That event tells the optimiser to consider star joins. It is probably there because your application needs it. Think twice and check with Oracle support before removing it.
There is no ALTER SYSTEM command to change event settings.
I have this entry in an init.ora
event="10076 trace name context forever, level 1"
I know it produces trace files. It must have been set up by a previous DBA
at this site. Other than shut down, edit the init file and start back up is
there an alter system command to shut this off.