The Deep-Sea Scientific Drilling Vessel Chikyu, operated by Japan Agency for Marine-Earth Science and Technology (JAMSTEC), has completed the Integrated Ocean Drilling Program (IODP) Expedition 343 for Japan Trench Fast Drilling Project (JFAST).
The scientific objective of this expedition was to reveal the frictional properties of the plate boundary fault which caused the Tohoku Earthquake and the associated tsunami. The drill site was offshore Ojika Penninsula, Miyagi Prefecture, where a large displacement of the seafloor during the earthquake was inferred from the previous research.
In this location, JAMSTEC conducted logging-while-drilling (LWD) to the depth of the plate boundary (850.5 m below seafloor) to obtain physical properties of the formations and recovered the core samples from the depth of 648 m to 844.5m across the fault zone.
However, installation of a long-term borehole temperature monitoring system to detect a frictional heat anomaly due to fault movement of the Tohoku Earthquake, was postponed because of the mechanical failure of transmitter cable of the Underwater TV System (UWTV). This operation will be retried this summer.
The obtained data and samples (LWD and core) in this expedition, as well as long-term temperature (instruments to be installed in this summer) data will be analysed comprehensively to delineate the slip characteristics (physical and chemical properties that define the frictional properties of the fault) and deformation mechanisms at the toe of the plate boundary.
These studies are fundamental investigations for understanding fault properties and mechanisms of a tsunamigenic faults near the trench axis. Such understanding is expected to contribute to mitigation of disasters caused by megaquakes and the associated tsunamis.
Subsea World News Staff , May 25, 2012