Kanto Plain Research Articles

Human activities, early farming and natural environment in the north-western Kanto Plain (Central Japan) during the Final Jomon–Early Kofun period (990 cal BCE–330 cal CE) inferred from palynological and archaeobotanical records

The emergence, spread and intensification of agriculture, the impact of early agriculture on the natural environment and the possible role of climate on subsistence economies and population dynamics are important research questions in Japanese geoarchaeology. New directly dated archaeobotanical records of the Middle Yayoi (390–200 cal BCE, 1σ error) and Early Kofun (210–330 cal CE) periods from the Ikegami archaeological site and a 1300-year palynological record from the nearby Morinji Marsh help address these questions in the Kanto Plain of Central Japan. The pollen record suggests that management of chestnut and horse-chestnut by Final Jomon people in the study region declined around 750 cal BCE. The microcharcoal record indicates that human-induced fire activity decreased after 990 cal BCE and reached a minimum 500 years later, which coincides with the hemispheric-scale Iron Age Cold Epoch and late Bond event 2. Increasing use of fire from ca. 500 cal BCE is contemporaneous with the earliest evidence of millet-rice cultivation from south-western Kanto and the Central Highlands. This and pollen-based indicators of crop cultivation around Morinji Marsh ca. 200 cal BCE are consistent with the 14C-dated arrival of the first full-scale rice farmers at Ikegami. Their food economy still had a noticeable wild plant component (e.g. beans, walnut, horse-chestnut and acorn), however, the archaeobotanical assemblages from the Early Kofun period show a higher focus on rice cultivation and no evidence of a wild plant component. Variations in the charcoal concentrations and archaeobotanical data from the study region help postulate three phases of farming intensification related to cultural diffusion and/or migration. These phases, dated to ca. 500–300, 300–100 cal BCE and 100 cal BCE–250 cal CE, correspond to the pottery typologically defined late Early–early Middle Yayoi, middle–late Middle Yayoi and Late Yayoi periods, respectively.

Evolution and controlling factors of natural levees during the past 4500 years derived from lowland archaeological ruins in central Kanto Plain, Japan

Lowland archaeological ruins are frequently used in conjunction with sediment cores to reconstruct geomorphological evolution on alluvial plains. Lowland ruins are, as a rule, heterogeneously distributed across alluvial plains and retain short chronological records when compared to sediment cores. Along the historic banks of the Tone River, in the central Kanto Plain, thorough surveying prior to major construction projects in the Tokyo metropolitan area uncovered a dense swath of lowland archaeological ruins. This study demonstrates the evolution of natural levees during the past 4.5 kyr by compiling data from uniformly distributed lowland archaeological ruins in the central Kanto Plain. The location and age of 774 lowland archaeological ruins and 101 radiocarbon dates from surficial fluvial sediments in 42 sediment cores were compiled and arranged chronologically. As a result, levees and river terraces aged < 4.5 ka were found to be contiguous with modern sedimentology in the Arakawa Lowland, while relatively young natural levees aged < 2.8 ka are contiguous with the present Nakagwa Lowland. The Tone River migrated from the Arakawa Lowland to the Nakagawa Lowland at ∼5 ka. Subsequently, sea levels lowered between 4 ka and 3 ka. Due to sea level lowering, a minor tributary of the Tone River partially eroded the alluvial plain, and relatively old geomorphology persisted in the Arakawa Lowland. In contrast, in the Nakagawa Lowland, the major tributary of the Tone River eroded the entire alluvial plain. Following sea-level rises up to 2 ka, natural levees aggraded and formed new surface sediments in the Nakagawa Lowland due to large sediment discharge from the major tributary of the Tone River. Natural levee evolution in the central Kanto Plain is influenced by both river migration and sea-level fluctuation.

