cruise report of yk05-09 leg.1 cruise m.v. yokosuka and shinkai …€¦ · akiko yatabe (tokyo...

Cruise Report of YK05-09 Leg.1 Cruise

M.V. Yokosuka and Shinkai 6500

Hajime Shiobara (University of Tokyo)Junichi Miyazaki (University of Yamanashi)

Hiroko Sugioka (Japan Agency for Marine-Earth Science & Technology)Hideki Kobayashi (Japan Agency for Marine-Earth Science & Technology)

Akiko Yatabe (Tokyo University of Marine Science and Technology)Yuko Fujita (University of Tsukuba)

Hirohito Matsumoto (University of Tsukuba)

July 11, 2005 (Yokosuka) ~ July 24, 2005 (Guam)

1. Overview of this cruise

1.1. Aims This cruise had two different aims of a biological research at Torishima seamount, and technical and geophysical

research for ocean bottom seismometers (OBS) have to be rescued around the Mariana trough. Dives of Shinkai 6500

were planned once for the former (#895) and four times for the latter (#896~#899) indicated as Fig. 1.1.

Fig. 1.1. Location map of 5 dive positions.

1.1.1. Origin and evolution of deep-sea Bathymodiolus mussels and symbiosis (#895 dive) The aim in this study is to examine whether “the evolutionary stepping stone hypothesis” is verified or not. Most of

deep-sea animals are assumed to have acquired their niche through ancestral invasion from shallow to deep-sea waters.

It is one of the most interesting questions how shallow-water ancestors can adapt to highly differentiated deep-sea

environments. Cold temperature, high pressure, lack of energy source etc. can be large obstacles for invasion of the

ancestors into deep-sea. As one of possible strategies, they exploited stepping stones that link shallow water habitats

to those of deep-sea. There they gradually acquired tolerance to cold temperature and high pressure and found a way

to obtain energy. Whale carcasses and sunken woods on the sea floor are considered as most likely stepping stones.

Therefore, in the evolutionary stepping stone hypothesis, deep-sea animals are derived form shallow water ancestors

through exploiting whale carcasses and sunken woods in their evolution.

Bathymodiolus mussels (Bivalvia, Mytilidae) are one of the major deep-sea macro-organisms, but mytilid mussels are

predominated in shallow water, especially in the tidal zone. Thus, there are large vertical and horizontal gaps between

major habitats of mytilid mussels and deep-sea habitats of Bathymodiolus. We found previously two species of

mytilid mussels, Adipicola pacifica and Adipicola crypta, in whale carcasses settled artificially at 225m depth off Noma

cape. Our DNA analysis of mitochondrial genes showed that they were closely related to Bathymodiolus mussels.

One of the species houses intracellular symbionts (chemosynthetic bacteria) for energy source and the other

extracellular symbionts. Since Bathymodiolus mussels have intracellular symbionts in their gills for their major

energy source, characteristics of Adipicola mussels possibly suggest ancestral and transient states in nutrition between

general mytilid mussels and deep-sea Bathymodiolus mussels.

Since Adipicola mussels were collected at relatively shallow water, we need to search for mussels with ancestral and

transient states in nutrition and in adaptation to cold water and high pressure. At the Torishima seamount, whale

carcasses were found at 4,050m depth in 1992 and have an animal assemblage around. In this study, we collect

mytilid mussels from the whale carcasses at the Torishima seamount and examine their phylogenetic relationships to

Bathymodiolus mussels by DNA analysis and their state of symbiosis by electron microscopy. We also examine

chemical composition of ambient water and sediments to gain an insight into environmental conditions in the whale

bone-dependent animal assemblage.

