WordPress at a glance
action is not described

network_site_users_created_user action-hook . WP 4.4.0

Fires after a user has been created via the network site-users.php page.

Usage

add_action( 'network_site_users_created_user', 'action_function_name_7920' );
function action_function_name_7920( $user_id ){
	// action...
}
$user_id(int)
ID of the newly created user.

Where the hook is called

In file: /wp-admin/network/site-users.php
network_site_users_created_user
wp-admin/network/site-users.php 82
do_action( 'network_site_users_created_user', $user_id );

Where the hook is used (in WP core)

wp-includes/ms-default-filters.php 31
add_action( 'network_site_users_created_user', 'wp_send_new_user_notifications' );