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海底下浅部の地質構造を明らかにすることは, 伏在断層の抽出, 水質の空間分布の解釈, 地下水の湧出経路の特定において重要である. 海底下の活断層の位置や分布は音波探査により調査されている. しかし, 音波探査では地下水についての情報は得られない. そこで, 地下水を含む海底下約50 mの範囲の地質構造をイメージングするために, 九州中部の有明・八代海を対象として, 曳航型海底電気探査を適用した. 両海は日本を代表する閉鎖性海域であり, 地下水資源が豊富な熊本・八代平野に面している. 測定に使用したケーブルの長さは250 mで, これに20本の電極を設置した. 有明・八代海にそれぞれ4本, 8本の計26 kmの測線を設定し, 信頼性の高い比抵抗データを得るために3極法を採用した. 海水の厚さを考慮した電位補正法と1次元インバージョン解析によって, 宇土半島周辺で正断層を示唆する特徴, および地下水湧出経路と考えられる幅200 mの高比抵抗帯の存在が明らかになった. 白川・緑川の河口では, 後氷期の厚い海成粘土層( 有明粘土層)の中に周囲に比べて高い比抵抗帯が現れた. これは海底地下水が陸源性野の淡水に起因し, この大規模な分布が高比抵抗帯に関連すると解釈した. 八代海測線のインバージョン解析結果からは, 日奈久断層の延長線上で比抵抗が大きく変化することがわかった. これは日奈久断層の繰り返し, かつ新しい動きによって, 地下水湧出経路が形成されているためと考えられる., Clarifying geological structure in shallow depth under the seam bottom is important to detect latent fault, interpret spatial distribution of water quality, and identify paths of groundwater discharge at the sea bottom. Although sonic prospecting has been used widely for investigating the position and distribution of submarine active faults, it cannot detect the features related to groundwater. The Ariake and Yatsushiro Seas in central Kyushu, southwest Japan are representative closed seas in Japan, facing the Kumamoto and Yatsushiro Plains being rich in groundwater resources. For imaging the geological structure containing groundwater down to 50 m depth, a towing electric sounding method was applied to these seas with a cable of 250 m length and 20 electrodes made in the cable. Four and eight measuring lines in total 26 km length were set in the Ariake and Yatsushiro areas, respectively, and a three electrode method was used to obtain accurate data. By a potential correction that considers the thickness of sea water and a 1D inversion analysis of the corrected data, a weak feature of a normal fault and a clear high resistivity zone with 200 m wide that may be related to the groundwater discharge were clarified near the Uto peninsula. For the zones near the mouths of the Midori and Sira rivers, high resistivity zones were detected in the thick post-glacial marine clay (the Ariake clay) and its cause was interpreted as the existence of the large volume of submarine groundwater. From the inversion results of the Yatsushiro Sea lines, remarkable change of the resistivity was highlighted at the extension line of the Hinagu fault. Consequently, recent and repeated movements of the Hinagu fault that formed permeable paths of the groundwater discharge were clarified.

地下水流動系は水平・垂直方向に広い範囲にわたるが, この解明は地下水資源の量と質に関する保全に不可欠である. これには深部地質構造の推定を可能とする電磁探査法の適用が有効である. 本研究では, この推定精度の向上を目的とし, 電磁波の周波数帯が異なるMT 法と AMT 法を組み合わせ, 比抵抗分布の 3 次元モデリング法を検討した. これを地下水資源が豊富な熊本平野を研究対象に適用したところ, 比抵抗分布より浅部と深部の地下水流動系は類似していることが明らかになった. また, 対象領域は第 1・2 帯水層を含む深度0～500m 間の浅層地下水流動系, 深度500～1500m 間で先阿蘇火山岩類を主とする浅層水理地質基盤, 深度2000～3500m 間で御船層群を主とする深層帯水層, およびそれ以深で肥後変成岩を主とする深層水理地質基盤から構成されることが推定できた., Clarification of groundwater system over wide horizontal and depth ranges is indispensable to the management and maintenance of the amount and quality of groundwater resource. Electromagnetic surveys are suitable to this clarification because of their capability of detecting deep geologic structures. This study proposes a spatial modeling of resistivity by a joint inversion of MT and AMT surveys data and a 3D interpolation method Kumamoto plain covering 35 km ×32 km, which is well-known as being rich in groundwater resource, is selected as a case study. Resultant 3D resistivity model elucidates that the shallow and deep groundwater flows are similar. In addition, a hydrogeologic model of the study is constructed as the shallow groundwater system including the first and second aquifers (0 to 500 m depth range), the shallow hydrogeologic basement rocks consisting chiefly of pre-Aso volcanic rocks (500 to 1500 m depth range), the deep groundwater system containing a large aquifer composed of the Cretaceous sandstone, Mifune formation (2000 to 3500 m depth range), and the Higo metamorphic rocks forming the deep hydrogeologic basement at the bottom.

