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Abstracts - Dgg2007.rwth-aachen.de - RWTH Aachen University

Abstracts - Dgg2007.rwth-aachen.de - RWTH Aachen University

Abstracts - Dgg2007.rwth-aachen.de - RWTH Aachen University


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Session MG Poster Raum: Kármán-Auditorium<br />

Marcus Fabian (Universität Bremen, Fachbereich Geowissenschaften, Meerestechnik/Sensorik) ,<br />

Heinrich Villinger<br />

The Bremen Ocean Bottom Accelerometer -OBA-<br />

Email: marcus.fabian@uni-bremen.<strong>de</strong><br />

The Bremen Ocean Bottom Accelerometer<br />

(OBA) is a new scientific tool to monitor local<br />

ocean bottom acceleration in three directions<br />

with high resolution in time and amplitu<strong>de</strong>. The<br />

instrument has six accelerometers of MEMStype<br />

(micro electro mechanical systems), which<br />

have a nominal resolution of 10 −5 m/s 2 and a<br />

bandwidth from DC to 300 Hz. As their resolution<br />

is in the range of ocean floor background noise<br />

and the sensors are of small physical dimensions<br />

27 mm x 27 mm x 16 mm) and have low<br />

current-consumption (≈ 17 mA, ± 6.2 V), they<br />

are best suited for long-time autonomous operation<br />

in <strong>de</strong>ep sea instruments like the OBA (Fabian<br />

& Villinger, in press). A newly <strong>de</strong>signed digitizer<br />

continuously samples and filters the acceleration<br />

data from all six sensors at 5Hz and writes<br />

the data to a CompactFlash card. The powerconsumption<br />

of the complete system is 996 mW.<br />

A 304 D-cell lithium battery pack powers the instrument<br />

for more than a year. Maximum operation<br />

<strong>de</strong>pth of the OBA is 6000 m.<br />

The OBA will be <strong>de</strong>ployed in autumn of 2007<br />

by means of the new ROV (remotely operated<br />

vehicle) ‘Kiel 6000‘ in the Logatchev Hydothermal<br />

Vent field (LHF), 14°N on the Mid-Atlantic<br />

Ridge in a <strong>de</strong>pth of 3000 m. Its position will<br />

be nearby the OBT (Ocean Bottom Tiltmeter),<br />

which was installed in May 2005 by the ROV<br />

‘Quest‘ (Fabian & Heesemann, 2006, Fabian &<br />

Villinger, in press) and was recovered and replaced<br />

by the ROV ‘Jason II‘ in February 2007 during<br />

cruise MSM04/3 of the new german research<br />

vessel ‘Maria S. Merian‘. The OBA will<br />

record until January 2009 simultaneously to the<br />

OBT. The 3-axis acceleration data from the<br />

OBA will complete long-time data tilt data of<br />

the OBT. Both instruments provi<strong>de</strong> data of local<br />

seismicity and tilt related to hydrothermal<br />

activity and crustal growth. Activity-phases in<br />

the LHF like enhanced seismicity or ocean floor<br />

<strong>de</strong>formations will be <strong>de</strong>termined and correlated<br />

with the data of co-workers in our research program<br />

(temperature, ocean bottom water pressure,<br />

test-sequences of local smoker-fluid chemistry<br />

and vent-fauna during the visits of the<br />

LHF between 2005 and 2009). The long-time<br />

data will be used as a proxy for changes in energy<br />

flux from the earth‘s mantle to the ocean and<br />

for variations and diversifications in local life<br />

cycles.<br />

The OBA is a part of the monitoring system<br />

of project LOLEM (Logatchev Longtime Environmental<br />

Monitoring) which is supported by<br />

the Deutsche Forschungsgemeinschaft (DFG)<br />

in the frame of Schwerpunktprogramm 1144:<br />

‘Vom Mantel zum Ozean: Energie-, Stoff- und<br />

Lebenszyklen an Spreizungsachsen‘.<br />

References:<br />

Fabian, M., Villinger, H. (in press). The Bremen<br />

Ocean Bottom Tiltmeter, OBT,- a technical<br />

article on a new instrument to monitor seafloor<br />

tilt and local seismicity, Marine Geophysical<br />

Researches.<br />

Fabian, M., Heesemann, B. (2006). Neigungswaage<br />

für Unterwasser- und Hochdruckanwendungen<br />

(<strong>de</strong>ep sea level), Gebrauchsmusterschrift<br />

(registered <strong>de</strong>sign) DE<br />

20.2006.013066 U1 - Universtät Bremen,<br />

Deutsches Patent- und Markenamt.<br />


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