/etc/nginx/nginx.confに
log_format ltsv "local_time:$time_local" "\thost:$remote_addr" "\tforwardedfor:$http_x_forwarded_for" "\treq:$request" "\tstatus:$status" "\tsize:$body_bytes_sent" "\treferer:$http_referer" "\tua:$http_user_agent" "\treqtime:$request_time" "\tcache:$upstream_http_x_cache" "\truntime:$upstream_http_x_runtime" "\tvhost:$host" "\tmethod:$request_method" "\turi:$request_uri"; access_log /var/log/nginx/access.log ltsv;
と書き加える。