You can send any request for author pages to a 404 with a simple action on parse_query
.
add_action( 'parse_query', '_404_author_archives' );
function _404_author_archives( $qr ) {
if( is_author() )
$qr->set_404();
}
That should send any requests for an author page to a 404.
If you wanted to go a bit further and remove the author rewrite rules you could also do that quite easily with a filter on author_rewrite_rules
.
add_filter( 'author_rewrite_rules', 'remove_author_rules' );
function remove_author_rules() {
return array();
}
Untested, but you’ll have to let me know if that’s not quite enough author elimination..