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King, G. E.*; Bossin, L.*; Kranz-Bartz, M.*; Wen, X.*; Schmidt, C.*; Herman, F.*; 小形 学; 末岡 茂
no journal, ,
Electron spin resonance (ESR) dating of quartz minerals offers a significant advantage over luminescence dating because of its later signal saturation. Whereas the luminescence thermochronometry system is limited to areas experiencing very rapid rock cooling (exhumation) of tens of mm/yr, recent studies have shown that ESR thermochronometry can resolve rates of <1 mm/yr over Quaternary timescales. However, the method has not yet been validated against samples with known thermal histories. To this end, we have investigated six known-thermal history samples from the MIZ1 borehole, Tono, Japan. The natural trapped-charge concentration of the different samples was constrained using a single-aliquot regenerative dose measurement protocol. As the samples had similar properties, we constructed a standardised growth curve to alleviate measurement times. Signal saturation of the Al-centre occurred at ~60 kGy and at ~7 kGy for the Ti-centre. Whereas the Al-centre exhibited single-saturating exponential growth, the Ti-centre exhibited significant sub-linearity in the low dose region, within which the natural trapped-charge concentrations were interpolated. The thermal stability of the different samples was measured using an isothermal holding experiment, whereby samples were dosed in the laboratory before being held at four fixed temperatures for durations ranging from 0 min to 10 h. As the thermal signal loss of the different samples was similar, we were able to fit all samples to derive a single set of thermal kinetic parameters. Finally, the data were inverted for borehole temperature using a Monte-Carlo approach. Whereas the Al-centre of all samples recovered borehole temperature within 1 sigma, the Ti-centre data failed to recover temperature, yielding temperatures ~20-30 deg. C above borehole temperature. The cause is likely related to the observed sub-linearity of the dose response curves which may be indicative of sensitivity change throughout analysis.
Malatesta, L.*; Weiss, N.-M.*; 塚本 すみ子*; 末岡 茂; 石村 大輔*; Gailleton, B.*; 西村 卓也*; 高橋 直也*; 片岡 香子*; 小松 哲也; et al.
no journal, ,
On January 1st, 2024, the Mw 7.5 Noto Peninsula earthquake ruptured on a series of coastal offshore reverse faults in the back arc of central Japan. The coastal rocks uplifted as much as 4.4 m. The coastline accordingly moved seaward by up to 200 m creating new wide bedrock platforms. Holocene terraces mapped along the northern coast suggest similar past ruptures. Many of the ruptured faults follow the coast at a depth of ca. 60 m below modern sea level, which strongly suggests that these faults define the extent of the continental domain. The Peninsula itself hosts 4767 unique mapped terraces ranging in age from Holocene to 1.02 Ma. The terraces associated with the last two interglacial high stands record a tectonic SE-tilting similar to that of the Mw 7.5 earthquake. Older terraces all record a spatially uniform rate of uplift across the Peninsula. We conclude that the faults that caused the most recent earthquake became the dominant structures on the Peninsula around 250 ka and that the Peninsula is in a state of transient equilibration. 80 km to the northeast of the Noto Peninsula lies the Island of Sado. The Island is made of two mountain ranges oriented SW-NE along the main tectonic lineation of the back arc, roughly parallel to the northern coast of Noto Peninsula. The marine terraces of the northern range, Oosado, record a strong southeast tilting synchronous and similar to that observed on the Noto Peninsula. The landscape morphology is not equilibrated to this pattern of deformation either. Earlier work suggested a hypothesis that the tilt is driven by a fault lying just offshore of the Oosado coast. Closer inspection of the bathymetry reveals a ramp at around -60 m reflecting a geometry similar to the Noto Peninsula. The lessons from the Noto Peninsula earthquake can be applied to Sado Island where information about the seismic cycle is lacking. It confirms the hypothesis and highlights a potential seismogenic source close to the shore.
Liebscher, A.*; Peti, L.*; Stockmann, M.*; Strusinnska-Correia, A.*; Tatomir, A.*; Goubel, A.*; 尾崎 裕介; 早野 明; 大野 宏和; 舘 幸男; et al.
no journal, ,
幌延深地層研究センターでは、経済協力開発機構/原子力機関(OECD/NEA)の協力の下、2023年2月から2029年3月まで幌延国際共同プロジェクト(Horonobe International Project: HIP)を実施している。HIPの目的は、幌延深地層研究センターの地下施設を活用して研究開発を国内外の機関の協力の下で実施し、先進的な安全評価技術や工学技術に関わる研究開発の成果を最大化することや、次世代の研究者/技術者を育成し知識を継承することである。HIPでは、物質移行試験、処分技術の実証と体系化、実規模の人工バリアシステムの解体試験の3つのタスクが実施されている。本発表では、これら3つのタスクにおける連邦放射性廃棄物機関(BGE;ドイツ)の協力内容や関心について述べる。
辰野 宇大*; 二瓶 直登*; 吉村 和也
no journal, ,
This study investigated the changes in Cs and cesium-bearing microparticles (CsMPs) deposition in the paddy field in the first year of resumption of farming after the accident. Furthermore, we evaluate the contribution of CsMPs on particulate Cs to grasp the impact of CsMPs on transfer factor (TF) of brown rice. As a result, the accumulation of Cs and CsMPs increased in the entire field of this study in the period from plowing to harvest. The deposition of Cs per unit area increased in the center and the four corners of the paddy field other than inlet and outlet. This may be due to the deposition of suspended matter in areas with relatively little water movement. On the other hand, there was no clear trend for CsMPs deposition in the paddy filed. There was no significant difference between TF values with and without the contribution of CsMPs to Cs concentration in the soil.
