The 18th Formation Evaluation Symposium of Japan, September 27 - 28, 2012
PRELIMINARY RESULT OF LOGGING WHILE DRILLING DURING
EXPEDITION 343, JAPAN TRENCH FAST DRILLING PROJECT
Yukari Kido1, Saneatsu Saito2, Yoshinori Sanada1, Moe Kyaw Thu1, Louise Anderson4, Marianne
Conin5, Weirin Lin3, Casey Moore6, Yasuyuki Nakamura2, Becky Cook7, Tamara Jeppson8, Monica
Wolfson9, Nobuhisa Eguchi1, Sean Toczko1, Lena Maeda1, Ikuo Sawada1, Tomokazu
Saruhashi1, James J. Mori10, Frederick Chester11 and Exp.343 Shipboard Science Party
1.CDEX, JAMSTEC, 2.IFREE, JAMSTEC, 3.KCC, JAMSTEC, 4.Univ. Leicester, 5.CEREGE, 6.Univ. California,
7.Univ. Southampton, 8.Univ. Wisconsin, 9.Univ. New Hampshire, 10.Kyoto Univ., 11.Texas A&M Univ.
drilling projects for 2012: to study the focal area of the
Tohoku EQ. However, there were questions as to where
This paper was selected for presentation by a JFES program committee following
review of an abstract submitted by the author(s).
we should drill. In planning the details, fundamental
information from bathymetry data was required. To
ABSTRACT
make a more precisely compiled map of the seafloor
During Expedition 343, measurement while drilling
before and after the Tohoku EQ and to understand
(MWD) and logging while drilling (LWD) were
surface deformation, we have compiled detailed seafloor
conducted at sites C0019B and C0019C 220 km offshore
from Miyagi Prefecture from April 1 to May 24. This
expedition was conducted in the framework of the Japan
Guard and JAMSTEC (Fig.1).
topographic images based on 0.002° (about 150 m)
gridded data obtained cooperatively by the Japan Coast
Trench Fast Drilling Project (JFAST) under the
Integrated Ocean Drilling Program (IODP). This is the
first program to drill through deepwater at the plate
boundary fault zone after the gigantic earthquake in
March 2011. The drill site is located off Oshika
Peninsula, just 10 km west of the Japan Trench at a water
depth of 6910 m. Our original plan is to penetrate the
plate boundary which is thought to be the fault zone for
the earthquake.
T
INTRODUCTION
It was 14:46 on March 11, 2011, an unforgettable day,
when the drilling vessel “CHIKYU” was ported and
preparing for the next expedition in Hachinohe, Aomori
Prefecture. When the earthquake occurred, CHIKYU
sustained damage the entire afternoon by the tsunami and
there was danger of losing one of the rear azimuth
thrusters on the port side of the ship. The ship’s hull was
also partially damaged. However, all of the crew and a
group of schoolchildren onboard for a field trip escaped
unharmed. Comparatively, therefore, the scale of the
damage was relatively small. However, the ship’s
schedule suffered serious disruption as a result of such
Fig.1 Compiled bathymetry map around the Japan
Trench. Asterisk shows the epicenter of Tohoku EQ.
damage. The research expedition had to be postponed.
It is very regretful that we could not finalize Nantroseize,
the Nankai Trough Seismogenic Project, which was
aimed at setting up an alert system in a borehole 1000 m
below the seafloor in March 2011. The devastating "2011
off the Pacific Coast of Tohoku Earthquake” (hereafter
Tohoku EQ) was much larger than most seismologists
expected. Because of the earthquake, CHIKYU has
WHAT’S NEXT? ― “THE JAPAN TRENCH FAST
DRILLING PROJECT” PLAN
In order to study the fault area of the Tohoku EQ,
carrying out technically challenging scientific drilling in
the rupture area was needed.
added
a new mission to her previously planned
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The 18th Formation Evaluation Symposium of Japan, September 27 - 28, 2012
One of the extraordinary features of the Tohoku EQ was
the size of the tsunami that was generated. For large
subduction zone earthquakes, often there is large slip on
deeper portions of the fault and less for the shallow
region near the trench. However, for the Tohoku EQ,
there was substantial movement in the shallow regions of
the fault, which caused the large tsunami.