1.1.2. In situ observation and rescue of long-term OBS (#896 ~ #899 dive) For researches of the Earth deep interior and seismic activity monitoring, we have developed the long-term ocean

bottom seismometers (LTOBS) since 1997, and have started practical observations from 1999 in several areas. The

LTOBS has been designed to be durable for long deployment period by using titanium parts in its pressure case, outside

frame and anchor releasing unit, exposed to the sea water. The anchor releasing unit is originally developed in 1980's,

and widely used for Japanese OBS by using a stainless steel plate that is solved at the slit exposed to the sea water by a

forced electric corrosion, that is controlled from the acoustic transponder system. Although we made several tests in

the laboratory to use the new anchor releasing unit with the titanium plate, there were still some troubles in the releasing

time, unexpectedly long and/or large variation in different areas, and in the worst case, the LTOBS never release the

anchor even if it replied well. As we could very little to refine it without the information of the true situation of these

LTOBS malfunctioned, this dive recovery of LTOBS is planned to observe the situation of OBS at the sea floor and

bring back to the ship. Of course, the data contained in the LTOBS is also important from the geophysical point of

view, because these long-term experiments are still rare and were performed by using limited number of LTOBS.

After the application of this cruise in the summer of 2004, five of eight broad-band OBS (BBOBS), using the similar

anchor releasing unit, in the French Polynesian sea caused the worst case trouble. As the headquarter of Jamstec

decided to recover all five BBOBS by using the Shinkai 6500 as a special case of the training dive for the operation

team, the first dive recovery for OBS deployed more than a year was performed in November 2004. This recovery

was perfectly completed, and we have found some important evidence; 1) the BBOBS were at level on the sea floor, 2)

the bottom of BBOBS stuck only a few centimeters into the sediment, 3) white material like fine sands was observed

near and under the slit of the anchor releasing unit in some of BBOBS, and 4) the function of forced electric corrosion

was performed about 50 % in all BBOBS, and anchor releasing units were not able to support weight of the anchor even

in the water. From the additional research on land, the main reason of this malfunction seemed in the very long

storage period, up to seven years, of lithium cells manufactured, those are used to feed the electric current for the

releasing unit. It made the lithium cells in high resistance, and impossible to supply enough current to the load.

The LTOBS to be rescued in this cruise might have different reason of the malfunction, because the number of cells,

the design of the transponder and the position of the anchor releasing unit, height from the bottom of the OBS, were

slightly different. These four LTOBS were deployed for three different experiments in 1999, 2001 and 2003, and these

recovery were any how about 80 % successful that was the large discrepancy to the case in the French Polynesian sea.

So that, there are still worth researching these four LTOBS to understand the reason, and the knowledge obtained

through this kind of basic research should help us to perform a reliable long-term ocean bottom observation in future.

1.2. Itinerary

1.2.1. Ship track

Fig. 1.2. Ship track during this cruise. Due to a typhoon, we took refuge in the eastward course.

1.2.2. Ship log

Date Time Comment.1 Comment.2 Position/Weather/Wind (Noon)

11,Jul,05 8:00 Research group embark 　　

　 12:00 leave port from JAMSTEC 　　

　 13:30 lecture about ship's life 　　

　 15:00 meeting research group and 6K team 　　

　　 head for survey area 　　

12,Jul,05 7:20 arrive at survey area、XBT measurement 　 12:00(JST)

　 9:30 stop the Dive beacause of bad sea condition head for the south 30-03N,141-31E

　 11:00 head for Torishima sea mountain 　 fine

　 15:32-16:09 MNBES 　 SW-6

13,Jul,05 8:00 prepare for Dive#895 　 12:00(JST)

　 9:51 6K landing 　 30-55N,141-49E

　 11:43 land on sea bottom D=4024m fine

　 15:33 leave the seafloor 　 SW-4

　 16:55 finish to dive、head for the next area 　　

14,Jul,05　 head for Mariana trough 　 12:00(JST)

　　　　 29-42N,146-46E

　　　 fine

　　　　 NE-5

15,Jul,05 　head for Mariana trough 　 12:00(JST+1)

　　　　 24-48N, 149-03E

　　　　 fine

　　　　 ESE-5

16,Jul,05　 head for Mariana trough 　 12:00(JST+1)

　 17:15 arrive at survey area、MNBES survey 　 19-11N,146-29E

　 17:20 measurement of distance for OBS 　 fine

　　　　 ESE-4

17,Jul,05 8:00 prepare for Dive#896 　 12:00(JST)

