Northern Part Of Central Japan Research Articles

Contribution of precipitation to groundwater flow systems in three major alluvial fans in Toyama Prefecture, Japan: stable-isotope characterization and application to the use of groundwater for urban heat exchangers

The isotopic compositions (D and 18O) of 177 precipitation samples collected at seven observation stations in Toyama Prefecture and one station in Gifu Prefecture in the northern part of central Japan were determined. The source and characteristics of the isotopes were clarified and their contribution to the groundwater flow systems of three major alluvial fans in the same area were investigated. The δD and δ18O values ranged from −113.3 to −26.7‰ and − 16.4 to −4.2‰, respectively. Precipitation samples collected from May to September (summer) and November to March (winter) plotted along two meteoric water lines, with d-excess = 10 and 30, respectively. Conversely, precipitation samples collected in April and October, and some samples in November to March, plotted between the two meteoric water lines. The contribution of precipitation to the groundwater systems was modelled based on the assumption that groundwater is a mixture of major river water and precipitation. According to the observed δ18O values for the precipitation, river water, and groundwater samples, the contribution of local precipitation to groundwater reservoirs ranged from 5 to 100%. Groundwater flows near the rivers did not always originate from 100% river runoff; however, the contribution of river runoff to groundwater decreased with increasing distance from the rivers, and groundwater flows far from the river were generated mainly by precipitation. The possibility of using groundwater for a ground-source heat pump system, for air conditioning in houses and to melt the snow on roads, is also discussed.

Geochemical Study of Groundwater in the Sho River Fan, Toyama Prefecture for Heat Usage by a Geothermal Heat Pump

Chemical and isotopic (D, O) compositions of 56 water samples from the Sho River fan, Toyama, northern part of central Japan, were analyzed to examine their water quality, origins, and water flow for geothermal heat extraction used for air-conditioning and melting of road snow by a geothermal heat pump (Geo-HP). Groundwaters are a mixture of two big river waters (Sho and Oyabe) and precipitation. Deep groundwaters from observation wells are characterized to be high in pH and enriched in HCO3 compared to the shallow groundwaters. These features may indicate that the shallow groundwater originated from a mixture of river water and precipitation moving to the north and becoming confined due to the presence of an impermeable layer. Groundwaters attain high pH due to ion exchange reactions with rocks containing clay minerals, where HCO3 concentration also increases.

Geochemical study of groundwater in the Sho river fan, Toyama Prefecture for heat usage by geothermal heat pump

Chemical and isotopic (D, 18O) compositions of 40 shallow groundwater, 14 observation well water and 2 river water samples in the Sho river fan, Toyama, northern part of central Japan, were analyzed to examine their water quality, origins and water flow in order to obtain baseline geochemical data for application of groundwater to geothermal heat pump (Geo-HP). Water temperatures of the groundwaters in the observation wells are almost constant at 15°C from surface to ca. 60 m in depth and increase up to 25°C at depth of 200 m with the thermal gradient of 6°C/100 m. This geothermal gradient is twice as high as that of the other areas in Japan, suggesting existence of high temperature geothermal sources beneath this region and a high potential for heat usage in winter. The isotopic results show that the groundwaters are a mixture of two big river waters (Sho and Oyabe rivers) and precipitation in the Sho river fan and that the contribution of infiltration from the Sho river has increased in recent 10 years. The Sho river has lower δ18O values than the Oyabe river. The groundwaters shallower than 80 m depth are of a Ca–HCO3 type. Deep groundwaters from observation wells were characterized by high in pH and HCO3 compared to the shallow groundwaters due to ion exchange with rocks containing clay minerals. The deep groundwaters are almost saturated or oversaturated with respect to calcite and dolomite, becoming confined due to the presence of an impermeable layer. In this paper, formation of calcite and iron hydroxide scale inside pipes of the Geo-HP was discussed from the chemical compositions of groundwater to examine whether the water is applicable to geothermal heat pump or not.

Provenance of quartzarenite clasts in the Tetori Group (Middle Jurassic to Early Cretaceous), Japan: Paleogeographic implications

There are many strata containing quartzite clasts in the Japanese Islands, but the on-land geology of the Japanese Islands has no candidate for the source rocks of the quartzite clasts. This study deals with the provenance of quartzite clasts of the Tetori Group (Middle Jurassic and Early Cretaceous) distributed in northern central Japan. Quartzarenite clasts from conglomerate beds of the Tetori Group are texturally subdivided into three types; the most abundant is matrix-bearing quartzarenite (type 3), followed by poorly sorted feldspar-bearing quartzarenite (type 2) and by well-sorted pure quartzarenite (type 1). To identify the provenance of quartzarenite clasts in the Tetori Group characteristics of quartzarenite sequences distributed in North China and Korea were studied and compared with those of the Tetori quartzarenite clasts. Texturally and geochemically, the quartzarenite clasts of the Tetori Group are very similar to pre-Mesozoic quartzarenites distributed in the south central and east central Korean Peninsula. Considering the previous results of depositional environments, paleomagnetism and paleocurrent studies on the Tetori Group, this study suggests that during deposition of the Tetori Group, the northern part of central Japan was probably land-connected with the central region of eastern Korea.

