WIP: Add tutorial showing how to plot focal mechanisms (beachballs)

[yvonnefroehlich]

Description of proposed changes

This PR aims to add a tutorial showing how to plot focal mechanisms using pygmt.Figure.meca. It focuses on how the display of the beachballs can be adjusted and modified:

• Filling the quadrants
• Plotting the P and T axes
• Plotting the components of a seismic moment tensor
• Adjusting the outlines
• Highlighting the nodal planes
• Adding offset from the event location
• Adding a label
• Using size-coding and color-coding

Related PRs (need to be merged before this PR is mergd)

• Add aliases for L, T, Fr : PR Figure.meca: Add aliases for "L", "T", and "Fr" #2546
• Expand docstring for scale: PR Figure.meca: Expand docstring for the scale parameter #2552
• Expand docstrings for compressionfill, camp, offset: PR Figure.meca: Expand docstrings for "compressionfill", "cmap", and "offset" #2553
• Add table for conventions to docs: PR DOC / Figure.meca: Use table for supported conventions #3811
• Add aliases for Fa, Fe, Fg, Ft, Fp: PR Figure.meca: Add aliases for "Fa", "Fe", "Fg", "Ft", "Fp" #3526

Backup of code for plotting the P and T axes

# %%
# Plotting the P and T axes
# -------------------------
#
# Wait for PR #3526

fig = pygmt.Figure()
fig.basemap(region=[-size, size] * 2, projection=projection, frame=frame)

fig.meca(
    spec=mt_dict_single,
    scale="1c",
    longitude=-2,
    latitude=0,
    Fa=True,
)

fig.meca(
    spec=mt_dict_single,
    scale="1c",
    longitude=2,
    latitude=0,
    Fa="0.2c/cd",  # Compute and plot P and T axes with symbols, Adjust size and symbols
    Fe="darkorange",  # Adjust fill of T axis symbol
    Fg="gray30",  # Adjust fill of P axis symbol
    Ft="0.8p,cornsilk",  # Adjust outline of T axis symbol
    Fp="0.8p,gray60",  # Adjust outline of P axis symbol
)

fig.show()

Preview: https://pygmt-dev--2550.org.readthedocs.build/en/2550/tutorials/advanced/focal_mechanisms.html

Reminders

• Run make format and make check to make sure the code follows the style guide.
• Add tests for new features or tests that would have caught the bug that you're fixing.
• Add new public functions/methods/classes to doc/api/index.rst.
• Write detailed docstrings for all functions/methods.
• If wrapping a new module, open a 'Wrap new GMT module' issue and submit reasonably-sized PRs.
• If adding new functionality, add an example to docstrings or tutorials.
• Use underscores (not hyphens) in names of Python files and directories.

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[yvonnefroehlich]

/format

[seisman]

Any specific reason that you need to define two focal mechanims here?

[yvonnefroehlich]

Hm. I think I wanted to have the moment tensor convention for section "Plotting the components of a seismic moment tensor" (around line 109) and later the Aki and Richards convention for the sections "Adjusting the outlines" (around line 143) and "Highlighting the nodal planes" (around line 173).

[seisman]

OK, I see your points. What about renaming them to shorter names like meca_aki/meca_mt?

[yvonnefroehlich]

My idea of the variable names was convention_datatype_amount:

• aki_dict_single
• mt_dict_single
• aki_dict_multiple
• aki_df_multiple

[seisman]

aki_df_dict is not used:

Suggested change

	# Set up a dictionary
	aki_dict_multiple = {
	"strike": [255, 173, 295, 318],
	"dip": [70, 68, 79, 89],
	"rake": [20, 83, -177, -179],
	"magnitude": [7.0, 5.8, 6.0, 7.8],
	"longitude": [-72.53, -79.61, 69.46, 37.01],
	"latitude": [18.44, 0.90, 33.02, 37.23],
	"depth": [13, 19, 4, 10],
	"plot_longitude": [-70, -110, 100, 0],
	"plot_latitude": [40, 10, 50, 55],
	"event_name": [
	"Haiti - 2010/01/12",
	"Esmeraldas - 2022/03/27",
	"Afghanistan - 2022/06/21",
	"Syria/Turkey - 2023/02/06",
	],
	}
	# Convert to a pandas.DataFrame
	aki_df_multiple = pd.DataFrame(aki_dict_multiple)
	# Set up a pandas.DataFrame with multiple focal mechanism parameters.
	aki_df_multiple = pd.DataFrame(
	{
	"strike": [255, 173, 295, 318],
	"dip": [70, 68, 79, 89],
	"rake": [20, 83, -177, -179],
	"magnitude": [7.0, 5.8, 6.0, 7.8],
	"longitude": [-72.53, -79.61, 69.46, 37.01],
	"latitude": [18.44, 0.90, 33.02, 37.23],
	"depth": [13, 19, 4, 10],
	"plot_longitude": [-70, -110, 100, 0],
	"plot_latitude": [40, 10, 50, 55],
	"event_name": [
	"Haiti - 2010/01/12",
	"Esmeraldas - 2022/03/27",
	"Afghanistan - 2022/06/21",
	"Syria/Turkey - 2023/02/06",
	],
	}
	)