　 9:50 6K landing 　 18-21N,146-08E

　 11:30 land on sea bottom D=3360m cloudy

　 13:27 OBS start floating 　 ENE-3

　 14:32 leave the seafloor 　　


18,Jul,05 6:25 arrive at survey area、MNBES survey 　 12:00(JST)

　 8:00 prepare for Dive#897 　 18-02N,144-16E

　 9:15 6K landing 　 fine

　 11:46 land on the sea bottom D=3797m E-2

　 14:20 OBS float ・6L leave the seafloor 　　


19,Jul,05 6:20 arrive at survey area 　 12:00(JST)

　 8:00 prepare for Dive#898 　　

　 9:52 6K landing D=4742m 17-14N, 144-23E

　 12:01 land on the sea bottom 　 rainy

　 13:16 6L leave the seafloor 　 SW-2


20,Jul,05 6:20 arrive at survey area 　 12:00(JST)

　 06:25-06:58 MNBES survey 　 20-13N, 140-46E

　 9:48 6K landing 　 cloudy

　 11:51 land on the sea bottom D=4616m E-4

　 13:00 6L leave the seafloor 　　


21,Jul,05　 head for GUAM ISLAND 　 12:00(JST)

　　　　 15-28N, 143-27E

　　　　 rainy

　　　　 SSE-4

22,Jul,05　 stop to port GUAM Island 　 12:00(JST)

　　

avoid big swell and stay at the east side of GUAM

Island 　

12-50N, 144-57E

　　　　 cloudy

　　　　 SSE-8

23,Jul,05　 stop to port GUAM Island 　 12:00(JST)

　　 avoid big swell, stay at the east side of GUAM 　 13-24N, 144-51E

　　　　 cloudy

　　　　 SSE-7

24,Jul,05 11:00 port at GUAM Island 　　

1.3. Participants list

1.3.1. ResearchersHajime Shiobara Ocean Hemisphere Research Center, Earthquake Research Institute, University of Tokyo

Associate Professor

Hiroko Sugioka IFREE, Japan Agency for Marine-Earth Science & Technology

Researcher

Junichi Miyazaki Faculty of Education and Human Sciences, University of Yamanashi

Associate Professor

Hideki Kobayashi Japan Agency for Marine-Earth Science & Technology, Extremobiosphere Research Center

Researcher

Akiko Yatabe The Graduate School of Marine Science and Technology, Tokyo University of Marine Science

and Technology

Doctor course graduate

Yuko Fujita The Graduate School of Life and Environmental Sciences, University of Tsukuba

Master course graduate

Hirohito Matsumoto College of Biological Sciences Second Cluster of colleges, University of Tsukuba

