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 Aquarius 3-component broadband seismometer
  • Digital feedback tri-axial broadband seismometer, operational at any angle, with a flat response between 120s and 100Hz
  • A three-axis magnetometer and a MEMS accelerometer record the seismometer’s 3D position on the seabed
  • Nominal velocity response: 2000 V/ms-1Nominal acceleration response: 200 V/ms-2
  • Tilt tolerance±180°
  • Flash memory and storage128 GB dual redundant, hot-swappable microSD card storage
  • Depths of up to 6000m for up to 18 months duration
  • high precision clock, typical drift <1ms per day
  • Battery pack (rechargeable lithium-ion) designed for deployments lasting up to 18 months. (1 hour to re-charge per 1 month deployment).

Data Communication:

  • Up to 9000 bps transmission of data between seabed and surface using acoustic communication
  • Single cable connection to the Güralp deck unit for Gigabit Ethernet data download, system configuration and external power
  • The acoustic link activates the burn-wire for release to the surface and an on-board satellite tracking system and LED strobe light guides recovery

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

  • Resolution 1mm variation in 1000m of water
  • Accuracy 0.25% of full-scale