SCG64-P01

Room:Convention Hall

Time:May 27 18:15-19:30

Occurrence of hydrothermal kaolin minerals beneath the Iheya North Knoll hydrothermal
field in the Okinawa Trough
TSUTSUMI, Saki1∗ ; ISHIBASHI, Jun-ichiro1 ; UEHARA, Seiichiro1 ; SHIMADA, Kazuhiko1 ;MIYOSHI, Youko2 ; NOZAKI, Tatsuo3 ; TAKAYA, Yutaro3
1

Department of Earth and Planetary Sciences, Graduate School of Sciences, 33 Kyushu University, 2 National Institute of Advanced Industrial Science and Technology, 3 Japan Agency for Marine-Earth Science and Technology
Introduction
Kaolin minerals is known as common alteration minerals observed in on land geothermal or fumarole area. On the other
hand, only few studies reported occurrence of kaolin minerals in seafloor hydrothermal fields. As an example, occurrence ofkaolin minerals was reported at the Jade site in the Izena Hole in the Okinawa Trough by Marumo and Hattori (1999). Recently,
seafloor drillings conducted at the Iheya North Knoll in the Okinawa Trough revealed occurrence of kaolin minerals in sedimentcores obtained from the vicinity of active hydrothermal fields. We conducted X-ray diffractometric analysis (XRD) and ScanningElectron Microscope (SEM) observation of the sediment samples. In this presentation, we report depth profiles of clay mineral
assemblage in sediment below active hydrothermal fields, with interest in the relationship with a profile of metal elements content
in the sediment.
Sampling and methods
Sediment cores were obtained by drilling at Hole C9016B (27 ⁰ 46.6’ N,126 ⁰ 54.6’ E, depth =1124m) in the vicinity of Aki
site during CK-14 expedition in 2014, and by drilling at Site BMS-I-4 (27 ⁰ 47.4’ N, 126 ⁰ 53.9’ E, depth=1048m) located
200 m east from the Original site, during TAIGA11 cruises in 2011. Identification of clay minerals was conducted by X-ray
diffraction technique (XRD) after separation of clay minerals and by scanning electron microscope (SEM) observation of bulk
sediment.
Results and discussion
In the Aki site, change of dominant clay mineral assemblage along depth was recognized as below; smectite and illite in 0-9
mbsf, illite and kaolin mineral in 9-11 mbsf, and illite and Mg-chlorite below 11 mbsf (to 91 mbsf). Detailed investigation of
the kaolin-rich layer revealed change of occurrence of kaolin minerals along depth as below; spherical kaolin minerals at 8.88
mbsf, plate-like kaolinite and tubular halloysite at 9.18 mbsf, and crystal kaolin minerals at 10.83 mbsf. It is interesting to noteoccurrence of sphalerite and barite were identified in the 9.18 mbsf sediment but not observed in 10.84 mbsf. Profile of traceelements content in bulk sediment (Nozaki et al., in this meeting) corresponded to the occurrence of sulfide/sulfate minerals inthe sediment. High contents of Ba, Zn and Pb were notable in the 9.81 mbsf sediment, whereas high contents of Cu and Ag wererecognized in the 10.28 mbsf sediment.
In the Original site, intense alteration represented by dominant occurrence of kaolin minerals was recognized in sediment fromjust a few 10 cmbsf to 3.5 mbsf. Also in the sediment from this site, occurrence of sphalerite, galena and barite was identified.
As mentioned above, occurrence of kaolin minerals associated with sphalerite and barite was recognized in relatively shallow
depth below the seafloor located at a few hundred meters apart from the active venting in two hydrothermal sites in the Okinawa
Trough.

Keywords: submarine hydrothermal deposit, clay minerals, submarine drilling

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SCG64-P02

Room:Convention Hall

Time:May 27 18:15-19:30

The structure of iron oxidized mounds at shallow marine hydrothermal environment in
Satsuma Iwo-jima Island, Kagoshima
KURATOMI, Takashi1∗ ; KIYOKAWA, Shoichi1 ; IKEHARA, Minoru2 ; GOTO, Shusaku3 ; HOSHINO, Tatsuhiko4 ;IKEGAMI, Fumihiko1 ; MINOWA, Yuto1
1

Kyushu University, 2 Center for Advanced Marine Core Research, Kochi University, 3 Geological Survey of Japan, AIST, 4 Japan
Agency for Marine-Earth Science and Technology

Satsuma Iwo-Jima, located 38km south of Kyusyu Island, Japan, is a volcanic island in the northwestern rim of Kikai caldera.
Here is preserved and identified on occurring iron precipitation at shallow ocean where can be recorded modern analogy of ironprecipitation and sedimentation. Iron oxidized mounds are developing at seafloor with hydrothermal activity (pH=5.5, 50-60
degree Celsius), and there is high deposition rate of iron-oxides (33 cm/year: Kiyokawa et al., 2012).
Result of sea sonar scan seismic images shows that the iron oxidized mounds in Nagahama bay are estimated about 7.8 m3 involume, which formed 2-3 thick mound at 32.68 m2 area for 20 years. Each mound is formed two layers: blackish hard layer
and brownish soft layer. The inside of samples is constructed from the aggregation of convex structure (3-4 cm) covered byhard layers as a rim. Petrographic observations indicate that both layers have filament-like forms, and the form in soft layer isperpendicular to that in the hard layer. The number of iron oxides particles observed on filament-like forms in soft layer increases
toward hard layer. Hard layer consists of aggregation of bacillus-like form as the chain of particle (about 2 um). At soft layer,on the other hand, bacteria-like form with smaller particles (<0.5 um) is observed. Bacteria-like form could be classified into
3 types (helix, ribbon-like, twisted). Furthermore, hard layers consist of ferrihydrite and opal-A (Si: 26.8%, Fe: 56.0%) andsoft one is composed by ferrihydrite, opal-A and silica mineral (Si: 36.5%, Fe: 43.5%). Mariprofundus ferrooxydans known
as iron-oxidizing bacteria belonging to Zeta-proteobacteria identified in this matter, but they are nothing at floating iron oxide
samples.
The process of forming iron oxidized mounds: 1. Soft layers were made by chemical and biological activity. The filament-likeforms at soft layer is the stalks of iron oxidizing bacteria. 2. The hard layers were made by adsorption of iron oxyhydroxidearound stalks. Iron oxidizing bacteria is prefer to the redox interface (Chan et al., 2011) such as the mixing zone located in hardlayer between hydrothermal fluid and seawater. 3. Hydrothermal activity form the liner structure at hard layer. Iron oxidized
mounds were formed by repeating of those process over ten times.
Based on the seismic data, the forming rate of iron oxidized mounds is about over 1.2 cm/yr. Formation of hard layers in thesemound is the result of adsorption of iron oxyhydroxide around stalks made by the activity of iron oxidizing bacteria. The ironproviding rate (2.474∗106 kg(Fe)/m.y./m2 ) from the Nagahama bay iron mounds is as about ten times as that of the HamasleyGroup sediment (2.51∗105 kg(Fe)/m.y./m2 ). Furthermore, if there is the Nagahama bay iron oxidized mounds at Archean,
6.0∗108 times of these mounds need to form the Joffre Member volume (360 m/2m.y.). In this study, we strongly suggest thatthe combination of chemical and biological reaction is important system to form large amount of iron oxide deposit.
Keywords: iron oxidizing bacteria, hydrothermal fluid, iron oxide, satsuma iwo jima, biomineralization

