Seminar Schedule < Institute For Research on Earth Evolution

2010

● IFREE ALL seminar information
The 45th IFREE ALL seminar on November 19 (Fri), 2010.
Place: Seminar room, annex 1F, YOKOSUKA HQ
Time: 16:00-17:00 on November 19 (Fri)
Speaker: Toru Sugiyama (Hierarchical System Research Team)

Title: Origin and acceleration process of energetic charged particles

Abstract:
  Energetic charged particles pouring from the space into the earth work
important roles for weather forecast both in space and atmosphere.
Therefore it is an important investigation how they are generated,
accelerated and convected into the earth�fs orbit in order to predict the
intensity of these particles. Observationally, they come from the Sun
and outer heliosphere with an intensity modulation by the solar
activity. A shock wave is one of the candidates for the acceleration
process. Here we focus on the solar energetic particles (SEP) and show
the investigation results from numerical and observational analysis.
After a large solar flare explosion on the sun�fs surface, shock waves
are excited and propagating into the heliosphere. With related the
explosion and the shock waves, the geomagnetic activity increases then
beautiful aurora are observed in the polar regions. In the same time,
the energetic particles are also excited by the shock waves. As noted
above, the energetic particles are one of the key items for the
forecasts, we have investigated the acceleration and propagation
mechanism of the particles around the shocks. On the contrast to the
conventional theory (Fermi acceleration), the spatial profile and energy
spectrum are both harder. The acceleration efficiency is also better.
These results suggest that the more particles are accelerated around the
shock, the more pour onto the earth. Indeed, this new result/model is
strongly supported by the marvelous agreement with the satellite
observation analysis in the space.

● IFREE ALL seminar information
The 44th IFREE ALL seminar on October 15 (Fri), 2010.
Place: Miyoshi Memorial Hall, Yokohama institute (YES)
Time: 16:30-17:30 on October 15 (Fri)
Speaker: Tetsuya Sakuyama (Mantle Evolution Research Team)

Title: Evolution of Cenozoic upper mantle beneath back arc region of the eastern part of Eurasian Plate: petrologic constraints from northwestern Kyushu and Korean basaltic activities

Abstract:
  Back-arc region, the area away from the place where surface
of the slab subducting below is at a depth of ~300km, is
characterized by high surface heat flow, slow upper mantle
velocity, and continual sporadic volcanisms. These lines of
evidence suggest that the upper mantle beneath not only
subduction zone but also back-arc region is influenced by
the subducting and stagnant slab.
  Eastern margin of the Eurasian Plate is a region where
Cenozoic back-arc volcanisms extensively and sporadically
occur over back-arc width of >1000km. Despite numbers of
geophysical and geochemical investigations on the upper
mantle and rocks in this region, number of analysis
combining phase petrology and geochemistry on volcanic
rocks, which is a good means to reveal thermal condition of
the previous uppermost mantle, is quite limited. Evolution
of thermal structure of the back-arc upper mantle during the
Cenozoic and their relationship with volcanisms are,
therefore, still poorly understood.
  To address the issue above we made systematic geological,
petrological, geochemical, and chronological investigations
on an back-arc Cenozoic volcanisms in northwestern Kyushu
and middle of the Korean Peninsula. Two volcanisms in
different locality show similarity and dissimilarity in
temporal geochemical variation. Both the volcanisms show
temporal increase of SiO2 content in primary melt and
decrease of K2O, TiO2, P2O5 contents, and incompatible trace
element abundance. Meanwhile, HFSE/LREE ratio of the basalt
from northwestern Kyushu temporally decrease, while that
from Korea does not. Isotope compositions of the basalt from
northwestern Kyushu temporally change toward sediment
composition on the Pacific slab, while that from Korea
change away from the sediment composition.
  Although eruption age of the two volcanisms are different,
we concluded that upper mantle beneath northwestern Kyushu
was hotter and more influenced by fluid released from the
slab than that beneath Korea. In order to reveal evolution
of the upper mantle beneath whole back-arc region in the
eastern margin of the Eurasian Plate, we need to investigate
samples from wider area with high time resolution.

