We propose a new technique for a joint inversion of apparent resistivity data from a vertical electrical sounding and peak-period of spectral ratio of horizontal microtremors to vertical one in order to infer resistivity and S-wave profiles simultaneously. Least-squares errors between the observed apparent resistivity and theoretical ones are minimized together with errors between the peak-periods of the horizontal-to-vertical spectrum of microtremors and theoretical ellipticity for fundamental-mode Rayleigh wave. We use a Simulated Annealing to minimize the misfit function defined by the summation of the two least-squared errors. First, we confirmed the performance of the method using synthetic data for a shallow soil model. The method reconstructs well the soil model, even though synthetic observed apparent resistivity data are incomplete. We, then, apply the method to actual observed data at a site in reclaimed area in Yokohama, Japan. The obtained profiles are in good agreements with results of geological and PS loggings. It is concluded that the proposed technique can be addressed as one of the easiest methods to infer shallow S-wave and resistivity profiles simultaneously.

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We can find many polygonal gravity anomalies in the gravity map series (1 : 200,000) published by Geological Survey of Japan, AIST. To analyze these gravity anomalies, the authors reviewed the computing equations based on the model bodies (vertical solid polygonal cylinder, polygonal cone, polygonal parabola, ellipsoid and error function shaped bodies). Some characteristics are described in the maps drawn by these computing equations.

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A helicopter-borne magnetic survey system was developed in use of a nose boom magnetic sensor, which enables safe and practical operation of low-altitude high-resolution survey even in mountainous regions of very steep topography and high elevation. The system consists mainly of airborne Cesium magnetometer, 3-axis fluxgate magnetometer, GPS receiver, navigation unit, data-acquisition PC, etc., incorporating with other equipment on the ground including base station magnetometer and reference station GPS receiver.
The nose boom magnetic sensor is situated rather near the helicopter body and cannot be free from its magnetic noise, though the boom itself is made non-magnetic. The 3-axis fluxgate magnetometer is the equipment to compensate aircraft's magnetic noise field. Theoretical consideration for passive magnetic compensation and the method of actual data processing for it are discussed. Then the software for magnetic compensation was developed and applied to the data of actual verification survey, and the procedure was proven to accomplish post-flight magnetic compensation properly.

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A way to apply the shortest path ray tracing (SPR) method to irregularly tetrahedralized velocity structure and its efficiency are described. SPR is the ray tracing method utilizing Dijkstra's shortest path algorithm in network graph theory. The tetrahedralization by Delaunay tessellation is one of the irregular parameterization of 3D velocity structure in travel time tomography. The irregular parameterization has great advantage of flexible expression of velocity structure though the computational costs in ray-tracing are relatively high. The hybrid ray tracing between SPR (for initialization) and pseudo-bending (for optimization) might be more economic. It has been known as the well proven scheme in the sense of the simplicity and robustness. Though SPR was originally developed under regular parameterization, it can easily be expanded to irregular parameterized structure without any theoretical modification. We propose a simple design of network for SPR that conforms the shape of tetrahedron. Generally, the cost and accuracy of SPR depends on the network design. In this paper, we have carried out a synthetic examination with a complex velocity model to assess the cost and accuracy of SPR with irregular network. Result reveals that the proposed ray tracing method is practically economic and accurate (almost the same accuracy as SPR under the regular cubic cell model). Further, it has potential to obtain more accuracy by lower costs due to the economical network integrated with flexible element size.

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In order to identify the underground objects, we often use a Ground Penetrating Radar (GPR) from the point of reducing cost and time. But it is not a few cases that the pavement situation prevents from underground prospecting.
From such background, we produced the prototype of the small GPR system to set into the drill head of the horizontal boring machine. And we are sure that it is highly possible to realize improving the limitation of exploration distance and resolution.
In this report, we described the goal specification required to such a small GPR, basic design of system and its performance. And we introduce the technical details concerned to the real time image processing algorithm for radar system which is mounted in the jacking drill head of a horizontal boring system.
The main functions of the image processing to use for a horizontal boring system are the followings.
1) Distance presumption : Presumes the distance between a drill head and pipe.
2) The piping direction distinction : Distinguishes the constructed direction of crossing pipe or parallel one.
3) Azimuth presumption : Presumes the azimuth of pipe against the moving axis.
As a result of experiments, it turned out that this algorithm was effective for the radar system of horizontal boring machine.

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沖縄県の遺跡調査は考古学分野で非常に注目されており, 20世紀末から盛んに実施されている。本論文では, 普天間基地のように広範囲の遺跡調査を実施する場合に有効な物理探査の方法を確立する目的で, 電気探査法, 表面波探査法および浅層反射法などの物理探査を実施して, 探査データを総合的に解釈した。
電気探査の結果, 本地域の地下は, 低比抵抗の島尻マージ, 高比抵抗の琉球石灰岩および低比抵抗の島尻泥岩の3層構造から成ることが明らかになった。また, 表面波探査法および浅層反射法による弾性波探査の結果, 本地域は高速度の琉球石灰岩を低速度の島尻マージが覆う2層構造から成ることが分かった。
浅層反射法からは琉球石灰岩の上面分布を反映する鮮明な連続する反射面が検出された。表面波探査法からは, 表層は0.3km/sの低速度の島尻マージ層で, その下位の琉球石灰岩層は0.5km/s以上の高速度を示すことが明らかになった。これらの物理探査の結果および既存の掘削資料などから総合的に解釈すれば, 本地域における埋蔵文化財の分布は, 比較的地下深部の高比抵抗かつ高速度の琉球石灰岩層の分布形状と一致することを確かめた。すなわち, 琉球石灰岩層の3次元分布は, 普天間地域の古地形を表すことが明らかになった。さらに, 本地域では琉球石灰岩層は, その風化の程度により新鮮な地層とドリーネなど地下水が流動している風化層とに区分されることが解明された。本研究の結果, 本地域の遺跡調査には電気探査が最も有効な物理探査の方法であることを確かめた。

