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Watanabe, Takahiro; Yamamoto, Yusuke; Kitamura, Akihisa*
Chigaku Zasshi, 132(5), p.417 - 437, 2023/10
To improve a geochemical discrimination method of paleotsunami deposit, quantitative analysis of major and trace elements in boring cores from the Shizuoka plain on the Pacific coast of middle Japan was performed using a portable energy dispersive X-ray fluorescence spectrometry system (portable XRF). Geochemical approaches by the portable XRF contribute to study of the simple and rapid methods for detecting paleotsunami deposits. Most of our quantitative data by portable XRF were good agreement with reported values measured by stationary-type energy dispersive XRF in previous studies. Therefore, the portable XRF can be applied to geochemical study in the samples from Shizuoka plain in our case.
Watanabe, Takahiro; Kagami, Saya; Yokoyama, Tatsunori; Niwa, Masakazu
Chigaku Zasshi, 132(4), p.353 - 361, 2023/08
U-Pb dating of detrital zircons in paleotsunami deposits from the 1662 CE Kanbun-Hyuganada sea earthquake, Miyazaki plain on the Pacific coast of southwest Japan, was performed by a laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-ICPMS) system at Tono Geoscience Center, Japan Atomic Energy Agency. Twenty-five zircon grains were separated from the paleotsunami deposits by chemical abrasion and analyzed by the LA-ICPMS. U-Pb ages of the detrital zircons showed from ca. 14 Ma to 2405 Ma, and the age spectrum revealed high relative probability values around ca. 100 Ma and 2000 Ma. Detrital zircons with the age of ca. 100 Ma in the 1662 CE paleotsunami deposits could be partly originated from the Shimanto supergroup in southwest Japan. Moreover, the age spectrum of detrital zircons with Precambrian grains from the paleotsunami deposits was similar with those of fore-arc sandstones from central Kyushu Island.
Harada, Takuya*; Nagata, Mitsuhiro; Ogita, Yasuhiro; Kagami, Saya; Yokoyama, Tatsunori
Chigaku Zasshi, 132(1), p.57 - 65, 2023/02
The Harachiyama Formation is Lower Cretaceous volcanic rocks, distributed in the eastern margin of the Kitakami Mountains in northeastern Japan. We performed whole-rock chemical analysis, zircon U-Pb dating and Hf isotope analysis from the Harachiyama Formation to constrain the formation age and discuss the origin of magma. The lava and tuff samples of the Harachiyama Formation from the Omoto and Tsukue areas support island-arc rhyolitic rocks (SiO
content 
70%), and yielded the weighted mean U-Pb ages of 127.8 
3.4 Ma and 129.2 2.6 Ma (2
), respectively. Eighteen zircon grains from two samples, dated between 141.6 Ma and 123.9 Ma, yielded positive 
Hf(t) values between +5.0 and +8.7. These ages and values are consistent with those of the Kitakami Granititods reported in previous studies. Therefore, it is suggested that the Harachiyama Formation have the same magmatic origin as the Kitakami Granitoid.
Sueoka, Shigeru; Tagami, Takahiro*
Chigaku Zasshi, 128(5), p.707 - 730, 2019/10
no abstracts in English
Sueoka, Shigeru; Shimada, Koji; Ishimaru, Tsuneari; Danhara, Toru*; Iwano, Hideki*; Yagi, Koshi*
Chigaku Zasshi, 127(6), p.795 - 803, 2018/12
no abstracts in English
Komatsu, Tetsuya
Chigaku Zasshi, 125(5), p.661 - 698, 2016/10
The Pamir is a mountain region of the westernmost part of the Himalayan-Tibetan orogen and extends 
300 km from north to south and 300-400 km from west to east. The Pamir lies on a double subduction zone, where two buoyant continental lithospheric plates have subducted several hundred kilometers deep into the asthenosphere. The southern plate is the northward-dipping Hindu Kush slab, and the northern plate is the southward-dipping Pamir slab. This paper reviews recent studies on the Cenozoic tectonic evolution of the Pamir in this unique tectonic setting.
