Ocean Bottom Seismometer network (OBS)

The OBS system can be used for: Earthquake monitoring, Detecting slope failures, Sub-seafloor imagery, Regional hydro-acoustic monitoring and ocean-land coupling studies, in deep water.

The OBS pool comprises a fleet of 18 NAMMU from K.U.M in Germany. It is a currently the smallest instrument designed for long-term deployments. The instrument has four simultaneous channels (three ground velocity and one broadband hydrophone) with 32 bit @ 250 sps, 142 dB at 300 mW total power consumption including its 120 sec broadband trillium compact seismometer from Nanometrics. Up to 8 instruments can be stacked on one pallet. The instruments are transported in a fitted laboratory “20 foot” container (standard 20 foot certified sea container: 8 feet wide, unladen weight 2.2 tonnes), which can be brought on-board the ship.

Additional specifications & Technical data

In the robust and shock resistant syntactic foam shell are integrated a titanium pressure tube of 210mm diameter with broadband seismometer Trillium Compact 120 sec, data logger 6D6 and battery pack, as well as titanium releaser KUMQuat, hydrophone and head buoy. Flasher, radio beacon and flag for localization are mounted outside. This configuration allows recording of one year. For 3-year recording additional batteries are added with a power-backpack for the OBS. Hence the OBS can also be deployed in extremely remote areas with access every couple of years only. The half pallet size simplifies the handling and enables to stack three of them in two rows on one pallet.

Anchor and float are asymmetrically designed: NAMMU descends to the seafloor and stays there for data recording in horizontal position but ascends to the water surface in vertical position.

Thanks to the new Data Logger 6D6 some additional features are possible including:

  • modular system with multiple channels: starting with 4 seismic channels, one can freely add additional channels for different purposes
  • a GPS-unit and also AIS can be incorporated
  • a CSAC (Chip Scale Atomic Clock) is available
  • it is possible to swap the storage device from outside the housing while recording

Size: half a pallet: 800mm x 600mm x 600mm

Weight: 155kg without anchor, 205kg with anchor, stackable; 50 units per container

Operation depth: 6000 meters

Frame: titanium, flexible. Buoyancy from syntactic foam

Power supply: 1-year recording: 90 Lithium cells

3-year recording: 270 Lithium cells

Data Logger: Seismic Data Logger 6D6

Releaser: K/MT 562 KUMQuat, titanium

Hydrophone: HTI-04-PCA/ULF

Seismometer: Broadband Seismometer Nanometrics Trillium Compact 120

Positioning: radio beacon, flasher, signal flag. AIS as an option

Anchor: steel anchor