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Modern technology of prestack depth migration brings directly depth section from seismic data acquired in the time domain. However, practical methods of time to depth conversion from time structure interpretation survive because of its flexibility in handling velocity and cost performance.
One of the frequent problems in time-depth conversion is depth mistie at well markers. The more the well, the more complicated technique needs to be considered to solve the entire mistie. We introduce to solve the mistie issue in depth conversion by use of Geostatistics on to well check shot data, which guarantees to maintain the input data unchanged after spetial estimation.
In addition to utilization of Geostatistics for conversion velocity estimation, we introduce error estimation criterion to evaluate the estimated velocity for the conversion. This criterion is evaluated comparing velocity variation at well markers. After the estimation of 3D velocity from available check shot data using Kriging approach, we evaluate velocity error distributions by means of sequential Gaussian simulation methods and extract the reliable part of velocity from the criterion. This extracted velocity data and well velocity data are integrated for final depth conversion.
We estimate three realizations of velocity error distributions, which give us 3 realizations of final velocity models. The results of depth conversion by those 3 velocity models vary the depth structure within 170 meters or 7% variation at average depth of 3000 meters structure. This 7% variation can be considered as the structural uncertainty after depth conversion except for the well locations in this sturdy.

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Detection and evaluation of contaminated soil and ground water by GPR method was discussed. The electric properties of soil and contaminant and their mixed material are significant for GPR. Some models for mixed material including CRIM model were discussed. As an example, CRIM model was compared with the measured parameters using sampled core, and showed good agreement under low water content condition. Generally, if soil is contaminated by hydrocarbon contaminant such as DNAPL and LNAPL, the contaminant will replace the water in soil. Consequently, the conductivity of the soil will decrease, and the dielectric constant of the soil will also decrease. We think GPR detect the change of the dielectric constant of the soil and can detect the anomaly caused by the contamination. However, we should note that if there is chemical or bio-chemical reaction related to the contamination, the phenomena will be much more complex. Then we showed some examples of GPR profiles, which were applied to soil contamination and ground water problems. We showed that the change of ground water table by 5cm can be detected by GPR, which means GPR has a good possibility for detecting small anomaly due to contamination, if the phenomena happen in a short period, or if we can measure the time-lapse data. When the contamination is steady state, we can use the combination of profile and CMP measurements by GPR. CMP measurement will provide good information about the material that causes reflection in profile GPR measurement.

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Disposed materials and their buried conditions vary considerably in some landfills. Geophysical prospecting methods can be used to investigate the internal conditions of such landfills without excavating. Rainwater permeates through landfills and various components dissolve as ions in pore water from fills. Resistivity of landfill relates so closely to the electrochemical properties of fills and their pore water that the electrical resistivity prospecting is supposed one of the most effective methods for the landfill investigations.
In order to examine the above effectiveness, five landfill sites were selected on basis of the reclamation area and the classification of waste. Resistivity measurements were carried out there. The concrete subjects are; (1) Effects on disposed material and leachate to resistivity profiles; (2) Use of resistivity tomography for obtaining more precise profiles; (3) Use of resistivity monitoring for interpreting the properties of the landfill.
Resistivity profiles are related closely to conditions of fills. In addition, the profiles of resistivity tomography are better than those of another resistivity methods in the respects of their resolution and temporal stability. Resistivity monitoring is extremely useful for interpreting temporal changes in landfill properties.
The next targets are to study the possibilities of the resistivity measurements for a quantitative analysis of landfill stability and the identification of buried waste materials.

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We report the results from three geo-electrical surveys carried out in a hydrocarbon-contaminated site, a volatile organic compound-contaminated site and a waste disposal site, respectively. In these cases, polluted soil and waste deposits show the electrical properties unlike those estimated from the original source. We try to explain these phenomena from the geo-electrochemical change caused by geochemical and biochemical decomposition. We conclude that induced polarization (IP) method from which many geo-electrical information (resistivity and some IP parameters) is obtained is effective in the investigation of contaminated soil and wastes. Moreover, the time-differential tomography which observes a temporal change of geo-electrical properties is also useful in above investigations. We expect that these geo-electrical information will be applied to the wide field including not only detection of the contaminated soil, but also monitoring of pollutants in ground and evaluation of hydraulic parameters for behaviour prediction and repair design of pollutant in soil.

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地下浅層に油系土壌汚染が存在する工場跡地において, 物理探査技術の有効性を検証するために実験を行った。実験結果により, 地中レーダ (GPR) および電磁気探査の組み合わせは汚染問題の検証について有効な手段である事を示した。
電気探査及び電磁探査による比抵抗構造は大局的に一致している。比抵抗が高くレーダ信号が弱い領域はLNAPLによる汚染区域と考えられる。また, 土壌サンプルにより, CRIMモデルを用いて誘電率, 土壌油分含有量との関係性を調べた。このように, 汚染物質の物理性質を把握することにより, 物理探査技術を用いて土壌汚染構造の検証が可能であると考えられる。

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