WP Multisite: Do a function after blog is activated

I think this is what you’re looking for:

add_action('wpmu_new_blog', 'insert_custom_datas1', 10, 6);
function insert_custom_datas1($blog_id, $user_id, $domain, $path, $site_id, $blogmeta) {
    // Your code here
}

Let us know how it goes?