Several half-periods of observed voltage data stacked in a SmartEM receiver, plotted as 2500 samples over a 2-s half-period. The transmitter is off for the central half of the plot. The Fluxgate (green, offset +20) and HTS (red, offset +10) data are vertically shifted from the LTS (blue) response for ease of visualization.
(a) The two-layer case (sea and subsea). (b) The four-layer case incorporating a resistive layer situated 1000 m below the seafloor, having a thickness of 100 m and a resistivity of 100 ohm-m. The sea depth is 1 km and the transmitter frequency is 0.25 Hz.