Sueoka, Shigeru; Umeda, Koji; Yasue, Kenichi; Niwa, Masakazu; Shimada, Koji; Ishimaru, Tsuneari; Danhara, Toru*; Iwano, Hideki*; Yagi, Koshi*
Chigaku Zasshi, 125(2), p.201 - 219, 2016/04
We applied multi-system thermochronology to the Tsuruga body of the Kojaku granite to constrain the cooling/denudation history of the Tsuruga area. Based on the thermochronometric results and other data, we reconstructed the cooling and denudation histories of the Tsuruga body as below: (1) the Tsuruga body intruded at c.a. 68 Ma at the depth of 4-5 km, (2) rapidly cooled down to c.a. 200
C by heat conduction within a few million years or less, and (3) slowly cooled due to peneplanation during the Cenozoic. This cooling/denudation history is consistent with the observations that cataclasite and fault gouge are dominant in the crush zones of the Tsuruga body, that similar slow cooling histories over the Cenozoic are estimated in the surrounding areas based on thermochronometric ages, and that the amount of denudation in the last few million years in the Tsuruga area is inferred at less than several hundred meters from the elevations of the uplifted peneplains.
Mirabueno, M. H. T.*; Torii, Masayuki*; Laguerta, E. P.*; Delos Reyes, P. J.*; Fujiki, Toshiyuki*; Bariso, E. B.*; Okuno, Mitsuru*; Nakamura, Toshio*; Danhara, Toru*; Kokubu, Yoko; et al.
Chigaku Zasshi, 123(5), p.751 - 760, 2014/10
Core drilling at site IRBH-2 within Irosin caldera, southern Luzon, reached 50 m. Systematic logging and documentation were done to describe the sediments. AMS 
C dates were obtained for plant fragments from the peaty layers. Lahars and fluvial deposits were the predominant deposits in the core sequence. The upper 12 m was comprised mostly by andesitic fluvial and minor lahars. Eight fallouts were intercalated with reworked sediments from depth interval of 20 to 50 m. The refractive index measurement of analyzed samples indicated that post-caldera eruptions generated andesite, dacite and minor rhyolite. The similarity in petrographic characteristics between the rhyolite fallout and the Irosin ignimbrite indicates that small-scale eruptions involving magma from the caldera event occurred during post-caldera stage.Young radiocarbon dates obtained from the peaty layers shows that volcaniclastic deposits in the upper levels were likely derived from the eruptions of Bulusan volcano.
Umeda, Koji; Tanikawa, Shinichi; Yasue, Kenichi
Chigaku Zasshi, 122(3), p.385 - 397, 2013/07
Long-term predictions of geological and tectonic disturbances are key issues for safety assessment of radioactive waste disposal, especially in the Japanese Islands. The geological predictions should be performed by extrapolating consistent mode and rate of crustal deformation during the neotectonic time frame. Multiple lines of geological evidence in Japan strongly suggests that the present mode of tectonics began during the late Pliocene to early Quaternary, and was fully developed by the middle Pleistocene. The uncertainty in predictions beyond the steady state crustal deformation would, in general, increase for long-term predictions using the extrapolation procedure. Consequently, the future geological and tectonic disturbances can be estimated with relatively high reliability during the next 100,000 years in Japan.
Kubo, Taiki*; Koike, Katsuaki*; Liu, C.*; Kurihara, Arata*; Matsuoka, Toshiyuki
Chigaku Zasshi, 122(1), p.139 - 158, 2013/03
Numerical simulations have been the most effective method for estimating flow pattern, flux, and flow velocity of the groundwater to precisely characterize large-scale groundwater systems. Spatial modeling of the 3D distribution of hydraulic conductivity over a study area is indispensable to obtain accurate simulation results. However, such spatial modeling is difficult in most cases due to the limitations of hydraulic conductivity data in terms of their volume and location. To overcome these problems and establish an advanced technique, we adopt geostatistics and combine a fracture distribution model with measured conductivity data, selecting the Tono area situated in Gifu Prefecture, central Japan for the field study. The size of the main target area covers 12 km (E-W) by 8 km (N-S), with a depth range of 1.5 km, and it is chiefly underlain by Cretaceous granite. Because the distribution of 395 hydraulic test data acquired along the 25 deep boreholes was biased, the data values were compared to the dimensions of simulated fractures using GEOFRAC. As a result, a positive correlation was identified. Using a regression equation for the correlation, hydraulic conductivity values were assigned to every simulated fracture. Then, a sequential Gaussian simulation (SGS) was applied to construct a 3D spatial model of hydraulic conductivity using those assumed values and actual test data. The plausibility of the resulting model was confirmed through the continuity of high and low permeable zones. The next step is a groundwater flow simulation using MODFLOW and the model. The simulation results were regarded to be appropriate because distribution of hydraulic head, locations of major discharge points, and anisotropy of hydraulic behavior of the Tsukiyoshi fault correspond to the results of observations.
