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Marine geophysical instrumentation: Videos from the deployment cruise 2012

Written by Karin Sigloch on . Posted in Technology

Deployments of geophysical instruments during the first RHUM-RUM Cruise Sep.-Oct 2012, aboard Marion Dufresne (cruise MD192, Leg2)

Films produced by Emmanuel Pons of the University of La Réunion.

Our main type of instrumentation: Ocean-bottom seismometers record the subtle motions of the ocean floor until we return in 2013. We are particularly interested in recording waves from earthquakes that occurred thousands of kilometers away, which illuminate the mantle deep beneath La Réunion. We are also interested in smaller regional earthquakes and the daily noise on the ocean floor.

Video: Assembly and setup of an OBS from the German DEPAS pool - 5'05" 

Video: Testing the acoustic releasers of the German OBS - 2'31"  

Video: Testing the acoustic releasers of the French OBS  - 2'42" 

Video: Deployment of station RR22 (a German DEPAS OBS)  - 1'26"

Video: Deployment of station RR28 (a French INSU OBS)  - 3'00"

Video: Deployment of station RR29 (a French INSU OBS)  -  1'56"

Video: Celebrating the last OBS deployment  -  4'13"

Bathymetry: the ship constantly surveyed the depth and shape of the ocean floor by sending and recording acoustic pings. Only a small fraction of the world's ocean floor has been mapped with a state-of-the-art multi-beam bathymeter such as the one on the Marion Dufresne, and new discoveries are common. Our colleague Dass Bissessur from the Mauritius Oceanography Institute explains the discovery of a picture-perfect seamount (in French).

Video: Dass Bissessur explains a new undersea volcano discovered at Waypoint 38 by bathymetric mapping

The magnetometer measures the magnetization of the seafloor, which gives information about how and when the ocean basins formed. It gets towed behind the ship and recorded constantly, except when the ship stopped. Here the sailors are redeploying the magnetometer after the end of a seismometer deployment.

Video: Deployment of the magnetometer  - 1'16"

The only instrument recovery during the cruise: an absolute pressure sensor was tested on the seafloor for several hours by our colleague Wayne Crawford from IPG Paris. Next year, we will return to recover our 57 ocean-bottom seismometers in a similar way.

Video: Test deployment and recovery of an absolute pressure sensor  -  4'26"

Video: Wayne Crawford explains the signal recorded by his absolute pressor sensor on the seafloor (in French)  -  5'37"

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Ocean bottom seismometers: the German DEPAS pool

Written by Guilhem Barruol on . Posted in Technology

The 48 broad band instruments that will be deployed around La Réunion during the RHUM-RUM experiment are provided by the German pool  DEPAS ("Deutscher Geräte-Pool für amphibische Seismologie" / "German instrument pool for amphibian seismology). They have the following characteristics  :

OBS DEPAS

  • Geophone, gimbal-mounted    Güralp CMG-40T, 60 sec - 50 Hz
  • Hydrophone    HighTechInc HTI-04-PCA/ULF, 100 sec - 8 kHz
  • Digital data recording unit    Send Geolon MCS, 24 bit, 1 - 1000 Hz, 20 GB
  • Acoustic release transponder    Kum K/MT 562 and Kum K/MT 8011M onboard unit
  • VHF radio beacon    Novatec RF-700A1 and Seimac DR500 bearing receiver
  • Xenon flashlight    Novatec ST-400A
  • Floating unit    Syntactical foam
  • Frame and pressure tubes    Titanium alloy
  • Anchor    Iron
  • Maximum deployment depth    6000 meters
  • Maximum deployment duration    19 months
  • Dimensions (excl. flag and beacons)    1.65 m x 1.30 m x 0.72 m
  • Dimensions (incl. flag and beacons)    2.80 m x 1.30 m x 0.72 m
  • Weight (excl. anchor) in air / in water    340 kg / -30 kg
  • Weight (incl. anchor) in air / in water    405 kg / 27 kg

More informations on the  instruments DEPAS on the AWI web site (Alfred Wegener Institute, Bremerhaven, Germany)

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Ocean bottom seismometers: the French INSU Pool

Written by Guilhem Barruol on . Posted in Technology

The 9 broad band  instruments that will be deployed during the RHUM-RUM experiment are provided by the French pool managed at the IPGP/INSU. They have the following characteristics:

OBS INSU Mise a leau

  • Sismométre large bande T240 Trillium
  • Capteur de pression différentiel (cf « A deep sea Differential Pressure Gauge » Charles Cox SCRIPPS Septembre 1984.)
  • Codeur delta sigma 24 bits, Dynamic range 130db @ 25 Hz Bandwidth, 121db @ 411 Hz Bandwidth, Signal to distorsion 115 dB.
  • Fréquence d’échantillonnage 62,5 Sample/Seconde sur 4 voies.
  • Horloge Seascan dérive <1seconde/an
  • Consommation 1,2W sous 15,6 V à 6,5 sps / 4 canaux
  • Batteries Lithium capacité max embarqué / 810AH
  • Profondeur 5000 mètres Max
  • Poids dans l’air 400 Kg
  • Poids dans l’eau lesté 45 Kg
  • Poids dans l’eau délesté -15 Kg

More informations of these broad band ocean bottom seismometers on the INSU web site.