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SCG64-P03

Room:Convention Hall

Time:May 27 18:15-19:30

Geochemistry of trace alkali elements in the seafloor hydrothermal fluids
EBINA, Naoya1∗ ; ISHIBASHI, Jun-ichiro2
1

Department of Earth and Planetary Sciences, Graduate School of Sciences, Kyushu University, 2 Department of Earth andPlanetary Sciences, Faculty of Science, Kyushu University
Hydrothermal fluid contains many elements at high concentrations as a result of fluid interaction with rock/sediment andseawater dusring fluid circulation beneath the subseafloor. In particular, Rb and Cs are known as ”soluble elements” which iseasily leached from the rock/sediment into the fluid because of their large ion radii. Thus, trace alkali element compositions ofhydrothermal fluids would provide information about water/rock interactions.
We determined Rb and Cs concentrations of hydrothermal fluids collected from four fields in the Izu-Ogasawara arc (Myojin
Knoll Caldera, Myojinsho Caldera, Bayonnaise Knoll Caldera and Suiyo Seamount), from six fields in the Mariana Trough(Alice Springs Field, Forecast Vent Field, Pika Site, Archean Site, Snail Site and Urashima Site), and from the Iheya North Knollhydrothermal field in the Okinawa Trough, to discuss their diversity.
Analysis of Rb and Cs concentrations of each sample was conducted using ICP-QMS. To determine the endmember Rb and Cs
compositions for each hydrothermal field, the analytical results of the samples were extrapolated to zero Mg concentration. The
endmember concentrations of Rb and Cs are plotted in Figure 1. In addition to the results of this study, data from hydrothermal
field in the EPR 21o N[1] and MAR (TAG and MARK)[6] located in sediment-starved mid ocean ridge setting, in the Escanaba
Trough and Guaymas Basin[2] located in a sediment-hosted setting, and in the Lau Basin[3] and Manus Basin[4] located in a
back-arc basin setting are plotted in the same figure. Moreover, compiled data for volcanic rocks and sediment material aroundthese hydrothermal field are overimposed as shaded region in Figure 1.
A range of Rb/Cs ratio of hydrothermal fluids from an arc setting (square symbols; Rb/Cs=12.8 to 26.7) can be distinctive thatfrom a back-arc setting (circle symbols; Rb/Cs=18.6 to 100.1). Rb and Cs concentrations in hydrothermal fluids from a sedimenthosted hydrothermal field is characterized by their substantially high concentrations. Moreover, it is likely that the range of Rb/Cs
ration of hydrothermal fluids are comparable for those of volcanic rocks/sediment surrounding these hydrothermal field. It would
be suggest that the distribution of Cs from rocks to hydrothermal fluids in arc setting is higher than one in other tectonic setting.
[1] Palmer and Edmond (1989) Earth and Plan. Sci. Let ., 95, 8-14.
[2] Campbell et al. (1994) U.S. Geol. Surv. Bull , No. 2022, 201-221.
[3] Mottl et al. (2011) Geochimica et Cosmochimica Acta , 75, 1013-1038.
[4] Reeves et al. (2011) Geochimica et Cosmochimica Acta , 75, 1088-1123.
[5] de Ronde et al. (2011) Miner Deposita , 46, 541-584.
[6] Campbell et al. (1988) Nature , 335, 514-519.

Keywords: trace alkali elements, hydrothermal fluids, arc, back-arc basin, sediment

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SCG64-P04

Room:Convention Hall

Time:May 27 18:15-19:30

Seismicity at the Kairei Hydrothermal Vent Field Near the Rodriguez Triple Junction in
the Indian Ocean
MORI, Taiyu1∗ ; SATO, Toshinori1 ; TAKATA, Hiroyoshi1 ; IMAI, Yuki1 ; NOGUCHI, Yui1 ; KONO, Akihiro1 ;YAMADA, Tomoaki2 ; SHINOHARA, Masanao2
1

Chiba Univ., 2 ERI, Univ. Tokyo

1. Introduction
In the first segment of the central Indian Ridge from the Rodriguez triple junction, the Kairei hydrothermal vent field exists
and extrudes hydrothermal fluid with richer hydrogen content compared to other hydrothermal vents in the world. Around theKairei hydrothermal field, serpentinized peridotite and troctolites, and gabbroic rocks were discovered. These deep-seated rocks
exposed around the Kairei field may cause the enrichment of H2 in the Kairei fluids. At the Kairei field, a hydrogen-based
subsurface microbial ecosystem and various hydrothermal vent macrofauna were found. In the ”TAIGA” Project (Trans-crustal
Advection and In situ reaction of Global sub-seafloor Aquifer), this area is a representative field of ”TAIGA” of hydrogen. To
investigate how the deep-seated rocks (originally situated at several kilometers below seafloor) are uplifted and exposed onto
seafloor, and the hydrothermal fluids circulate in subsurface, we conducted a seismic refraction/reflection survey and seismicity
observation with ocean bottom seismometers (OBSs). This presentation will show seismicity of the survey area.
2. Observation and methods
We conducted a seismic survey around the Kairei hydrothermal field from January 27 to March 19 in 2013 using S/V Yokosuka
of Jamstec (YK13-01, YK13-03). We used 21 OBSs. We determined hypocenter locations in a 3D velocity structure. The 3D
structure is estimated by Takata et al. (2015, This Meeting). We used NonLinLoc software (Lomax, 2000), which can estimate
earthquake locations in 3D media.
3. Results
From the 50 days seismicity observation, we found more than 5000 micro earthquakes in this area. A swarm of micro earthquakes exists at a location about 1-3 km northwest of the Kairei field. The swarm has a NNW-SSE strike, parallel to the ridgeaxis. The depth of the swarm is very shallow (˜4 km from seafloor). The focal mechanisms in the swarm are normal type. These
indicate that this swarm shows normal fault activity parallel to the ridge axis. This swarm may be related to the hydrothermal
activities of the Kairei field. At the first segment of the central Indian Ridge, many micro earthquakes occurred. The depth ofthese events is about 3-6 km from seafloor, and deeper than that of the swarm near the Kairei field. The focal mechanisms at
the segment are normal type with the T axis parallel to the plate motion. At the non transform offset, there are no lineaments ofearthquakes and left lateral strike slip mechanisms are dominant.
Acknowledgements
We thank the captain and the crew of S/V Yokosuka of Jamstec for their support. This work was supported by Grant-in-Aid for
Scientific Research on Innovative Areas of the Ministry of Education, Culture, Sports, Science and Technology (Grant Number
20109002, TAIGA project).

