Long-term underwater geophysical observatory

iMARL will include a fixed seismic, hydroacoustic and absolute pressure instrument set, for long term monitoring at a single site. The contruction of this OBS is well underway by Guralp Systems Ltd.
The aim is to

  1. monitor seismic signals from a wide range of sources especially from microseisms and local and distant earthquakes
  2. detect and measure tsunamis

The system will:

  • comprise of a broadband Ocean Bottom Seismometer (OBS) with Absolute Pressure Gauge (APG)
  • be able to communicate through an acoustic link to a buoy moored in the vicinity of the underwater module
  • the buoy will be equipped with a satellite communication system to allow near real-time communication between the seafloor station and the onshore national data centre at DIAS

Additional specifications & Technical data

  • Guralp Maris 3-component broadband seismometer
  • flat velocity response between 120s and 100Hz
  • self-noise of -165 db re (m/s2)2/Hz @ 10s
  • sensitivity 2000 V/m/s
  • can operate at any angle and orientation
  • suitable for deployment at depths up to 3,500m
  • high precision clock, typical drift <1ms per day
  • battery pack designed for deployments lasting up to 1 year
  • ~300mW power consumption

Data Communication:

  • acoustic modem for data transfer from sea floor to see surface
  • BGAN Satellite modem with antenna mounted on a motorized gimbal with automatic satellite tracking for data transfer between buoy and onshore data centre
  • possibility to upgrade underwater communication to ethernet via cable

Absolute Pressure Gauge (APG) (capable of tsunami detection):

  • standard mode: resolution of parts per million on the full scale (400 bars), ~100mW power consumption
  • nano resolution mode, with resolution of parts per billion on the full scale (400bars), ~258mW power consumption