Expand gallery example "Focal mechanisms" to use "*fill" and "pen" (#…

…2433)

examples/gallery/seismology/meca.py

@@ -3,17 +3,20 @@
 ----------------
 
 The :meth:`pygmt.Figure.meca` method can plot focal mechanisms or beachballs.
-We can specify the focal mechanism nodal planes or moment tensor components as
-a dictionary using the ``spec`` parameter (or they can be specified as a 1-D
-or 2-D array, or within a specified file). The size of plotted beachballs can
-be specified using the ``scale`` parameter.
+We can specify the focal mechanism nodal planes or moment tensor components
+as a dictionary using the ``spec`` parameter (or they can be specified as a
+1-D or 2-D array, or within a file). The size of the beachballs can be set
+using the ``scale`` parameter. The compressive and extensive quadrants can
+be filled either with a color or a pattern via the ``compressionfill`` and
+``extensionfill`` parameters, respectively. Use the ``pen`` parameter to
+adjust the outline of the beachballs.
 """
 
 import pygmt
 
 fig = pygmt.Figure()
 
-# generate a map near Washington State showing land, water, and shorelines
+# Generate a map near Washington State showing land, water, and shorelines
 fig.coast(
     region=[-125, -122, 47, 49],
     projection="M6c",
@@ -23,18 +26,27 @@
     frame="a",
 )
 
-# store focal mechanism parameters in a dictionary based on the Aki & Richards
+# Store focal mechanism parameters in a dictionary based on the Aki & Richards
 # convention
 focal_mechanism = dict(strike=330, dip=30, rake=90, magnitude=3)
 
-# pass the focal mechanism data through the spec parameter. In addition provide
+# Pass the focal mechanism data through the spec parameter. In addition provide
 # scale, event location, and event depth
 fig.meca(
     spec=focal_mechanism,
     scale="1c",  # in centimeters
     longitude=-124.3,
     latitude=48.1,
     depth=12.0,
+    # Fill compressive quadrants with color "gray70" (light gray)
+    # [Default is "black"]
+    compressionfill="gray70",
+    # Fill extensive quadrants with color "cornsilk"
+    # [Default is "white"]
+    extensionfill="cornsilk",
+    # Draw a 0.5 points thick dark gray ("gray30") solid outline via
+    # the pen parameter [Default is "0.25p,black,solid"]
+    pen="0.5p,gray30,solid",
 )
 
 fig.show()