The Design of a Parameterization Scheme for 137Cs Based on the WRF-Chem Model and Its Application in Simulating the Fukushima Nuclear Accident

Based on the Weather Research and Forecasting Model Coupled with Chemistry (WRF-Chem) atmospheric chemistry model, a parameterization scheme for the radioactive isotope caesium (137Cs), considering processes such as advection, turbulent diffusion, dry deposition, and wet deposition, was constructed, enabling the spatial distribution simulation of the concentration and deposition of 137Cs. The experimental simulation studies were carried out during the high emission period of the Fukushima nuclear accident (from 11 to 17 March 2011). Two sets of comparison experiments, with or without deposition, were designed, the effects of wind field and precipitation on the spatial transport and ground deposition of 137Cs were analyzed, and the influence of wind field and precipitation on 137Cs vertical transport was analyzed in detail. The results indicate that the model can accurately simulate the meteorological and 137Cs variables. On 15 March, 137Cs dispersed towards the Kanto Plain in Japan under the influence of northeastern winds. In comparison to the experiment without deposition, the concentration of 137Cs in the Fukushima area decreased by approximately 286 Bq·m−3 in the deposition experiment. Under the influence of updrafts in the non-deposition experiment, a 137Cs cloud spread upward to a maximum height of 6 km, whereas in the deposition experiment, the highest dispersion of the 137Cs cloud only reach a height of 4 km. Affected by the wind field, dry deposition is mainly distributed in Fukushima, the Kanto Plain, and their eastern ocean areas, with a maximum dry deposition of 5004.5 kBq·m−2. Wet deposition is mainly influenced by the wind field and precipitation, distributed in the surrounding areas of Fukushima, with a maximum wet deposition of 725.3 kBq·m−2. The single-station test results from the deposition experiment were better than those for the non-deposition experiment: the percentage deviations of the Tokyo, Chiba, Maebashi, and Naraha stations decreased by 61%, 69%, 46%, and 51%, respectively, and the percentage root mean square error decreased by 46%, 25%, 38%, and 48%, respectively.

Impacts of Local Topography on Snowfall Distribution in the Kanto Plain: A Case Study

Impacts of Local Topography on Snowfall Distribution in the Kanto Plain: A Case Study

The climatology of cold‐air damming in the Kanto Plain, Japan

AbstractThe climatological characteristics of cold‐air damming (CAD) were statistically investigated on the Kanto Plain throughout the year. We detected 397 CAD events from 1991 to 2020 using hourly surface observation data from the Japan Meteorological Agency. The statistical analyses revealed the following characteristics: (1) CAD is most frequent in autumn followed by spring; (2) strong CAD is more frequent in the cold season than in the warm season; (3) The long‐term trend in CAD frequency is not obvious; (4) 53% of the events finish in 12 h or less, and 17% of them continue for 24 h or more. CAD with precipitation tended to be stronger than that without precipitation, and the latter was more frequent in the nighttime than in the daytime, indicating the contribution of diabatic processes to the development of CAD. Analysis of synoptic fields in CAD cases using long‐term reanalysis data revealed six patterns that differed in the intensity and position of surface highs and lows, corresponding to the typical seasonal sea level pressure fields.

Future projections of wet snow accretion and snowfall in Kanto Plain, Japan, using a large ensemble climate simulation

AbstractSnowfall and wet snow accretion in the Kanto Plain, including the Tokyo Metropolitan Area, significantly impact the lives of people there. This study used a large ensemble simulation to predict future changes in the frequency of snowfall and wet snow accretion, and the accumulated snowfall and wet snow accretion during an event. We assessed wet snow accretion using a model that considers the effects of temperature, precipitation, wind speed, and humidity. The future snowfall event frequency and accumulated snowfall were predicted to decrease by 0.73 year−1 (61%) and 0.69 mm (11%), respectively, under +2‐K future climate projections from those under the present climate. 87% and 13% reduction in future snowfall events was due to increasing temperature and reduced frequency of extratropical cyclone passages, respectively. Moreover, the future frequency of wet snow accretion events and accumulated wet snow accretion are predicted to decrease by 0.84 year−1 (90%) and 0.73 kg m−1 (29%), respectively, from those in the present. 91% and 9% reduction in future wet snow accretion events was due to increasing temperature and reduced frequency of extratropical cyclone passages, respectively. Snowfall and wet snow accretion risk are predicted to decline under the +2‐K future climate projections from those under the current climate. The risk can decrease more significantly in the coastal areas than in the inland areas. We hope that the information provided in this study will help policymakers of local governments in the Kanto Plain to implement appropriate measures against future snowfall and wet snow accretion.

