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Figure 3c: Estimates of tilt direction (degrees clockwise from H1) and tilt angle. Top: coherence, phase and admittance spectra from the daily average spectra. Orange dots show the narrow bandwidth (``tilt-freqs``) used to calculate mean values (bottom row). The plots on the top row are shown at the tilt direction. Bottom: Mean coherence, phase and admittance as a function ot the tilt direction. The correct coherence peak is selected as the direction for which the phase is within +/- 90 degrees from 0. The admittance is used to calculate the tilt angle.
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3. QC for clean station averages
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Figure 4: The orientation of maximum coherence between the vertical and the two
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horizontal components for M08A during March 2012. (Left) Coherence as a function
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of angle from the H1 component. (Right) Phase as a function of the angle.
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(Bottom) Tilt direction measured from the H1 component as a function of time.
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In this example, the coherence is low indicating low tilt noise.
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Figure 4: Tilt orientation estimates for M08A during March 2012. (Left) Coherence as a function
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of azimuth measured clockwise from the H1 component. (Middle) Phase as a function of the azimuth.
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(Right) Admittance and related tilt angle as a function of the azimuth. Dotted lines indicate estimates for "bad" days (i.e., with too few good windows).
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(Bottom) Tilt direction, tilt angle and maximum coherence as a function of time. Symbols marked by an "x" indicate estimates for "bad" days.
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The legends show the mean and 2-sigma error on the "good" estimates.
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In the MATLAB version of ``ATaCR``, the "Angle from H1" (Figure 4 in the manual) corresponds to a counter-clockwise rotation of H1 and H2, and the orientation is chosen at the lowest phase. Here, the angle corresponds to a clockwise rotation and the estimate is chosen to lie between 0 and 180 degrees. There is therefore a 225-degree difference between those two estimates, and the plots are mirrored.
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In the MATLAB version of ``ATaCR``, the "Angle from H1" (Figure 4 in the manual) corresponds to a counter-clockwise rotation of H1 and H2. Here, the angle corresponds to a clockwise rotation and the estimate is chosen to lie within +/- 90 degrees from a phase value of 0. Furthermore, we use a circular mean (as opposed to a linear mean) to calculate the phase, and consider a narrower range of tilt frequencies closer to 0 Hz, where tilt effects are most pronounced. This results in a different plot between the ``OBStools`` version and the MATLAB ``ATaCR`` version, but these differences should not affect the tilt noise removal process.
Copy file name to clipboardExpand all lines: docs/index.rst
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OBStools is a package containing Python tools for processing broadband
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ocean-bottom seismic (OBS) data. Current functionalities include removing
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vertical component noise from tilt and compliance effects, and calculating
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compliance functions from vertical displacement and pressure data. The code uses
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vertical component noise from tilt and compliance effects, calculating tilt orientation from three-component seismic data, and calculating compliance functions from vertical displacement and pressure data. The code uses
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the ``StDb`` package for querying and building a station database and
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