SIT03-P01

Room:Convention Hall

Time:May 26 18:15-19:30

Continuous measurements of electrical conductivity of synthetic peridotite under changing temperature: Melting effect
SUEYOSHI, Kenta1∗ ; HIRAGA, Takehiko1
1

Earthquake Research Institute, The University of Tokyo

Transport properties of the mantle (ex. electrical conductivity, viscosity, and seismic attenuation) sharply changes during ascend of the mantle especially at around mantle solidus. Electrical conductivity is considered to be the most sensitive property
to the presence of partial melt. To understand how partial melting changes the conductivity of ascending mantle (ex. mid-oceanridge), we measured the electrical conductivity of synthesized peridotite samples, which have different manners of melting withtemperature, during slow increases and decreases in temperature under atmospheric pressure.
Three types of samples, forsterite (80%) + diopside (20%), forsterite (95%) + diopside (5%) and forsterite (50%) + enstatite(40%) + diopside (10%) with addition of 0.5% spinel, were synthesized from Mg(OH)2 , SiO2 , CaCO3 and MgAl2 O4 powders
with particle size of <50 nm. We continuously measured the electrical conductivity of these samples at temperature range from1100 ℃ to 1400 ℃. Microstructures of the samples quenched from above solidus were observed by scanning electron microscopy(SEM) in order to measure the melt fraction.
The electrical conductivity at well below (>50 ℃) solidus of the forsterite + diopside samples exhibited a linear distribution
in their Arrhenius plots indicating that a single mechanism controls. Such linear relationship was no longer observed at higher
temperature regime exhibiting its exponential increase until the temperature reached to produce a phase assembly of forsterite +melt. In addition, the grain size dependence on electrical conductivity disappeared at temperature between 1350 ℃ and 1360 ℃,indicating that the effective conductive path changed from grain boundary to other path. The result indicates that there is a phaseassembly of forsterite + diopside + melt phase at around 1360 ℃ which has not been appeared in the previously reported phase
diagram (Kushiro and Schairer, 1963).
Monotonic increase of electrical conductivity was observed above solidus of the forsterite + enstatite + diopside + spinel sample, and such increment is considered to be strongly related melt fraction changing with temperature, which is supported fromSEM observation.

Keywords: electrical conductivity, peridotite, partial melting, melt fraction

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SIT03-P02

Room:Convention Hall

Time:May 26 18:15-19:30

Measurement of single crystal elasticity of Gold (Au) under high temperature and highpressure
YONEDA, Akira1∗ ; FUKUI, Hiroshi2 ; HIRAO, Naohisa3 ; KAMADA, Seiji4 ; BARON, Alfred51

ISEI, Okayama Univ., 2 Univ. of Hyougo, 3 JASRI, 4 Graduate school of Science, Tohoku University, 5 RIKEN

Single crystal elasticity of gold (Au) has been measure by inelastic X ray scattering method under high pressure. A few tens
micrometer Au single crystal was prepared from a large commercial crystal by using FIB technique. The small crystal was placed
inside a gasket hole of DAC apparatus. We succeeded to measure single crystal elasticity at 0.8 GPa and 3.2 GPa; the pressures
were determined by the Ruby scale. ˜100 peaks were observed at each pressure, and used to constrain the three independent
constants of C11 , C12 , and C44 . The resulted elastic constants are consistent with the previous data at ambient pressure.
We observed that C11 and C44 increase with increasing pressure, and C12 decreases with increasing pressure. We will expand
the pressure range and temperature range of the measurement to establish the equation of state of gold with unprecedentedaccuracy.

Keywords: Gold, single crystal, elasticity, high pressure

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SIT03-P03

Room:Convention Hall

Time:May 26 18:15-19:30

High temperature generation using semiconductor diamond heater at high pressure
ITO, Eiji1∗ ; YONEDA, Akira1 ; XIE, Longjian1 ; TSUJINO, Noriyoshi11Institute for Study of the Earth’s Interior, Okayama University

Melting relations of the Earth materials are information essentially important to clarify the early differentiation and evolutionof the Earth. Nevertheless melting experiments using the Kawai-type apparatus under mid mantle conditions are impossible
because of limited temperature generation. Following Shatsky et al. (2009), we have tried to generate temperatures higher than3500 K adopting B-doped semiconductor diamond heater. In order to carry out melting experiments at higher than 50 GPa, weadopt sintered diamond anvils. Temperature (T) is estimated by extrapolating a T-W (power) curve constructed up to 2600 C
based on the W/re thermocouple measurement. Our T-generation reached ca. 4700 C at 55GPa.
Keywords: High temperature generation, Semiconductor diamond heater, Kawai-type apparatus, sintered diamond1/1

SIT03-P04

Room:Convention Hall

Time:May 26 18:15-19:30

Numerical Simulation on Subduction of the Pacific Plate into Northeast China and theSeismogenic Mechanism of Earthquake
JIAO, Mingruo1∗ ; BO, Zhang1
1Earthquake Adimistration of Liaoning Province, Shenyang, 110034, P.R.China

