Laser probe 40Ar/39Ar age dating can be applied in two ways. One is in situ spot age dating of a thin section using a pulsed laser, and the other is stepwise heating of a single mineral using a continuous laser. In the last 10 years, advances in technology have allowed us to apply the laser probes in various ways in Earth and planetary sciences. Stepwise data provide diffusion characteristics in each single mineral. The spatial resolution of laser pits can be as small as 5 microns, which is comparable to the figure for electron probe microanalysis. Utilizing this high resolution, 40Ar/39Ar applications combined with petrology are expected to contribute to a new understanding of argon diffusion and the Earth's history.
Petrography or observation of petrographic texture is one of the most basic techniques for microanalysis of natural samples. Secondary ion mass spectrometry (SIMS) has been applied to isotope and trace element analyses in micron-size minerals in various natural samples evaluated by conventional petrography, e.g., search for the oldest rock, mineral and life, and for presolar grains. However, elemental texture and isotopic texture often indicate a different evidence of origin and evolution of the sample. In this paper, we reviewed SIMS history in cosmo-and geo-chemistry from a viewpoint from point-analysis to area-analysis. Here we propose that promotion of isotopic texture research, isotopography, is an important future trend of cosmo-and geo-chemistry. We also propose that further diffusion study in minerals under various Pressure-Temperature conditions is necessary. The analysis of isotopography by diffusion gives a quantitative scale of geospeedmetry of natural samples.
X-ray computerized tomography (CT) is a non-destructive method by which crosssectional images of rocks and minerals are obtained using X-ray attenuation. Threedimensional structures of samples can also be obtained by constructing a number of successive images. This review discusses high-resolution X-ray CT machines including an industrial machine in commercial use and that developed by our group at SPring-8, which is the largest synchrotron radiation facility in Japan. Spatial resolution of CT images, which is determined by X-ray detectors and X-ray beam size, is practically limited by sample size due to the limited numbers of X-ray detectors. A resolution of about 1 μm was realized at SPring-8. This resolution is the lower limit for imaging with simple optics. The contrast of an X-ray CT image is expressed as a two-dimensional distribution of CT values, which related to the X-ray linear attenuation coefficient (LAC), , μ. CT values of standard minerals were measured to compare with their values of μ. As μ is a function of X-ray photon energies, beamhardening occurs when we use polychromatic beams. Thus, we cannot compare CT and μ values directly with the industrial scanner, which aplies a polychromatic X-ray beam. If the CT and μ values are normalized by a standard mineral having similar size as samples for the photon energy or the accelerating voltage of an X-ray tube, both values agree well as long asμis less than about 2.5 × μ of Fo92 olivine. We can compare CT and μ values directly in the SPring-8 machine, where monochromatic X-ray beams are available. In this case, normalized CT and μ values agree well in various materials havinga large μ at least including metallic iron. However, absolute CT values are slightly smaller than μ by about 10%, which is probably due to scattered X-ray beams, although the exact reason is not known at present. The high-resolution X-ray method was applied to three-dimensional structures of chondrules, which are characteristic constituents of primitive meteorites, named chondrites. It is known from external shapes and internal textures, which are related to distributions of voids and platy olivine crystals, that chondrules spin at high revolutions of about 50-500 rps during their formation in the primordial solar nebula. This greatly constrains the formation mechanism of chondrules.
The maximum attainable pressure in a multi-anvil type of high-pressure apparatus (MAA) is limited to about 27 GPa when using tungsten carbide (WC) as anvil material. Recently a remarkable innovation has been made for the MAA by adopting sintered diamond (SD) as anvil material. So far pressures up to 49 GPa has been confirmed in SD anvil assembly without any reduction of the specimen volume. Therefore, phase equilibrium and melting experiments of Earth materials have been extended to conditions deep into the lower mantle. The results will substantially advance our understanding of the structure of the lower mantle and the state of Earth early in its history.
Understanding the evolutionary history of the Earth requires studies on the transport properties of constituent materials at high pressures and high temperatures prevailing deep in the Earth's interior. Utilization of intense synchrotron radiation X-rays combined with large-volumes high-pressure apparatus started in the mid 1980's and has brought about new insights on the science of the Earth's interior. Falling sphere viscometry using X-ray radiography enabled us to determine the pressure and temperature dependence of the viscosity of the Fe-FeS melt, which is a candidate for the outer core of the Earth. Studies on phase transition kinetics using in-situ X-ray diffraction revealed the important role of metastable assemblages in the subduction of slabs and consequent material exchanges between upper and lower mantles. Further development of the experimental and analytical technique is expected in the research fields of deformation mechanics and element diffusion for Earth's materials.
