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

Session MG Poster Raum: Kármán-Auditorium
Marcus Fabian (Universität Bremen, Fachbereich Geowissenschaften, Meerestechnik/Sensorik) ,
Heinrich Villinger
The Bremen Ocean Bottom Accelerometer -OBA-
Email: marcus.fabian@uni-bremen.de
The Bremen Ocean Bottom Accelerometer
(OBA) is a new scientific tool to monitor local
ocean bottom acceleration in three directions
with high resolution in time and amplitude. The
instrument has six accelerometers of MEMStype
(micro electro mechanical systems), which
have a nominal resolution of 10 −5 m/s 2 and a
bandwidth from DC to 300 Hz. As their resolution
is in the range of ocean floor background noise
and the sensors are of small physical dimensions
27 mm x 27 mm x 16 mm) and have low
current-consumption (≈ 17 mA, ± 6.2 V), they
are best suited for long-time autonomous operation
in deep sea instruments like the OBA (Fabian
& Villinger, in press). A newly designed digitizer
continuously samples and filters the acceleration
data from all six sensors at 5Hz and writes
the data to a CompactFlash card. The powerconsumption
of the complete system is 996 mW.
A 304 D-cell lithium battery pack powers the instrument
for more than a year. Maximum operation
depth of the OBA is 6000 m.
The OBA will be deployed in autumn of 2007
by means of the new ROV (remotely operated
vehicle) ‘Kiel 6000‘ in the Logatchev Hydothermal
Vent field (LHF), 14°N on the Mid-Atlantic
Ridge in a depth of 3000 m. Its position will
be nearby the OBT (Ocean Bottom Tiltmeter),
which was installed in May 2005 by the ROV
‘Quest‘ (Fabian & Heesemann, 2006, Fabian &
Villinger, in press) and was recovered and replaced
by the ROV ‘Jason II‘ in February 2007 during
cruise MSM04/3 of the new german research
vessel ‘Maria S. Merian‘. The OBA will
record until January 2009 simultaneously to the
OBT. The 3-axis acceleration data from the
OBA will complete long-time data tilt data of
the OBT. Both instruments provide data of local
seismicity and tilt related to hydrothermal
activity and crustal growth. Activity-phases in
the LHF like enhanced seismicity or ocean floor
deformations will be determined and correlated
with the data of co-workers in our research program
(temperature, ocean bottom water pressure,
test-sequences of local smoker-fluid chemistry
and vent-fauna during the visits of the
LHF between 2005 and 2009). The long-time
data will be used as a proxy for changes in energy
flux from the earth‘s mantle to the ocean and
for variations and diversifications in local life
cycles.
The OBA is a part of the monitoring system
of project LOLEM (Logatchev Longtime Environmental
Monitoring) which is supported by
the Deutsche Forschungsgemeinschaft (DFG)
in the frame of Schwerpunktprogramm 1144:
‘Vom Mantel zum Ozean: Energie-, Stoff- und
Lebenszyklen an Spreizungsachsen‘.
References:
Fabian, M., Villinger, H. (in press). The Bremen
Ocean Bottom Tiltmeter, OBT,- a technical
article on a new instrument to monitor seafloor
tilt and local seismicity, Marine Geophysical
Researches.
Fabian, M., Heesemann, B. (2006). Neigungswaage
für Unterwasser- und Hochdruckanwendungen
(deep sea level), Gebrauchsmusterschrift
(registered design) DE
20.2006.013066 U1 - Universtät Bremen,
Deutsches Patent- und Markenamt.
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