2483e263_TCL_TK_Command_Reference_Guide__Configure_Option
[Resource Name] offRelief [Resource Class] OffRelief [Description] (Tk 8.4+) Specifies the relief for the radiobutton when the indicator is not drawn and the radiobutton is off. Options are: flat, raised (default), and sunken. [Configure Option] 
-offrelief type
TCL/TK Command Reference Guide