This volume is a follow-up of PAGEOPH Topical Volume 167 (2010) and again reports on the latest advances in science and technology that have been achieved to monitor compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). This progress in the development and testing of new sensor technologies and analysis methodologies in all relevant scientific disciplines improves the detection, location and characterization of CTBT-relevant events. In particular the latter poses a challenge for smaller events, where natural or manmade but CTBT-irrelevant sources can generate false positive...