Kumamoto Plain Research Articles

Investigation of the subsurface structure at the target site in Kumamoto, Japan, and the distributed data of the blind prediction exercise: report for the experiments for the 6th international symposium on effects of surface geology on seismic motion

This technical report explains details on the results of the investigation to build a subsurface structural model and a selection of earthquake data at the target site of the blind prediction exercise for “The 6th International Association of Seismology and Physics of the Earth’s Interior/International Association of Earthquake Engineering International Symposium on the Effect of Surface Geology on Seismic Motion (ESG6).” The selection process of the target site in the Kumamoto Plain, Japan, in ESG6 was explained with a historical review of the blind prediction tests in the previous ESG conferences. We have collected existing subsurface structural and earthquake data and conducted geophysical and geotechnical surveys in and around the target site to generate important velocity structure and the earthquake data used in the blind test. Microtremor data were obtained in triangular arrays ranging in side lengths from 1 to 962 m, and active surface wave data were derived along a 36-m line at the site. These data were provided for the prediction of a subsurface structural model in the first step of the blind prediction exercise. We also conducted a velocity logging in a borehole to a bottom depth of 39 m at the site and laboratory tests of soil samples from the borehole. We constructed a velocity profile of the shallow and deep sedimentary layers from a combination of the geophysical and geotechnical data at the site, and validated it by comparing the characteristics of the ground motion data from the moderate event. This “preferred velocity model” was provided as a standard model to the participants in the second and third steps of the blind prediction test to predict the earthquake ground motions of a moderate event and the mainshock of the 2016 Kumamoto earthquake.Graphical

Postseismic deformation following the 2016 Kumamoto earthquake detected by ALOS-2/PALSAR-2

I have been conducting a study of postseismic deformation following the 2016 Kumamoto earthquake using ALOS-2/PALSAR-2 acquired till 2018. I apply ionospheric correction to interferograms of ALOS-2/PALSAR-2. L-band SAR gives us high coherence enough to reveal surface deformation even in vegetated or mountainous area for pairs of images acquired more than 2 years. Postseismic deformation following the Kumamoto earthquake exceeds 10 cm during 2 years at some spots in and around Kumamoto city and Aso caldera. Westward motion of ~ 6 cm/year was dominant on the southeast side of the Hinagu fault, while westward shift was detected on both sides of the Futagawa fault. The area of latter deformation seems to have correlation with distribution of pyroclastic flow deposits. Significant uplift was found around the eastern Futagawa fault and on the southwestern frank of Aso caldera, whose rate reaches 4 cm/year. There are sharp changes across several coseismic surface ruptures such as Futagawa, Hinagu, and Idenokuchi faults. Rapid subsidence between Futagawa and Idenokuchi faults also found. It is confirmed that local subsidence continued along the Suizenji fault, which newly appeared during the mainshock in Kumamoto City. Subsidence with westward shift of up to 4 cm/year was also found in Aso caldera. Time constant of postseismic decay ranges from 1 month to 600 days at selected points, but that postseismic deformation during the first epochs or two is dominant at point in the Kumamoto Plain. This result suggests multiple source of deformation. Westward motion around the Hinagu fault may be explained with right lateral afterslip on the shallow part of this fault. Subsidence along the Suizenji fault can be attributed to normal faulting on dipping westward. Deformation around the Hinagu and Idenokuchi faults cannot be explained with right lateral afterslip of Futagawa fault, which requires other sources. Deformation in northern part of Aso caldera might be the result of right lateral afterslip on a possible buried fault.

Modeling of the Subsurface Structure from the Seismic Bedrock to the Ground Surface for a Broadband Strong Motion Evaluation in Kumamoto Plain

During the 2016 Kumamoto earthquakes, two earthquakes of seismic intensity 7 were observed in Mashiki Town, the foreshock (MJMA6.5) of April 14 and the main shock (MJMA7.3) of April 16, resulting in significant damage to structures near the fault. The distribution of damage of houses and other buildings [1] showed a tendency in which damage was concentrated in areas near the surface earthquake fault where the main shock presumably occurred. However, there were locations with slight damage even though they were immediately above the fault and locations with a relatively significant damage even though they were far from the fault. These phenomena are highly likely to be a result of soil structure. First, we built an initial geologic model by collecting boring data in areas of the Kumamoto plain near the fault where damage was severe. Next, we observed microtremors, collected earthquake observational records, and adjusted the layer thickness and S-wave velocity of the initial geologic model. Finally, we built a shallow and deep integrated ground model, compared it to the building damage distribution, and discussed the implications.

