For my reconstruction I am building closing plate polygons. I have a .shp with a set of polylines that define a subduction zone. I want to indicate the polarity of said subduction using the gpml:SubductionZonePolarity attribute. However, when I save the shapefile and restart GPlates, the file has lost the attribute “gpml:SubductionZonePolarity”. However, I can save this information when I save it as a .gpml file.
Q: Is it in general not possible to assign attributes such as subduction polarity to a .shp file? Are there any other attributes of other plate boundaries (i.e. transforms and mid-ocean ridges) that I should be aware of that are not saved in a .shp file?