Ocean Bottom Seismometer - OBS
Ocean Bottom Hydrophone - OBH

Sensors at the sea floor are used to observe acoustic and seismic events.
Seismic and acoustic signals may be caused by different sources, by earth quakes and tremors as well as by artificial sources. Computing and analyzing the data yields information about the kind of source and, in case of natural seismic events, the geophysics and geology of the sea floor and the deeper crust. The deployment of OBS along a profile will give information about the deep structure of the Earth's crust and upper mantle in offshore areas.

Since the OBS/OBH works with hydrophones as well as with geophones, both names, OBS (Ocean Bottom Seismometer) and OBH (Ocean Bottom Hydrophone) are used for this observation and registration system. Combined with marine Multi-Channel Seismic (MCS) profiles, OBS is an economical alternative to ship-bounded Common MidPoint (CMP) methods in seismics. One aspect as an example: for MCS/OBS one vessel including the seismic array is necessary, while CMP requires two vessels each equiopped with seismic array.

OBS may be equipped with a maximum of a three-component geophone in addition to a hydrophone, and thus it needs a capacity of more than 144 Mbyte, which would be the minimum for an adequate MCS profiling. In a typical survey, the instruments should be operational for several days, which requires a data storage capacity of more than 500 Mbyte. Other experiments, such as tomographic investigations within a 3D-survey or seismological monitoring, demand even larger capacities.

Technical specifications of OBS are given in the data sheet of the Equipment Pool as a WORD-formatted document - today unformunately without figure due to restricted webspace.
OBS was developed by industrial management and organisatoric guidance of GEOMAR Technologie. GEOMAR Technologie was organising and combining the research and development activities of enterprises in sea technology and of science and academia. OBS today is part of the GEOMAR Equipment Pool and may be rent as well as bought.

Points of interest for the user:

Finally, remarks by scientists working with the OBS/OBH (see: Cruise Report RV SONNE 96, E. Flüh and W. Weinrebe, 1994):
“ The seismic traces gained.. are then reprocessed.. . And the data processing goes on and on resulting in new questions to the Earth's underground.
Finally, the GEOMAR OBS will be deployed again and again and again ... prooving its reliability . “

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Sorry, partially only in German:
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