Disturbances of Temperature-Depth Profiles by Surface Warming and Groundwater Flow Convection in Kumamoto Plain, Japan

Subsurface temperatures depend on climate and groundwater flow. A lack of observations of subsurface temperature collected over decades limits interpretation of the combined influences of surface warming and groundwater flow on subsurface thermal regimes. Subsurface temperature-depth profile data acquired for Kumamoto Plain, Japan, between 1987 and 2012 were collected and analyzed to elucidate regional groundwater and heat flows. The observed and simulated temperature-depth profiles showed the following: subsurface water flows from northeast to southwest in the study area; the combined influence of surface warming and water flow perturbation produces different temporal changes in thermal profiles in recharge, intermediate, and discharge areas; and aquifer thermal properties contribute more than hydraulic parameters to the perturbation of temperature-depth profiles. Spatial and temporal evolution features of subsurface thermal regimes may be utilized to investigate the influence of surface warming events on subsurface water and heat flows at the basin scale.

Geochemical Processes Controlling Fluoride Enrichment in Groundwater at the Western Part of Kumamoto Area, Japan

This paper first time reports the geochemical processes that are controlling fluoride enrichment in the groundwater of western Kumamoto area, Japan. Fifty (50) groundwater samples were collected and analyzed for the study where fluoride (F−) concentration ranges from 0.1 to 1.57 mg/L. About 58 % of the shallow groundwater and 26 % of the deep groundwater samples contain fluoride concentration beyond the Japanese drinking water permissible limit (0.8 mg/L). High F− is largely accumulated in the stagnant zone of the Kumamoto Plain area and associated with Na-HCO3-type groundwater. High pH, high HCO3, low Ca2+, and high Na+ are the major characteristics of high-F− groundwater. Hydrolysis of F−-bearing minerals and desorption of F− from hydrous metal oxides are considered to be the primary sources of fluoride in groundwater. A positive correlation between F− and Na+/Ca2+ ratio (r 2 = 0.53) indicates that major ion chemistry plays a significant role in fluoride mobilization. Weakly alkaline nature of groundwater with high pH (7.05–9.45) expedites the leaching process of exchangeable F− from F−-bearing minerals as well as favors desorption of F− from metal oxide surfaces. High HCO3 − and high PO4 3− in the groundwater facilitate desorption process as competing anions, while high Na+/Ca2+ ratio largely control this process by decreasing positive-charge density of the metal-oxide surfaces. High Na+/Ca2+ ratio is attributed due to the cation-exchange process, while high pH and HCO3 − are the result of both silicate hydrolysis and microbial reduction processes. In addition, calcite and fluorite seem to have a control on groundwater fluoride geochemistry.

Redox processes and occurrence of arsenic in a volcanic aquifer system of Kumamoto Area, Japan

Sources, distributions, and controlling factors for mobilization of arsenic (As) in Kumamoto basin were investigated relating to the determination of redox processes of the study area. Groundwater and sediment core samples were analyzed. Nitric acid digestion and sequential leaching experiment of sediment core samples revealed that the source of As in the groundwater is geogenic and leached primarily due to the sediment–water interactions. Unlikely, similar relations of total As with total Fe, Mn, and Al in acid extracts, leaching experiments showed a positive relation of Astotal with Fetotal and Altotal indicated that Fe and Al oxides/hydroxides are abundant and may be the major adsorbent of As in low pH condition. Arsenic concentrations in groundwater ranges from 0.1 to 60.6 μg/l. High As concentrations occurred in anaerobic stagnant groundwaters from Kumamoto plain area with high dissolved Fetotal, Mntotal, and Altotal, moderately dissolved HCO3 −, PO4 3−, SO4 2−, and low concentrations of NO3 − and DOC suggesting the reducing condition of subsurface aquifer. There is a range of As(III)/As(T) ratios from mostly arsenate to mostly arsenite. Groundwater pH was relatively high, and high As occurred at higher pH range. It is assumed that desorption of As from metal oxide surfaces was facilitated by the elevated pH, which is considered as an important process for As mobilization. In addition to this, a wide range of δ34SSO4 values (8.3–57.6 ‰) indicates that sulfur is undergoing redox cycling mediated by microbial activities. Following δ34SSO4 results, it is anticipated that dissolved As is coprecipitated as sulfides in the presence of dissolved Fe(II) in some places, though at this moment, there is no direct evidence of coprecipitation or sequester of As with Fe and sulfide ion. Finally, a combination of the following three variables are considered potentially important causes for the high dissolved As concentrations in groundwater of Kumamoto area—(1) high groundwater pH, (2) anoxic redox conditions, and (3) stagnant groundwater in younger age sediments, which have not been well flushed since burial.

