Our Earth is finite, so is oil which supports present industrialized civilization. While most people are unwilling to accept “peak oil”, the global oil production is about to peak even before 2010, the gap increasing between the demand and supply. I discuss (1) importance and implication of Peak Oil, (2) essential vulnerability of industrialized agriculture also supported by oil, and (3) importance of EPR (Energy Profit Ratio) for energies. Now that our future survival in Japan-Island is at stake, our long accustomed “concept and civilization importing” from continental Europe and US is no longer viable. From [Muda] to [Mottainai] is vital for Japanese survival.

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Reprocessing of spent fuel is used to separate re-usable uranium and plutonium from the radioactive waste in Japan. The resulting liquid containing high-level radioactive waste (HLW) is vitrified in stainless steel containers. In accordance with the national program, vitrified HLW is completely isolated from the human environment in storage facilities for 30 to 50 years for cooling, and will be safely disposed underground deeper than 300m, based on the Specified Radioactive Waste Final Disposal Act (Final Disposal Act), promulgated in June 2000. Repository operation will be then started around 2033∼2038.
In October 2000, The Nuclear Waste Management Organization of Japan (NUMO) was established as an implementing organization of HLW disposal, based on the Final Disposal Act and started to solicit openly for volunteer municipalities for selection of Preliminary Investigation Areas in December 2002.
This paper describes Japanese HLW disposal program focusing on the current activities of NUMO. Furthermore the outline of the site investigation is shown, and the item which NUMO expects geophysical exploration technology is stated.

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There are many abandoned coal and lignite mines, underground shelters excavated during the Second World War, hastily filled underground rooms and pipes during the re-construction following the Second World War all over Japan. Due to degradation of these cavities, sinkholes or ground subsidence resulting in casualties and damages to residential areas properties have been increasing in recent years. In addition, torrential rains and/or earthquakes make necessary to investigate the instability of such abandoned underground cavities.
The behavior of rock mass between the ground surface and shallow underground openings is very complex and it is affected by the mechanical behavior (deformation, local failures, loosening), weathering, and deterioration, following the excavation, underground water seepage. In this article, the author describes damages caused by ground subsidence, sinkholes and their mechanism associated with environmental factors, the collapse risk of abandoned mines. Furthermore, the importance of the development of exploration and surveying techniques to detect the location and geometry of abandoned underground cavities is disccused.

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Slope failures and debris flows due to heavy rainfall are frequent in Japan, which have damaged many lives and properties. They have occurred in this country under geological conditions prone to slope unstability, and under meteorological conditions such as typhoon, frontal rain and snowfall.
In this paper we have reviewed the mechanism of slope failures due to heavy rainfall, and introduce the knowledge and the technology especially in geophysical investigation about where and when slope failures occur due to heavy rainfall.

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Earthquake off the coast of Sumatra Island occurred on December 26, 2004 and caused serious damages not only by the physical vibration but also by Tsunami induced by the earthquake. In such an event, it is requested to collect all the available information within minimal time frame. In this particular case, the observation by ASTER was programmed with the highest priority. As a result, ASTER data was acquired 12 times in a month over damaged areas. Within them, there were two good scenes over Bandah Aceh, Indonesia and they are compared with J-ERS1 and Landsat ETM+ data acquired before the Earthquake, and damaged areas were clearly identified. Synergism with other remote sensors such as IKONOS, Quick Bird, and, in near future, PALSAR data will strengthen the monitoring capability.

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本報告では, 周波数領域インヴァージョンと残差スペクトルによるサイト近傍効果推定スキームを組み合わせた減衰トモグラフィーのアプローチを紹介する。小規模データセットによるテストケーススタディとして, 減衰トモグラフィスキームを日本列島に適応し, 地下の3次元減衰構造を推定する。解析の結果, Qp^-1分布は日本列島直下において非常に空間変化 (2-3度の角距離程度) に富んでいる事が示された。このような地下構造の不均質は, 日本列島直下のテクトニクスと関連していると考えられる。