Kranz-Bartz, M.*; King, G. E.*; Bernard, M.*; Herman, F.*; Wen, X.*; 末岡 茂; 塚本 すみ子*; Braun, J.*; 田上 高広*
no journal, ,
The influence of Quaternary climate on mountain topography remains a topic of debate, largely due to the challenges associated with measuring surface processes over the recent geological past. A compelling location to investigate mountain erosion in response to Quaternary climate change is found in the Tateyama Mountains, part of the northern Japanese Alps, due to its distinct geomorphological features. The Japanese Alps uplifted within the last 1-3 million years and have undergone multiple glaciations during the late Quaternary. In this study, we employ novel ultra-low temperature thermochronometres based on the luminescence and electron spin resonance (ESR) from feldspar and quartz, respectively, in combination with inverse modelling to derive rock cooling and exhumation rate histories on timescales of 10
-10
years within the Tateyama region. The four luminescence signals have already reached their upper dating limit, indicating maximum exhumation rates of ca. 1-1.5 mm/yr. In contrast, ESR signals from Al and Ti centres provided ESR ages ranging ca. 0.3-1.1 Ma, suggesting that surface processes were active during the Pleistocene. A negative age-elevation relationship reveals a reduction in local relief at the scale of the cirque basin over the past million years. However, a positive age-elevation trend observed in samples from near the mountain summit deviates from this pattern. Inverse modelling shows rock cooling rates ranging 20-80
C/Myr, with slightly faster cooling in cirque-floor samples. Thermal kinematic modelling reveals erosion rates of 0.5-1 mm/yr in the cirque basin, which are higher than those observed from periglacial and slope processes in the same area. Our data suggest that Quaternary climate change, coupled with distinct surface processes, has significantly altered the slopes of the Tateyama mountains, leading to a localized decrease in relief within individual cirque basins during the second half of the Quaternary.
佐久間 一幸; Wainwright, Haruko*; Xu, Z.*; Lawrence, A.*; Hazenberg, P.*
no journal, ,
汚染物質が地下水から河川に移行すると、下流域の住民に影響を及ぼすサイトもある。予測モデリングは、サイト内の詳細な地下構造と地下水流動モデル、および広範囲な輸送のための流域スケールモデルを含む必要があるため、困難である。気候変動の影響が多くのサイトで大きな懸念事項となっている現在、サイトと流域スケールの両方で、水収支の変化とそれが汚染物質輸送に及ぼす影響を一貫した方法で表現できることが重要である。本研究では、集水域内の地下水から河川水への汚染物質輸送を記述するために、サイト・丘陵地スケールの詳細な2次元地下水モデルと流域スケールの3次元モデルを結合させる新しいシミュレーションのフレームワークを導入する。リチャーズ方程式と移流分散方程式に基づき、汚染源から河川への汚染物質の流出量を推定し、2次元サイト/丘陵スケール地下水モデルの幅と両モデルの涵養量を考慮した境界条件を流域スケールのモデルに適用する。サバンナリバーサイトF-Areaで収集された表流水と地下水のトリチウム濃度データセットに基づき、本フレームワークの実証と検証を行った。その結果、本手法が河川水中の汚染物質濃度をうまく再現できることが示された。
安邊 啓明; 他26名*
no journal, ,
スタイロライトは、圧力溶解による脱水で形成される、複雑に指交した形状を示す岩石中の剥離構造であり、古応力の推定に有用である。スタイロライトの形成は蒸発岩堆積後の堆積空間の形成に寄与する可能性があることから、蒸発岩中のスタイロライト形成時の応力条件を明らかにすることが重要である。本研究では、2024年2月から4月にかけてイタリア沖のティレニア海で掘削されたIODP第402次航海コア試料中の蒸発岩に見られるスタイロライトを分析した。スタイロライトを写真撮影、トレースし、離散フーリエ変換法を用いて解析することで、異なる粗さ指数を持つ2つのスケーリング領域を分離する遷移長Lを推定した。多くのスタイロライトについてLは2mm程度だった。これに基づいて推定される応力値はコアの回収深度と整合的であることから、蒸発岩中のスタイロライトが応力の推定に有用であることが示唆された。
Poulaki, E. M.*; 安邊 啓明; 他31名*
no journal, ,
デタッチメント断層に沿ったひずみの局在化と上昇速度の制御機構、およびマントル上昇中の蛇紋岩化と火成活動の役割は、まだ十分に解明されていない。IODP第402次航海では、ティレニア海の大陸-海洋遷移部を掘削し、この背弧海盆における新生代後期の伸長過程で上昇・定置したマントル物質を回収した。試料の分析の結果、岩相の不均質性と既存構造の存在が断層のすべり挙動に大きな影響を与えることが示された。また、岩石の年代測定を行い、せん断帯の進化過程を制約することができた。