Change author base

function pm_detect_author_permalink($request) {
    global $wp;

    // Parse the URI
    // URL Format: blog/%author%
    preg_match('/blog\/([^\/]+)(?:\/page\/([\d]+))?/', $wp->request, $parts);

    if(!empty($parts[1])) {
        $author_slug = sanitize_title($parts[1]);
        $author = get_user_by('slug', $author_slug);

        if(!empty($author->user_login)) {
            $request = array(
                'author_name' => $author->user_login
            );
        }

        // Support pagination
        if(!empty($parts[2])) {
            $request['paged'] = (int) $parts[2];
        }
    }

    return $request;
}
add_filter('request', 'pm_detect_author_permalink');

function pm_change_author_base() {
    global $wp_rewrite;

    $wp_rewrite->author_base = 'blog';
    $wp_rewrite->author_structure = '/' . $wp_rewrite->author_base . '/%author%';
}
add_action('init', 'pm_change_author_base', 999);