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Elastic coefficients in the Biot theory (Biot coefficients) for fluid-saturated porous media are expressed by conventional elastic coefficients and porosity. Practical applicability of this theory is established by it. Derivation of Biot coefficients is generally performed by the deformation analysis in which the total stress is resolved into two components: the effective stress and the fluid (hydrostatic) stress. Use of this pair of stress components has been developed as powerful tools in soil mechanics, where soils are assumed to be the granular media whose solid parts consist of grains with point-contact. It is a problem to be considered whether the same premise underlies the expressions of Biot coefficients or not. In this point of view, we discuss the concept of this pair of stress components, and we remark that it is used in two different aspects as follows: The first aspect is evaluation of the shear resistance resulting from solid friction. In this case the effective stress is regarded as the key factor controlling the solid friction. The second aspect is utility for the deformation analysis. By converting the total stress into the above pair of components we can evaluate dilatation of the solid material and the skeleton separately. The first aspect needs the premise of granular media, but the second aspect is free from such restriction. The utility in the second aspect is demonstrated by actual evaluation of Biot coefficients. In this evaluation, we particularly assume propagation of the longitudinal plane wave as the situation of stress field. This situation is directly connected to geophysical application. Expressions of Biot coefficients as the result agree with those derived by other authors based on the situation of hydrostatic compression.

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We propose a new analysis method of microtremor circular arrays for detecting phase velocities of Rayleigh waves in microtremors, aiming to conduct the microtremor array observations with fewer restriction of seismometer arrangement than the spatial autocorrelation (SPAC) method. The method is based on the complex coherence function (CCF) of the Rayleigh waves formulated by Shiraishi and Matsuoka (2005) to study the relationship between wave sources and observation points on an array. In this method, the values of the Bessel function J₀ (kr) (k: wave number, r: distance between observation points) that generate phase velocities are obtained as a solution of the simultaneous equations of CCFs, while they are calculated from the directional average of CCFs in the SPAC method. Therefore, our method allows observation points not equally spaced on the circumference.
From theoretical studies of this method for a circular array, it was found that seismometers on the circumference could be set at almost any place with the condition of symmetrical seismometer arrangement. Moreover, a field experiment have confirmed that the phase velocity obtained from the proposed method agreed with that of the SPAC method.

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The Linearized Inverse Scattering Analysis using Born approximation is applied to the Biot's Poroelastic model for the visualization of scatterers in porous media. Spatial and frequency distribution of the scattering amplitude is used for the shape reconstruction of a scatterer in which solid frame and/or pore fluid properties are different from surrounding media. The inversion method is based on the field integral expression of the scattered field, its linearization by Born approximation, and a direct inversion method by using the Inverse Fourier Transform. In this paper, theoretical background and numerical formulations of the method are described, and some examples of the reconstructed form of scatterers using simulated scattered field are shown. The examples show the applicability of the inversion method to the fluid filled porous material. The limited aperture problem is also discussed using the numerical results. It is shown that the reconstruction of scatterer geometry is still available with some degree of the lack of information.

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There are a number of aged railway tunnels constructed of block linings in Japan. Most materials of the block are the bricks. These tunnels have some problems in their structural integrity. An effective non-destructive test method for such problems is hence expected. We have developed a new system for tunnel concrete linings by which the thickness and whereabouts of cavities, etc. can be detected. We recently started a research to evaluate quantitatively the defects of tunnel brick linings, especially the joint loss, with this system. As the results, it was discovered that the defects of the lining could be evaluated with two numerical factors obtained from this system. One factor is maximum amplitude obtained from the wavelet transform of a sound wave of striking, and another one is a frequency where the maximum amplitude is shown. By evaluating with these factors, the structural integrity of brick linings can be immediately classified into three degradation stages.

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A template matching method for detection of isolated objects in GPR (Ground Penetrating Radar) images is proposed. Echoes from point-like or line-like targets such as cable ducts and utility pipes form characteristic patterns in images measured by GPR. Such characteristic patterns in the images are searched as candidates of the targets by using template matching. Then the candidate is tested whether it effectively reduce the norm of the image or not when the template is subtracted from its neighborhood. The template is prepared based on a model of the targets and response of the GPR. The template matching enables identification of the target position and elimination of transient response of GPR at the same time. Effects of errors in models on identification of the targets are evaluated by numerical simulations to show the method can identify the targets even when small errors exist in the model. Also, it is successfully tested by using field data to obtain a 3D image of a flexible duct. The method takes time comparable to diffraction stack migration to process images and produces images easier to understand than the diffraction stack migration.

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