Undergraduate

Masayuki Toizumi Nippon Marine Enterprises

Chief Marine technician

Ayumi Mizota Nippon Marine Enterprises

Marine technician

1.3.2. Captain and crew of YokosukaSadao Ishida Captain

Takafumi Aoki Chief Officer

Tsutomu Satou 2nd Officer

Takeshi Egashira 3rd Officer

Eiji Sakaguchi Chief Engineer

Kimio Matsukawa 1st Engineer

Takashi Ota 2nd Engineer

Yuji Mori 3rd Engineer

Satoshi Watase Chief Electronics Operater

Katsutoshi Kitamura 2nd Electronics Operator

Makio Nakamura Boat Swain

Mikio Ishimori Able Seaman

Katsumi Shimizu Able Seaman

Takao Kubota Able Seaman

Keiji Shikama Able Seaman

Shozo Fujii Able Seaman

Toshiki Okuyama Sailor

Kiyoshi Yahata No.1 Oiler

Katsuyuki Miyazaki Oiler

Tomoyuki Hashimoto Oiler

Yoshinori Yamaoka Oiler

Ryota Suzuki Oiler

Yoshitaro Tamiya Chief Steward

Shinsuke Tanaka Steward

Teruyuki Yoshikawa Steward

Toyonori Yoshikawa Steward

Tadayuki Takatsu Steward

1.3.3. Operation team of Shinkai 6500Yoshiji Imai Operation Manager

Toshiaki Sakurai Assistant Operation Manager

Yoshitaka Sasaki 1st Submersible Staff

Kazuki Iijima 1st Submersible Staff

Itaru Kawama 1st Submersible Staff

Fukuo Suda 1st Submersible Staff

Yoshinari Ono 1st Submersible Staff

Masanobu Yanagitani 2nd Submersible Staff

Keita Matsumoto 2nd Submersible Staff

Hirofumi Ueki 3rd Submersible Staff

Yosuke Chida 3rd Submersible Staff

Fumitaka Saito 3rd Submersible Staff

Kensuke Totsuka 3rd Submersible Staff

2. Origin and evolution of deep-sea Bathymodiolus mussels and symbiosis (#895 dive)

2.1. Research On 13th July 2005, we found whale remains at 30°55.08’N and 141°48.95’E in the Torishima seamount. Whale

vertebrae lay on the sea floor of 4,020m depth. Although the position of whale remains was slightly different from

those reported previously (30°55.45’N, 141°49.72’E, 4037m in Wada et al., 1996 etc.), we judged by an arrangement of

vertebra that it was the same remains as that investigated in 1992, 1993, and 1997. Since the position on the map was

also different from that reported previously (Fujioka et al., 1993), we present a new map in Fig. 2.1. The vertebrae

were not deposited by sediments and could be discernible clearly, although it takes 8 years since the last expedition in

1997. Originally 22 vertebrae were found in 1992 and 2 of them were collected for the research work in 1992 and

1993. However, we found a row of 18 vertebrae and thus 2 vertebrae were missing. Two clusters of bones were also

found at a distance from the row of vertebrae. One of them was composed of two bones and the other of three.

Those were assumed to be fragments of jaw bones, but could not be identified precisely form their configuration.

Jawbones possibly decayed more rapidly than vertebrae. The vertebrae and jawbones reserved an animal assemblage

that was predominated by mytilid mussels, tubeworm-like annelids, and squat lobsters (Fig. 2.2). Mytilid mussels

covered the surface of bones and tubeworm-like annelids flourished from the bottom of bones. The density of these

animals was not uniform among bones. Some other animals that settled and moved on the bones were observed. We

collected animals by a slurp gun and next two vertebrae by arms. Vertebrae were numbered from BB-1 to BB-22 in

the previous work (Fujioka et al., 1993). We could not specify which number of vertebrae we collected, because their

arrangement was disordered when compared with that reported previously. We tentatively identified the vertebrae as

BB-9 and BB-11. Subsequently we collected animals and sediments from the sites of vertebrae BB-9 and BB-11 by a

rake sampler. The sample list of animals we collected is shown in Table 2.1. The animals will be identified by

specialists. We also collected sediments by two MBARI core samplers from the sites of vertebrae BB-9 and BB-11

and ambient water by single Van Dorn sampler approximately 1m above vertebrae. For the control we collected

sediments and water by single MBARI core samplers and Van Dorn sampler elsewhere.

Fig. 2.1. Map showing the research site (*) at the Torishima seamount.

Fig. 2.2. Whale bones and associated animals. a: row of vertebrae. b: bertebrae BB-9 and BB-11

indicated by arrows. c: vertebrae with mytilid mussels, squat crabs and tube worm-like annelids. d:

jawbones.

Table 2.1. Sample list 　　　　　

Sample Name No Locality Lat. Long. Depth

Mollusca

bivalve

Mytilidae 43 Torishima Seamount 30-55.08N 141-48.95E 4020




others 5 Torishima Seamount 30-55.08N 141-48.95E 4020

gastropod

limpet shell 1 Torishima Seamount 30-55.08N 141-48.95E 4020

several species 19 Torishima Seamount 30-55.08N 141-48.95E 4020

Arthopoda

crustacean

Galatheidae

(Munidopsissp.) 17 Torishima Seamount 30-55.08N 141-48.95E 4020


Annelida

tubeworm-like many Torishima Seamount 30-55.08N 141-48.95E 4020

enclosed in sand pipe 10 Torishima Seamount 30-55.08N 141-48.95E 4020

free-living? 22 Torishima Seamount 30-55.08N 141-48.95E 4020


Echinodermata

echinoid 1 Torishima Seamount 30-55.08N 141-48.95E 4020

ophiuroid many Torishima Seamount 30-55.08N 141-48.95E 4020

holothuroid? 1 Torishima Seamoun 30-55.08N 141-48.95E 4020

Porifera? 3 Torishima Seamount 30-55.08N 141-48.95E 4020

Chordata

cetacean

vertebra 2 Torishima Seamount 30-55.08N 141-48.95E 4020

bone fragment 2 Torishima Seamount 30-55.08N 141-48.95E 4020

During the #895 dive, three MBARI core samples and two bottom water samples were recovered. The results of

