS/MNB/ (OBS)

*20

CCGS for 150 OBS operation, coring, heat flow, 100 OBS from JASMTEC

Portcall Victoria 1 Transit/UG Victoria to off Mexico 9

Guerrero Seismic Gap (#27)

MCS/(OBS) Off Mexico *10UNAM ship for OBS operations

Transit/UG Mexico to Nicaragua 3 Bend Fault System & MoHole (#03) Heatflow(#60)

MCS/OBS/ PC/HF

Off Nicaragua 30European ship for OBS (+ GEOMAR ROV?), heat flow

Full waveform inversion (CRISP-riser)(#17)

MCS/(OBS) Off Osa Peninsula *20

European and/or US ship for additional OBS support:~30 days; shooting can be shared (~30 days)

Portcall Puntarenas 1 Transit/UG Puntarenas to Hawaii 15 Transit/UG Hawaii to JAMSTEC **12

Total Days 141

Table 2. Proposed expedition schedule for EPIC-II

(see EPIC-II proposal for details) Mission (proposal ##)

Operation Site Days

Transit/UG JAMSTEC to Hawaii **12

Leg1(#39/18) surface/ROV East. Pac. 31

(18) CMAR(Japan/US/France/UK/Australia/Canada/Ne

w Zealand)Portcall Galapagos

Leg2(#18/9) surface/ROV 32Portcall Valparaiso

Leg2B Hot subduction zone (#32)

MCS/OBS south Chile Triple Junction

**20

Portcall Valparaiso

Leg3 (#9/23) surface/ROV 44Portcall Easter

Leg4 (#9/23) surface/ROV 40Portcall Tahiti

Leg4B Deep mantle volatile reservoir(#33)

ROV/rock sampling

20

Portcall Tahiti Leg5 (#9/23) surface/ROV 41

Portcall Brisbane

Transit/UG

Brisbane to JAMSTEC

14

Total Days 254

Table 3. Proposed expedition schedule for EPIC-I (Year 2)

Mission (proposal ##)

Operation Site DaysCollaboration

Transit/UG JAMSTEC to CNS-W 5

Cretaceous superchron (#35)

ROV Deeptow mag.

CNS-W to CNS-E 20

Transit/UG CNS-E to Cascadia 4

Cascadia Slip to trench/transition from normal to oblique subduction (#29)

PC/HF/OBS Recovery

15

CCGS for 150 OBS operation, coring, heatflow 100 OBS from JASMTEC

Transit/UG Victoria to off Mexico 9Guerrero Seismic Gap (#27)

PC/HF/OBS Recovery

Off Mexico *10UNAM ship for OBS

operationsTransit/UG Mexico to Nicaragua 3

Bend Fault System & MoHole (#03) Heatflow(#60)

ROV/PC/HF Off Nicaragua 30European ship for OBS (+

GEOMAR ROV?), heatflow

Transit/UG

Nicaragua to JAMSTEC

15

Total Days 111

Notes:

* JAMSTEC operation is conducted only if a shiptime from other institution is available.

** Transit from JAMSTEC to Hawaii may be skipped if EPIC-I and EPIC-II cruise can be combined

together.

UG=Underway geophysics (bathymetry, magnetic, gravity, subbottom profile), PC=Piston coring,

Notes: MNB=bathymetry swath mapping, SBP=Sub-Bottom Profiling, PC=Piston core, HF=Heat flow

Fig. 2 Proposed survey track for EPIC-I and EPIC-II expeditions. White symbols and letters are for EPIC-I, and

yellow symbols and letters are for EPIC-II. Filled circles=survey sites, filled squares=potential ports for the portcall,

Tr=Transit, CNS=Cretaceous Normal Superchron, (##)=estimated days. Note that the transit days (~24 days) between

JAMSTEC and Hawaii can be saved if the EPIC-I expedition is taken over by EPIC-II at Hawaii instead of at JAMSTEC.

See EPIC-II proposal for more details on the EPIC-II expedition.

Fig. 3 EPIC-I Primary Site off Nicaragua (Morgan et al., proposal #3).

Fig. 4 EPIC-I subsidiary site off Canada (Riedel et al., proposal #29)

Fig. 5 EPIC-I subsidiary site off Mexico (Ito et al., proposal #27)

Fig. 6 EPIC-I subsidiary site off Osa Peninsula, Costa Rica (Ranero et al., proposal #17).

5. Relevance to other scientific projects in Japan and/or abroad

This expedition is intended to supplythe site survey data for the IODP proposals.

See Tables for potential collaborations with other countries.

6. Remarks