Teleconnection and climatic oscillation in aquifer water level in Kumamoto plain, Japan

AbstractRelative little is known about the interaction between climate change and groundwater. Analysis of aquifer response to climatic variability could improve the knowledge related to groundwater resource variations and therefore provides guidance on water resource management. In this work, seasonal and annual variations of groundwater levels in Kumamoto plain (Japan) and their possible interactions with climatic indices and El Niño Southern Oscillation (ENSO) were analyzed statistically. Results show the following: (1) The water level in the recharge area mainly fluctuates at 1‐ and 2‐year periods, whereas the significant periodicity for water level oscillation in the coastal aquifer is 0.5 year. (2) The aquifer water levels are possibly influenced by variability in precipitation, air temperature, barometric pressure, humidity variances and ENSO. Relative high correlations and large proportions of similarities in wavelet power patterns were found between these variables and water levels. (3) Aquifer response to climatic variances was evaluated using cross wavelet transform and wavelet coherence. In recharging aquifers, the ENSO‐induced annual variations in precipitation, air temperature, humidity and barometric pressure affect aquifer water levels. The precipitation, air temperature and humidity respond to ENSO with a 4‐, 6‐ and 8‐month time lag, respectively, whereas the ENSO imparts weak influence on the barometric pressure. Significant biennial variation of water levels during 1991–1995 is caused primarily by precipitation and humidity variations. In the coastal aquifer, the 0.5‐year variability in ENSO is transferred by precipitation, barometric pressure and humidity to aquifer water levels, and the precipitation/humidity influence is more significant comparing with the barometric pressure. Copyright © 2014 John Wiley & Sons, Ltd.

Co-kriging for modeling shallow groundwater level changes in consideration of land use/land cover pattern

This study aimed at clarifying the relationship between the dynamics of land use/land cover (LULC) changes and decline in the groundwater levels, and specifying an LULC category strongly affecting such decline in a Quaternary sedimentary basin. Groundwater level data recorded at 26 observation wells for a 14-year period in the Kumamoto Plain, central Kyushu, southwest Japan, were used for the analysis. The general trends of LULC were detected by a satellite image classification technique and surface spline method, which highlighted the decreases in groundwater-recharge materials. As the next step, those trends of groundwater levels that were closely correlated with rainfall were removed from the level data set, and the resultant residual component levels were applied to co-kriging analysis with LULC categories. Co-kriging provided a detailed map of groundwater level variability. Furthermore, we propose a method, prediction of residual of groundwater level (PWL), to infer future residual groundwater levels from the supposed LULC pattern by co-kriging-based modeling. PWL was demonstrated to be effective because it clearly represented the decrease and increase in negative residual level areas, depending on the extent of rice fields in the past and in predicted future distribution scenarios.

Separation of dissolved Kr from a water sample by means of a hollow fiber membrane

Summary We investigated extraction of the krypton (Kr) radioisotope 85 Kr from groundwater having an ultra-low concentration with a Kr extraction system using an external inflow type hollow fiber membrane. Our aim was to develop a system able to effectively extract Kr isotopes from a large volume of groundwater (10 4 L) in field studies for measurement of 85 Kr radioactivity. Before testing our Kr extraction system in the field, we determined experimentally the conditions necessary for effective extraction of Kr isotopes from groundwater. We investigated the efficiency of Kr extraction from water by extracting trace amounts of Kr in the laboratory. With our system, we were able to extract 99% of Kr and O 2 dissolved in water at water temperatures ranging from 11 to 29 °C and with a flow rate of less than 24 L/min, confirming that the separation efficiency of the system was sufficient for extraction of Kr isotopes from groundwater. We then used our method to extract 85 Kr from groundwater at sites at Kyoto University in Osaka and on the Kumamoto Plain in central Kyushu, Japan. We showed that this technique for extracting 85 Kr from the groundwater can be an effective tool for investigating the residence time of young groundwater.