onboard analysis of ammonia in the pore water squeezed from the core samples are shown in Table 2.2. It indicates

that ammonia concentrations obtained from just beneath the bone still higher than the sediment obtained from near the

bone. The other geochemical analyses will be done after back to the off shore laboratory.

Table 2.2. Onboad analysis of ammonia concentrations in interstitial wate from MBARI core samples

Dive No. Sample No. HN3 mM Note

895 G-1 0.003 1 cm below sea floor

　 G-2 0 4 cm below sea floor





　 W-1 0.076 1 cm below whale bone






　 Y-1 0.038 1 cm below whale bone

Y-2 0.042 4 cm below whale bone



　 Y-５ 0 13 cm below whale bone

2.2. Future study In order to examine whether “the evolutionary stepping stone hypothesis” is verified or not, we will elucidate a

phylogenetic position of mytilid mussels collected at the Torishima seamount by DNA analysis of mitochondrial COI

and ND4 genes. One of the two species collected off Noma cape, Adipicola crypta, was more closely related to

Bathymodiolus mussels rather than to congeneric Adipicola pacifica. Based on morphological definition,

Bathymodiolus mussels belong to the subfamily Bathymodiolinae, which includes the other genus Tamu. Our results

showed that, Adipicola crypta was a member of Bathymodiolinae from a genetical viewpoint. This species houses

intracellular symbionts and thus adopts a strategy to overcome lack of energy source as in Bathymodiolus. On the

other hand, Adipicola pacifica is not genetically a member of Bathymodiolinae and belongs to an outgroup very closely

related to Bathymodiolinae. The species houses extracelluar symbionts. Therefore, Adipicola crypta and Adipicola

pacifica indicate transition (extracellular to intracellular symbiosis) in nutrition to adapt to deep-sea water. However,

it is unlikely that the two species adapt to cold water and high pressure, because they can live up to 1,000m depth.

Mytilid mussels from the Torishima seamount were collected at 4,000m depth and definitely have tolerance to cold

water and high pressure. It is important to specify whether the mytilid mussels are closely related to Bathymodiolus

mussels or not, that is whether the mytilid mussels have a phylogenetic position ancestral to Bathymodiolus or not.

It is also important to gain an insight into whether the mytilid mussels house symbionts or depend on filter-feeding as

in general mytilid mussels and which type of symbiosis (extracellular or intracellular or transient) they adopt. We will

examine the presence or absence of chemosynthetic bacteria in their gills by electron microscopy.

It is necessary to identify precisely animals listed in Table1 for compiling constituents of the animal assemblage on

the whale carcasses. The animals will be identified by specialists. We will compare our data with those reported

previously to investigate faunal changes depending on decay of the whale bones since 1992 when the whale carcasses

were first discovered.

Unique benthic communities developed around whale-falls have been reported all over the world, the TOWBAC

(Torishima seamount whole-bone animal community) is one of the oldest cases, which found during a dive by the

submersible Shinkai 6500 in 1992 (Fujioka et al., 1993, Wada et al., 1993). Although several reports have been

published, geochemical environment around TOWBAC has not been studied. In this study we aim to clarify the

geochemical environment and the source of nutrition and energy for the associated animals. For reaching the goal, we

plan to analyze distribution of reduced chemical species in bottom seawater and sediment around the bones. Sulfides,

ammonia, and methane can be recovered from pore water samples squeezed from the sediment cores. Concentrations

of ammonia were measured onboard. Concentrations of total organic matter and total nitrogen will be also measured

using the sediment samples. In addition carbon, nitrogen, and sulfur isotope compositions of soft tissues from the

animals associated with the substrate matter (suspended matter in bottom water and sulfide, methane and ammonia in

sediment) will be measured to clarify their nutrition and energy sources.