The First Reported Case of Spotted Fever in Fukui Prefecture, the Northern Part of Central Japan

The First Reported Case of Spotted Fever in Fukui Prefecture, the Northern Part of Central Japan

Active Tectonics in the Hokuriku Region, northern part of central Japan, based on Deformed Fluvial Terraces

Active Tectonics in the Hokuriku Region, northern part of central Japan, based on Deformed Fluvial Terraces

Palaeomagnetic and chronological study of Miocene welded tuffs in the northern part of Central Japan: tectonic implications for the latest stage of arc formation of Japan

Kinematical adjustment of tectonic blocks has occurred in the latest stage of arc formation of Japan within central Japan. Miocene welded tuffs have been sampled for chronological and palaeomagnetic studies from the northern part of central Japan. Zircon fission-track dating confirms Middle to Late Miocene ages (13.7-5.0 Ma) for the Yatakezawa, Shiobara, Kawaji, Kinugawa, Katashinagawa, Okkai and Ashio Formations. Characteristic directions with high unblocking temperature component above 560°C are isolated from 36 sites. Palaeomagnetic directions after tilt correction provide a Miocene characteristic palaeomagnetic direction of the northern part of central Japan (36.8°N, 139.3°E): D = 7.3°, I = 50.3°, α 95 = 6.6°. Presence of normal and reversed polarities, and a fairly long time average exclude the effect of geomagnetic field secular variation. Comparison with the Miocene palaeomagnetic poles of the neighbouring blocks indicates that the northern part of central Japan and northeast Japan behaved as a unified block since 15 Ma, whereas the Kanto Mountain region moved kinematically as an independent block from the northern block comprised of central Japan and northeast Japan at least between 16 Ma and 12 Ma. The boundary between the northern part of central Japan and the Kanto Mountain was in a convergent regime with dextral strike slip. A southward force exerted from the northern part of central Japan, as well as a northward force by the Izu-Bonin ridge, induced the clockwise rotation of the Kanto Mountain region. The northern part of central Japan had welded completely with the Kanto Mountain region by 6 Ma.

妙高火山群の活動史 “多世代火山”

The Myoko volcano group, consisting of five stratovolcanoes, Myoko, Kurohime, Iizuna, Yakeyama and Madarao, is situated in the northern part of central Japan. Twenty one volcanic rocks from the early stage of volcanic successions of Myoko (5 samples), Kurohime (4 samples), Iizuna (9 samples) and Madarao (3 samples) were dated with K-Ar methods. On the basis of previously well studied geology and petrology of the volcano group and chronology of marker tephra layers in this area together with newly obtained K-Ar ages, volcanic history of the Myoko volcano group was discussed in detail. The results confirmed the genetical story of the volcanoes by Hayatsu (1985), i. e., the Myoko volcano has grown by four stages of active volcanisms with three distinctive pauses and each stage has a chemical fractionation trend from basalt to dacite through andesite during a volcanism, and other volcanoes were also in the same story though number of stages was variable : three for Kurohime and two for Iizuna and Madarao, and the fractionation trend was little changeable. This paper calls this type of volcano “poly-generation volcano”.Growth mechanism of the poly-generation volcano was also revealed in detail : life span of each generation, that is time span of each stage of activity, is nearly constant, 20-50 kyrs though some exceptions but total amount of volcanic ejecta decreases with time, e. g., 40-20-7-5 km3 for Myoko, and pause period between any two active volcanic stages decreases with time from 100-160 kyrs of early pause to ca. 10 kyrs of late one.This poly-generation volcano is common in Japan and should be studied in further detail from view points of igenous petrology and tectonics of magmatism as well as geothermal energy and volcanic hazards.