Transition of Woodlands around Farmyards at Settlements in the Northwestern Part of the Kanto Plain

Transition of Woodlands around Farmyards at Settlements in the Northwestern Part of the Kanto Plain

関東平野内陸部における水位回復期以降の浅層地下水について −水理水頭と地下水流動の一時的変化−

関東平野内陸部における水位回復期以降の浅層地下水について −水理水頭と地下水流動の一時的変化−

Variability of Future Increases in Summertime Extreme High Temperatures on the Kanto Plain, Japan

Variability of Future Increases in Summertime Extreme High Temperatures on the Kanto Plain, Japan

Quantitative influences of interannual variations in meteorological factors on surface ozone concentration in the hot summer of 2018 in Japan

In this study, the high surface O 3 episodes in the hot summer in Japan in July 2018 are studied using two models, NHM-Chem and ASUCA-Chem. The model performances are similar to each other with both models tending to overestimate the observed surface O 3 by ∼5–10 ppbv. The meteorological factors causing the interannual changes of surface O 3 are investigated through sensitivity tests of NHM-Chem using meteorological fields of different years, i.e., July 2007 and 2012. July 2007 and 2012 represent cold and normal summers, respectively, with respect to the monthly mean surface temperature in Japan. The hot summer provides favorable conditions for the O 3 formation, such as a higher temperature and a higher solar radiation. However, the monthly mean surface wind speed in July 2018 is greater than that of the other periods, causing a negative effect on the monthly surface O 3 concentrations because of faster dilution and diffusion in certain locations. Over the Kanto plain, which is the most populated region of Japan, the monthly mean surface temperature is ∼2 K higher than the normal values; however, both observation and simulation demonstrate that the monthly mean surface O 3 is lower than the normal temperature summer (July 2012) by 4–6 ppbv. The sensitivity tests indicate that the enhanced biogenic volatile organic compound emissions increase surface O 3 by 4–5 ppbv, but the wind field changes decrease surface O 3 by 9–10 ppbv. Heat wave is associated with high surface O 3 episodes; however, the monthly mean value is a mixed result of many other meteorological events in addition to the heat wave. The interannual changes in the monthly surface O 3 can vary depending on magnitude of the positive and negative effects at each location. • Monthly surface O 3 in hot summer is studied by ASUCA-Chem and NHM-Chem. • Increased BVOC emission due to higher temperature enhanced monthly surface O 3 . • Greater wind speed during the period results in decreased monthly surface O 3 .

A 3-kyr plateau of middle Holocene higher sea levels on the central Kanto Plain, Japan

Middle Holocene higher sea levels during 7–4 ka in Asia, Australia, and South America varied in duration and stability. Abundant archaeological excavations have been carried out in the Tokyo urban area, which is situated on the alluvial and coastal lowlands of the central Kanto Plain. In this study, 74 sea-level index points and 241 limiting data points were compiled from Japanese scientific papers and excavation reports for 109 locations on the central Kanto Plain. These data suggest that the relative mean sea level changed from −4 ± 1.5 m at 8 ka to 3 ± 1.5 m during 7–4 ka, to −1.5 ± 1 m at 3 ka, and then to 0 ± 1 m during 2–0 ka. During the 7–4-ka sea-level plateau on the central Kanto Plain, the sea level did not fluctuate. The height distribution at 52 locations on the central Kanto Plain shows that sea level remained stable for 3 kyr, with no local differences in the duration, in an area of 90 km × 90 km. The temporary sea-level drop at 3 ka corresponds to the “Yayoi regression”, which has been previously reported on the central Kanto Plain, although its driving mechanism is unknown. Crustal deformation can be neglected as less important than the spring tidal range, which was ca. 3 m at 7 ka on the central Kanto Plain. By using a dense dataset to confirm the occurrence of a middle Holocene higher sea-level plateau on the central Kanto Plain, this study strongly suggests that glacier melting occurred two steps, at 7 ka and 4 ka.