Keywords: TAIGA Project, hydrothermal field, seismicity, Triple Junction in the Indian Ocean

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SCG64-P05

Room:Convention Hall

Time:May 27 18:15-19:30

Petrographical and morphological charaeter or volcanicrocks dredgard around the Sumisu
calderam, Izu-Ogasawara arc
UEHARA, Taiki1∗ ; SAKAMOTO, Izumi1 ; YAGI, Masatoshi1 ; INOUE, Tomohito1 ; OKAMURA, Satoshi2
1

School of marine science and technology, 2 Hokkaido Education University,Sapporo Campus

The Izu-Ogasawara arc is located the south of Izu peninsula. It opens for total extension approximately 1,500km, approximately 400km in width. In addition, it is an active oceanic island arc of the volcanic activity. A volcanic zone of the Quaternary
period ranges to the Shititou-Ioushima ridge in the Izu-Ogasawara arc to the north and south and constitutes a volcanic front.
There are many submarine volcano with caldera in the Izu-Ogashawara arc (Murakami,1997).
In this study, mention of the topography of Smith caldera gathered by Tokai University Bousheimaru from May 9, 2014 throughMay 15 and the rock analyzed it.
As a result, (1)the diameter of the Sumisu caldera is 9km (2)the depth of the water of the outer rim of a volcanic crater top
is 30m (3)caldera wall is steep than the outer slope (4)stepped terrain development in the caldera outside slope (5)water depthof caldera bottom 900m (6)there exists a central cone of relative height 100m in the center. As a result of bottom sampling,
fresh rhyolite volcanic rock and volcano-clastic rock were gathered from a caldera bottom and the central cone. Flesh rhyolite
volcanic rock rhyolite was gathered in the lower caldera wall and central part. By the petrochemistry composition, a value of
SiO2 was concentrated in two places of 49.6(wt.%)˜51.1(wt.%) and 67.5(wt.%)˜69.4(wt.%). Typical bimodal volcanic activity
was confirmed from this caldera.
From the slope of the back arc side, flat basalt and a large quantity of pumice and acid plutonic rocks were collected. A large
quantity of dacite quality pumice (quality of corner stone) was gathered at the same time, too. Therefore, bimodal volcanic
activity was estimated in the back arc side than not including volcanic rock of the quality of andesite.
Keywords: Smith caldera, Bimodal volcanism, Spatter ejecta, Dacitic pumice

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SCG64-P06

Room:Convention Hall

Time:May 27 18:15-19:30

Petrological study on Marcus Island
KAWANO, Takaomi1∗ ; HIRANO, Naoto2 ; MORISHITA, Taisei3
1
3

Graduate School of Science and Faculty of Science, Tohoku University, 2 Center for Northeast Asian Studies, Tohoku University,
Hydrographic and Oceanographic Department, Japan Coast Guard

Marcus-Wake seamount trail is located in West Pacific Seamount Province (WPSP), where the oceanic plate is oldest in theworld, around 160 Ma Pacific plate. WPSP had occurred during Cretaceous and was reconciled with current active hotspotsof French Polynesia in South Pacific. Marcus (Minami-tori) Island is located 50 km away from Marcus-Wake seamount trail
to the north. Most of seamounts, particularly well-studied seamounts, are more voluminous than the edifice of Marcus Island,
whereas no islands and atolls are found around the island within 500 km. In this study, mineralogical and whole rock analysis oflava samples, obtained in submarine survey of northwest flank of Marcus Island, are adopted in order to compare with volcanic
samples from WPSP and South Pacific islands of active hotspot volcanism. High TiO2 in relic of chrome spinel indicates the
typical intra-plate volcanism to be similar characteristics with those of WPSP. Major element compositions reveal normal-alkali
basalts. Nb/Zr and Nb/Y ratios can classify the origins of shallow mantle plume, not in superplume as old Polynesian hotspots,
like the Marcus-Wake seamounts of WPSP. Therefore, Marcus Island was produced from intraplate volcanism which differs fromhotspot activities forming the Marcus-Wake seamounts.
Keywords: Marcus-Wake seamount trails, seamount, WPSP, HFSE, superplume, alkali-basalt

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SCG64-P07

Room:Convention Hall

Time:May 27 18:15-19:30

Olivine xenocrysts in lava of petit-spot volcano
TAKI, Arashi1∗ ; HIRANO, Naoto2 ; YAMAMOTO, Junji3 ; MACHIDA, Shiki4 ; ISHII, Teruaki5
1

Graduate School of Science, Tohoku University, 2 Center for Northeast Asian Studies, Tohoku University, 3 Hokkaido University
Museum, 4 Department of Resources and Environmental Engineering, Waseda University, 5 Fukada Geological Institute
Petit-spot is a small volcano erupted on the seafloor. The magma comes from asthenosphere, just below oceanic lithosphere,
through a crack in subducting plate. The petit-spot volcanoes appear globally on the seafloor where the plate is flexing (e.g.,
Japan and Chile Trenches). The petit-spot lavas and entrained mantle materials have been already reported from areas of Japan
Trench oceanward slope (Sites A), and of NW Pacific (Site B). Although the discovery of the petit-spots has been anticipatedfrom Site C (offshore of Fukushima, south of Site A), lava samples and entrained mantle materials have never been reported. To
examine the activity of the petit-spot volcanoes, we conducted the nine submersible dives of the SHINKAI 6500 submersible
during cruise YK14-05 of R/V Yokosuka at Site C in April 2014.
Alkaline pillow lavas were collected from the Site C during cruise YK14-05. Eruption age is at the time between 0.31 and 2.1
Ma estimated on the basis of the thickness of paragonite on quenched glass rind. The lavas are classified into basanite, and include
large amount of olivine (>10% normative olivine). Large (1-5 mm) olivines have anhedral morphology. The large olivines show
forsterite numbers (Fo) of 88-90 and NiO contents of 0.3-0.5 wt. %, corresponding to the composition of the primitive mantle
peridotite. On the other hand, the small olivines surrounding the large olivines have similar range of compositions (Fo of 84-87,
CaO contents of >0.1 wt. %) to those of groundmass olivines. These observations imply that large olivines are fragments ofmantle peridotites, that is, these are mantle xenocrysts. If these are xenocrystic olivines, it tells us the cryptic aspects of an old
oceanic lithosphere. Fo values of the present olivine xenocrysts are slightly lower than those of the mantle xenoliths reported
from Site A and B (90-93). The chemically heterogeneous mantle might be existed in the subducting NW Pacific plate.
Keywords: petit-spot, olivine, xenocryst