Funaki, Hironori; Ishiyama, Koji*; Waseda, Amane*; Kato, Susumu*; Watanabe, Kunio*
Chigaku Zasshi, 121(6), p.929 - 945, 2012/12
Molecular and carbon isotope compositions of hydrocarbon gas have information related to their generation, migration and accumulation, and serve evaluations of gas permeability in sedimentary rocks. We conducted headspace gas analysis at the cores (below 500 m depth) to evaluate gas permeability in Neogene sedimentary rocks in the Horonobe, Hokkaido, Japan. As a result, it was shown that hydrocarbon gases were almost biogenic methane. Further analysis of these data indicated that concentration and carbon isotope of methane varied carbon isotopic fractionation during anaerobic microbial oxidation and migration near the faults. A formation of high concentration and light carbon isotope of methane at present in the study area is low gas permeability and is less affected by secondary post-generic process.
Iwatsuki, Teruki; Ishii, Eiichi; Niizato, Tadafumi
Chigaku Zasshi, 118(4), p.700 - 716, 2009/00
It is required to demonstrate the long-term variation of hydrochemical condition for the geological isolation of high level radioactive waste. This study illustrates the relationship among the past geological processes and hydrochemical condition, and estimate the long-tern variation of groundwater chemistry at deep part of Horonobe area, Japan.
C datingsOgami, Takashi*; Sugai, Toshihiko*; Fujiwara, Osamu*; Yamaguchi, Masaaki*; Sasao, Eiji
Chigaku Zasshi, 118(4), p.665 - 685, 2009/00
The depositional process of the latest Pleistocene to Holocene shallow marine and fluvial sequences is investigated by using five drill cores from the Kiso river delta, central Japan. Based on facies analysis, the sediments were classified into 5 units; A: basal gravel, B: fluvial to intertidal sand and silt, C: transgressive lag deposit, prodelta mud or sandy silt, D: delta-front-slope sandy silt or sand, delta-front-platform sand, E: delta-plain to fluvial sand and silt. Detailed age-depth curves of each cores are reconstructed based on 107 AMS C ages. The curves are divided into four sections; I: mainly consists of unit B with rapid accumulation (7.3-21.4 mm/yr), II: mainly consists of unit C with moderate accumulation (2.4-2.8 mm/yr), III: mainly consists of unit D with rapid accumulation (6.7-17.8 mm/yr), IV: consists of unit D and E with moderate accumulation (1.3-3.9 mm/yr). The section boundaries of I/II and II/III reflect inundation into the bay and achievement of progradational delta-front slope, respectively. The expanding rate of the bay is 10 m/yr during 10,200-7,900 cal yrs BP. The progradation rates of the delta are 3-4 m/yr (6.500-4,100 cal yrs BP), 5 m/yr (4,100-1,300 cal yrs BP), 10 m/yr (1,300 cal yrs BP to the present). These indicate the transition from transgression to regression occurred between 7,800 to 7,300 cal yrs BP. The geological cross section along the Kiso river coupled with isochrones indicates following history. (1) 10,000-7,280 cal yrs BP (K-Ah horizon): During the expansion of the bay, onlap of unit C on unit B is visible, and unit C overlapped all the core sites. (2) 7,280 cal yrs BP to present: Isochrones younger than 6,500 cal yrs BP are similar each other and cross unit boundaries of C/D and D/E. This demonstrates units C, D and E are contemporaneous heterotopic facies formed by progradational delta.