The Pacific Plate is subducted into Northeast China up to 660km deep, leading to a series of deep earthquakes in Hunchun
zones of Jilin province, which was noticed by seismologists in the past. As the only deep-earthquake belt in China, its occurrencetime, locations and magnitudes are closely associated with Japan trench earthquakes and shallow earthquakes in Northeast China.
Until now, seismologists attached great importance to this phenomenon and researched it in various aspects. On the one hand,research results confirmed the above phenomenon. On the other hand, masses of important results were obtained including thestructure of the Pacific subducting plate, lithosphere structure in Northeast China, the earthquake focal mechanism and the seismic dynamic mechanism about the deep and shallow earthquakes. But until now, there is seldom systematic research about therelationship among the Pacific plate, deep and shallow earthquakes using numerical simulation method. Therefore, this paper
will study their relationships and furtherly explore the tectonic stress field and dynamics environment in Northeast China.
Based on the geology data and the seismic velocity structure in Northeast China, we built the 2D vertical model along the 45
degree latitude ranging from 104 to 144 degree longitude with 0-660km deep to simulate the Pacific plate subducting to Northeast
China using finite element numerical simulation method. According to motion rate of the Pacific plate to the Eurasian plate, theboundary conditions are given. The model with the typical tectonic belts, such as Tanlu fault, can explain the earthquake mechanism and study the stress fields and displacement fields. Besides the relationship between fault belts and shallow earthquakes isdiscussed.Through numerical simulation and comprehensive analysis, some conclusions are obtained as follows:(1) The Pacific plate subduction into Northeastern China is the main dynamic resource causing a series of deep-focal andshallow-focal earthquakes. The stress field shows that there are two main areas of stress concentration under the subduction of
the Pacific plate. It can help us to explain the relationship about the seismogenic mechanism between deep and shallow earthquakes.
(2) The displacement field and deformation field are given. The results show the displacement field and deformation field
are controlled by the Pacific plate subduction rates. Exist of low veloticy medium in the middle crust layer is in favor of theoccurrence of the shallow earthquakes.

Keywords: numerical simulation, subduction of the Pacific plate, deep and shallow earthquakes, Northeast China

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SIT03-P05

Room:Convention Hall

Time:May 26 18:15-19:30

S-velocity structure of the crust and uppermost mantle of East Asia from ambient seismic
noise
WITEK, Michael1∗ ; NING, Shuoxian1 ; KANG, Tae-seob2 ; VAN DER LEE, Suzan1 ; CHANG, Sung-joon3 ;NING, Jieyuan4
1Northwestern University, 2 Pukyong National University, 3 Kangwon National University, 4 Peking University

We have collected continuous vertical-component broadband data from 1109 seismic stations in regional networks across
China, Korea, and Japan for the year 2011, and we have measured over half a million Rayleigh wave group velocity dispersion
curves from one-year stacks of station-pair ambient seismic noise cross-correlations. The Rayleigh wave group velocity dispersion curves are regionalized on a tessellated spherical shell grid in the period range 10 to 50 s to produce maps of Rayleighwave group velocity distributions. Maps at 10 seconds period match well with geologic features at the surface. In particular, weobserve low group velocities in the Songliao, Bohai Bay, Sichuan, Ordos, Tarim, and Junggar Basins in China, and the Ulleung
and Yamato Basins in the East Sea (Sea of Japan). Higher group velocities are observed in regions with less sediment cover.
At periods around 30 s, we observe group velocity decreases going from east to west in China, representing an overall trend ofcrustal thickening due to the collision between the Indian and Eurasian plates. The Ordos and Sichuan blocks show higher groupvelocities relative to the eastern margin of the Tibetan Plateau, possibly reflecting low temperatures in these cratons. Using theRayleigh wave group velocity distributions, we have performed 1D linear inversions at each node on the spherical shell grid toretrieve S-velocity perturbations with respect to the reference model LITHO1.0 of Pasyanos et al. (2014). This has allowed us
to construct a 3D model of the crust and uppermost mantle for East Asia. We observe large-scale lateral variation in the crust
compared to the LITHO1.0 model. From 50 to 100 km depth, we observe a low-velocity mantle wedge underneath Japan andthe Strait of Korea, and at 100 km depth we see a general trend of increasing S-velocities from east to west, possibly reflecting
temperature/water content variations in the mantle.
Keywords: East Asia, tomography, ambient noise

