The ‘seismogram’ of a sailing ship

We thought of doing some basic ‘seismic’ analysis of the R/V Marcus G. Langseth.

In the last few days we have been surveying the ocean seafloor. This process requires that the ship sail in the form of a grid in order for the echo sounder to map the bathymetry of the entire area. In between matters and watching the survey proceed, we thought of doing some basic ‘seismic’ analysis of the R/V Marcus G. Langseth. We recorded the ‘seismic’ trace using a laptop’s accelerometer. The data is in three components (dimensions): west-east (X), north-south (Y), and up-down (vertical, Z). As expected the sway of the ship dominated the recording. From frequency analysis we find that the strongest frequency in the traces is about 0.1 Hz, which corresponds to a period of 10 seconds… No surprises here that this probably is the period of the sea waves.

A three-component seismogram recorded on board the R/V Marcus G Langseth whilst sailing through the Atlantic Ocean. A long period wave dominates the signal in each of the components, west-east (X), north-south (Y) and vertical (Z).
A three-component seismogram recorded on board the R/V Marcus G Langseth whilst sailing through the Atlantic Ocean. A long period wave dominates the signal in each of the components, west-east (X), north-south (Y) and vertical (Z).
Spectral analysis: Frequency spectrum with time for the west-east (X) component seismogram. Low frequencies (
Spectral analysis: Frequency spectrum with time for the west-east (X) component seismogram. Low frequencies (<0.5Hz) have the largest amplitude on the power scale (db).
Spectral analysis: Frequency spectrum for the entire seismogram. The largest amplitude is at 0.1 Hz (10 seconds period).
Spectral analysis: Frequency spectrum for the entire seismogram. The largest amplitude is at 0.1 Hz (10 seconds period).
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