Kosaka, Hideki*; Kagohara, Kyoko; Miwa, Atsushi*; Imaizumi, Toshifumi*; Kurosawa, Hideki; Nohara, Tsuyoshi
Chigaku Zasshi, 117(5), p.851 - 862, 2008/10
To understand the development process of the fault zone, fission-track ages of rocks and rock facies are investigated in western margin of the Ou Backbone Range of Northeast Japan. Fission-track dating was carried out for 5 acid volcanic rocks from the late Pliocene to Pleistocene strata which were deposit associated with mountain belt growth. Statistically significant ages obtained are 1.50.1 Ma (OB-03) and 1.850.1 Ma (YG-01) for the Tazawa Formation, 1.60.3 Ma (FT-01) for the Kurisawa Formation,0.930.14 Ma (FT-02) and 2.70.3 Ma (FT-03) for the Senya Formation. According to the fission-track dating in this study, ages of the mountain belt growth with acid volcanic activity are estimated to before 1 Ma.
Kagohara, Kyoko*; Imaizumi, Toshifumi*; Miyauchi, Takahiro*; Sato, Hiroshi*; Uchida, Takuma*; Echigo, Tomoo*; Ishiyama, Tatsuya*; Matsuta, Nobuhisa*; Okada, Shinsuke*; Ikeda, Yasutaka*; et al.
Chigaku Zasshi, 115(6), p.691 - 714, 2006/12
The eastern marginal fault zone of the Yokote Basin is one of seismogenic reverse faults developed in Northeast Japan, generating the 1896 Riku-u Earthquake (M7.2). We discussed the relationship among fault traces, geomorphic displacements and fault geometries on the Senya fault, based on a data from high-resolution seismic reflection profiling, investigations in tectonic geomorphology and structural geology, with the help of the balanced cross section method. By the restoring the balanced cross sections, the horizontal shortening amount is estimated to be totally 3 km through the thrust system, and the thrusting is retroactive to 2.4 Ma. Depending on the strike of fault traces and the morphotectonic features, the Senya fault is subdivided into three, the northern, central and southern portion. The initiation of thrust front migration is ca.1.6 Ma at the central portion and 0.6 Ma at the northern portion. This means that the central portion preceded the northern portion as an emergent fault, and suggests that the initial propagated fault extends from the fault end to the boundary fault.
Tsuruga, Kayoko; Kasahara, Junzo; Mikada, Hitoshi*; Yamaoka, Koshun; Fujii, Naoyuki
Chigaku Zasshi, 115(1), p.51 - 71, 2006/02
This paper proposes the idea (Exploration of Asperities-Reflectors System, EARS) for getting to know the occurrence of large - huge earthquakes which take place along a subduction plate boundary. A large earthquake along the subducting plate boundary is considered to occur repeatedly in the particular asperity, which is the region of strongly coupled zone of two plates. The regions other than asperities along the plate boundary are considered as stable - quasi-stable region in which slow-slip may release the strain energy caused by the oceanic plate subduction. The intensity of coupling and the heterogeneities in a particular large asperity is not possible to know at present. The strong seismic reflections from the subducting plate boundary were found in the aseismic forearc region in the Japan Trench. Similar strong PP reflections were also observed in the NE region of the Hamana Lake and the same region has also showed large aseismic slip detected by GPS. When we map the asperities-reflectors system, the continuous monitoring of seismic reflection intensity may give the change of the physical state at the subducting plate boundary. The rapid change may trigger a large earthquake at an adjacent asperity. We introduce the innovative measurement system, ACROSS, which has been developed for active monitoring by continuous sinusoidal elastic waves and also describe the recent submarine OBS system. To obtain real-time monitor of the transmission signals from ACROSS at the potential regions near the trenches can be done by use of submarine cables. A newly built system planned in the Tonankaki region should consider this requirement.
Tsuruga, Kayoko; Ogawa, Katsuro*; Nagao, Hiromichi; Hasada, Yoko; Fujii, Naoyuki*; Kasahara, Junzo; Kumazawa, Mineo
Chigaku Zasshi, 114(4), p.659 - 664, 2005/04
The 1st International Workshop on 'Active Monitoring in the Solid Earth Geophysics' was held in Mizunami city, Gifu, from June 30, 2004 to July 2. This paper discusses the significance of the active monitoring of the earth, and reports the summary of the workshop.
; Yanagida, Makoto*; Fujiwara, Osamu; Ozawa, Akio*
Chigaku Zasshi, 109(3), p.366 - 382, 2000/00
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