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SCG64-P08

Room:Convention Hall

Time:May 27 18:15-19:30

Petrological analysis of Fe(III)-rich serpentine in the Central Indian Ridge serpentinites
SHIMIZU, Shota1∗ ; MIZUKAMI, Tomoyuki1 ; SODA, Yusuke1 ; MORISHITA, Tomoaki1 ; ARAI, Shoji1 ;TAKAHASHI, Yoshio2
1

School of Natural System, College of Science and Engineering, Kanazawa University, 2 Department of Earth and Planetary
Science, Graduate School of Science, The University of Tokyo
Aqueous fluids at serpentinite-hosted hydrothermal vent fields near mid-oceanic ridges are characterized by high concentrations of dissolved reducing chemical species, such as H2 , H2 S and hydrocarbons, and aid development of unusual chemosynthetic
ecosystems. Petrological, geochemical and experimental works suggest that the cause of the H2 -rich fluids is oxidation of Fe
during water-rock reactions in ultramafic lithosphere to form magnetite. However, a recent micro-XANES study of the MidAtlantic Ridge serpentinite indicates that serpentine can be a primary phase for Fe3+ prior to magnetite. In order to understandthe role of Fe3+ -rich serpentine in the H2 production, we made petrological analyses of serpenitinite exposed at the southern endof the Central Indian Ridge (CIR), very close to the Kairei Hydrothermal Field where high temperature, H2 - and Si-rich fluids
are emitting. Serpentinite samples used in this study (dredged using Hakuho-maru from Yokoniwa Rise) include 11-13 modal %of bastite after Opx indicating that the protoliths are mantle peridotite with harzburgite compositions.
Base on microscopic observations and micro-Raman and EPMA analyses, we identified three types of serpentine after olivine.
The most dominant one is characteristically brownish under microscope and optically isotropic. The Raman O-H bands are distinct from those of typical serpentine polymorphs but can be explained as composites of chrysotile and lizardite. Therefore, wecall this type of occurrence as “brown serpentine aggregate” . It occupies about 70 vol % of the samples. Extensive replacementof olivine by brown serpentine (Stage I) was followed by formation of Fe-rich lizardite along pre-existing magnetite (Stage II),
resulting in a mesh-like texture. During a later stage of hydrothermal alteration (Stage III), the mesh texture has been partly or
fully overprinted by a vein-like texture consisting of Fe-poor well-crystalline lizardite and crack-filling chrysotile at its center.
The microtextural evolution represents stepwise serpentinization probably during uplifting of the CIR mantle lithosphere.
Distribution and mineral chemistry of “brown serpentine” indicate that SiO2 activity was a significant driving force of theformation. Total oxide compositions of “brown serpentine” are significantly lower than that of lizardite implying fine-grained
aggregates with porous nature. They can be interpreted as a product of high reaction rate under high temperature conditions.
Preliminary micro-XANES analyses of “brown serpentine” at a mesh center revealed that about 70% of Fe in the serpentine isFe3+ . Assuming that this value is applicable to the whole sample and that the bulk Fe content is constant during serpentinization,
we estimate that the contribution of “brown serpentine” in H2 generation was as large as that of magnetite. Total H2 produced bycomplete hydration of olivine 1kg is estimated to be 9.6L (the contribution of “brown serpentine” is 4.5L), which is equivalent
to the amount of H2 dissolved in 54kg of the Kairei hydrothermal fluid (8 mM H2 ). Conversion of Fe3+ -serpentine to Fe-poorserpentine + magnetite at shallower parts may cause a minor absorption of H2 although we do not have sufficient data to quantify
it. The maximum estimation of this study implies a high water/rock ratio in hydrothermal system beneath CIR.

Keywords: Mid-oceanic ridge, hydrothermal field, serpentinite, ferric iron, hydrogen

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SCG64-P09

Room:Convention Hall

Time:May 27 18:15-19:30

Lithosphere-Asthenosphere boundary beneath NW Pacific Ocean detected with seismic
waveform data
ABE, Yuki1∗ ; KAWAKATSU, Hitoshi1 ; SHIOBARA, Hajime1 ; ISSE, Takehi1 ; SUGIOKA, Hiroko2 ; ITO, Aki2 ;UTADA, Hisashi1
1

Earthquake Research Institute, The University of Tokyo, 2 Japan Agency for Marine-Earth Science and Technology

We have conducted seismic observation around the Shatsky Rise in the northwest Pacific Ocean at 18 stations equipped witha broadband ocean bottom seismometer (BBOBS) for understanding the structure of the Earth’s interior and the mechanism ofplate motion (Normal Mantle Project). It is important to estimate the upper mantle structure beneath these stations, for revealing
existence of partial melt and water in the oceanic upper mantle.
We calculated P-wave and S-wave receiver functions (PRF, SRF) with waveform data obtained from the BBOBSs. We analyzed
teleseismic events occurring between June 2010 and September 2014, whose magnitudes are over 5.5. Epicentral distances ofthe events used for calculating PRF are between 30o and 90o , and those for calculating SRF are between 55o and 90o . Carefulhandling is required for the data obtained at stations northwest side of the Shatsky Rise because the data are largely affectedby reverberations in the thick sediments (Abe and Kawakatsu, 2014, SSJ Fall Meeting). We eliminated frequency components
higher than 0.1 Hz from SRF with a Gaussian filter because noise level of the observed waveforms in the frequency domainaround 0.2 Hz is high. Frequency components higher than 0.05 Hz were eliminated from PRF for preventing contamination by
reverberations in the sediments. We averaged PRFs and SRFs for each station, and obtained a broad negative peak on averaged
PRFs and a broad positive peak on averaged SRFs, between 5 s and 10 s. Both these peaks correspond to velocity decrease
with depth in the upper mantle. We synthesized PRF and SRF with a model, which contains a discontinuity at depths between
30 km and 150 km, where velocity decreases between 0% and 20% with depth, and searched a model that explains both PRF
and SRF obtained at each station. From the search, a model with 8% drop in velocity at 85 km in depth and a model with 4%
drop in velocity at 125 km in depth explain the data observed at the northwest and southeast side of the Shatsky Rise the best,
respectively. Kawakatsu et al. (2009 Science) detected a discontinuity with downward decreasing velocity at 80 km in depth byan RF analysis of waveform data from borehole BBOBS on north side of Shatsky Rise, and they interpreted the discontinuity
as the Lithosphere-Asthenosphere boundary (LAB). The discontinuity detected in this study may also correspond to LAB. The
structure of the oceanic crust and sediments and water depth of a station may affect the waveform of RFs. Therefore, we now
check how correctly we can constrain the depth and the drop in velocity with different assumptions of the shallower structure.
Keywords: oceanic plate, receiver function, Northwest Pacific Ocean, Lithosphere-Asthenosphere boundary