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SIT03-P06

Room:Convention Hall

Time:May 26 18:15-19:30

One-dimensional shear velocity structure beneath Okinawa trough inferred from surface
wave phase velocity
KOBAYASHI, Reiji1∗ ; FUKUDA, Keisuke2 ; TASAKI, Naoko3 ; ETOH, Ayano4
1Kagoshima University, 2 Kagoshima University, 3 Kagoshima University .Now at JMSDF, 4 Kagoshima University. Now at
Kasaki Clinic
Structures beneath back-arc basins or marginal seas are as important as those just beneath island arcs to understand the wholesystems of subduction zones. However number of studies on structure beneath back-arc basins is limited because of few seismicstations in back arc basin.
This study focuses on the structures beneath Okinawa trough. Philippine sea plate is subducting along the Ryukyu trench
and the Ryukyu arc is an island arc of this subduction zone. Okinawa trough is located in backarc region of Ryukyu arc and isconsidered to be a region of backarc spreading. Crustal structure along the Okinawa trough has been investigated by the Japan
Coast Guard (e.g. Horiuchi et al., 2011) and the Moho depth has been obtained. For the upper mantle structure, Nakamura
et al. (2003) inferred three dimensional P and S-wave structure by body wave tomography and several studies inferred three
dimensional S-wave tomography as a surrounding part of continent by surface wave tomography (e.g., Huang and Zhao, 2006).
However, the mantle dynamics beneath the Okinawa trough has not been well imaged.
As the first step of investigation of the mantle dynamics beneath the Ryukyu arc and Okinawa trough, we inferred onedimensional shear-wave velocity structure of crust and uppermost mantle beneath the Okinawa trough. We also inferred thatbeneath East China Sea continental shelf.
We measured phase velocities of Rayleigh and Love waves by two-station method and obtained dispersion curves. We usedstations of F-net of National Research Institute for Earth Science and Disaster Prevention (NIED), China Digital Seismograph
Network (CDSN), and Global Seismograph Network (GSN).
We then inferred one-dimensional shear-wave average structure along the path by genetic algorithm. We assumed radialanisotropy in uppermost mantle (Moho to 220 km) and isotropy in other layers.
Shear wave velocities just below the Moho beneath the Okinawa trough is significantly lower than that beneath the continental
shelf. It may suggest partial melting due to upwelling beneath the Okinawa trough. However, the velocities around 220 km
is higher than that beneath the continental shelf, suggesting that origin of the upwelling is not deep. The upwelling could bea passive flow like that beneath mid-ocean ridge. SV velocities beneath western part of the Okinawa trough is lower than SH
velocities, while SV and SH velocities beneath eastern part are similar to each other. This radial anisotropy may be caused by
the shape of the cracks of partial melt or preferred orientations of mantle minerals.

Keywords: Okinawa trough, backarc spreading, seismic structure, surface wave

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SIT03-P07

Room:Convention Hall

Time:May 26 18:15-19:30

P-wave velocity anomalies of the plume beneath the French Polynesia
OBAYASHI, Masayuki1∗ ; YOSHIMITSU, Junko1 ; SUGIOKA, Hiroko1 ; ITO, Aki1 ; ISSE, Takehi2 ;SHIOBARA, Hajime2 ; SUETSUGU, Daisuke1
1

D-EARTH, JAMSTEC, 2 ERI, Univ. Tokyo

The French Polynesian region is characterized by positive topographic anomalies of 700 m, a concentration of hotspot chains.
Many seismic tomography results show a broad low-velocity anomaly in the lower mantle continued from the base of the mantle.
These observations suggest that a large-scale mantle flow rises from the bottom of the mantle beneath the region. Joint JapaneseFrench broadband seismological observations were performed from 2001 to 2005 with 10 island stations from the Polynesian
PLUME project (Barruol et al. 2002) and 10 broadband ocean bottom seismometers (BBOBSs) from the Polynesian BBOBS
project (Suetsugu et al. 2005). A P-wave
tomography using the data from these projects revealed that large-scale low-velocity anomalies (on the order of 1000 km indiameter) from the bottom of the mantle become smaller-scale low-velocity anomalies (on the order of 100 km in diameter) at
the depth of about 1000 km. However the connection of the small-scale low-velocity anomalies to the surface hotspots was not
unrevealed because of the poor resolution in the upper mantle.
A new P-wave tomography with better resolution in the upper mantle was obtained by adding data from BBOSBSs around
Society Islands deployed along the TIARES project during 2009 - 2010 (Suetsugu et al. 2012) and by taking the finite frequency
effect into account for the frequency-depended differential travel times. The frequencydepended differential travel times weremeasured by multi-band cross correlating P waveforms. The new P-wave tomography shows strong low-velocity anomalies
beneath the Society Islands and Pitcairn in the upper mantle although they do not extend to the 660-km discontinuity. This model
also shows that small-scale low-velocity anomalies in the uppermost lower mantle. The low-velocity anomalies in the depth
range about 550 - 900 km are smaller both in lateral area and amplitude than those in most of the upper mantle and the lowermantle. The velocity patterns are well correlated each other in the depth range but are not correlated with the patterns above andbelow, indicating the mantle beneath the French polynesia can be divided into 3 layers in terns of radial correlation.
Keywords: Tomography, Plume, Mantle, French Polynesia

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