3. In situ observation and rescue of long-term OBS (#896 ~ #899 dive)

3.1. Research and recovery Possible reasons of malfunction in the anchor releasing had been speculated before the dive rescue as followings; 1)

the anchor releasing unit is in the sediment so as not to be corroded the titanium plate at the slit without the circulation

of sea water nearby, 2) the underwater connector or cable becomes short circuit or has water leak that makes impossible

to feed enough current to the anchor releasing unit, 3) the lithium cells for the anchor releasing unit become low

capacity due to self-discharge or high resistive due to long storage, and 4) the electro-chemical reaction of the titanium

plate generates different type of oxide covering the surface to protect for corrosion as the worst story.

The four dives for LTOBS observation and rescue was competed with minimum time due to correct positioning

performed at deployment comparable to the navigation error of Shinkai 6500 and existence of echo backs by the sonar

system. One LTOBS, MRG46 deployed most recently, still had battery capacity for the receiving circuit of the

acoustic transponder to enable us to navigate by measuring the distance between it and Shinkai 6500. It had a new

type of the acoustic transponder that enables to monitor the output voltage and current, and also the anchor releasing

unit is located near the flange of the titanium sphere, but three others had it just above the cylinder weight of anchor.

The overview and situation of LTOBS are in Table 3.1. and Figure 3.1.-3.4. Generally, all four LTOBS were almost in

level to the sea floor and the bottom of LTOBS were below the sediment surface about 15 cm in maximum (MR01).

Although we did not have enough time to observe for PHS7 due to possible bad weather condition, it seemed the same

condition to MR01 at the blind side, because the anchor releasing unit at one side had been severely corroded by the

inspection on board (Fig. 3.8.). The forced electric corrosion were in progress but had stopped in all LTOBS, although

two LTOBS, MR03 and MR01, had completed the corrosion at one side of two anchor releasing units. The titanium

plate remained were not able to support the weight of anchor in the water in all LTOBS like as the cases of BBOBS in

the French Polynesian sea. Although first two LTOBS, MRG46 and MR03, were made self pop-up by releasing from

the manipulator at the sea floor and left anchors, two more LTOBS were recovered with anchors to save total operation

time reducing the search of the LTOBS at the sea surface.

Fig. 3.1. MRG46. The anchor releasing units are located near the flange of the titanium sphere.

Fig. 3.2. MR03. One side of the releasing unit was completely corroded (left).

Fig. 3.3. MR01. One side of the releasing unit was completely corroded (left).

Fig. 3.4. PHS7. Large amount of rust was around a SUS dummy cap miss-attached, but the leak was small amount.

Table 3.1. LTOBS list

The third column indicates the date of usual recovery but not succeeded. Except for MRG46, acoustic transponder

battery for receiving circuit were exhausted due to long installation, which capacity is designed for two years.

The inspection on board was performed immediately. As expected the situation at the sea bottom, all anchor

releasing units looks corroded about half as indicated in Figs. 3.5.–3.9. As mentioned before, the lower left picture of

Fig. 3.8. shows the severely corroded releasing unit (lower half), that might be covered by the sediment. Another

possibility of the degraded under water cable and connector was not found.

Fig. 3.5. Upper half of MRG46's releasing unit.

OBS Site

dive point

Date of

deployment

Date of

NG recovery

Date of

rescue

Reply from

transponder

Releasing system

(type and position)

Seismic data

Clock battery

MRG46

#896

16 June,

2003

17 April,

2004

17 July,

2005Yes New, high

All

Exhausted

MR03

#897

29 Sep.,

2001

3 Feb.,

2003

18 July,

2005No Old, low

All

Alive

MR01

#898

1 Oct.,

2001

5 Feb.,

2003

19 July,

2005No Old, low

UD missed

Alive

PHS7

#899

21 Nov.,

1999

11 July,

2000

20 July,

2005No Old, low

All

No backup

Fig. 3.6. Upper half of MR03's releasing unit. Left one seems the side of complete corrosion.