● IFREE ALL seminar information
The 43rd IFREE ALL seminar on September 17 (Fri), 2010.
Place: Seminar room, annex 1F, YOKOSUKA HQ
Time: 16:00-17:00 on September 17 (Fri)
Speaker: Daisuke Nishiura (Earth Surface Dynamics and its Predictive Modeling Research Team)

Title: Particle Suspension Dynamics in a Simple Shear Flow

Abstract:
  Particle suspensions are used in various industrial fields of food,
chemical engineering, civil engineering, and medication. In these fields,
high-precision controlling of the suspension rheology, based on exact
understanding of the particle suspension dynamics, is required to realize
a comfortable life with safe and quality. On the other hand, there are
magmatic flow, geological layer and mudflow on ocean floor as particle
suspension studied in geosciences. Here, a fluidic effect of such as pore
water in layer or water vapor and melt in magma has been considered
in order to explain the dynamics of Earth’s interior. Unfortunately, several
researches may not get out delusion in terms of the fluidic effect.
This could not be avoided because it is very difficult to experimentally
observe microscopic behavior such as a fluid velocity and pressure
under tough conditions of high temperature and high pressure in Earth's
interior. However, the explanation for the fluidic effect should be on the
clear and reliable results obtained by the detailed observation of particle
motion and fluid flow. Thus, discrete element method combined with
computational fluid dynamics was developed to obtain the information of
particle-particle and particle-fluid interactions and to visualize a microscopic
fluid flow and individual particle motion. This numerical method for the
multiphase problem of particles and fluid was provided to end the delusion,
which would turn uncertain experimental interpretation into more reliable
consideration.
  In this study, the rheological behavior of particle suspensions was
investigated by using the simulation, which also relates to magmatic flow.
The simulation was carried out for the suspensions of various particle
concentrations under simple shear flow condition, and the shapes of
simulated particle were two types of sphere and rectangle plate.
Curious phenomenon that is the formation of circular hole whose area is
absence of particles in the suspension was found at certain condition.
There are two factors for the hole formation. One is a vortex formation
owing to the existing of particles which disturbs fluid flow in a shear direction.
Another is the ease of the condensation of particles, which is influenced
by coefficients of friction and restitution of particle, and particle shape.
On the day, as the detail of simulation results will be presented,
please find further capability of our simulation method as application
for geoscience.

● IFREE ALL seminar information
The 42nd IFREE ALL seminar on August 27 (Fri), 2010.
Place: Miyoshi Memorial Hall, Yokohama institute (YES)
Time: 16:30-17:30 on August 27 (Fri)
Speaker: Satoru Tanaka (Deep Earth Structure Research Team)

Title: Inner core hemisphericity

Abstract:
    Inner core hemisphericity is one of the hottest topics for recent inner core
studies as well as inner core anisotropy and super rotation. The travel times
of PKP(DF) phases that propagate in the shallow part in the east-west
directions (equatorial paths) are characterized by a hemispherical distribution;
fast anomalies (about +0.5%) are identified in the hemisphere centered on Asia, called as the Eastern hemisphere,and slow (about -0.5 %) in that centered on Americas, the Western hemisphere. Furthermore, PKP(DF) traveling in the north-south directions (polar paths) indicate small fast anomalies
(about +0.5 % or less) in the Eastern hemisphere, and large fast anomalies
(about +3 %) in the Western anomalies. These observations are interpreted as
hemispherical heterogeneity in the upper inner core and inner core anisotropy
existing in only the Western hemisphere. Interestingly, a similar hemispherical
difference is observed in attenuation structure of the inner core.
The Q value of uppermost inner core in the Eastern hemisphere is small
(about 300)v for both equatorial and polar paths, those in the Western hemisphere are large (about 600) and small (about 250) for equatorial and polar paths, respectively.
     So far, the hypothesis of inner core hemisphericity has been confirmed
by many studies not only using body waves but also free oscillation observations.
For long time, as many researchers had considered that this structure is curious and unexpected one, its geodynamical interpretation had been avoided.
However, several mechanisms are recently proposed to explain this curious structure.
Some researchers consider that the convection in the outer core affected by
heterogeneous heat flow at the core-mantle boundary creates the pattern,
and the others propose that inner core convection plays an important role.
On the other hand, seismological structure of the hemisphericity is still in debate, for example, its depth extent and the lateral boundary between two hemispheres.
Also, the relationship between hemisphericity and super rotation is not clear.
Therefore, further observations and deep discussion would be highly encouraged.

