Abstract
The Geological Survey of Japan and the National Research Institute for Earth Science and Disaster Prevention have been jointly proposing an ultradeep continental scientific drilling JUDGE (Japanese Ultradeep Drilling and Geoscientific Experiments) which is designed to penetrate through the subduction zone of the Phillipine Sea plate at 10 km depth. In the JUDGE project, observation and monitoring of the decollement zone is one of the most important issues. The technical problems regarding drilling and observation are also reviewed.
