Appendices 5-13 - Nautilus Cares - Nautilus Minerals

List of Figures
Figure 1. Geographical location of the proposed mining operation (red square)....................... 6
Figure 2. Third octave source spectra. Red - measured spectrum of the Pacific Ariki, blue -
extrapolated spectrum for mining vessel.......................................................................................... 9
Figure 3. Source location for the subsea mining operation showing detailed bathymetry. The
dotted magenta lines show the bathymetry profiles used for the propagation model runs............. 11
Figure 4. Bathymetry profiles used for propagation modelling for source location P1........... 12
Figure 5. Comparison between acoustic reflection coefficients for a basalt seabed (blue), the
equivalent fluid seabed (red), and the sandy silt seabed (green). Acoustic properties of the
materials are given in Table 2. ....................................................................................................... 12
Figure 6. Water column sound speed profile used for propagation modelling. ....................... 13
Figure 7. Plots of predicted received level vs. range and depth for azimuths from 0! to 135!.
Top four plots are for seabed model A., bottom four plots are for seabed model B. ..................... 15
Figure 8. Plots of predicted received level vs. range and depth for azimuths from 180! to 315!.
Top four plots are for seabed model A., bottom four plots are for seabed model B. ..................... 16
Figure 9. Zoomed view of plots of predicted receive level vs. range and depth for the eight
different azimuths (seabed model A).............................................................................................. 17
Figure 10. Scatter plot of received levels as a function of range for all depths and azimuths.
Blue 'x' are for seabed model A, red '+' are for seabed model B. Solid line is for spherical
spreading with a source level of 196.4 dB re 1 "Pa @ 1m. Broken line is cylindrical spreading
with a best-fit source level of 172 dB re 1 "Pa @ 1m. ................................................................... 18
Figure 11. Predicted maximum level at any depth as a function of range and azimuth. Top
plot is for seabed model A. Bottom plot is for seabed model B.................................................... 19
Figure 12. Extrapolated transmission loss vs. range assuming cylindrical spreading without
(blue) and with (red) absorption. .................................................................................................... 21
Figure 13. Distribution of received pygmy blue whale call components heard in the Perth
Canyon in 2000. ............................................................................................................................. 27
List of Tables
Table 1. Characteristics of the Pacific Ariki and the vessel under consideration for the mining
operation........................................................................................................................................... 8
Table 2. Seabed acoustic data used in propagation modelling................................................. 11
Table 3. Range beyond which all received levels are expected to be below the specified
threshold. Spherical spreading results are based on a point source with a source level of 196.4 dB
re 1 "Pa @ 1m. ............................................................................................................................... 14
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