● IFREE ALL seminar information
The 41st IFREE ALL seminar on July 16 (Fri), 2010
Place: Seminar room, annex 1F, YOKOSUKA HQ
Time: 16:00-17:00 on July 16 (Fri)
Speaker: Takehiro Miyagoshi (Mantle and Core Dynamics Research Team

Title: Thin sheet convection with zonal flow and helical current coils in the spherical magnetohydrodynamic dynamo

Abstract:
     We have performed geodymano simulation with low Ekman number (Ek=O (10E-7))
and high Rayleigh number (several hundred times larger than the critical
Rayleigh number). We found new convection structure and dynamo process in
the core from our simulation results. The convection is organized as a set
of sheet plumes, rather than columnar cells. The width of each sheet is very
thin, less than 3% of the spherical radius. Each sheet plume is branching
and keeps its azimuthal width. The sheet plume is surrounded by the westward
zonal flow. The flow speed of the zonal flow is slow than that of the sheet
plume. In three dimensional view the structure of the zonal flow is
cylindrical along the rotation axis. Strong magnetic fields are generated by
the sheet-plume flows. The magnetic field is organized as many flux tubes
with current coils around them. The radius of each current coil is almost
the same as the sheet plume width. Magnetic energy is amplified in current
coils. Magnetic flux tubes are connected each other by large scale helical
magnetic field lines in the spherical shell.

● IFREE ALL seminar information
the 40th IFREE ALL seminar on June 18 (Fri), 2010
Place: Miyoshi Memorial Hall, Yokohama institute
Time: 16:30-17:30 on June 18 (Fri)
Speaker: Kenichiro Tani (Crust Evolution Research Team)

Title: Continental crust formation in intra-oceanic arc. Continental crust growth through arc collision.

Abstract:
    Island arcs are widely considered to be magma factories that produce
new crust of andesitic composition from basaltic oceanic crust through
modification by subduction zone magmatism. It is also proposed that
collision of island arcs are critical for continental growth, since the
average composition of continental crust is also andesitic; i.e., the
dominant product of island-arc magmatism. This has yielded the generally
accepted hypothesis that juvenile continental crust was formed at island
arcs, and the continents developed through repeated collision and
accretion of successive island arcs.
    The Izu-Bonin-Mariana (IBM) arc is a well-studied intra-oceanic arc,
where the detailed seismic velocity structure shows a ~6 km thick middle
crust, implying the presence of a granitic layer with andesitic composition.
The northern end of the IBM arc has been colliding with the Honshu arc for
the past 15 million years, resulting in the accretion of juvenile IBM arc crust
on to the Honshu arc, forming a syntaxes called the Izu collision zone (ICZ).
    Thus by understanding the tectonomagmatic processes during the
juvenile continental crust formation at the IBM arc and later accretion
with a mature (i.e. continental) arc at the ICZ, we have the potential to
comprehensively understand how continental crust forms and grows into continents.
    This approach has led to our new discovery of the first direct evidences
for both juvenile granitic crust formation in the IBM arc and syncollisional
granitic magma formation at the ICZ. These discoveries, augmented with
new geochemical and geochronological data, provide novel insights into
solving the long-standing question of how continental crust is formed
and grew during the early history of the Earth.