Fig. 3.7. MR01's releasing unit. Lower two photos show half of releasing unit at the anchor. Left pair photos of the

releasing unit seem the side of complete corrosion.

Fig. 3.8. PHS7's releasing unit. Lower left one might be in the sediment.

3.2. On land research in laboratory and future plan After the return of M.V. Yokosuka to Japan on 10 August, the battery packs of the acoustic transponder including

cells for the anchor releasing unit were examined in the laboratory at ERI. Figs. 3.9.–3.12. show the overviews and

cells for the anchor releasing (right) unit, and the results of measurement is in Table 3.2. In contrast to the case of

BBOBS in the French Polynesian sea, the length of storage is not so long except for MR01. All cells indicate normal

voltage in open circuit, above 3.9 V, it means cells are not exhausted and did not feed so much current but the required

amount for successful releasing is only a few percent to the capacity of the cell (7 Ah).

The battery pack of PHS7 has been stored at the sea floor for five years, which is adequate to test the progress of

internal resistance increased. It will help us to find a better procedure to start the recovery after long deployment, and

also a new design of the acoustic transponder including a refreshing circuit for these cells. Recently, we have changed

the thickness of the titanium plate of the anchor releasing unit, that should make easy to be corroded in shorter time.

Fig. 3.9. Battery pack of MRG46. Only this one has 9 cells.

Fig. 3.10. Battery pack of MR03.

Fig. 3.11. Battery pack of MR01.

Fig. 3.12. Battery pack of PHS7.

Table 3.2. Battery pack of 4 LTOBS

OBS Site# cells

Voltage

Date of

packaging

Voltage of individual cell

(CSC93C 3B30, 7 Ah)

Manufactured

date of cells

(year/week)

Length of

storage

MRG469

35.28 V24 May, 2003

3.919 – 3.920 – 3.920 – 3.920 – 3.921 –|

3.920 – 3.920 – 3.920 – 3.920 –|

2002 / 36 x 8

2002 / 44 x 1

1 year &

26 weeks

MR038

31.33 V12 Sep., 2001

3.916 – 3.917 – 3.917 – 3.917 –|

3.917 – 3.917 – 3.916 – 3.917 –|2000 / 18

2 years &

36 weeks

MR018

31.28 V12 Sep., 2001

3.912 – 3.907 – 3.907 – 3.914 –|

3.913 – 3.911 – 3.911 – 3.912 –|1998 / 16

4 years &

38 weeks

PHS78

31.31 V4 Nov., 1999

3.914 – 3.915 – 3.913 – 3.916 –|

3.915 – 3.914 – 3.915 – 3.915 –|1997 / 32

2 years &

46 weeks

3.3. Geophysical data Part of the seismic data recovered by this cruise was immediately analyzed with the data already obtained. The

experiment between 2001 and 2002, ten LTOBS were deployed in the Mariana area including two LTOBS, MR01 and

MR03. Finally, nine of ten LTOBS data were used for the seismic activity research and tomography of the upper

mantle structure. One example of the result is indicated in Fig. 3.13. By the land global seismic observation network,

only 60 earthquakes were detected in the same period, the LTOBS array finally determined more than 3000 earthquakes.

The fine hypocenter distribution obtained clearly show the deep double seismic zone up to the depth of 200 km, that is

well known at northeast Japan but practically first time at Mariana by the local observation.

Fig. 3.13. Deep double seismic zone and mantle structure model in Mariana (near 18.5°N). Small circles

indicate earthquakes determined and colors indicate deviation from the standard velocity model (IASP91) for

Vp (left) and Vs (right), respectively. Relatively high velocity zone (blue), right to bottom, corresponds to the

subducting oceanic plate (slab).

4. Dive track map

5. Acknowledgements Researchers in this YK05-09 Leg.1 cruise really appreciate the captain and crew of M.V. Yokosuka, and the operation

team of Shinkai 6500 for their adequate and kind operation that enables the completion of all five dives planned, under

the bad weather condition of typhoons. And also we thank for scientists and staffs in universities, Jamstec / IFREE

and NME for their kind supports for this cruise.

cruise report of yk05-09 leg.1 cruise m.v. yokosuka and shinkai …€¦ · akiko yatabe (tokyo...

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