What is this Tiria town ? Never heard of it ! And only 3 years before Chaz's adventure in Phantasy Star IV..strange we didn't know or discover this town in the game...
It could be one of those ruined towns around the Kadary region. Those places were never given official names. Of course, that's just speculation. It could just as easily be any number of "off screen" places retroactively added to the planet.