● IFREE ALL seminar information
the 39th IFREE ALL seminar on May 14 (Fri), 2010
Place: Lecture room at 1F, YOKOSUKA HQ
Time: 16:00-17:00 on May 14 (Fri)
Speaker: Seiichi Miura (Lithosphere Structure Imaging Research Team)

Title: Upgrading of Multi-channel reflection seismic (MCS) system of R/V Kairei.

Abstract：
JAMSTEC has been conducted seismic surveys using R/V Kairei to understand
mechanisms of great and large earthquakes occurred in offshore region since
late 1990's. From the seismic surveys, we have succeeded to acquire the
structural images such as splay faults of the Nankai Trough and interplate
sedimentary layers of the Japan Trench, contributing to understanding
seismogenesis of subduction zones. Moreover, intensive seismic surveys in
the Izu-Bonin-Mariana region using ocean bottom seismometers (OBS) has
enabled us to understand the development history of oceanic island arcs and
back arc basins, and to propose a model of differentiated crustal materials.
These results are based on the seismic data of deep structural survey with
large volume airgun array and long distance seismic lines. For next step for
structural studies, integration with ocean drilling and material sciences
such as D/V Chikyu is necessary. In 2008, upgrading of Multi-channel
reflection seismic (MCS) system of R/V Kairei was conducted to acquire
high-resolution structural imaging. In this seminar, I will show an outline
of the upgrading of MCS system including difficulty, and acquired structural
images.

● IFREE ALL special seminar
Debrief session
Place : Miyoshi Memorial Hall, Yokohama institute
Date : 2010/5/10 (Monday) 16:30-17:30
Speaker : Mikito Furuichi
Title ： Sorry, no English title.
Abstract：Sorry, no English abstract.

● IFREE ALL special seminar
Time: 14:00 - 17:00 on April 27(Tue)
Place: IT Build. 4F Room:403-404, Yokohama, JAMSTEC

Schedule: Sorry, no English Schedule

● IFREE ALL seminar information
the 38th IFREE ALL seminar on April 2 (Fri), 2010
Place:Lecture room at 1F, YOKOSUKA HQ
Time:2nd April (Fri) 16:00-17:00
Speaker:Teh-Ru Alex Song (Earth Informatics and Geophysical Network Research Team)

Title:
1. Subducting Slab Ultra-Slow Velocity Layer Coincident with Silent Earthquakes in Southern Mexico
2. Temporal velocity change associated great Sumatra earthquakes

Abstract:
1. Subducting Slab Ultra-Slow Velocity Layer Coincident with Silent
Earthquakes in Southern Mexico
Great earthquakes have repeatedly occurred on the plate interface
in a few shallow-dipping subduction zones where the subducting
and overriding plates are strongly locked. Silent earthquakes (or
slow slip events) were recently discovered at the down-dip extension
of the locked zone and interact with the earthquake cycle.
Here, we show that locally observed converted SP arrivals and
teleseismic underside reflections that sample the top of the subducting
plate in southern Mexico reveal that the ultra-slow velocity layer (USL)
varies spatially (3 to 5 kilometers, with an S-wave velocity of ~2.0 to 2.7
kilometers per second). Most slow slip patches coincide with the
presence of the USL, and they are bounded by the absence of the USL.
The extent of the USL delineates the zone of transitional frictional behavior.

2. Temporal velocity change associated great Sumatra earthquakes
Repeating earthquakes have been used to monitor seismic velocity
changes before and after large earthquakes. Previously studies observe
temporal changes in travel time between common source and receiver
and link such observations to possible earthquake precursors and
strong motion induced damages near surface.
However, it is difficult to associate the observed temporal velocity change
with earthquake process without knowing where the observed velocity
changes are located. Here I will introduce our recent work on modeling
travel time changes before and after 2004 and 2005 great earthquakes
in Sumatra. We use travel time measurements for high-frequency seismic
coda waves, Rayleigh waves and Love waves as constraints to locate
velocity change and its amplitude. I will briefly introduce modeling result
and discuss how it can be related to earthquake process.