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SCG64-P10

Room:Convention Hall

Time:May 27 18:15-19:30

Sharp gravity increase following an outer-rise earthquake: possibility of viscoelastic rebound by melt-rich channel
MATSUO, Koji1∗ ; FUKUDA, Yoichi1 ; TANAKA, Yoshiyuki2
1

Kyoto University, 2 The University of Tokyo

We are going to talk about postseismic gravity increase by outer-rise earthquakes, and explain their geophysical mechanism
through viscoelastic theory.
Keywords: outer-rise earthquake, melt-rich channel, viscoelastic rebound, GRACE, postseismic gravity change

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SCG64-P11

Room:Convention Hall

Time:May 27 18:15-19:30

Earthquake induced deposits during the 2004 off Kii Peninsula earthquakes at a terminal
basin
ASHI, Juichiro1∗ ; OMURA, Akiko1 ; OKUTSU, Natsumi1 ; YAMAGUCHI, Asuka1 ; IRINO, Tomohisa2 ;MURAYAMA, Masafumi3 ; IKEHARA, Ken4 ; NAKAMURA, Yasuyuki5
1

The University of Tokyo, 2 Hokkaido University, 3 Kochi University, 4 AIST, 5 JAMSTEC

Submarine paleoseismology has been advanced mainly by investigation of distribution and age of seismogenic turbidite deposits. However, we have to pay attention to the following issues for the usage of this method. 1) Turbidity currents are also
triggered by flood, wave, rapid sedimentation and so on. 2) It is hard to determine a seismic source region by investigationof turbidites originated from more than one sediment-provenance. 3) Tuibidity current does not provide sedimentary record or
remove the former sequence in some cases. In order to avoid these problems, a terminal basin with a limited small provenancearea and without direct river input is an appropriate target. The term ”a terminal basin” is a sedimentary depression surrounded
by topographic heights that capture all sediments supplied from outside.
The sedimentary basin located between the Kumano forarc basin and the outerarc high corresponds to a terminal basin 250
meter deeper than the surroundings. The core sample collected by R/V Shinsei-maru KS-14-08 from this basin includes thinvery fine-grained sand at 17 cm below seafloor and mud with silty clay laminae above it. The surface 17 cm thick mud layer isinterpreted to be younger than 1950 because Cesium-137 measurements show constant high value above 17 cm and lower value
than detection limit below it. Moreover, excess Pb-210 values show constant high above 17 cm and rapid decrease downward
below it. This indicates a sedimentation event for a short period of time. Because the sampling site is isolated from river flood
sedimentation area, earthquake shaking is the most plausible trigger of sediment gravity flow. The 2004 off the Kii peninsula
earthquakes is a potential candidate within the historical earthquakes in this area after 1950.
Sidescan sonar WADATSUMI survey was conducted in this area in December 2004 just after the Kii peninsula earthquakes.
The sidescan sonar image at the terminal basin shows extremely low backscattering intensity suggesting surface veneer of very
high water content mud derived from earthquake triggered turbidity flow.
Keywords: turbidite, turbidity current, sedimentary basin, accretionary prism, submarine landslide

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SCG64-P12

Room:Convention Hall

Time:May 27 18:15-19:30

Microstructure analysis of earthquake-induced deposits associated with the 2004 off Kii
Peninsula earthquakes
OKUTSU, Natsumi1∗ ; ASHI, Juichiro1 ; OMURA, Akiko1 ; YAMAGUCHI, Asuka1 ; SUGANUMA, Yusuke2 ;MURAYAMA, Masafumi3
1

Atmosphere and Ocean Research Institute, The University of Tokyo, 2 National institute of Polar Research, 3 Center for Advanced Marine Core Research , Kochi University
An ENE-WSW elongated depression is located between the southern margin of the forearc basin and the outer ridge off Kumano and a terminal basin that captures all sediments supplied from outside is developed in it. No sediment is supplied from therivers to this basin, so it is an adequate site to study paleoseismology using seismogenic turbidites.
The result of the Cs-137 and Pb-210 measurements indicates that the upper 17-cm mud layer was deposited immediately
after the 2004 off Kii Peninsula earthquakes (Ashi and others, in this Session). We herein investigate the characteristics of theearthquake-induced deposits based on several measurements including their compositions, grain sizes, X-ray CT images, andanisotropy of magnetic susceptibility (AMS).
We observed a very thin fine-grained sand layer of 6 mm thick at 17 cm below seafloor and a massive mud below it on the core
split section. On the other hand, the X-ray CT image shows seven silty clay laminations thinning upwards at 6 -15 cm below
seafloor, and homogeneous clayey silt above it. The AMS parameters decrease upwards in the interval showing parallel/crosslaminations and the lowest value is measured in the overlying silt layer, whereas grain sizes have no significant change. These
results indicate that the upper 17 cm layer beginning from the very fine-grained sand can be interpreted to be formed by a lowdensity sediment gravity flow. Below the depth of 17 cm, the deposition is mainly composed of muddy sediments with a woodchip-enriched thin bed and a very fine-grained thin sand layer at the depth of 32 cm. Structural observations by X-ray CT scanner reveal characteristic structures yielding various orientation oblique to bedding plane at the mud layer 17 cm below seafloor,
suggesting that the structure is likely formed by coseismic deformation accompanied by the earthquake in 2004 or earlier ones.
Magnetic fabrics derived from AMS measurements and the structure observed by X-ray CT scanner also agree to this picture.
Keywords: turbidity current, anisotropy of magnetic susceptibility, X-ray CT, event deposit

