MTT40-01

Room:201A

Time:May 27 16:15-16:30

Data-driven approaches to frontier of earth and planetary sciences
KUWATANI, Tatsu1∗ ; NAGATA, Kenji2 ; OKADA, Masato2 ; KOMAI, Takeshi1
1Graduate School of Environmental Studies, Tohoku University, 2 Graduate school of Frontier Sciences, University of Tokyo

It is important to extract essential processes and structures from observed data sets in order to understand the dynamic behaviorof the earth and planetary systems. Recently, many powerful methodologies have been proposed to extract useful informationfrom high-dimensional data sets in information sciences. Since the summer of 2013, we have launched a big scientific project
entitled as ’Initiative for high-dimensional data-driven science through deepening sparse modelling’ supported by the Ministryof Education, Culture, Sports, Science and Technology in Japan (http://sparse-modeling.jp/index e.html). The main purposeof this project is to develop the innovative mathematical methodology for understanding the world of nature by tight fusion of
information science and natural science. The project includes a wide variety of natural sciences such as biology, medicine, brain
science, earth and planetary sciences and astronomy. Two main key technologies are important to develop data-driven sciences:
One is ’Bayesian estimation’, which is a probabilistic methodology which can estimate cause from effect by reversing law ofcausality, and the other is ’Sparse modeling’, which is a mathematical framework which can effectively extract a small numberof essential explanatory variables from high-dimensional data sets. In this presentation, based on these two key technologies, wewill overview data-driven analytical technologies with some examples (Kuwatani et al., 2014a Earth, Planets and Space ; 2014b
Physical Review E ; 2014c Scientific Reports ).

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MTT40-02

Room:201A

Time:May 27 16:30-16:45

Estimation of bulk composition for meteoritic samples using handheld XRF
NIIHARA, Takafumi1∗ ; MIYAMOTO, Hideaki1 ; HONG, Peng K.1 ; OGUMA, Midori1 ; DOHM, James M.1
1

UMUT

Over 50,000 meteorites are recovered in hot and cold desert, and most of these meteorites are thought to originate from asteroids. The Hayabusa mission confirmed that the samples from asteroid Itokawa (S-type) have compositions similar to ordinarychondrites, therefore meteorites and asteroids have direct correlation, and thus the importance of meteorites increases to understand small bodies that could record early solar system histories. Direct comparison of meteorites and asteroids may produce
important information of the surface materials of asteroids. Surface chemical composition can be obtained by onboard instruments such as APXS and GRS. On the other hand, bulk chemical composition for most meteorites are missing (only 10% havebeen analyzed) due to a limited mass of each sample. Therefore, most meteoritic samples cannot be analyzed using conventional
techniques (e.g. INAA and XRF). To solve this issue, we are now developing an analytical procedure using a handheld XRF(Olympus Delta) to estimate bulk chemical composition without any sample preparation, although the accuracy of measurement
is relatively lower than conventional techniques. The tube voltages of 40 kV and 10 kV are used for heavy elements (heavier
than Ti) and light elements, respectively. The fundamental parameter method is adopted for calculation of elemental abundancesand gives us semiquantitative values. One big problem of this method is analyzable elements are limited; light elements (lighter
than Mg) cannot be detected with our instrument. In this presentation, we will report preliminary results of the precision and accuracy of measurement tested through geochemical standard (JB-3, JA-3, and JG-1a, supplied from geological survey of Japan).
We currently calibrated for 6 major elements (Si, Ti, Al, Fe, Mn, and Ca) and can analyze within the variation of <5 % (GSJ
values +/- 1 wt. %) in powder condition (soil cup with Mylar filter). Our purpose of this study is to expeditiously analyze thecomposition of a slab (or block) of the meteorites without any kind of sample preparation. We will continue to calibrate usingslabs of diverse rock types stored in the UMUT.
Keywords: meteorite, asteroid, bulk composition

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MTT40-03

Room:201A

Time:May 27 16:45-17:00

Microscopic model for nucleation pathways of polymorphic minerals from solutions
OKAMOTO, Atsushi1∗ ; KUWATANI, Tatsu1 ; OMORI, Toshiaki3 ; HUKUSHIMA, Koji2
1

