Indian Ocean Acoustic Observatory

The hydroacoustic observation network OHASISBIO

External collaborations: ENSTA Bretagne

OHA-SIS-BIO – HydroAcoustic Observatory of SISmicity and BIOdiversity – is a multidisciplinary and long-term (2010-2020) hydroacoustic observation programme. It consists of a network of 6 to 10 autonomous hydrophones immersed in the water column. Installed at the beginning of 2010, it is maintained every year during the annual trip of the N.O. Marion Dufresne to the French Southern Islands. This observatory has a two main objectives:

  • To carry out the most exhaustive possible acoustic monitoring of the seismicity associated with the three spreading ridges of the Indian Ocean, with contrasted opening rates (70 to 15 mm / year), and the deformation of the central Indian basin over a period the most representative possible;    
  • To record, over several annual cycles, the acoustic activity of large whales in the Southern Ocean, a key area of ​​their habitat and migration.

There are three additional goals. Indeed, the collected data revealed unexpected information on the noise of the sea state (microseismic noise) and the discharge of Antarctic glaciers in the Southern Ocean. This information, in the long term, would help validating prediction models of the sea state or estimates of the importance of climate change on Antarctic glaciers. Finally, our network provides as many sites on where to detect P waves from remote and distant earthquakes, which are converted into acoustic waves at the foot of the hydrophone moorings; these arrival times help constraining global tomography models.

Location of acoustic events from hydrophones of the OHASISBIO network alone (blue and yellow diamonds) between January 2012 and January 2013 (~ 8000 events; Tsang-Hin-Sun et al., 2016). Located by 4 or more hydrophones (red dots) or only 3 hydrophones (white dots).

Additional information

Contact: Jean-Yves Royer (

OHASISBIO site locations (2018):