Geostatistical model for correlating declining groundwater levels with changes in land cover detected from analyses of satellite images

A combination of satellite-data processing and geostatistical spatial modeling is examined to investigate long-term changes in groundwater levels within a catchment basin and identify the causes of the changes. The data processing was used to obtain an accurate image classification of land covers while the geostatistical modeling was used to interpolate residual components of groundwater levels by removing identified trends from the original data. Our case study focused on the Kumamoto Plain, situated in central Kyushu, southwest Japan, where all of the water supply is derived from groundwater. A Linear Spectral Mixture was adopted to the 10 sub-scene images of Landsat 5 Thematic Mapper (TM) and Landsat 7 Enhancement Thematic Mapper Plus (ETM+) sensors covering the study area for a 16-year period (1987–2003); this proved to be highly effective in detecting declining amounts of groundwater-recharging material. Descriptive statistical parameters from the groundwater-level data were integrated with the process of identifying, characterizing, and removing the trend components that are closely correlated with rainfall. Variogram modeling and ordinary kriging were used to construct a spatial model of the residual groundwater-level data. Finally, a multivariate model is proposed to estimate the degree of reduction in groundwater levels. The correlation coefficients between the observed and estimated residual levels by the multivariate regression model at 14 wells for the cross-validation range from 0.95 to 0.98. This demonstrates the applicability of the model to both the local areas around well sites and across the entire study area. To deepen the regression result, the Tukey honestly significantly different statistical test was applied. The test clarified that changes in land cover from rice field to urban areas have the greatest impact on reductions in groundwater within the recharge area.

Spatial modeling of discontinuous geologic attributes with geotechnical applications

Geologic data obtained by drilling investigations, field measurements, and laboratory tests are irregularly distributed with respect to location both horizontally and vertically. Spatial discontinuities impact soil classification, hydraulic conductivity, and chemical content. In this study, a three-dimensional modeling method, which combines the optimization principle method and a stochastic simulation method, was developed (OPTSIM). This method consists of three steps: the transformation of geologic attributes into binary (0 or 1) under certain thresholds, the three-dimensional interpolation of these transformed binary data, and the construction of conditional cumulative distribution functions (CCDF) by repeatedly changing the threshold and interpolation analysis. The Monte Carlo method was then used to inversely determine the attributes from the constructed CCDFs. Three types of attribute expressed by value, code, and class were examined. The OPTSIM was applied to spatial modeling of geotechnical structures in the Kumamoto plain, southwest Japan, using two kinds of data, lithologic units and physical soil properties. Resistivity data obtained by electric logging and the locations of screens were linked to geologic distribution. The constructed model contributed to the location of chief aquifers and estimates of amount of shallow groundwater. A combination of granular composition, N value, and water content was examined. Transgression and regression patterns following the last glacial stage were also inferred through this analysis. In both applications, discontinuities in lithologic units and soil properties resulting from fault movements and sea-level changes were successfully expressed in the distribution models.

Transient effects of surface temperature and groundwater flow on subsurface temperature in Kumamoto Plain, Japan

Groundwater flow systems evaluated from observed hydraulic potentials agree well with the regional and local groundwater flow system estimated from subsurface temperature in Kumamoto Plain. Subsurface temperature could be a good trace to detect the groundwater flow systems. Repeated measurements of groundwater temperature shows that the subsurface temperature increased during the last 15 years due to surface warming in the groundwater recharge area, and decreased in the discharge area because of decreasing in groundwater flow and recharge rates. These results are also supported by the analytical solutions of subsurface temperature to the heat conduction–advection equation under the condition of surface warming.

Hydrogeological and ground-water resource analysis using a geotechnical database

An application of a geotechnical database system for primary evaluation of ground-water resources in a sedimentary basin is proposed. The database consists of 1200 borehole logs including geologic columns,in situ test results, ground-water level, water quality data, and resistivity logs. The Kumamoto plain, situated in southwest Japan, is chosen as a study area. The evaluation process consists of two steps: (1) modeling of shapes of water-bearing strata, and (2) modeling of distribution of physical quantity which has some relationship with the porosity of those strata. In step (1), the shapes of upper and/or lower surface of the pyroclastic flow deposits and the andesitic lava were determined, whereas the three-dimensional distribution model of resistivity was constructed from resistivity logging data obtained from 100 boreholes and using the proposed interpolation method in the step (2). An empirical equation between the porosity and the resistivity of the lava was also identified. The integration of two types of model and the empirical equation contributed to an estimate of the total volume of the ground-water under the study area.