山麓の火山灰層からみた妙高火山中央火口丘の活動と年代

Myoko volcano, situated in the northern part of Central Japan, is one of the composit stratovolcanoes whose life histories have been studied in detail. In this paper, ten volcanic ash layers belonging to the central cone stage of Myoko volcano are described, and more detailed volcanic history of the central cone stage is compiled in connection with the informations already known.The result are summarized as follows:(1) The central cone stage started ca. 5, 800 years ago. The central cone, Mt. Myoko, was almost built at the early time of the stage.(2) The youngest magmatic eruption of Myoko volcano took place ca. 4, 200 years ago, and produced pyroclastic flows and pyroclastic surges.(3) The youngest steam explosion of Myoko that was confirmed took place ca. 3, 000 years ago, and produced small pyroclastic surges.(4) For 1, 600 years between 5, 800 and 4, 200 years ago, a series of eruption whose ejecta were kept as an obvious stratum at the foot of Myoko volcano took place at the average rate of once for 200 or 300 years. After the violent eruption of ca. 4, 200 years ago, Myoko rapidly became less active, and the eruption in the similar scale took place only once or twice for ca. 4, 200 years up to the present.(5) The central cone stage was dominated mainly by the activity of dacitic magma, and coincided with the time when pyroclastic flows and pyroclastic surges were apt to be produced by explosive eruptions.

B33 中部日本北部に分布する新第三紀火山岩類の Sr 同位体比について

B33 中部日本北部に分布する新第三紀火山岩類の Sr 同位体比について

A Local Population of the Japanese Ptarmigan on Mt. Yakeyama

Recentry, two populations of the Japanese Ptarmigan are found on Mt. Hiuchi (8, 075 ft.) and Mt. Yakeyama (7, 872 ft), Kubiki Mountain Range, northern part of central Japan (Fig. 1). Oen sub-adult group of the bird was observed on Mt. Yakeyama in 1969, which suggested a possibility of its breeding on the mountain.The ptarmigan is one of the national monuments in Japan. Few ecological observations on the ptarmigan are carried out on Mt. Fuji (12, 385 ft.), Mt. Hiuchi and Mt. Iizuna (6, 288 ft).Extinction of the ptarmigan caused by human works on Mt. Fuji (the highest mountain in Japan) was reported by Chiba in 1971.Detailed observations of the ptarmigan on Mt. Yakeyama were made during June 24-28, 1971 to get some ecological informations. Vegetations of the mountain, size and structure of the population, their nest and eggs and evaluations of their habitat are reported on this paper.Mt. Yakeyama is a cone-shaped mountain that has a large crater on the top. The top has a very poor vegetation causing by active volcano. Some patches of Pinus pumila are found on southern slope near the top, and Alnus maximowiczii surrounds the mountain (Fig. 6).Two pairs of ptarmigan showed up on the southern slope above 7, 544 ft. high. One nest containing six eggs nearly hatched was found in deep Pinus pumila bush (Fig. 3).Summer and winter droppings (Figs. 2-a, 2-b) and sandbaths are marked on the map (Fig. 5).This seems to show their habitat on this mountain.They come down to get foods (buds appearing on snow) as low as 5, 904 ft. in winter, on the other, in summer they stay mostly around the top to avoid terrestrial predators.A few ptarmigans were observed in early spring and late fall on Mt. Myoko (8, 023 ft.) where no nest had been reported. These records suggest the possibility of temporary shortdistance migration in snow season.Breeding site of the bird supposed to be restricted to pine bush on this mountain. Two or three breeding pairs supposed to lay their eggs in this bush (the second pair would lay their eggs after the first nestlings were fledged): they seem to use the same nesting site alternatively. In many cases, chickens of the Japanese Ptarmigan were found in June in other mountains whereas some immediately after hatched were observed on Mt. Yakeyama in August.

Geodetic work in Japan with special reference to the Matsuchiro earthquakes

Geodetic surveys, first‐order leveling, triangulation with electro distance measurements, and geomagnetic and gravity surveys have been conducted by the Geographical Survey Institute in and around the area of the Matsushiro earthquake swarm in the northern part of Central Japan during the period from 1965 to 1968. During this period leveling surveys were resurveyed every three months in the vicinity of Matsushiro and the other surveys were made at approximately six‐month intervals. From the results of the surveys, the following facts have been found.Extraordinary vertical deformations have continued near Mt. Minakami, with upheaval from October 1965 to September 1966 through the first and second peaks of seismic activities, followed by a subsidence. The maximum rate of the upheaval motion was about 50 mm per month. On the other hand, in the Omachi‐Matsukawa region, which is about 30 km from the central area of the earthquake swarms, anomalous reversals of the pattern in the vertical deformation have occurred, for which the period also seems to be about six months. The mean rate of up and down motion was about 40 mm per six months. Such a reversible vertical deformation was also found in the large region along the first‐order leveling routes through Nagano, Ueda, Matsumoto, and Omachi during the whole period of about three years, 1965–1968.

Further Note on the Seismic Activity of the Northern Part of Central Japan

Further Note on the Seismic Activity of the Northern Part of Central Japan