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SCG64-P13

Room:Convention Hall

Time:May 27 18:15-19:30

Application of C-14 dating on Calyptogena shells for historical fault activity analysis off
Tokai, Nankai Trough
YAGASAKI, Kazuhiro1∗ ; KURAMOTO, Shin’ichi2 ; ASHI, Juichiro1 ; YOKOYAMA, Yusuke1 ; MIYAIRI, Yosuke1
1

Atmosphere and Ocean Research Institute, UTokyo, 2 Center for Deep Earth Exploration, JAMSTEC

Cold seeps are frequently found at tectonically active continental margins including areas such as the Nankai and Tokai regions.
The fluid conduits created by the tectonic activities often form cold seeps, releasing hydrocarbon rich fluids such as methane.
Substances such as this are essential for supporting Calyptogena bivalve communities to survive through a symbiotic processwith the chemosynthetic bacteria. The lifespan of bivalves can be ephemeral due to the conduits altering from tectonic eventsof converging plate margins, or the source of the hydrocarbon depleting over time. These characteristics may suggest that the
Calyptogena bivalve shells may hold important information on historical fault activities of the area.
Marine samples originating from the deep sea have often been difficult to radiocarbon date due to the complicated calibration
processes involved. Deep circulating ocean currents and sub seafloor seepage of hydrocarbons are main factors responsible forthe necessary complex calibration calculations, referred to as the dead carbon effect. DSV Shinkai 2000 discovered an unusuallylarge Calyptogena bivalve colony in 1997, ranging approximately 200m2 off the Daini Tenryu Knoll off Tokai in Japan. Bivalve
colonies found are composed mainly of dead shells with few spots of living communities remaining. Past tectonic events may
have influenced the methane hydrate layer below to destabilise, releasing significant amounts of methane fluid and gas to theseafloor, consequently allowing bivalves to flourish (Kuramoto, 2001; Ashi et al., 2002; Otsuka et al., 2010).
Amino acid racemisation dating technique was employed on the same shells by Misawa (2004) revealing two different age
groups of 0∼500 years (white shells) and 1000∼2000 years (brown shells), yet the technique was prone to temperature andpH change. This study therefore proposes a novel application of radiocarbon dating of such bivalves to further understand theinteraction between local active faults and the bivalve community. Current 14 C age measured range between 1868–1949 year
cal AD, coinciding with the 1854 Ansei Tokai earthquake (M8.4). Seafloor mapping, seawater analysis and EPMA and SEM
structural analysis of shells from ROV HyperDolphin Dives 1355 and 1377 during NT14-07 and NT02-08 respectively, will also
be reported.

Keywords: Radiocarbon dating, Cold seep, Calyptogena shell, Active fault, Methane

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SCG64-P14

Room:Convention Hall

Time:May 27 18:15-19:30

Distribution of methane hydrate BSRs and shallow thermal structure in the Nankai subduction zone
OHDE, Akihiro1∗ ; OTSUKA, Hironori1 ; KIOKA, Arata1 ; ASHI, Juichiro1
1

Atmosphere and Ocean Research Institute, The University of Tokyo

Thermal structure in subduction zones influences pore pressure and diagenesis such as consolidation, dewatering, cementation, and constrains physical propertiies of fault-slip plane. Methane hydrate is a clathrate that consists of water and methane.
Recently, it attracts attentions not only for marine resources but also for estimates of thermal information below the seafloor using the characteristics of its stabilization under low-temperature and high-pressure conditions. Precise two-dimensional thermal
structure ranging from the seafloor to BSR depths is calculated taking topographic effect into account, because subsurface heatflow is affected by bathymetry features.
Geothermal gradients in rougher topography tend to be widely different from that in flat seabeds. To remove this effect, I
evaluated the effect by conducting the simple two-dimensional thermal calculation of Blackwell et al. (1980). Additionally, I
calculate the Base of Gas Hydrate Stability zone (BGHS) taking into consideration the thermal structure coupled with the topographic effect.
A deepening trend of BSR depths landward of trough floor is confirmed as suggested in previous studies. This observation yields countertrend because the BSR depth should be deepest in the trough floor as methane hydrate is stable under lowtemperature and high-pressure conditions. Thus, observed BSR depths suggest that heat flow actually decreases landward of thetrough floor.
The investigated BSR depths are constrained from deep heat flux, and vary basically landward of the trough floor. But, in thisstudy, BSR depths are deeper around anticline parts and shallower around sycline. Theoretically, the convex-upward seabed issubject to cooling owing to cold bottom seawater, while the convex-downward one is less subject to the cooling. Evaluationsof this kind of topographic effect suggest that sycline can be explained by only the topographic effect. Thus, thermal regime
calculated from BSR depths does not change in sycline or slope areas.
In this study, the BSR was confirmed for the first time at the prism toe. The detailed BSR distribution map can contributeto disaster prevention because BSRs have potential to being fault-slip planes. In the Nankai area, geothermal gradient values
scatter, but the values can be explained by considering subducting plate age, topographic effect, and sedimentation or erosion.
In addition, while distances from seafloor to BSR depths are different even under the same water pressure, the calculation taking
topographic effect into account revealed to be able to explain these depth changes. Moreover, the calculated thermal structure
over BSR depths considering topographic effect seems to be accurate, because estimated BGHS depths and BSR depths fit welltogether. Understanding precise BSR depths enables to precisely estimate deposited amount of methane hydrate. This study
provides thermal information essential for seismic simulations in subduction zones and for laboratory experiments as analogues
to seismic ruptures in plate boundary faults.

Keywords: Nankai sucduction zone, methane hydrate BSRs, shallow thermal structure

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SCG64-P15

Room:Convention Hall

Time:May 27 18:15-19:30

Physical property of sea bottom surface estimated from fin whale vocalization
IWASE, Ryoichi1∗
1