Precise seafloor bathymetric surveys began with the appearance of the multi-beam echo sounder. It was able to observe the seafloor topography in detail using multi-beam sounding technology. To this day, the multi-beam sounding technology is revealing many significant seafloor features. In recent years, multi-beam technology for shallow and deep waters has significantly advanced. Also, the processing and application technology for multi-beam bathymetric data has significantly advanced, corresponding to the progress of peripheral technologies, such as dynamic motion sensors and GPS. The synthetic aperture technique has been successfully applied to the multi-beam echo sounder, SeaBeam 2000, and has shown features of the seafloor in considerable detail. Furthermore, the three-dimensional acoustic-image animation technique has been developed using SeaBeam 2000 swath bathymetry and IZANAGI side-scanning sonar data. The animation around the earthquake focus sea area provides us with a lot of seafloor topographical information efficiently and accurately.
The development of deep sea research systems-manned and unmanned submersibles-made it possible to carry out visual surveys of the deep seafloor at any depth on the earth. These surveys have revealed a great number of phenomena that occur on the seafloor, such as hydrothermal vents and chemosynthetic biological communities at mid-oceanic ridges. Unmanned submersibles include ROV (Remotely Operated Vehicle), UROV (Untethered Remotely Operated Vehicle), which have thrusters and are operated by mother ship through a tether cable or a thin optical fiber respectively, AUV (Autonomous Underwater Vehicle) which moves under pre-programmed commands and does not have a cable, and deep-tow system which is also operated by mother ship through. a cable but does not have a thruster. In order to see objects under very low illumination in deep seas, a Super-HARP (High-gain Avalanche Rushing Amorphous Photoconductor) video camera which is far more sensitive than CCD cameras, was developed. Recently, the Super HARP Hi-vision video camera, which provides high-resolution video images, has been developed. The location of the submersible in water is obtained by three acoustic positioning systems. These are called LBL (Long Base Line), SBL (Short Base Line), and SSBL (Super Short Base Line) positioning systems. In order to achieve effective dive surveys by manned submersibles or ROVs, it is necessary to select dive points by considering the results of pre-surveys carried out over a wide area, including bathymetric mapping using multi-narrow beam echo sounder, side-scan sonar survey, and deep-towed camera surveys. Submersibles enable not only visual observation, but also sampling and geophysical measurement at aimed points on the deep seafloor. In order to construct multi-disciplinary real-time and long-term deep seafloor observatories, such as off Hatsushima Island Observatory and VENUS off Okinawa Island Observatory, or to carry out borehole measurements, submersibles have been playing important roles in installing instruments, extending cables, and connecting connectors of instruments to underwater telemetry systems, or in recovering data. Submersibles are also necessary when searching for the causes of events observed by the observatory. The ROV and the Super HARP Hi-vision video camera made it possible for many scientists on board to see high-resolution video images of the seafloor simultaneously as if they were viewing it with the unaided eye. The AUV will enable surveys over wide areas in the near future. However, observations by submersibles are limited by survey time. On the other hand, long-term observatories enable observations only at fixed points. Complimentary observations using both long-term observatories and submersibles are expected in order to extend survey area in terms of both temporality and spatiality to provide an understanding of phenomena that occur on the seafloor.
The autonomous underwater vehicle (AUV) has been recognized as a new platform for observing the underwater world. It can dive freely around the target of the mission prescribed in its computer prior to launching. Throughout a dive, it does not require the operator and the support vessel to help it to execute its mission. It has no umbilical cable, which is fitted to remotely operated vehicles currently used for underwater operations and observations and usually causes problems for the operator. This paper presents the state of the art of the AUV and how it can be used in underwater science.
To better understand the dynamics of the Earth's interior, we need more observational data from the planet's oceans. In particular, we lack time series data, which require long-term observations. It is essential to probe the Earth not only from the seafloor but also from sub-seafloor boreholes. The reasons are twofold. First, there are geodetic and seismic measurements that should be made in a low-noise environment, preferably within competent rocks. Second, there are many critical measurements that can be made in situ or close to where active bio-geological processes occur. In this regard, we are at a stage where we may make substantial progress. In recent years, a number of successful emplacements of borehole observatories have been made. In 2006, a new type of scientific drilling vessel equipped with a riser capability and blowout prevention to allow deeper drilling than available at present will become part of a major international drilling program. Borehole observatory constructions will be accelerated to complete a truly global seismic network for obtaining clearer tomographic images, to establish regional geodetic networks to monitor strain buildup at plate boundaries, or to set up local multiple-component observatories to understand active processes at hydrothermal vents, fluid flow pathways, or seismogenic zones.