Tohoku University, 2 University of Tokyo, 3 Kobe University

Rock-forming processes in the Earth (e.g., reaction, mass transport, deformation) are usually too slow for us, and thus it isdifficult to obtain the direct time-series data of the system. Therefore, it is important to develop the methodology how we extract
the information on dynamics of rock-formation from “frozen pictures” (textures). In this study, as an example, we focus on the
nucleation of metastable phases from solutions, because the formation of metastable minerals is essential on the progress of somerock-forming reactions (hydrothermal and metamorphic reactions), and often provides unique textures.
A phenomena, that a metastable mineral firstly crystallizes from liquid and translates into more stable phases, has been known
as the Ostwald rule, and such phenomena has been reported in crystallization of various materials, including proteins, clay minerals, iron oxides, carbonate (Pouget et al., 2009) and silica (Morse and Casey, 1988). Okamoto et al. (2010) found characteristic
textures of silica that cristobalite is formed as a cover of spherical amorphous silica particles, and that quartz is formed withina deposit of cristobalite. The phenomena following the Ostwald rule would result from competitive processes of bulk chemical
potential and interface energies for solid-solid and solid-liquid; however, the detailed dynamics is not clear.
Inspired by the occurrences of silica polymorphs, we present a microscopic model (two-dimensional Potts lattice gas model;c.f., Sanders, 2007) for understanding nucleation mechanism of polymorphic phases from solutions. We construct a system
which is composed of a solvent (s4) and three polymorphic solid phases (s1, s2, s3). The configuration energy is expressed as
combination of interaction term and bulk chemical potential. One of the most characteristic features of this model is that bothstate and position of the solid phases are updated by Metropolis dynamics. We evaluated the equilibrium conditions by exchange
Monte Carlo method (Hukushima and Nemot, 1996), as well as temporal evolution of the system. At temperature higher thancritical temperature (kbT/J = 1.1), nucleation of the solid phase does not occur. At lower temperature, a large nucleus of theleast stable phase is initially formed and then it translates into more stable phases following the Ostwald rule. The resulting
textures are similar to those observed in natural system (i.e. silica precipitates from aqueous solutions), indicating that our simplified model captures an essential process of the Ostwald rule. The free energy surface of the system, which has several local
minimums, changes depending on temperature and cluster size, which controls the nucleation pathways. In usual, the interfacial
energies among the minerals are much more difficult to be estimated than bulk chemical potential (i.e., solubility); therefore, thecharacteristic textures among the polymorphic minerals could be useful for evaluating the magnitudes of the interfacial energies
relative to the chemical potential values, by comparing the snapshots of the configuration in the microscopic model.
References
Hukushima, K., and Nemoto, K., 1996. J. Phys. Soc. Japan, 65, 1604-1608.
Morse J. W. and Casey W. H., 1988. Am. J. Sci. 288, 537-560.
Okamoto, A., Saishu, H., Hirano, N., and Tsuchiya, N., 2010. Geochimica et Cosmochimica Acta, 74, 3692?3706.
Pouget, E.M., Bomans, P.H.H., Goos, J.A.C.,et al., 2009, Science, 323, 1455-1458.
Sanders D. P., 2007. Phys Rev B, 75, 132101.

Keywords: rock texture, Ostwald step rule, nucleation, Monte Carlo Simulation, Potts model, interfacial energy

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MTT40-04

Room:201A

Time:May 27 17:00-17:15

Data-driven imaging of seismic wave field in the Tokyo metropolitan area based on lasso
MIZUSAKO, Sadanobu1 ; NAGAO, Hiromichi1∗ ; HIROSE, Kei2 ; KANO, Masayuki1 ; HORI, Muneo1 ;SAKAI, Shin’ichi1 ; NAKAGAWA, Shigeki1 ; HONDA, Ryou3 ; KIMURA, Hisanori4 ; HIRATA, Naoshi1
1Earthquake Research Institute, The University of Tokyo, 2 Graduate School of Engineering Science, Osaka University, 3 Hot
Springs Research Institute of Kanagawa Prefecture, 4 National Research Institute for Earth Science and Disaster Prevention
Rapid prediction of damage due to large earthquakes on constructions such as buildings and bridges through a numericalsimulation that computes seismic responses of all constructions provides important information for making a decision of priority
order relating to rescue and rehabilitation activities without waiting for on-site reports. Such a simulation requires ground motion
input to each construction, which usually distributes much denser than seismometers. An estimation of the ground motion should
rely on data-driven modeling from observational data because of insufficient information related to hypocenters or undergroundstructure models needed in a numerical simulation of seismic wave propagation.
We propose a new methodology based on lasso (least absolute shrinkage and selection operator) for the purpose of data-driven
imaging of seismic wave field in an urban area from seismograms obtained by a dense array. The target of this study is the Tokyo
metropolitan area, in which MeSO-net (Metropolitan Seismic Observation network) consisting of 296 accelerometers has been
established. We assume that a Taylor’s expansion model is capable of estimating the seismic wave field at an arbitrary point fromseismograms at nearby observatories. This model is reduced to a multivariate linear regression of which the matrix of predictors
is a set of products of positions of the observatories, the outcome matrix consists of the observational data, and the coefficientmatrix to be estimated consists of the partial derivative coefficients. The coefficient matrix is estimated by group lasso, which
minimizes an evaluation function consisting of a loss function given as the squared discrepancy between the observation data
and the regression model, and a regularization term based on the L2 norm for selection of grouped variables. The reason why we
implement group lasso rather than ordinary lasso is that it can avoid the dependency of subjective coordinate settings in time andspace.
We have applied the proposed method to synthetic seismograms obtained from an analytic solution of seismic wave fieldassuming that an earthquake of M7 class occurs in a horizontally-layered underground. The resulting image reproduced better
than those obtained by other methods such as the ordinary least square, ridge regression, and lasso. We have also applied thesemethods to the actual MeSO-net data when the 2011 Earthquake off the Pacific coast of Tohoku occurred, and confirmed thatgroup lasso reproduced the actual seismic wave field better than other methods.
Keywords: urban mega earthquake, MeSO-net, sparse modeling, lasso, imaging, regularization

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MTT40-05

Room:201A

Time:May 27 17:15-17:30

AIC model selection in microboudin palaeo-piezometer
MATUMURA, Taroujirou1∗ ; MASUDA, Toshiaki2
1

Graduate school of science and Technology, Shizuoka University, 2 Institute of geosciences, Shizuoka University

Microboudin structure is a deformation structure of rocks at microscopic scale. It is formed as the fracture of mineral grains
and their subsequent separation within the matrix minerals, which accompanies with infiltration of matrix minerals into the interboudin gaps by flowing. In particular case in which microboudin structure consists of columnar minerals such as tourmaline,
amphibole, and piemontite embedded within quartz or calcite matrix minerals, it can be utilized as a palaeo-piezometer if a
set of data (proportion of boudinaged columnar mineral grains with respect to the their aspect ratio) is supplied. Estimationof the magnitude of palaeo-stress in the rock is generally a difficult subject, although many geologists have been recognized
its importance. The microboudin palaeo-piezometer can estimate the magnitude of stress with increasing strain of rocks undermetamorphic conditions. However, flow of rocks is generally treated by the viscous model with a Newtonian material. In thispresentation, we measure the relative quality of both elastic and viscous models by using the Akaike Information Criterion (AIC)
for selecting model. The set of data for the palaeo-piezometer is given by measurements of total 6171 tourmaline grains within
9 quartoze metamorphic rocks, which are collected from the greenstone belt around a granite complex in East Pilbara, Western
Australia. It was clarified that AIC shows that the elastic model is preferable to the viscous one.
Keywords: Microboudin structure, palaeo-piezometer, AIC, Model selection

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MTT40-06

Room:201A

Time:May 27 17:30-17:45

Application of principal component analysis to seafloor basalt and its quantitative interpretation
UNO, Masaoki1∗ ; KUWATANI, Tatsu1 ; UEKI, Kenta2
1

Graduate School of Environmental Studies, Tohoku University, 2 Japan Agency for Marine-Earth Science and Technology, Department of Solid Earth Geochemistry
Bulk chemical compositional data of rocks consist of tens of elements, and analysis of high dimensional data is needed forinterpretation of such data sets. In the traditional studies, a certain pairs of elements were empirically chosen to represent specificprocesses such as degree of melting and effect of crystal differentiation. To elucidate hidden processes without using empiricalknowledge, principal component analysis (PCA) has been utilized for the interpretation of the compositional variations of sediments and igneous rocks (Kuwatani et al., 2014; Ueki, 2014). For example, application of PCA to compositions of arc basalt
has revealed that principal components differ among volcano, and distinguishes processes such as mixing and crystal differentiation (Ueki, 2014). To further develop the application of PCA to the interpretations of bulk rock compositions, a quantitativeevaluation of contribution rates and factor loadings are needed. In this study, to establish a quantitative interpretation of factor
loadings, bulk compositions of seafloor basalt are chosen for PCA, and the results were quantitatively compared with theoretical
fractionation processes.
Sample data sets were from seafloor basalt collected from Cocos plate by IODP expedition 334. The samples were collectedfrom the depth of 99-164 meter below seafloor (mbsf). As these samples were collected from narrow region, it is expected thatthe processes controlling the compositions of these basalt are relatively simple. Empirical factors such as Nb/Zr and Cr/Zr ratios
suggest that the compositional variations of the samples originate from different degree of melting and crystal differentiations(Uno et al., in prep.).
Principal component analysis was applied to the compositions of 43 basalt samples for 10 major elements (Si, Ti, Al, Fe, Mg,
Mn, Ca, Na, K, P), and 33 minor elements (Li, Sc, V, Cr, Co, Ni, Cu, Sr, Rb, Y, Zr, Nb, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb,
Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, Pb, Th, U).
The first three principal components account for 80% of the data variance: the contribution factor of PC1 is 52%. The factor
loading is high for Middle REE (MREE) and low for incompatible elements (i.e., elements that partition preferentially to silicate
melt compared to rock) such as Rb and Ba. The PC2 has contribution factor of 19%, and factor loadings are high for Ni, Co
and heavy REE (HREE), whereas those are low for incompatible elements such as Rb, Ba and Th. As the factor loadings ofPC2 change continuously from high values for compatible elements to low values for incompatible elements, the PC2 suggest
fractionation of melt. The PC3 contributes 8% of the data variance, and factor loadings are high for Cs, Li, U, and loss on ignition(i.e., bulk water content). As solubility for aqueous fluids are high for these elements, the PC3 suggests chemical alteration byaqueous fluids.
The depth profiles of PC1-3 are consistent with the empirical factor of Nb/Zr, Cr/Zr ratios and the amount of altered minerals,
respectively. These results suggest that the bulk compositions of seafloor basalt of the Cocos plate are controlled by crystal
differentiation, degree of melting and hydrothermal alteration.
For the quantitative interpretations of the PCA, the factor loadings of each PCA were compared with the various kinds ofpartition coefficients. For PC2, the patterns of factor loadings can be quantitatively explained by the partition coefficients ofbasaltic melt/peridotite. On the other hand, PC1 cannot be explained by simple melt/mineral partitioning, but can be explained
quantitatively by olivine/pyroxene partitioning. These quantitative relations between factor loadings and partition coefficientsshow the effectiveness of PCA for elucidating fractionation processes.
In this presentation, the cause of quantitative relation between the factor loadings and fractionation processes will be discussed.
Keywords: principal component analysis, seafloor basalt, elemental differentiation, Costa Rica

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MTT40-07

Room:201A

Time:May 28 09:00-09:15

Distribution mechanism of heavy metals revealed by correspondence analysis in the Natori River, Send
NAKAMURA, Kengo1∗ ; KUWATANI, Tatsu1 ; KAWABE, Yoshishige2 ; KOMAI, Takeshi1
1

Tohoku University Graduate School of Environmental Studies, 2 National Institute of Advanced Industrial Science and Technology
It is important to understand the distribution mechanism of heavy metal elements in environmental systems, because the toxicities of various metals and metalloids significantly affect health risks. The heavy metals concentrations are controlled by awide of variety environmental factors. This study aims to clarify main influence factors on the heavy metal distribution in thesediment, soil, river in the Natori River, Sendai City.
We firstly produced geochemical maps for heavy metal concentrations (As, Pb and Cr) of river sediment, neighboring soil
(bulk component, soluble component in 1N HCl and in pure water) and river water. The heavy metals concentrations in riverwater increase from upper stream to down stream, whereas heavy metal concentrations in river sediments and soil vary little
from upper stream to downstream. There are no anomalous distributions of heavy metals in the studied area, although manyanthropogenic materials are found in sediment, soil and river water.
The correspondence analysis was used to investigate relationships of heavy-metal concentrations between sediment, soil (bulkcomponent, soluble component in 1N HCl and in pure water) and river water. The results indicate that the heavy metals (As, Pb
and Cr) in sediment, soil and river water are dominantly controlled by natural sedimentary processes, such as denudation andsedimentation. The proposed method could be further applied for other pollutants in various environment systems.

Keywords: geochemical map, heavy metals, factor analysis, risk assessment

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MTT40-08

Room:201A

Time:May 28 09:15-09:30

Spatial modeling of metal contents in a kuroko-type deposit with application to estimatingore-solutions paths
UCHIKURA, Risa1 ; KUBO, Taiki1 ; LIU, Chunxue2 ; KASHIWAYA, Kouki1 ; KOIKE, Katsuaki1∗ ;YAMADA, Ryoichi3
1

Graduate School of Eng., Kyoto Univ., 2 School of Urban and Environment, Yunnan Univ. of Finance and Economics, 3 Graduate
School of Sci., Tohoku Univ.

Demand for metal resources has largely increased because of constructing sustainable society and innovative technologies.
This trend will continue in the future, which requires accurate characterization of ore grade in a metal deposit and deep understanding of ore generation mechanism for exploring new deposits. Based on that background, this study is aimed to (i) develop
a method for highly precise spatial modeling of metal contents in a metal deposit and (ii) clarify a physical law that formed
a deposit. Matsumine mine, the largest kuroko deposit in the Hokuroku district, Akita Pref., northern Japan, is selected as acase study site. Kuroko is a Japanese term that was used originally in the mining industry for massive, compact black-ore. It
mainly contains sphalerite, galena, and pyrite. Kuroko deposits are massive sulfide deposits associated with felsic to intermediate
submarine volcanic activity (e.g. Yamada and Yoshida, 2013).
Geological columns at 77 sites and the metal contents of Cu, Zn, and Pb (chief metals of kuroko) at 1457 measurement points
were used for the spatial analyses over a region of 500 m×1000 m in the horizontal direction and 300 m along the verticaldirection from 0 to -300 m a.s.l. 3D geological model was produced by classifying the columns into ten main rock types andcalculating their appearance probabilities at each grid point using 3D optimization principle method (Koike et al., 1998). Geostatistics, known as the best linear nonbiased estimator, was adopted for 3D modeling of metal contents. The result of variography
clarified that, common to the three metals, the spatial correlation structures of the metal contents was well approximated by thespherical model. Correlation length (range) along the horizontal direction is longer by a factor of 2 to 3 than that of the vertical direction, which implies the horizontal extents of ore solutions. Ordinary kriging (OK) was selected as a spatial modelingmethod, because its estimation accuracy was higher than a multivariate kriging.
Through an integration of 3D geological and metal-content models, high content zones were revealed to be overlapped withthe patchy kuroko zones and extend horizontally as connecting the zones. Secondary sedimentation of kuroko ores by smallscale volcanic activity and subsequent submarine landslide is one possible cause of this extent. Assuming that the transport ofore solutions and the deposition of metals are approximated by an advective-diffusion spread phenomenon, the advective velocities and the diffusion coefficients were calculated at each grid point by an combination of the metal content model and an
advection-diffusion equation. One noteworthy feature detected is that the advective velocities are mainly directed upward andthe grid points with this direction are continued in the distributions of silicious ore and rhyolite. This may imply the main pathsof ore solutions. The biased signs of vertical diffusion coefficients, 2 to 1 is considered to originate from the general trend of
metal contents, which is higher in the shallow parts than the deep parts. Our next step is to improve the metal content estimationby combining a physical law of the deposit formation, which may be expressed by the above advection-diffusion equation, andkriging.
Acknowledgments: The authors wish to express their gratitude to Dowa Metals & Mining Co., Ltd. and Hanaoka Eco-System
Co., Ltd. for providing the precious drilling investigation materials and cooperating to organize them.
References
Koike, K., Shiraishi, Y., Verdeja, E. and Fujimura, K (1998) Three-dimensional interpolation and lithofacies analysis of granular composition data for earthquake-engineering characterization of shallow soil, Mathematical Geology , v. 30, no. 6, p.
733-759.
Yamada, R. and Yoshida, T. (2013) Kuroko deposits and related back-arc volcanism in the Hokuroku district, Jour. Geol. Soc. Japan ,v. 119, Supplement, p. 168-179.
Keywords: Kuroko, Geostatistics, kriging, spatial modeling, advection-diffusion equation, Matsumine mine

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MTT40-09

Room:201A

Time:May 28 09:30-09:45

Bayesian analysis of nonlinear dynamics in heterogeneous reactions – toward understanding of rock-forming processes –OMORI, Toshiaki1∗ ; KUWATANI, Tatsu3 ; OKAMOTO, Atsushi3 ; HUKUSHIMA, Koji2
1

Kobe University, 2 The University of Tokyo, 3 Tohoku University

Heterogeneous reactions, which occur at interface between two phases, play important roles in rock-forming processes. In
heterogeneous reactions, dynamics are intrinsically nonlinear, because surface area governs actual reaction rates and changes
temporally. In general, even static surface area, not to mention the temporal change of surface area, is very difficult to be measured. Therefore, it has still been difficult to determine kinetic parameters of heterogeneous reactions even by well-designed
laboratory experiments, because we can only use nonlinear and incomplete data sets.
In this study, we develop novel methodologies which estimate kinetic parameters from nonlinear dynamics of heterogeneous
reactions using a Bayesian probabilistic approach. With an increasing demand of data-driven analysis, the Bayesian estimation
has been widely applied to various fields in the natural sciences including physics, medicine, brain science, and earth sciences(e.g. Watanabe et al., 2009; Naruse et al., 2009; Shouno and Okada, 2010; Omori et al., 2013; Kuwatani et al., 2014; Omori,2014). In this study, we first formulate probabilistic models of nonlinear dynamics of heterogeneous systems based on state
space model. Sequential Monte Carlo Method and EM algorithms are employed for the proposed state-space model in order
to simultaneously estimate time course of heterogeneous systems and kinetic parameters underlying nonlinear dynamics. The
proposed method provides a very suitable framework for inversion analysis of nonlinear dynamics from incomplete datasets.
In this study, we focus a simple heterogeneous reaction, in which the solid reactant changes to solid product via intermediate
product dissolved in fluid phase. It can be regarded as one of the most fundamental and substantial heterogeneous reactions forsolid-fluid interactions. Using our proposed method, the reaction rate constants of dissolution and precipitation as well as the
temporal changes of solid reactants and products were successfully estimated only by the observable temporal change of the dissolved intermediate product. The proposed method can be potentially applied to actual laboratory experiments of heterogeneous
kinetics in various fields of earth and planetary sciences.
Keywords: data analysis in geoscience, data-driven approach, Bayesian statistics, nonlinear dynamics, heterogeneous reaction,
rock-forming processes

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MTT40-10

Room:201A

Time:May 28 09:45-10:00

Deconvolution analysis of reflectance spectra of synthetic clinopyroxenes using the exchange Monte Carlo method
HONG, Peng1∗ ; MIYAMOTO, Hideaki1 ; NAGATA, Kenji2 ; SUGITA, Seiji3 ; NIIHARA, Takafumi1 ;JAMES, Dohm M.1 ; HENMI, Ryodo1 ; OKADA, Masato2
1

Univ. Museum, Univ. of Tokyo, 2 Complexity Sci. & Eng., Univ. of Tokyo, 3 Earth & Planetary Sci., Univ. of Tokyo

Deconvolution analysis of reflectance spectra has been a useful method to infer mineral composition and crystal structure.
Clinopyroxene (CPX) is one of the most important mineral groups due to both its rich abundance on solid bodies in the solar
system and distinguished absorption features. The band centers of visible to near-infrared (Vis/NIR) spectra of CPX are known
to vary due to total iron and calcium content. Klima et al. (2011) characterized the Vis/NIR spectra of synthetic CPX basedon a modified Gaussian Model (MGM). The numerical algorithm of the widely used MGM (Sunshine et al., 2011), however,utilizes the steepest descent method, which has a local minima problem. With bad initial parameters, the steepest descent method
converges into a local minimum, thus the analyzer needs to manually adjust initial parameters and calculate the model repeatedly
to obtain the desired solution. In order to avoid the local minimum problem, we analyzed Vis/NIR spectra of CPX using Bayesian
spectral deconvolution with the exchange Monte Carlo method (Nagata et al., 2012). This method is an improved algorithm of
the Markov chain Monte Carlo method, aimed to both avoid local minima traps and remove the arbitrariness originated frominitial parameters. We used the Vis/NIR spectra of CPX, measured by Klima et al. (2011) at 5 nm intervals over the wavelength
range of 0.3-2.6 µm. We chose only sieved powder samples whose grain sizes are smaller than 45 µm with individual grains
about 15-25 µm in size. We collected 31 CPX spectra with wide ranging Ca, Mg, Fe compositions (8-52%, 0-52% and 3-90%,
respectively). We found that: (1) 1 µm band shifts regularly to longer wavelengths with an increase of Ca content; (2) 1 µm
band shifts to shorter wavelengths with an increase of Fe content, although the variance is larger than that of orthopyroxene; (3)for Ca contents <30%, 2 µm band shifts to longer wavelength as a function of Ca, while for Ca contents >30%, the center of
2 µm band remains almost constant at ˜2.4 µm; and (4) the center of 2 µm band of augites (Ca <˜20%) does not depend on Fe
content significantly, while the center of 2 µm band of pigeonites (Ca >˜20%) shifts to longer wavelengths as a function of Fe
content. These results are consistent with Klima et al. (2011), suggesting that the exchange Monte Carlo method can yield thesame results obtained by conventional MGM analysis. The successful application of the exchange Monte Carlo method to wide
range of CPX would pave the way for further deconvolution analysis of reflectance spectra of mineral mixtures, such as olivine,orthopyroxene, and clinopyroxene.

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MTT40-11

Room:201A

Time:May 28 10:00-10:15

Study on direction finding method based on sparsity
OTA, Mamoru1∗ ; KASAHARA, Yoshiya1 ; GOTO, Yoshitaka1
1

Kanazawa University

Investigating characteristics of plasma waves observed by scientific satellites in the Earth’s magnetosphere is the effective key
to understand not only generation mechanisms of the waves but also a plasma environment which influences its generation andpropagation conditions. In particular, direction finding of the waves is important for understanding the propagation characteristics
of VLF waves. In order to find the directions, the wave distribution function (WDF) method was proposed. This method canestimate direction of arrival for multiple waves included in electromagnetic waves observed by the satellite, and the estimateddirection is represented as wave energy density distribution (WDF). For the estimation of WDFs, this method uses dispersion
relation for the plasma surrounding the satellite. However, this estimation is an ill-posed problem and cannot determine a uniquesolution. In order to obtain a unique solution, therefore, we need to give some prior information. In previous work, some models
were proposed as the prior information, and its performance was evaluated by using computer-generated data.
In the present study, we propose a new method using a sparsity assumption of the WDF. This assumption expresses that theeffective direction of arrival to explain the data is a smaller number, therefore, it can be expected that the reconstructed WDF
by the new method is more precise than conventional methods. In conventional evaluations, the spectral matrix which is used as
the input data of the estimation was assumed precisely calculable. However, in the case of the actual observation data, there is aproblem about how to calculate precise spectral matrix. We examined the problem that arises in the case that the WDF method
is applied for the actual observation data.
Keywords: Waves in plasma, Ill-posed problem, Wave distribution function, Sparsity

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MTT40-12

Room:201A

Time:May 28 10:15-10:30

Data-driven spatial modeling of frictional features at plate subduction zones
KANO, Masayuki1∗ ; SUZUKI, Akihiro2 ; NAGAO, Hiromichi1 ; KOMAKI, Fumiyasu2
1

Earthquake Research Institute, The University of Tokyo, 2 Graduate School of Information Science and Technology, The University of Tokyo
Frictional properties at a plate boundary are considered to control the time evolution of fault slips, so that clarification of their
spatial distribution is one of the major issues to predict the states in the Earth’s crust.
Recently, various aspects of the whole earthquake generation such as intervals of occurrence times, interseismic tectonic loading, afterslips, and episodic slow slips, were qualitatively reproduced, empirically giving the frictional parameters in the rateand state friction law [e.g., Kato and Yoshida (2011), Hori and Miyazaki (2011)]. For a more realistic simulation, the frictionalparameters should be quantitatively determined based on observational data and theoretical prior information. Data assimilation(DA) is a computational technique based on the Bayesian statistics to integrate numerical simulation models and observational
data [Higuchi et al. (2011)], which is widely used in geoscience including the solid earth science [e.g., Nagao et al. (2013)].
DA has also been applied to clarify the frictional features at plate boundaries, which are considered to control postseismic phenomena, estimating the frictional parameters in afterslip regions [e.g., Fukuda et al. (2009), Mitsui et al. (2010), Kano et al.
(2013), Kano (2014)]. These previous studies assumed that the frictional parameters were unrealistically uniform in the entire
fault region or subjectively divided the afterslip region into several areas in each of which the frictional feature is uniform inorder to avoid substantial computational cost due to too much high-resolution spatial grids never to be determined by the limited
observations on the Earth’s surface. Therefore, it is meaningful to develop a method to divide the region appropriately in an
automatic and objective way. We propose a data-driven procedure consistng of the k -means-based clustering method to obtaincandidate division patterns in the afterslip region and the Akaike’s Information Criterion to determine the optimum model among
the candidates. We have confirmed that the model obtained by an application to synthetic data is almost the true one. We willreport results when the proposed mothod is applied to the case of the afterslip region of the 2003 Tokachi-oki earthquake. Thismethod will help to extract the large-scale frictional features and make relevant simulations more effective, objective and realistic.

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MTT40-13

Room:201A

Time:May 28 10:30-10:45

Principal Component Analysis based determination of chemical differentiation processesof volcanic rocks
UEKI, Kenta1∗
1

Japan Agency for Marine-Earth Science and Technology

Bulk chemical compositions of igneous rocks represent sums of a series of chemical processes during generation and migration of magmas. Various processes from the mantle to the crust in various pressures, temperature and chemical composition
modify magma composition (e.g., Annen et al., 2006). Multivariable analysis can be used to investigate such reactions involving
multi-element and multi process.
Differentiation in terms of major element composition is controlled by non-linear thermodynamic relation (e.g., Ueki andIwamori, 2014). As such, major element composition can be a proxy for the pressure and temperature of the source regionof magma. However, major element composition is often overwritten by shallower processes because it exhibits a relatively
restricted degree of freedom in terms of composition. On the other hand, trace element shows a large degree of freedom. In addition, the concentration of a specific trace element can be a tracer of a reaction in which a specific phase is involved, because thepartition coefficient of a specific element in phases show wide range of variation. Moreover, partition of trace elements between
phases exhibits a weak non-ideality, and can be modeled with a simple equation. Consequently, trace element concentrations canbe used as a proxy of a specific phase and chemical mass reaction process during the formation of the rock (e.g., Depaolo, 1981;
Pearce et al., 2005).
In this study, principal component analysis is used to analyze compositional variations of volcanic rocks in Northeastern Japan
Arc. 14 trace elements of 262 samples including basalt to rhyolite, sampled from 17 different volcanoes in a volcanic cluster ofnortheastern Japan, called the Sengan region, are processed with principal component analysis.
The result of the principal component analysis shows that the only 3 processes are enough to cover the ∼90% of the geochemical variation of the magmas of the Sengan region. It is estimated that the three principal components represent magma mixing,
crystallization-fractionation of mafic minerals at deep crustal depth and crystallization-fractionation of plagioclase at shallower
crustal depth, respectively. This result shows that intermediate-felsic magmas (SiO2 >60 wt. %) can only be derived throughmagma mixing, not by crystal fractionation. No mantle signature is observed; indicating that differentiation processes in the arc
crust, are the primary controlling factor to derive compositional variation in terms of trace element. The first principal component (magma mixing) shows good correlations with petrological observation (core composition of plagioclase phenocryst), andgeophysical observations (distribution of seismic low velocity zone in the crust; Nakajima et al., 2001 and geothermal gradient;
Tamanyu, 1994), indicating consistent description between the trace element principal components, major element composition,and petrological information such as mineral composition can be derived from the analysis.
Keywords: volcanic rock, multivariable analysis, magma, arc, Northeastern Japan

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MTT40-14

Room:201A

Time:May 28 11:00-11:15

Bayesian inversion with sparsity constraint for spatial distribution of afterslip
NAKATA, Ryoko1∗ ; KUWATANI, Tatsu2 ; OKADA, Masato3 ; HORI, Takane1
1

JAMSTEC, 2 Tohoku University, 3 University of Tokyo

Heterogeneous distribution on the plate interface is considered to be the manifestation of heterogeneity in plate coupling, which
may slip as earthquake sources in the future. However, it seems to be difficult to resolve clearly such heterogeneous distribution
for M7 class earthquakes in offshore region because of stations only on land and narrow expected heterogeneous area.
We demonstrated the reproducibility of spatial distribution of afterslip following a M˜7 earthquake through numerical experiments, which estimate slip distribution on the plate interface from displacements observed on the free surface (Nakata et al.,2014). We calculated synthetic displacement data from the result of numerical simulation conducted for the afterslip followinga M 6.8 earthquake, for existing global navigation satellite system stations on land (GEONET) and planned ocean floor pressuregauge network stations (DONET). The spatial distribution of fault slip is estimated using a Kalman filter-based inversion. The
slip distribution estimated by using ocean floor stations demonstrated the heterogeneity of plate coupling within the coseismicarea of the M 6.8 earthquake with a radius of 10 km. The estimated slip amount in the coseismic area is nearly half of the peak
one around it, although no slip is the true answer. This discrepancy is caused by the smoothness constraint in the inversion.
To improve the reproducibility of the slip distribution, it is necessary to introduce different type of constraints. We have incorporated three constraints into the evaluation function as follows: First is continuous and smooth constraint in non-zero slip area.
Second is the sparsity constraint that the number of subfaults with non-zero afterslip is significantly smaller than that of residualarea. Third constraint is discontinuity between locked area (slip = 0) area and afterslip area.
By developing a method of Kuwatani et al. (2014), we proposed an evaluation function combined with Markov random field(e.g., Kindermann & Snell, 1980; Geman & Geman, 1984) model and sparse modeling (e.g., Tibshirani, 1996). Obtained afterslip distribution that minimizes the evaluation function could be resolved heterogeneity due to the M˜7 seismic source sharper
than that using previous methods.

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MTT40-15

Room:201A

Time:May 28 11:15-11:30

Cluster analyses on bulk elemental compositions of meteorites
MIYAMOTO, Hideaki1∗ ; NIIHARA, Takafumi1 ; KURITANI, Takeshi2 ; HONG, Peng1 ; SUGITA, Seiji1 ;JAMES, Dohm1
1

University of Tokyo, 2 Hokkaido University

Meteorites are now determined to be precious samples from extraterrestrial bodies and thus identifications of the corresponding
meteorite types of the targeted bodies of asteroid missions are among the major goals of asteroid missions. Besides such scientificimportance, rapid identification of the surface materials during the reconnaissance phase is also critically important even for
maneuvering a spacecraft. Modern spacecraft carry cameras/spectrometers in the visible to infrared wavelengths, which are
powerful tools in identifying surface materials. However, irradiation by cosmic and solar wind irons as well as bombardment byinterplanetary dust particles modify the surface of airless bodies through processes known as space weathering. Impact events
also mix mateirals at the surface of the body. These processes may flatten or change the absorption characteristics of reflectancespectra. In this sense, elemental compositions, which can be obtained by X and gamma-ray spectrometers, may be useful forthe above purpose. However, it has not been investigated extensively how well we can classify these planetary materials basedon elemental composition alone. In this study, we perform principal component and cluster analyses on 12 major and minor
elements of the bulk compositions of 500 meteorites reported in the NIPR database. Our unique approach, which includes
using hierarchical cluster analysis, indicates that meteorites can be classified into about 10 groups purely by their bulk elemental
compositions. We suggest that Si, Fe, Mg, Ca, and Na are the optimal set of elements, as this set has been used successfully toclassify meteorites of the NIPR database with more than 94% accuracy. Principal components analysis indicates that elemental
compositions of meteorites form 8 clusters in the 3 dimensional space of the components. The three major principal components(PC1, PC2, and PC3) are interpreted as degree of differentiations of the source body (i.e., primitive vs. differentiated), degree ofthermal effects, and degree of chemical fractionation, respectively. Though the exact ranges of elements of each cluster sufferfrom the systematic intra-laboratory error, realized through comparing our results with those of another elemental composition
database, our new method shows promise in the classification of the surface materials of a small body into a known group of
meteorites, having a significant bearing in future reconnaissance.
Keywords: meteorite, bulk composition, cluster anaysis, asteroid, XRF

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MTT40-16

Room:201A

Time:May 28 11:30-11:45

Application of advanced statistical analysis in geoscience and its evolution
KOMAI, Takeshi1∗ ; KUWATANI, Tatsu1
1

Tohoku University

An innovative methodology using sparse modelling as Bayes’ theorem for discrimination between tsunami deposits and marine
stratum is significantly important, because of its identification of sedimentation origin and evidences of past tsunami event
frequency. The authors started an interdisciplinary research area for innovative modelling in the field of geoscience. One of
the topics is the geo-statistical sparse modelling of tsunami deposits and soils using metal elements. Sparse modelling is basedon fundamental principle of sparseness; most important information is embedded in the low-dimensional subspace for highdimension data.
Keywords: geoscience, statistical analysis, sparse modeling

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