Research conducted to date has shown seafloor
movement of as much as 50 m horizontally and 10 m
vertically near the trench axis. Typically, the
plate-boundary fault zone in the region of
the accretionary wedge near the trench is considered to
be weak, so large stress does not accumulate during the
time before the earthquake. This means that a large
slip is not expected when great subduction earthquakes
occur. Nevertheless, from experience with the
Fig.2 (a) (upper left) Site location with bathymetry map.
Tohoku EQ, we know that this is not always the case. In
order to understand how the fault moved with such a
large displacement in this region, scientists from a wide
range of fields gathered to discuss the fault conditions
that led to the large slip and devastating tsunami from the
Tohoku EQ. A plan to drill through the fault zone, was
developed and a completed an IODP drilling proposal
was written.
(b) (right) Close-up location information. (c) (lower left)
Planned drilling site with seismic section.
properties of the fluids and rock. Thus the name of
the project, JFAST, requires
a
particularly rapid
mobilization of IODP research facilities to measure the
time-dependent properties. The main goal of the JFAST
project is to understand the very large fault slip
that occurred on the shallow portion of the subuction
zone during the Tohoku EQ. This large slip of 50 meters
caused the devastating tsunami. In order to understand
how the fault moved with such large displacement in this
region, the JFAST project has three main objectives. The
first is to detect the fault zone by use of logging
technologies. The second is to sample the fault materials
in order to analyze the physical properties. The third is to
This expedition was called the Japan Trench Fast
Drilling Project (JFAST) and was conducted by the
Integrated Ocean Drilling Program (IODP). This is
the first program to drill at a subduction plate boundary
fault zone quickly after a large earthquake. It often takes
more than 5 years to complete a drilling proposal and
plan and an additional 5 years to execute the actual
drilling in the IODP program. However, this expedition
was implemented extraordinarily fast because of the
recognition of the importance for a rapid drilling by the
scientific community, involved organizations, and the
Japanese government.
make
temperature
measurements
to
estimate
the frictional stress during the earthquake.
GREAT CHALLENGE OF DEEP WATER
The proposed drilling site is located just west of the axis
of the Japan Trench with ultra deep water depth of 6910
m, and the CHIKYU must drill as much as 1000 m
below the seafloor to reach the fault zone. In the history
of deep-sea scientific drilling projects, only one other
expedition has successfully drilled in greater water depth,
which was 7,034 m in the Mariana Trench in 1978 to
obtain a sample 15.5 m below the seafloor. The JFAST
used a total of about 8,000 m of drill string to reach the
sea bottom and penetrate the fault zone. It was thus a
great scientific, engineering, and record-setting
challenge.
After careful consideration by scientists and operational
engineers, and based on a precise bathymetry chart and
seismic structural sections obtained before and after the
Tohoku EQ, a drill site located off Oshika Peninsula, 10
km west of the Japan Trench at a water depth of 6910 m,
was chosen.
IMPORTANCE OF UNDERSTADING DYNAMICS
The key to understanding the dynamics of large ruptures
is to know the level of dynamic friction on the fault. One
of the most direct ways to estimate the fault friction
during the earthquake is to measure the residual heat at
the fault zone. Theoretical calculations show that
EXPEDITION PLAN
The main operations to be completed during the
expedition consist of drilling two boreholes; the first hole
is dedicated to collecting downhole geophysical data to
determine the in situ stress state and locate the fault zone,
and the second hole is dedicated to retrieving core
samples from across the Tohoku EQ slip surface. Each
measurements need to begin within about
2
years following the earthquake in order to accurately
resolve the diminishing temperature signal. Several
important time-sensitive measurements are needed
for reliable estimates of friction, including the fault
temperature, fault zone permeability, and chemical
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