Luminescence chronology for identifying depositional sequences in an uplifted coast since the Middle Pleistocene, eastern Japan

Feldspar post-infrared infrared stimulated luminescence (pIRIR) dating is an advantageous trapped-charge dating method concerning late Quaternary sedimentary records for its direct applicability to clastic sediments and wide time coverage. Its application to depositional sequences in various coastal settings potentially improve our understanding of long-term sea-level changes and regional tectonics that the sequences record. The Kanto coastal plain, eastern Japan is situated in a unique tectonic setting near the triple junction of plate boundaries and characterized by extensive development of the Last Interglacial raised marine terrace in contrast to the longer-term subsidence trend. In this article, we document the application of feldspar pIRIR dating to a 35-m-long sediment core collected from the marine terrace in the northeastern Kanto plain and examine how effective its chronology is for identifying depositional sequences related to the relative sea-level fluctuations since the Middle Pleistocene. The sediment core shows a succession of seven facies units, A to G, in ascending order, representing the shallow marine to shelf (units A to C), fluvial to brackish salt marsh (unit D), beach to shoreface (unit E), fluvial to aeolian (unit F), and loess (unit G) sedimentation. According to pre-tests, pIRIR at 225°C after prior infrared stimulated luminescence at 50°C (pIRIR225) was chosen as an optimal signal for dating. pIRIR225 is characterized by modest anomalous fading with an average g2days-value of 1.8%/decade. Fading-corrected pIRIR225 ages are consistent with the stratigraphy. Units A and B are dated as Marine Oxygen Isotope Stage (MIS) 7 and units C to F as MIS 5. However, uncertainties of individual age estimates do not allow further chronological correlation. Instead, using sea-level changes inferred from characteristic facies transitions as additional constraints, units C to F can be correlated to sub-stages in MIS 5. Unit E represents coastal progradation during the MIS 5c sea-level highstand, which refines the date of the marine terrace around the core site as MIS 5c and revises up the rate of the tectonic uplift accordingly. Our results exemplify a successful application of feldspar pIRIR dating for identifying depositional sequences formed in relations to 100-kyr glacial cycles, in which, with additional information of the sedimentary facies, higher-frequency sequences may be defined.

Coastal progradation associated with sea-level oscillations in the later phase of the Last Interglacial period, central Japan

Stratigraphic records of minor sea-level highstands in Marine Oxygen Isotope Stage (MIS) 5c and 5a are valuable archives of late Pleistocene sea levels and paleoenvironments, but have been identified less commonly in siliciclastic coastal systems than the highstand of MIS 5e. In the Kanto Plain, central Japan, the Iioka terrace comprises the seaward margin of the uplifted Last Interglacial (MIS 5) marine terrace. Sedimentological characterization, post-infrared infrared stimulated luminescence (pIRIR) dating, and tephra and paleontological analyses of the Iioka terrace allow identification of a wave-dominated coastal sedimentary system that prograded onto the Pliocene-Pleistocene basement during MIS 5c and 5a. The pIRIR ages of the coastal deposits range from ca. 80 to 112 ka and define a seaward younging trend, which is corroborated by the seaward lowering of the terrace surfaces. In an outcrop in the seaward part, two pIRIR ages were obtained above and below the tephra layer On-Pm1 (95.7 ka), supporting the general validity of the pIRIR chronology. The elevation of beach facies in the landward part (ca. 53 m above the present sea level) abruptly lowers (to ca. 37 m) and is further truncated by fluvial incision in the seaward part. The pIRIR ages include uncertainties that prevent distinction between MIS 5c and 5a. However, the abrupt and large gap in the beach levels between the central and seaward parts suggests the presence of a minor unconformity between MIS 5c and 5a; contemporary uplift may account for the gap. The Iioka terrace is thus interpreted as representing the successive downdip accretion of depositional sequences controlled by relative sea-level changes in the later Last Interglacial period. The refined characterization of the Iioka terrace allows reevaluation of the tectonic uplift rate of this area as ca. 0.7 mm/yr, twice the rate assuming correlation of the deposits with MIS 5e. Such refinement is likely elsewhere if marginal marine terraces are characterized in detail, as carried out here.