ASTERとLandsatによる計40シーンの衛星画像データを用い, 塩類集積土壌域の空間分布とその時間変化を詳細に抽出できる手法について検討し, これをタリム盆地北部のオアシス周辺に適用した. まず, 衛星画像データの反射スペクトル情報から, 植生の活性度, 表土の性質, および土壌の含水の程度に対する正規化指標SAVI, NDSI, NDWIを計算し, これらの大小関係を同時に表せるNDXI画像を提案した. 2004年のASTERデ－タからNDXI画像を作成した結果, 雨期では塩類集積土壌が雨水と混合するので塩類集積土壌の分布域は特定できないが, 乾期（夏季）になれば植生の分布域・活性度の時間的変化は小さくなり, 塩類集積土壌の分布が顕著になることがわかった. このNDXI画像によれば土壌水分量の大小によって塩類集積のメカニズムが異なることが示された. 次に, LandsatとASTERのNDXI画像を最尤法によって分類した結果, 固定砂丘の変化が最も大きく, 面積が半減し, この多くが農地を含む植生域と塩類集積土壌の面積の単調増加に寄与していることがわかった. さらに, 土壌サンプルに対して測定された反射スペクトルと塩分濃度から, 反射率と塩分濃度との相関性に対する1次回帰式を求め, これを塩分指標（SI）と定義した. 衛星画像にSIを適用した結果, 2003年になると塩分濃度が全体的に増加し, 塩類集積土壌の大部分は30 ppt以上の高濃度であり, 流動砂域も塩分濃度が高い状態にあることが明らかになった., Leakages from the soil waterway, improper irrigation, and incomplete drain system have raised the groundwater levels in arid areas and caused salinization, i.e. accumulation of salts in the top soils. Vulnerability of salinization is also controlled by topographic properties and soil conditions. This study focuses on a desert area in the northern Tarim Basin, northwest China, because the rapid progress of salinization has been reported. One main factor for the salinization in the study area is the excessive water supply in the agriculture lands. For clarifying the salinization process, 40 scenes of satellite imagery in total by Landsat T‚l/ETM+ (acquisition years: 1990 and 2000) and Terra/ASTER (acquisition years: 2003, 2004, and 2006) were selected. Three normalized difference indices on vegetation, soil, and water and a color composition of the indices were adopted to detect surface changes in the period from 1990 to 2006. As a result, the salinized soils were found to have extended in the downstream, and their area increased monotonously with the time while the area of fixed dunes decreased largely. We proposed a Salinity Index to extract correctly the salinized areas from the ASTER images by refereeing to the reflectance spectra of the soil samples. This Salinity Index clarified that the salinized soils have high salt concentrations over 30 ppt and the concentrations of the moving sands are also high. In addition, the high salinity accumulation in the downstream of farmlands was identified, which implied a strong effect of agricultural development on the salinization.

In this study, a low-cost, rapid and qualitative evaluation procedure using a fuzzy set analysis for assessment and prediction of liquefaction potential of saturated sandy grounds is presented. Eight items affectinlg liquefactiorn resistance of ground including geology, geomorphology, seismic (relative site amplification and intensitiy increments), and geotechnicail items (sandy layers thickness, water table level, thickness of surface layers, and type of soils) are considered to express the basic characteristics of liquefaction potential of the ground. These items are chosen and established from a review of the various literatures, engineering judgment, available statistical data, and previous observations of liquefaction in the world. A set of evaluation criteria was established or selected for each item and a total of eight factors is used in the proposed evaluation system. In the proposed evaluation system, liquefaction potential of ground is assessed and expressed in linguistitcs terms based on the considered criteria. Then the linguistic data is analysed by using fuzzy sets. The liquefactioin index is defined for assessment of liquefaction potential of soils. An example of application of the method is presented to liquefaction potential analysis of saturated soft ground in northwestern Iran (Gilan plain). The studied area was suffered catastrophic earthquake in June 1990, and the properties of the earthquake were widespread liquefaction several huge landslides and more than tens other slope failures. This study revealed that, the proposed method is able to predict the liquefaction of the ground for preparation of hazard potentil maps and zoning, which is useful for general hazard assessment and delineation of areas., 飽和した砂質地盤における液状化ポテンシャルの算出のために, ファジィ集合理論を用いた低コストで迅速な評価手法を検討した. このシステムでは, 表層地質, 地形, 地盤振動の増幅率・震度を含む地震工学的特性, および砂層の厚さ・地下水位・表土層の厚さ・土質を含む地盤工学的特性の8項目を用い, 各項目には液状化に対しての評価規準を設定した. 個々の評価基準は自然言語で表現されるので, これにメンバーシップ関数を与え, ファジィ集合演算によって液状化ポテンシャルを算出した. 本研究で提案する評価システムを, 1990年6月に地震の被害を被ったイラン北西部のGilan平野に適用した. 液状化ポテンシャルの高い部分は, この地震によって液状化した砂質地盤と概ね対応しており, 本システムの有用性が確かめられた.