JAMSTEC / CREST, JST

At the cabled observatory off Kushiro-Tokachi in Hokkaido, fin whale vocalizations, which have the frequency range of 1520 Hz and the duration of about 1 second, were sometimes observed not only with hydrophones but also with ocean bottom
seismometers (OBSs) mainly in winter seasons. By using the waveform data of both hydrophone and OBS at OBS1 at theobservatory observed from 13:44 to 14:59 JST on December 10th in 2004, the location of the fin whale was estimated. The
localization was done based on the incident orientation which was estimated from the horizontal particle motion observed with
the OBS and the horizontal range between the OBS and the whale estimated from the time difference of multi-path arrival(TDOMA) in sound pressure data of a hydrophone which includes the reflection at both seafloor and sea surface. During theabove observation period, 62 vocalizations were used, whose direct and multi-path arrivals were both identified. The waveforms
were band-pass filtered between 10 and 25 Hz and the incident orientation of the particle motion was estimated by applying
principal component analysis and by obtaining eigen vector of first main component. As a result it was found that the whale wasmoving south-south-east near the east of OBS1.
In the previous study carried out in the northeast Atlantic (Harris et al., 2013), the incident angle which was estimated fromthe apparent emergent angle in the sediments observed with the OBS was used instead of the TDOMA for the localization of thewhale. However, the apparent emergent angle is affected by the density and P-wave (pressure wave) velocity of both sediments
and water, and is also affected by SV-wave (share wave) velocity of the sediments, which are mostly unknown. This time, theauthor compared the apparent emergent angle in the sediments observed with the OBS with the incident angle estimated from the
TDOMA in order to examine the consistency of those estimations. As a result, good correlation between the apparent emergent
angle and the incident angle was confirmed, and the critical incident angle of pressure wave in seawater was estimated to be 60
degrees. Accordingly, the P-wave velocity in sediments was estimated to be about 1.7 km/s according to Snell’s law, assumingthat sound velocity in water was 1.5 km/s and SV-wave velocity in sediments was very slow.
Keywords: fin whale vocalization, incident angle, apparent emergent angle, critical angle, seismometer, hydrophone

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SCG64-P16

Room:Convention Hall

Time:May 27 18:15-19:30

Crustal density structure derived from gravity modelling using results of seismic crustal
structure surveys
FUJIOKA, Yukari1∗ ; ISHIHARA, Takemi2
1

Japan Coast Guard, 2 National Institute of Advanced Science and Technology

The Japan Coast Guard (JCG) has conducted marine gravity surveys in Japan’s adjacent seas as part of collecting marinerelated information to the development and use of the oceans, and possesses enormous amount of marine gravity data. We
calculated crustal thickness distribution in the Western Pacific area by applying the gravity inversion method (Ishihara and Koda,
2007) using these data.
Free air anomalies obtained from the satellite altimetry (Sandwell et. al., 2014) were used as a reference in order to correct
deviations of marine gravity values of each surveys. In the long wavelength components, gravity data observed and these fromthe satellite altimetry match well. In the short wavelength components, maritime gravity data were used in preference because
gravity data from the satellite altimetry include a few mGal of noises with wavelength of 20-30 km.
The initial density structure model consists of five layers; sea water, sediments, upper crust, lower crust and mantle. The depthsof layers of the initial model reflect results of JCG’s seismic crustal structure surveys: the depth of basement as boundary between
sediments and upper crust is made by interpolation of the depth of the strong reflectors in the reflection cross section obtained
from multichannel seismic reflection surveys, and the depths of the top of the lower crust and the Moho are made by interpolationof the depth of area whose velocity gradient of seismic velocity structure cross section obtained from seismic refraction surveys,
respectively.
The differences of the observed free air anomalies from the gravity anomalies obtained by model calculation for the initial fivelayer model were divided into some components by their wavelengths because they include the effects due to the structure suchas inhomogeneity in the mantle. The depths of the top of the lower crust and the Moho were obtained by inversion calculation
using their anomaly contributions, then the crustal thickness distribution was estimated. According to the results, most of large
seamounts are associated with the Moho convex downward, however, some of them have almost no Moho lows below them.
Keywords: gravity, inversion calculation

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SCG64-P17

Room:Convention Hall

Time:May 27 18:15-19:30

Seafloor crustal deformation at the Kumano Basin and along the Nankai Trough
TADOKORO, Keiichi1∗ ; FUJII, Cosmo1 ; YASUDA, Kenji1 ; IKUTA, Ryoya2 ; UEMURA, Yuichi1 ;MATSUHIRO, Kenjiro1
1

Nagoya University, 2 Shizuoka University

Our research group performs monitoring of sea-floor crustal deformation with the GPS/acoustic system at four sites (KMN,
KMC, KMS, and KME) on the Kumano Basin. We have already measured 16, 6, 20, and 10 times at KMN (from 2005), KMC(from 2012), KMS (from 2004), and KME (from 2008) sites, respectively. The battery at KME site ran out in the previous year,
and we cannot continue to measure at the site. The research vessel we used is Asama of Mie Prefecture Fisheries ResearchInstitute.
We carried out correction of travel-times of acoustic ranging wave and removal of incorrect results of KGPS positioning andship’s attitude measurement before the benchmark position analysis for improving data quality before deriving site velocities.
We also fix a correction parameter, related to the relative position of GPS antenna and transducer, at an averaged value for thebenchmark position (weight center) determination.
We obtained the horizontal site velocities from linear trends of the time series of benchmark position through the robust
estimation method (Tukey’s Biweight estimation), adopting REVEL model for the plate motion. The steady horizontal site
velocities with relative to the Amurian Plate are: 45+/-2 mm/yr in N78+/-5W direction (KMN), 46+/-5 mm/yr in N75+/-4W(KMS), and 32+/-12 mm/yr in N69+/-21W (KME). These results show no significant difference in the site velocities at the threesites. We installed two different benchmarks on the same weight center position at KMS site. The horizontal site velocity ofthe other set of benchmark has no significant difference compared to the above-mentioned one at KMS site, which shows highprecision of our system.
During the 2011 Tohoku earthquake, it is estimated that the large slip of 40-50 m on the plate interface immediately adjacentto the trench axis. It is, therefore, essential to measure the slip deficit also at the same region along the Nankai Trough. For thisreason, we installed a new site, TCA and TOA, on the seafloor 15 and 35 km from the trough axis, respectively. We have alreadymeasured four times at the two new sites. A transducer is equipped at the bottom of the research vessels we used, Shinsei Maru
and Kaiyo Maru No.3, and we can perform acoustic ranging for distances more than 6,000 m above 5 knot. Now we are carryingout the benchmark position analysis, with checking the effect on the benchmark positioning of sound speed structure in the sea,
as well as the data quality of KGPS.