Study for Evaluation of Socio-economic Impact by Sea Level Rise Based on the Unit Values of Land Use in Kumamoto Plain, Kyushu Island, Japan

A rapid sea level rise (SLR) caused by global warming has been predicted by many researchers recently. The rise may have a great impact on human life in coastal regions all over the world. For the reason, a detailed preliminary assessments of the impact is required in order to implement measures to counteract SLR among many governments. SLR will change environmental conditions especially in coastal regions all over the world. The change will induce natural disasters such as various types of floods, land use, vegetation, geomorphological conditions, hydrological circumstances.But the unit value method, that enables us to evaluate the total loss by them easily, was developed based on the idea of the property density, which was calculated by combination with land use information and data of socio-economic properties.In this study, Kumamoto plain was selected as a typical coastal plain in Japan and was also the most suitable area for evaluating affected properties in combination with the unit value method and the ground elevation map.Socio-economic properties includes price of real estate (yen/m2), productivity (yen/m2/year), working population (persons/km2), residential population (persons/km2), household article (yen/m2), and stock (yen/m2). Their density forms each unit value every land use.The following estimation was an extreme case study based on the premise that there is no countermeasure against the future SLR in the Kumamoto plain. If 1 meter SLR occur in future, we can estimate the followings: approximately 10km2 of land is drowned and its value, app. four hundreds of billions yen is lost, app. twenty billions yen of building is inundated, app. 1 billion eight hundreds millions yen per year of productivity is lost, app. ten thousands persons of resident, app. one thousand persons of worker, app. sixteen, billions yen of household article, app. one billions yen of depreciative property and app. one hundred million yen of stock have to be withdrawn inland.This study was carried out for establishing a simple evaluation method of impact by SLR in foreign countries where there is little data. And we could succeed to combine unit value and land use, and gave value of added productivity to land use which is the minimum unit of geographical phenomena.Near future, we may also apply the unit value method for evaluating the loss of various natural disasters easily and rapidly.

Noble gases dissolved in groundwater in a volcanic aquifer: Helium isotopes in the Kumamoto Plain

This study Investigates a tracing method using dissolved noble gases to survey the groundwater flow in a large groundwater basin. The tracing method is based on measuring the concentrations of noble gases and the ratio of helium isotopes in groundwater samples. Since it is very difficult to detect trace amounts of noble gases and helium with high accuracy in a 15-ml groundwater sample, dissolved gases were extracted and purified, then a high-resolution mass spectrometer was used for measurement and comparison with standard samples. We used this method with samples from a confined aquifer formed by the deposition of pyroclastic flow in the Kumamoto Plain on the west side of Mt. Aso in central Kyushu, Japan. The groundwater basin under the plain is divided into four small basins, based on the helium concentrations and isotope ratios, with two major groundwater flows. One flow is buried by the Aso pyroclastic flow along the old Kase River; the other is along the Tsuboi River Valley. These two groundwater flows were identified from the different helium isotope-ratios. The helium component from the deep mantle is mixed into the groundwater under the Kumamoto Plain. Finally, data on the concentrations and ratios of3He to4He in groundwater samples were used to determine the location of faults in the volcanic aquifer.

Development of the Hydrogeological Survey Method Using the Natural Dissolved Noble Gases for the Site-Characterization for Radwastes Disposal

AbstractThis study focused on developing the tracer method using the dissolved natural noble gases. The method measures precisely helium and neon dissolved in groundwater for dating. Since the dissolved helium consists of three different components (Atmospheric He, Radiogenic He and Mantle He), if it is possible to separate total dissolved helium into each component, the mixing rate between young groundwater and ancient will be predicted in in-situ groundwater. Then, dating of young groundwater is determined by measuring tritium and tritiogenic 3He in a groundwater sample. On the other hand, the dating method for old groundwater is not still verified. In this study, the old groundwater age is predicted by the accumulating rate of radiogenic helium through the alpha decay of uranium and thorium contained in rock.This tracing method was applied to a confined aquifer in the Kumamoto plain (10km × 20km ), where the groundwater flow and the geohydrological formation of aquifer was investigated in detail in the past. The groundwater in the area consists of mixture of young groundwater (less than 20 yrs old) and ancient isolated groundwater (more than 1000 yrs old). Furthermore, the drastic change in the helium isotopic ratio revealed unexpectedly the existence of active faults covered in groundwater basins. Consequently, the method using the dissolved noble gases is practicably available for investigating the geohydrologic formation of aquifer at the early stage of the site characterization.