● IFREE ALL seminar information
the 37th IFREE ALL seminar on February 19(Fri), 2010
Place: Miyoshi Memorial Hall, Yokohama institute
Time: 12th March (Fri) 16:30-17:30
Speaker: Yujiro Suzuki (Earth Informatics and Geophysical Network Research Team)

Title: 3-D numerical simulations of the dynamics of volcanic eruption clouds

Abstract:
Volcanic activities are important sources of information that can be
used to infer the conditions of solid earth. During an explosive volcanic
eruption, a mixture of volcanic ash and gas is released from the volcanic
vent as an eruption cloud. It rises as a turbulent plume (i.e., eruption column)
and/or laterally spreads in a stratified atmosphere as a gravity current
(i.e., umbrellacloud). The height of eruption column, the altitude of spreading
umbrella cloud, and so on are the observable data, whereas the source
conditions at the vent are hard to directly observe. In order to reveal the
relationship between the observable data and the source condition
at the vent, I have developed a 3-D numerical model of eruption clouds
[Suzuki et al., 2005]. This model was tested by the example of the
Pinatubo 1991 eruption [Suzuki and Koyaguchi, 2009].
In this talk, I will also present my recent study of turbulent mixing in
eruption clouds which governs the dynamics of eruption clouds
[Suzuki and Koyaguchi, 2010].

Suzuki, Koyaguchi, Ogawa, and Hachusu (2005), A numerical study
of turbulent mixing in eruption clouds using a three-dimensional
fluid dynamics model, JGR, B08201.

Suzuki and Koyaguchi (2009), A three-dimensional numerical simulation
of spreading umbrella clouds, JGR, B03209.

Suzuki and Koyaguchi (2010), Numerical determination of the efficiency of
entrainment in volcanic eruption columns, GRL, in press.

● IFREE ALL seminar information
the 36th IFREE ALL seminar on February 19(Fri), 2010
Place: Miyoshi Memorial Hall, Yokohama institute
Time: 19th February (Fri) 16:30-18:00
Speaker: Masataka Kinoshita, Yasuyuki Kano, Saneatsu Saito, Expeditions 319 and 322 Science Party

Title: Preliminary Reports on NanTroSEIZE Stage 2

Abstract:
The Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) program is
a coordinated, multiexpedition drilling project designed to
investigate fault mechanics and seismogenesis along subduction
megathrusts through direct sampling, in situ measurements, and
long-term monitoring in conjunction with allied laboratory and
numerical modeling studies. In 2007 through 2008, IODP Expeditions
314, 315, and 316 were carried out as NanTroSEIZE Stage 1. A transect
of eight sites was selected for riserless drilling to target the
frontal thrust region, the midslope megasplay fault region, and the
Kumano forearc basin region.

In 2009, the second stage of NanTroSEIZE was completed, including two
IODP Expeditions 319 and 322. Expedition 319 included riser drilling,
analyses of cuttings and core samples, downhole measurements and
logging, and casing at Site C0009 in the Kumano forearc basin as well
as riserless drilling, logging while drilling (LWD), casing, and
observatory operations at Site C0010 across a major splay fault that
bounds the seaward edge of the forearc basin near its updip terminus.
Site C0009 marked the first riser drilling in IODP history. This
allowed several scientific operations unprecedented in IODP, including
carefully controlled measurements of in situ pore pressure,
permeability and minimum principal stress magnitude, real-time mud gas
analysis, and laboratory analyses of cuttings throughout the entire
riser-drilled depth range. We conducted a leak-off test at one depth
interval and successfully deployed the wireline Modular Formation
Dynamics Tester 12 times to directly measure in situ stress magnitude,
formation pore pressure, and permeability. At riserless Site C0010,
operations included drilling with measurement while drilling (MWD)/LWD
across the megasplay fault to 555 mbsf, casing the borehole with
screens at the depth of the fault, conducting an observatory dummy
run, and installation of a temporary pore pressure and temperature
monitoring.

