地球惑星科学専攻　地球科学輻合部特別講演会

日時: 2012年7月11日(水) 16：30〜18：00
場所：京都大学 理学研究科６号館３階３０３号室

講演題名：「Japan Trench Fast Drilling Project (JFAST)：
　　　　　 2011年東北地震の巨大滑りを理解するための掘削調査」
講演者：James J. Mori（京大防災研 地震防災研究部門 地震発生機構研究分野）

講演要旨：
　IODP Expedition 343, Japan Trench Fast Drilling Project (JFAST), sailed
from April 1 to May 24, 2012, with the main goal of investigating the area of
very large fault displacement during the 2011 Tohoku, Japan earthquake. A
borehole site near the Japan Trench was chosen with the objective of reaching
the main slip zone of the earthquake at a depth of 800 to 1000 meters below
seafloor (mbsf).  Huge fault displacements (30 to 50 meters) on this portion
of the megathrust are thought to be largely responsible for the tsunami that
devastated much of the coast of northeast Honshu, so understanding of the fault
properties and rupture mechanisms of this area is a primary research issue for
the earthquake.  For these investigations, there were planned temperature
measurements in the immediate vicinity of the fault to determine the level of
dynamic friction during the earthquake.  Also, anticipated core sampling of
the actual fault zone should provide direct observations of the physical
properties of fault and material for shore-based testing.
　The drilling operations had many technical challenges, mainly related to the
very deep water of more than 6800 meters. A new record was established for
the greatest total depth from the sea surface of a research borehole. One
successful borehole produced geophysical parameter data collected with
Logging While Drilling (LWD) tools, from the seafloor through the inferred
plate boundary at a depth of about 820 mbsf.  Another borehole produced core
that sampled depths from 648 to 845 mbsf, including the identified plate
boundary. All data collected during the expedition are now being carefully
analyzed by onboard and onshore researchers, to understand the faulting
mechanisms of the 2011 Tohoku earthquake.

問い合わせ先： 藤　浩明（輻合部，内線：3939）