A high-resolution bathymetric survey of the eastern half of the Gulf of Aqaba (within Saudi waters) and the Strait of Tiran was conducted on board the R/V Thuwal from May 20th to June 7th, 2018. We used a Kongsberg EM710-MK2 multibeam echo sounder (operating in the 70-100 kHz range) calibrated with CTD (Conductivity, Temperature, Depth) profiles. In order to maximize the range capability and to reduce interference from multiple returns we used a transmit fan which sequentially divides the signal into three sectors with distinct transmit frequencies and waveforms. We limited the system to a swath of 2000 m (i.e. 1000 m swath on each side of the beamer) in order to ensure appropriate beam density as to grid the data in a 10 m wide pixel raster across the track. Similarly, the survey speed was kept at 5-6 kn (~10 km/h) to limit the spacing between successive survey points and to ensure that the maximum pixel width is 10 m along the track as well. Survey lines were acquired every ~1000 m in deep water and 500 m near the shore, to ensure a double coverage of each point in opposite directions. The results were imported into the commercial SiS multibeam software and used to correct the incoming multibeam data. Then, the bathymetric data were automatically screened for obvious outliers and, additionally, we manually identified and removed remaining spurious data points. From this dataset, we built a Digital Elevation Model (DEM) of the bathymetry by averaging raw data values to a 30 m horizontal grid. The vertical resolution of the DEM is controlled by the pulse duration of the acoustic signal. The vertical resolution (R) can be calculated following R = v⋅d/2 with v the wave propagation velocity in water and d the duration of the signal. During the data acquisition, we tuned the pulse duration at 2 ms, and calibrated the wave propagation velocity with the CTD casts with values ranging between 1535 and 1558 m/s. Thus, it implies that the vertical resolution is 1.5 m. If you use these data, please refer to Ribot M., et al. (2021). Active faults' geometry in the Gulf of Aqaba, southern Dead Sea fault, illuminated by multibeam bathymetric data. Tectonics, 40, e2020TC006443. https://doi. org/10.1029/2020TC006443.
|Date made available
|Mar 16 2021