Field mapping activity for an active volcano mainly in the Torrid Zone is usually hampered by several problems such as steep terrain and bad atmosphere conditions. In this paper we present a simple solution for such problem by a combination Synthetic Aperture Radar (SAR) and geostatistical methods. By this combination, we could reduce the speckle effect from the SAR data and then estimate roughness distribution of the pyroclastic flow deposits. The main purpose of this study is to detect spatial distribution of new pyroclastic flow deposits termed as P-zone accurately using the β°data from two RADARSAT-1 SAR level-0 data. Single scene of Hyperion data and field observation were used for cross-validation of the SAR results. Mt. Merapi in central Java, Indonesia, was chosen as a study site and the eruptions in May-June 2006 were examined. The P-zones were found in the western and southern flanks. The area size and the longest flow distance were calculated as 2.3 km2 and 6.8 km, respectively. The grain size variation of the P-zone was mapped in detail from fine to coarse deposits regarding the C-band wavelength of 5.6 cm., {"references":["S. A. Carn, \"Application of Synthetic Aperture Radar (SAR) imagery to\nvolcano mapping in the humid tropics: A case study in East Java,\nIndonesia\", Bulletin of Volcanology, vol. 61, 1999, pp. 92-105.","D. Massonnet, P. Briole, and A. Arnaud, \"Deflation of Mt. Etna\nmonitored by spaceborne radar interferometry\", Nature, vol. 375, 1995,\npp567-570.","F. Sigmundsson, P. Durnand, and D. Massonnet, \"Opening of an eruptive\nfissure and seaward displacement at Piton de la Fournaise volcano\nmeasured by RADARSAT satellite radar interferometry\", GRL, vol. 26,\n1999, pp. 533-536.","H.A. Zebker, P. Rosen, S. Hensley, and P. Mouginis-Mark, \"Analysis of\nactive lava flows on Kilauea volcano, Hawaii, using SIR-C radar\ncorrelation measurement\", Geology, vol. 24, 1996, 495-498.","B. Voight, E. K. Constantine, S. Siswowidjoyo, R. and Torley, \"Historical\neruptions of Merapi volcano, Central Java, Indonesia, 1768-1998\", J.\nVol. and Geoth. Res., vol. 100, 2000, pp. 69-138.","N. Shepherd, \"Extraction of beta nought and sigma nought from\nRADARSAT CDPF products\", Report AS97-5001 Rev. 2, Canadian\nSpace Agency, Ottawa, Ont., Canada, 1998.","N. F. Glenn and J. R. Carr, \"Establishing a relationship between soil\nmoisture and RADARSAT-1 SAR data obtained over the Great Basin,\nNevada, U.S.A.\", Canadian Journal of Remote Sensing, Vol. 30, No. 2,\n2004, pp. 176-181.","R. F. Fudali and W. G. Melson, \"Ejecta velocities, magma chamber\npressure and kinetic energy associated with the 1968 eruption of Arenal\nvolcano\", Bulletin of Volcanology, vol. 35, 1971, pp. 383-401.","G. Lube, S. J. Cronin, T. Platz, A. Freundt, J. N. Procter, C. Henderson,\nand M. F. Sheridan, \"Flow and deposition of pyroclastic granular flows: a\ntype example from the 1975 Ngauruhoe eruption, New Zealand\", Journal\nof Volcanology and Geothermal Research, vol. 161, 2006, pp. 165-186."]}