SQL Server Audit Action Group:
DATABASE_PRINCIPAL_CHANGE_GROUP
This group tracks the creation modification or deletion of database principles which include database users, database roles and application roles.
If you enable this group in a server audit specification, it will track changes to principles in all databases within that SQL Server instance. If you enable this group inside a database audit specification, it will only track changes to principles within that particular database.
LOGbinder for SQL Server
events generated under this
Audit Action Group: