FRONTIER RESEARCH ON EARTH EVOLUTION, VOL. 2 Data and Sample Analysis Seiji Tsuboi In the researches of the Earth science, various kinds of techniques are used to study Earth’s evolution and its current dynamical structure. These techniques cover from seismological and geomagnetic approach to mineralogical and geochemical analysis. It happens frequently in the Earth science that newly developed technique and newly obtained data have broadened our understanding of the Earth’s image dramatically. In this regard, the development of new technique in observation and sample and data analysis is essential in the Earth science. The roles of this program are a development of a new technique for analysis and maintenance of observation network and database. This program consists of three groups, which are the Sample Analysis Group, Pacific Data Network Group, and Geophysical Data Processing Group. Since the provenance of this program was the Center for Data and Sample Analysis of IFREE, the activities of these groups are closely connected to each program of IFREE. The disciplines of each research groups are quite different in nature but the collaboration and communication among these groups are the essence of IFREE, which pursues multidisciplinary research. (b) In-situ Sr isotope measurements of mineral Most of the previous geochemical and isotopic studies on igneous rocks have been conducted on a “whole-rock” basis. Insitu geochemical and isotopic analyses of phenocryst are required to be developed to decode dynamic processes from magma generation to solidification such as magma mixing. Therefore, we have established the method for in-situ measurement of Sr isotopes in minerals (mainly plagioclase) through the micro-drill sampling followed by TIMS measurements. The method has been applied to in-situ analysis of Sr isotopes of plagioclase from the Zao Volcano, NE Japan. As a result, we found Sr isotopic compositions are variable among the rim and core of the mineral, ground mass and whole rock. This is the collaborative work with Institute for Geothermal Sciences, Kyoto University. Pacific Data Network Division Pacific Data Network Division has developed database system for geophysical data recorded through the operation of Pacific regions geophysical observation network. It also has developed a new technique for data analysis of both seismological and electromagnetic data. Sample Analysis Division One of the tasks of the Sample Analysis Division is to conduct comprehensive analyses on chemical compositions and physical properties of rock and fluid samples. For this purpose, the effective analytical techniques have been developed in the Division, and accurate and precise geochemical data have been produced, in order to decode the geochemical characteristics (major and trace elements, isotopic compositions, and radiometric dating) of solid samples, such as igneous rocks, sedimentary rocks, and fossils, and fluid samples, such as pore water. (a) Computation of theoretical seismogram Pacific data network division has been working for the development of a numerical technique to produce precise synthetic seismograms for realistic 3D Earth model. By using SpectralElement Method on the Earth Simulator, it has been shown that it becomes possible to calculate synthetic seismograms, which are accurate up to 3.5 sec and longer for realistic 3D Earth model. This technique has been applied to 2002 Denali fault earthquake in the United States. (a) Evolution of early continental crust Well-preserved oceanic sedimentary rocks in Archean greenstone belts give insights into the ancient oceanic environment and the evolution of continental crust, if it existed, in the early history of the Earth, as eroded continental crust would have contributed to the chemical composition of Archean seawater. We show Re and Os isotope analyses of Archean Marble Bar cherts from the Pilbara craton, NW Australia, that provide evidence for the existence of early Archean continental crust. Re-Os isotopic data of the Marble Bar cherts form an isochron with an age of 3.45 ± 0.88 Ga. The initial 187 Os/ 188 Os ratio is 0.932 ± 0.074, which is extremely high compared with that of 3.45 Ga chondritic mantle. Continental crust generally possesses high 187 Os/ 188 Os ratios and other geochemical reservoirs could not have easily obtained such high Os isotope ratios, especially by early Archean times. Therefore, the high Os isotope ratio implies that a significant amount of continental crust material contributed to the isotopic composition of the Marble Bar cherts, which leads us to conclude that evolved continental crust already existed as early as 3.45 Ga. (b) Electromagnetic data distribution system IFREE Center for Data/Sample Analyses, Pacific Data Network Division develops a new unified electromagnetic field (EM) data distributing system and its service opened last August (service URL: http://www.jamstec.go.jp/pacific21/index.html). By using this system, data users can get EM data of several independent data centers by one system in theory, which can reduce efforts of data users to access all the data centers and can increase the amount of the EM data usages. Multi data formats are supported to improve the usability of data by data users. In addition to a conventional OHP format, WDC 1-min, INTERMAGNET IMF V1.22, INTERMAGNET CD-ROM (supported by only simple search), IAGA2000, and IAGA2002 formats are supported, which are frequently used by the EM communities. When the data user requests to download data in one output format, a data server converts data in an original OHP data format into ones in a requested output format. Then requested data files are gzip-compressed and archived in a tar file. Finally a data user can download a tararchived data file via http port and can use it easily in a requested format. 1 FRONTIER RESEARCH ON EARTH EVOLUTION, VOL. 2 The main feature of this development is multi-thread processing of conversion of data formats, which can drastically reduce the real-time of the process of data archive creation. To examine the performance of our system, the real-times of the process of data archive creation of this system were compared with ones of an EM data distributing service by WDC Kyoto, which is frequently used for the EM data users (http://swdcwww.kugi.kyoto-u.ac.jp/index.html). As the result of the tests, this system is faster by 2 to 5 times than the system of WDC Kyoto and its performance is found to be effective one. Seismic Data Processing Division Seismic data processing division has been constructing a crustal structure database. It has developed a data-publication web site of the database in order to broadly disclose the data. The seismic data processing division has started to develop an integrated imaging method of MCS and wide-angle reflection data. (a) Construction of geophysical database To promote crustal studies at IFREE, the seismic data processing division has been constructing a crustal structure database. A major objective of the database is to create an integrated model that is composed by different physical properties of rocks: density, magnetic susceptibility, velocity, reflectivity, acoustic impedance, resistivity and so on. These physical properties can be derived by geophysical data that have been collected in structural studies using R/Vs Kairei and Kaiyo of JAMSTEC, as well as drillings by ODP and possibly IODP. Preparation for publication of the seismic reflection data has been completed and the all data from 1996 to 2002 can be seen on the web site. The seismic refraction data obtained by Ocean Bottom Seismometers are now in the progress of preparation. Concerning gravity and geomagnetic data, many data are collected along the survey lines of 2D seismic surveys and some are collected specially at the night-time survey. Therefore the data with the survey track and other inventory information is also scheduled to be disclosed. According to a user's needs, the obtained data, such as raw data and a correction coefficient value, is also due to be offered. Furthermore not only images but also field data are available through the web. (b) Seismic Data Analysis The Seismic Data Processing Division conducts data processing of multi-channel seismic (MCS) reflection data obtained by IFREE’s cruises and also develops new techniques that are efficiently used for sophisticated processing in the crustal studies. We started the development of an integrated imaging method of MCS and wide-angle reflection data in order to combine each advantage in the subsurface imaging and to figure out crustal structures more precisely. In general, the MCS data can clearly delineate structures < 10 km in depth but are not appropriate in imaging of those > 10 km. On the other hand, the wide-angle seismic reflection data obtained by OBS have the contrary characteristics in the structural imaging. Here we adopt the Kirchhoff integral method as the algorism of prestack depth migration for the integrated imaging. This method is often used in the migration processing of MCS data, however there are few application examples for that of wide-angle data. We have applied this technique to actual data and confirmed that the results are satisfactory. 2