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SCG64-P18

Room:Convention Hall

Time:May 27 18:15-19:30

Improvement in the accuracy of GPS/Acoustic measurement using a multi-purpose mooredbuoy
IMANO, Misae1∗ ; KIDO, Motoyuki2 ; OHTA, Yusaku1 ; TAKAHASHI, Narumi3 ; FUKUDA, Tatsuya3 ;OCHI, Hiroshi3 ; HINO, Ryota2
1

Graduate School of Science, Tohoku University, 2 International Research Institute of Disaster Science, 3 Japan Agency for
Marine-Earth Science and Technology
In 2011 Tohoku-oki earthquake (Mw 9.0), seafloor geodetic observation using GPS/Acoustic measurement revealed that large
co-seismic slip occurred along the Japan trench (Kido et al., 2011; Sato et al., 2011). For clarifying the mechanism of plateboundary earthquakes and forecasting Tsunami immediately, it is necessary to monitor seafloor crustal deformation and Tsunami
in the source region. DONET and the GPS buoy system monitor Tsunamis in offshore. On the other hand, horizontal seafloor
crustal deformation is measured by GPS/Acoustic surveys, which are mainly carried out by campaigns several times a year.
Therefore, we cannot obtain information on co-seismic and post-seismic crustal deformations immediately. Considering theabove, JAMSTEC, JAXA, Tohoku University have jointly developed a continuous observation system using a moored buoy andhave started its sea-trial at Kumano-nada in 2013 and 2014 (Takahashi et al., 2014). In this study, we evaluate the accuracy ofthe estimate of horizontal seafloor crustal deformation using the data obtained by this system in the 2014 sea-trial. Moreover, we
propose an analysis for improving positioning accuracy.
In general, GPS/A survey is carried out near the center of the transponder array, which cancel out the effect of the time?variationof layered sound speed structure. Due to violation in the assumption of layered structure, positioning accuracy of each shot is
20 ˜30 cm. By repeating this in a campaign observation half a day, we realize to measure crustal deformation in a few cm order(Spiess et al., 1998). On the other hand, the buoy is moored by slack cable for observation at strong tide and the acoustic ranging
is carried out at a point away from the array center. A set of acoustic ranging consists of 11 pings an interval 65 seconds. This
cycle repeated once a week. Therefore, it is not possible to cancel the time variation of the speed sound. Based on the above andthe fact that our target is detecting of the co-seismic slip associated with massive earthquake just above the source region, we aimthat positioning accuracy is 1m order.
In the acoustic ranging, each travel time is obtained by picking up the maximum peak in correlogram between transmitted andreceived waves. In the current system, only 1ms of correlograms (8bit, sampling frequency: 100 kHz) are sent to land station tosave bandwidth in the satellite communication. However, by investigating the raw data recovering after sea-trial, it is revealed
that the travel time of multi-path at sea surface is often sent to land station through the process mentioned above. Imano etal. (2014) proposed the new method to pick up the earliest peak of peaks in a correlogram for a single acoustic signal. We
estimate the array center based on Kido et al. (2006) using the travel time obtained by the conventional method and the travel
time obtained by Imano et al. (2014). The standard deviation of the estimated array center using the travel time obtained by theconventional method is 3.7 m (East-West component) and 2.6 m (North-South component) in the data in a week, 5.2 m (E-W)
and 3.9 m (N-S) in the data in the entire period. On the other hand, the standard deviation using the travel time obtained by
Imano et al. (2014) is 0.45 m (East-West component) and 0.34 m (North-South component) in the data in a week, 3.6 m (E-W)
and 2.2 m (N-S) in the entire period. The apparent fluctuation of the estimated array center of the latter is smaller than that of
the former, in the same week data in particular. However, the fluctuation of the array center is a few meter order in the entire
observation period. Therefore, we should take measures such as re-analyzing after determining the position of each transponderin the accuracy about 10 cm in order to aim that the accuracy of GPS/A measurement using the buoy system is 1 m order in the
future. In this presentation, we demonstrate and discuss how much the accuracy is improved after the measure.

Keywords: Seafloor crustal deformation, Moored buoy

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SCG64-P19

Room:Convention Hall

Time:May 27 18:15-19:30

GANSEKI: Utilize fieldwork information for studying JAMSTEC rock samples
TOMIYAMA, Takayuki1∗ ; SOMA, Shinsuke2 ; HORIKAWA, Hiroki1
1

JAMSTEC, 2 Marine Works Japan, Ltd.

Japan Agency for Marine-Earth Science and Technology (JAMSTEC) carries out several tens to more than a hundred of observation cruises each year, using research vessels e.g. ”Mirai,” ”Kairei,” ”Kaiyo,” ”Yokosuka,” and ”Natsushima”. Activities
during each cruise differ depending on individual research projects, and more than ten of these cruises involve rock collecting
activities. Rock samples are recovered using deep-sea submersibles such as ”Shinkai 6500”, ”Hyper-Dolphin”, ”Kaiko 7000II”
and ”Deep Tow”, and dredgers. These activities yield tens to more than a hundred of rock samples each year.
JAMSTEC considers its rock sample collection as a common property of human community [1], which can be a resource forresearch and education of earth-ocean sciences. After up to 2 years of moratorium period during which only on-board researchers
can access to samples, JAMSTEC makes the rock samples accessible to second-hand users with research/educational purposes.
The information of JAMSTEC rock samples is published through the ”GANSEKI” database [2]. Using GANSEKI, users canaccess to the various information such as basic information (metadata) of 20,663 sampling activities, archive information (inventory data) of 12,243 physical samples, geochemistry data of 19,508 analyses, thin-section photos, publication, and links for
associated databases. JAMSTEC rock sample collection includes not only relatively new samples, which were collected after theestablishment of curatorial handling in 2008, but also old samples from ’80s or ’90s, which were donated by researchers.
After the major update of GANSEKI in 2013, which improved the searchability and visibility of user interfaces, the curatorial
team has been maintaining inter-database network around GANSEKI. In addition to the cruise and dive information in the DARWIN database[3], GANSEKI users can now access to the abundant field information such as sampling processes, geological andgeometrical information, which can be recognized through watching dive photos/movies in the ”J-EDI” database [4] and tracing
3D dive tracks on the ”JDIVES” data viewer [5]. It is not easy even for experienced researchers to organize and utilize hugedata obtained during individual cruises or dives. The inter-database networking among GANSEKI and associated databases areadvantageous not only for second-hand users, but also for on-board researchers themselves.
References: [1] ”Basic Policies on the Handling of Data and Samples” http://www.jamstec.go.jp/e/database/data policy.html.
[2] ”Geochemistry and Archives of Ocean Floor Rocks on Networks for Solid Earth Knowledge Information (GANSEKI)”
http://www.godac.jamstec.go.jp/ganseki/e. [3] ”Data Research System for Whole Cruise Information in JAMSTEC (DARWIN)”
http://www.godac.jamstec.go.jp/darwin/e. [4] ”JAMSTEC E-library of Deep-sea Images (J-EDI)” http://www.godac.jamstec.go.jp/jedi/e.
[5] ”JAMSTEC deep-sea Data-Image Virtual Exploration System (JDIVES)” http://www.godac.jamstec.go.jp/jdives/e.
Keywords: marine geology, rock sample, curation, database

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