FK(velocity/slope) filter

[Shihao-Yuan]

Description

Implementing a frequency-wavenumber (F-K) filter to isolate seismic waves within a specified range of apparent velocities. This filter can also function as a directional filter, allowing for the selection of waves propagating in specific directions, such as upward/downward or leftward/rightward.

Relevant discussions #405

Checklist

I have (if applicable):

• referenced the GitHub issue this PR closes.
• documented the new feature with docstrings or appropriate doc page.
• included a test. See testing guidelines.
• your name has been added to the contributors page (docs/contributors.md).
• added the "ready_for_review" tag once the PR is ready to be reviewed.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.84%. Comparing base (99f4468) to head (32b7c18).
Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #413   +/-   ##
=======================================
  Coverage   99.84%   99.84%           
=======================================
  Files         109      109           
  Lines        8843     8894   +51     
=======================================
+ Hits         8829     8880   +51     
  Misses         14       14           

Flag	Coverage Δ
unittests	99.84% <100.00%> (+<0.01%)	⬆️

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[d-chambers]

Hey @Shihao-Yuan,

The failure above is caused by incomplete test coverage. When you click on the details you can see the lines that aren't covered. In this case, the problem was with the case where the input patch was already in the FK domain.

I just pushed a couple of tweaks. Mainly, I grouped the internal logic of slope_filter into sub functions just to improve organization. I also added some more tests and made the function general so it can work with dimensions of any name (not just time and distance).

Let me know what you think.

[d-chambers]

@Shihao-Yuan, feel free to squash and merge when you are happy with the PR.