The Australian Transport Safety Bureau (ATSB) is leading a sea floor mapping and underwater search for missing Malaysia Airlines flight MH370 in the southern Indian Ocean. Geoscience Australia is providing advice, expertise and support to the ATSB.
The search comprises two planned phases. Phase one, a bathymetric survey providing a detailed map of the sea floor topography of the search area and phase two, an underwater search using side scan sonar.
Bathymetry is the study and mapping of sea floor topography. It involves obtaining measurements of the ocean depth and is equivalent to mapping topography on land. The bathymetric survey undertaken in the search for MH370 has resulted in a map that charts the contours, depths and hardness of the ocean floor.
Prior to the bathymetric survey, very little was known about the sea floor in the MH370 search area, as few marine surveys have taken place in the area. Existing maps of the sea floor were coarse, having been derived from satellites and only providing a general indication of water depth.
Figure 1: Coarse three-dimensional model of sea floor terrain
Figure 1: This model of the sea floor terrain was based on coarse pre-existing data, which was derived from satellite gravity measurements and ocean passage soundings. The MH370 bathymetric survey was undertaken to gather more detailed and higher resolution data in preparation for the underwater search phase.
Figure 2: The image on the left shows data at around 3400-metre resolution (data acquired predominantly by satellite altimetry), while the image on the right shows data with a combination of 250-metre and 50-metre resolutions (data acquired by bathymetric surveys from a vessel). The higher resolution data on the right more accurately reveals seabed features. This figure is for illustrative purposes only and does not show data from the search area.
The survey vessel Fugro Equator and the Chinese survey vessel Zhu Khezhen collaborated on the bathymetric survey, using multibeam sonar to gather data. That data—which was reviewed, corrected and analysed by experts at Geoscience Australia— revealed many seabed features for the first time. Newly discovered sea floor features include:
- seamounts (remnant submarine volcanoes),
- ridges (semi-parallel) up to 300 meters high, and
- depressions up to 1400 metres deep (compared to the surrounding seafloor depths).
The data also revealed finer-scale seabed features that were not visible in the previous low-resolution, satellite-derived bathymetry data.
Figure 3: Detailed three-dimensional model of sea floor terrain
Figure 3: A three-dimensional model of the sea floor terrain in the MH370 search area was developed from high resolution (90-metre resolution) data from the bathymetric survey and revealed many seabed features for the first time.
Over 200,000 square kilometres of the sea floor were surveyed. The data collected in the bathymetric survey was used to build a comprehensive map of the sea floor in the search area, to be used in navigation for the underwater search. The ATSB also used the data when planning for search timings, methods, procedures, safety precautions and priority areas for each vessel to search.
While initial bathymetric survey operations have been completed and phase two has begun, further bathymetric survey work may recommence if the need arises.
Data collected as part of the bathymetric survey will be publicly released by Geoscience Australia in due course.
Visualisation of Sea Floor Terrain
Before the underwater search for MH370 could begin, it was necessary to accurately map the sea floor to ensure that the search is undertaken safely and effectively. Bathymetry survey vessels spent months at sea, scanning the sea floor with multibeam sonar to gather detailed, high-resolution data. The data has revealed many seabed features for the first time. This computer-animated ‘flythrough’ shows a visualisation of some of the sea floor terrain in the search area.
More information on bathymetry can be found on the Geoscience Australia website.
The MH370: Factsheet – Multibeam Sonar provides information on multibeam sonar, a widely used tool in bathymetric surveys.
Information about the search for MH370 can be found on:
- the ATSB’s website, and
- the Joint Agency Coordination Centre website