防災分野における衛星リモートセンシングの適用 その可能性と期待

Disasters are originated through very complicated processes in which various conditions and causes are interrelated each other. These conditions and causes are distinguished into two categories, namely, primary cause and inducement.The primary cause includes natural and artificial conditions subject to natural hazards, and the inducement means various natural hazardous phenomena to cause disasters.The informations expecting to be obtained from satellite remote sensing are the ones concerning to the above mentioned primary cause and inducement of wide area, periodic or real time nature which are hardly obtained effectively and economically by the traditional means for observation, measurement and investigation.These informations will be very useful for the technological improvement of three important aspects in disaster prevention as follows: the first is watching and forecasting unusual natural phenomena, the second is exact holding the actual state of a disaster and the third is the estimation of a disaster by exact holding primary cause and inducement likely to occur.The significance of satellite remote sensing in the field of disaster prevention exists in the improvement and promotion of scientific and technological capabilities for the three aspects mentioned above.In this report, the author describes various possibilities and expectations on the application of satellite remote sensing in the field of disaster prevention based on many studies carried out or carried on in and outside of country.As to the first aspect, watching and forecasting for storm rainfall and flash flood, snow coverage and thawing, iceberg, huge volcanic eruption and diffusion of volcanic ash cloud into atmosphere, big forest fire, etc. by means of geosynchronous and orbital satellite data are emphasized. Further, the effectiveness of marine observation in the future by means of active remote sensors such as altimeter, scatterometer and synthetic aperture radar is stressed.For the second aspect, some case studies using Landsat MSS data carried out by the author and his colleagues in the National Research Center for Disaster Prevention are mainly described.The studies include detection of the damage of rice fields due to flooding in the lower Ishikari River basin in 1981 and in Kumamoto Plain in 1982, detection of the coverage of volcanic products due to the eruptions of Ontake Volcano in 1979 and of Miyakejima Volcano in 1983, and detection of landslides due to heavy rainfalls and earthquakes occurred during 1978 to 1984.The effectiveness and usefulness of Landsat MSS data are demonstrated by showing the good coincidence of the analytical results with ground truth data.Concerning to the third aspect, the author describes his ideas how to utilize remote sensing data in this aspect in which estimation methods of disasters such as flood, landslide, volcanic eruption and erathquake are outlined.He put an emphasis on the synthetic use of extracted informations from remote sensing data with other various informations necessary for the estimation of disasters.

44. Subsurface geology of Kumamoto plain : Stratigraphy and geological structure of Aso Pyroclastic Flow deposits.(Abstracts of Papers Submitted for the Meeting of the Society)

44. Subsurface geology of Kumamoto plain : Stratigraphy and geological structure of Aso Pyroclastic Flow deposits.(Abstracts of Papers Submitted for the Meeting of the Society)

Characteristics and classification of an unirrigated anthropogenic-alluvial soil found in the Kumamoto Plain

Abstract In Japan anthropogenic-alluvial soils excluding irrigated rice soils are lagging for behind other genetic soil types in pedological investigations. Although there are some investigations of anthropogenic-alluvial soils used for mulberry plantations, orchards, vegetable gardens, and seeding beds for trees, the main object of these investigations is not pedological. Kanno et al. (1) reported that unirrigated anthropogenic-alluvial soils used for vegetable growing in the Chikugo Plain resemble the “Alochthonous brown warp soil” defined by Kubiena (2). First of all, it is of great importance to accumulate general data for unirrigated anthropogenic-alluvial soils and to develop the classification principles for them. Classification problems will be settled in accordance with the accumulated data. This paper deals with characteristics of an unirrigated anthorpogenic-alluvial soil found in the Kumamoto Plain and with classification principles for it. These principles have almost never been described for a pedological standpoint in Japan.