Phylogeographic analysis of Ligidium japonicum (Isopoda: Ligiidae) and its allied species reveals high biodiversity and genetic differentiation in the Kanto region, Japan

AbstractResearch of the diversity and evolutionary history of Japanese soil invertebrates is scarce. Molecular data analysis can help to elucidate species classifications and evolutionary processes. We analyzed the mitochondrial cytochrome oxidase subunit I (COI) and nuclear 28S rDNA genes and the morphology of the male pleopod 2 endopod of Ligidium japonicum and its allied species from 67 sites in Hokkaido, Honshu and Shikoku, where only L. japonicum is thought to occur. We found males of the L. japonicum complex with a pleopod 2 endopod morphology matching that of the L. japonicum syntype specimens, except for the number of denticles at the inner margin. There were also more than five species that differed morphologically from the L. japonicum complex, and most of these species had allopatric distributions despite the absence of obvious barriers. A time‐calibrated molecular phylogeny implied that the L. japonicum complex of the Kanto region first differentiated allopatrically in the mountains; this was followed by independent dispersal of three lineages to the Kanto Plain and Boso Peninsula, where secondary contact occurred. Two of the three sympatrically distributed L. japonicum complex lineages had a significant difference in the number of denticles at the inner margin of male pleopod 2 endopods. This variation implies the presence of cryptic species within the L. japonicum complex.

Tornadogenesis in a Quasi-Linear Convective System over Kanto Plain in Japan: A Numerical Case Study

Abstract The environmental characteristics and formation process of a tornado spawned by a quasi-linear convective system (QLCS) over Kanto Plain, Japan, are examined using observations, a reanalysis dataset, and a high-resolution numerical simulation with a horizontal grid spacing of 50 m. The QLCS environment responsible for tornadogenesis was characterized by small convective available potential energy and large storm-relative environmental helicity due to strong vertical shear associated with a low-level jet. The strong low-level jet was associated with a large zonal pressure gradient between two meridionally aligned extratropical cyclones and a synoptic-scale high pressure system to the east. The numerical simulation reproduced the tornado in the central part of the QLCS. Before the tornadogenesis, three mesovortices developed that were meridionally aligned at 500-m height, and a rear inflow jet (RIJ) associated with relatively cold air originated from aloft and developed on the west side of the QLCS, while descending from rear to front. Tornadogenesis occurred in the southernmost mesovortex at the northern tip of the RIJ. This mesovortex induces strong low-level updrafts through vertical pressure gradient force. A circulation analysis and vorticity budget analysis for the mesovortex show that environmental crosswise vorticity in the forward inflow region east of the QLCS played a significant role in the formation of the mesovortex. The circulation analysis for the tornado shows that frictional effects contribute to the increase of circulation associated with the tornado. Moreover, environmental shear associated with horizontal and vertical shear of the horizontal wind also contribute to the circulation of the tornado.

Development of InSAR Neutral Atmospheric Delay Correction Model by Use of GNSS ZTD and Its Horizontal Gradient

Interferometric Synthetic Aperture Radar (InSAR) often suffers from atmospheric disturbances due to the microwave propagation delay effect, which limits the surface displacement detection accuracy to an order of centimeters or more. Here I developed a new neutral atmospheric delay correction model for InSAR by using the global navigation satellite system (GNSS) zenith total delay (ZTD) and its horizontal gradient data. The proposed model at first retrieves the regularly gridded ZTD distribution at sea level and the linear height dependence from GNSS ZTD and gradient observations by the least squares method. Then, the gridded ZTD is projected onto the InSAR coordinate to correct the neutral atmospheric delay. I evaluated the correction model performance by applying it to L-band ALOS-2/PALSAR-2 ScanSAR interferograms over the Kanto plain in Japan. The correction result showed that by applying the proposed delay correction the phase standard deviation decreased by 33.87 % on average. By comparing it with the generic atmospheric correction online service for InSAR (GACOS) model and the correction by the Japanese regional mesoscale weather model (MSM), the proposed GNSS-based model outperformed others in my test case. The sensitivity test indicated that including the delay gradient could improve delay reproducibility under situations with fewer available GNSS stations. Although the proposed correction model&#x2019;s applicability depends on the number of available GNSS stations at the area of interest, the proposed model has a potential to effectively mitigate the neutral atmospheric delay and to improve the detection ability for smallamplitude surface displacements.