To understand the Earth's geophysical phenomena, it is important to obtain multicomponent, continuous, long-range, and real-time marine data in global scale. To carry out observations in the sea, the most reasonable way at present is to use submarine cables for communication and power supply. There are cable projects using decommissioned submarine cables in Japan. GeO-TOC and VENUS projects. The H2O project is a US version of the VENUS project. Outlines of the two systems are presented with some new results. Some other projects using new fiber optic cables have been continued in Japan, but most of these projects are oriented toward seismic observations. The NEPTUNE and J-NEPTUNE projects are the most attractive projects in the near future to build multi-disciplinary observatories as Internet networks in the sea.
This paper briefly summarizes the current status of the development and the distribution of digital geographic information in Japan and new emerging technologies associated with geographic information. Rapid improvements to computer hardware and software, together with the dissemination of computer networks, especially the Internet, have had enormous impact on the development and use of geographic information. Paper maps, which used to be the most commonly used media for communicating geographic information, have been digitized and used with a geographic information system (GIS) for many different applications. Although the digital geographic information thus acquired still has some characteristics inherited from paper maps, new technologies including Web GIS, GPS, and 3D GIS are considered to further expand the domain and enhance the potential of geographic information. Digital geographic information has been standardized by ISO, which will also streamline data exchanges between different GISs and hence reduce the cost of GIS development. Despite these new developments related to GIS, actual implementation of GIS in government offices has not been accelerated due to organizational problems associated with conventional business customs and lack of employees' knowledge and experience of IT. Although it may take some time to overcome these problems, the author sees a further expansion of the use of geographic information as Japan and its people accept new concepts and lifestyles introduced by IT.
The power of interferometric Synthetic Aperture Radar (SAR) when applied to studies of crustal deformation has been fully demonstrated by Massonnet et al. (1993, 1994) and Zebker et al. (1994) for the Landers, California earthquake of June 28, 1992. This method is unique in its capability of providing a two-dimensional representation of a deformation with a dense spatial coverage over most of the globe. Since 1994, the Geographical Survey Institute (GSI) has been conducting a study on applications of differential InSAR (Interferometric SAR) for the detection of crustal deformations associated with earthquakes and volcanic activities. Crustal deformations of many episodes were mapped by InSAR, such as those due to the 1994 Northridge earthquake, the 1995 Hyogo-ken Nanbu earthquake, the 1995 Neftegorsk earthquake, and volcanic deformations of Mt. Iwate and Mt. Usu. These interferograms played an important role in constructing geophysical models.
GIS (Geographic Information System) has been widely applied in many scientific domains. However, to keep the database “current” is still a “bottle-neck” which is an obstacle to the application and the promotion of GIS techniques and products. In this paper, we start with an analysis of why the updating of database is difficult and what problems exist in GIS database updating. The problems are analyzed from following three of viewpoints : 1) data sources; 2) automatic object extraction; 3) change detection. The possibility of using high-resolution satellite imagery for GIS database updating is examined with several samples.
Some results of application studies of GPS retrieved tropospheric delays on weather prediction (GPS Meteorology) conducted in Japan are outlined. It is suggested that the nationwide GPS array in Japan (GEONET) of Geographical Survey Institute (GSI) is an excellent all-weather water vapor sensor applicable to regional weather predictions by Japan Meteorological Agency (JMA). It is also found that a sophisticated analytical model developed for GPS meteorology can remove drifts due to water vapor delay appearing in the horizontal solution of GPS positioning in summer.
Continuous measurement using dense permanent GPS array plays an important role in monitoring crustal deformations to understand tectonics of the region and mechanisms of earthquakes and volcanic eruptions. Since 1994, a nationwide GPS array of the Geographical Survey Institute detected a variety of crustal deformations caused by the plate motion, earthquakes and volcanic eruptions. In addition, interesting transient phenomena have been observed by continuous GPS. In this paper we discuss impacts of continuous GPS measurement on seismological and volcanological studies.
This paper reviews the evolution and advancement of satellite remote sensing. The history of satellite remote sensing began with the Television and Infrared Observation Satellite launched by the U.S.A in 1960s and was followed by many Earth observation satellites. We present the physical principle of observation from space as well as recent Earth observing data. We discuss the characteristics and tendencies of rapid advances in satellite remote sensing. In the near future extensive Earth observation data will be available to the Earth's scientific community. We emphasize that scientists should retrieve crucial information on global change from advanced Earth observation data.
The comprehensive Earth science database, GeoRef, is introduced in this paper. GeoRef is one of the Earth science databases with the largest number of references (about 2.2 million), and is managed by American Geological Institute (AGI). GeoRef provides not only an environment for searching references, but also for delivering the necessary references and for making written reference lists. To verify the usefulness of GeoRef, we compared several cases of searches using GeoRef, Web of Science and Swet Scan. Although GeoRef was not able to pick up more references than Web of Science, GeoRef generally collected suitable references and showed its usefulness of searching particularly in the geological category. However, it was revealed that GeoRef was relatively slow to incorporate the latest information.