Expedition 322 (Subduction Inputs) was designed to document
characteristics of incoming sedimentary strata and igneous basement
prior to their arrival at the subduction front. Coring was conducted
at two sites in the Shikoku Basin on the subducting Philippine Sea
plate. Site C0011 is located on the northwest flank of the Kashinosaki
Knoll, whereas Site C0012 is located near the crest of the knoll.
Coring at Site C0011 failed to reach the total depth target. Coring at
Site C0012, however, penetrated 33 m into igneous basement and
recovered the sediment/basalt interface intact at ~540 mbsf. The age
of basal sediment is >18.9 Ma. The merger of lithofacies and age-depth
models from the two sites captures all of the important ingredients of
basin evolution; including an unrecognized interval of late Miocene
tuffaceous/volcaniclastic sandstone designated the middle Shikoku
Basin facies. An older (middle Miocene) turbidite sandstone/siltstone
facies with mixed detrital provenance occurs in the lower Shikoku
Basin; this unit is broadly correlative with similar Miocene
turbidites on the western side of the basin. Another result came from
geochemical analyses of pore water and hydrocarbons at Site C0012.
Pore fluids on top of the basement high show clear evidence of a
seawater-like source, with chlorinity values increasing toward
basement because of hydration reactions and diffusion; the fluids are
largely unchanged by the effects of focused flow and/or in situ
dehydration reactions associated with rapid burial beneath the trench
wedge and frontal accretionary prism. Thus, Site C0012 finally
provides a reliable geochemical reference site for the subduction
zone.

● IFREE ALL seminar information
the 35th IFREE ALL seminar on January 22(Fri), 2010
Place: Lecture room at 1F, YOKOSUKA HQ
Time: 22th January (Fri) 16:00-17:00
Speaker: Akio Kawano (Geochemical Dynamics Research Team, IFREE)

Title: Molecular and quantum approaches for atmospheric aerosol formation

Abstract:
Aerosol particles are ubiquitous in Earth's atmosphere. They affect
climate, atmospheric chemistry, and human health. It is well known
that gas-phase nucleation is an important source of atmospheric
aerosol particles. Despite an extensive effort to investigate
atmospheric aerosol formation in the past, the detailed mechanisms
and chemical species involved in the phenomena are still unclear.
Ion-induced nucleation by atmospheric ions is of growing interest
because it considered one of important mechanisms for atmospheric
aerosol formation. Classical approaches are incapable of the
quantitative treatment of atmospheric nucleation processes.
Application of more sophisticated molecular-based methods may
advance the understanding of the processes. We discuss the recent
developments of computational methods for atmospheric nucleation
based on molecular and quantum theories.

● IFREE ALL seminar information
IFREE ALL Christmas Seminar

Place	:	Seminar room, annex 1F, YOKOSUKA HQ
Time	:	25th. December 2009 (Fri) 16:30 -
Speaker	:	Kawabata Hiroshi
		Nishiura Daisuke

Title: Collaboration between igneous petrology (IFREE3B) and numerical simulation (IFREE1C) revealed how melt channels are formed in a crystallizing magma

Abstract:
We have investigated the shear-induced melt localization and the evolution
of microstructures within a crystallizing magma based on petrology and
3-D numerical simulation. The Miocene Oto-zan lava flow in southwestern
Japan records the localization of melts and aqueous vapors in response to
a flow-induced shear strain developed in a lava flow. Reconstruction of
the crystallization processes indicates that the observed localization occurred
before the magma reached to a crystal fraction of ca. 0.6 and a temperature
of ca. 900 C. We proposed that the localization does not require "fracturing"
event often considered in previous models. The localization occurs as a mirror of
the cyclic cluster formation. The clusters are steadily formed in a suspension
containing tabular particles (e.g., plagioclase) over a wide range of crystal
fraction after the onset of the Bingham rheology. This self-organizied texture is
governed by a simple well-known rule that stress vector on a plane depends on
plane orientation in a simple shear flow.