The former suggestions are fine but you may also consider this one
First, It depend on whether your account has select right on other schemas
If it does, then this may work :
SELECT TABLE_NAME, OWNER FROM ALL_TABLES;
OR
SELECT TABLE_NAME
FROM ALL_TABLES
WHERE OWNER IN ('schema1','schema2' ,...)
OR
WHEN LOGGED IN AS SYSDBA
SELECT TABLE_NAME
FROM ALL_TABLES
WHERE OWNER IN ('schema1','schema2' ,...)
This statement lists all tables and their owners for you
Hope it works