Fix typo

Author: yvonnefroehlich

examples/tutorials/advanced/focal_mechanisms.py

@@ -65,7 +65,7 @@
 # to ``spec``). Additionally the ``convention`` parameter is required if ``spec`` is
 # an 1-D or 2-D numpy array; for the input types dictionary and ``pandas.Dataframe``,
 # the focal mechanism convention is automatically determined from dictionary keys or
-# :class:`pandas.DataFrame` column names. The ``scale`` parameter controlls the radius
+# :class:`pandas.DataFrame` column names. The ``scale`` parameter controls the radius
 # of the beachball. By default, the value defines the size for a magnitude of 5 (i.e.,
 # a scalar seismic moment of M0 = 4.0E23 dyn cm). Appand ``"+l"`` to force the radius
 # to be proportional to the seismic moment.