When plotting focal mechanisms with fig.meca, labels can be added above each beach-ball by including a label in the last column of the focal mechanism file that is being fed into the spec parameter. How do I change the size of the label text?
Currently, there is not a good way to my knowledge. Here is a workaround (warning: no guarantees that this will work in future releases, as it is not an intended use of the scale parameter):
fig.meca(spec="meca.dat", convention="aki", scale="1c+f36p,Helvetica,black")
I have opened a GitHub issue https://github.com/GenericMappingTools/pygmt/issues/1466 to add support for customizing the label appearance.