Basal topography of the post-LGM incised-valley fills beneath the central area of the Kanto Plain, Japan

Basal topography of the post-LGM incised-valley fills beneath the central area of the Kanto Plain, Japan

Marker Tephra Layers Indicating the Lowest Part of the Quaternary System Found in the Moroyama Hills and Kawajima Core, Western Kanto Plain, Central Japan

Vitric tephra layers named Ushinosawa tephra from the Moroyama Hills in the western Kanto Plain, and KJT-380.5 tephra and KJT-384.15 tephra from the 600 m-long Kawajima core in the central part of Kanto Plain are described. Magnetic polarities suggest these tephra layers are intercalated at the lowest part of the Matuyama choronozone. Ushinosawa and KJT-380.5 tephra layers are characterized by low K2O concentration in volcanic glass, and can be correlated with Reiho tephra of the Tokai Group in Suzuka City, Mie Prefecture. KJT-384.15 tephra is characterized by a high K2O concentration in volcanic glass and can be correlated with newly described Onbebashi 1 and 2 tephras of the Tokai Group. These tephra layers can be considered to be wide spread marker tephras. This is the first report on widespread marker tephras just above the Gauss–Matuyama boundary in Japan. These marker tephra layers are expected to be a valuable key bed for exploring the Neogene–Quaternary boundary in various parts of Japan in the future.

Basic performance of a spatial autocorrelation method for determining phase velocities of Rayleigh waves from microtremors, with special reference to the zero-crossing method for quick surveys with mobile seismic arrays

SUMMARY We theoretically and empirically demonstrate the usability of the zero-crossing method for quick microtremor surveys in earthquake engineering (i.e. microtremor array surveys), namely shallow (&amp;lt; a few kilometres) surveys with small-scale (&amp;lt; 1 kilometre in radius) mobile seismic arrays with a short observation time (&amp;lt; a few hours). The zero-crossing method is a type of spatial autocorrelation (SPAC) method that determines phase velocities based on multiple frequencies at which the SPAC coefficient curve crosses zero. It is theoretically shown that the zero-crossing method is robust against incoherent noise and that the use of the first zero crossings (i.e. those at the lowest frequencies) is more robust against inadequate conditions of the microtremor wavefield than the use of later zero crossings (i.e. those at higher frequencies). We used microtremor array data with maximum array radii and observation durations of 400 m and 120 min on average, respectively, at 445 observation sites in the Kanto Plain, Japan, for validating the practicality of using the first zero crossings. As an illustration of the robustness against low signal-to-noise ratios (SNRs), we show that with the zero-crossing method, low-sensitivity (i.e. low-SNR) seismometers provide the same analysis results as those obtained with high-sensitivity seismometers, even when the power spectral densities for the low-sensitivity seismometers are close to the self-noise level. We then show that a reference phase velocity dispersion curve (RPVDC), created mainly based on the first zero crossings at each site, has a spatial distribution that well corresponds to the geology and topography and is consistent with that obtained in a previous study. We inverted five RPVDCs to model 1-D S-wave profiles and validated them using S-wave profiles obtained from velocity logs at nearby deep (e.g. hundreds of metres) boring wells. The accuracy of phase velocities at the later zero crossings for three-sensor/four-sensor arrays and all zero crossings for two-sensor arrays are statistically examined (maximum of 9805 data) based on a comparison with the RPVDCs. The disadvantage of the zero-crossing method is that it can only provide information on phase velocities at discrete wavelengths up to a maximum wavelength of 2.6r (i.e. corresponding to the first zero-crossing point), where r is the radius of a seismic array. Therefore, the RPVDCs were then used to examine the upper limit of the analysable wavelength ranges for the conventional SPAC method for microtremor array surveys. Based on a few hundred three-sensor/four-sensor arrays, it was found that for arrays with radii larger than several tens of metres, three-quarters of the upper limit wavelengths (ULWs) stayed within 5r. For arrays with radii smaller than this value, the ULWs strongly depended on the array radius; the ULWs dramatically increased with decreasing array radius. For example, for arrays with an r value of 0.6 m, half of 336 data ranged between 26r and 54r, and the maximum ULW reached 186r. This strong size dependence can be explained by differences in SNR.

Inversion of Love waves in earthquake ground motion records for two-dimensional S-wave velocity model of deep sedimentary layers

We propose a new waveform inversion method to estimate the 2D S-wave velocity structure of deep sedimentary layers using broadband Love waves. As a preprocessing operation in our inversion scheme, we decompose earthquake observation records into velocity waveforms for periods of 1 s each. Then, we include in the inversion only those periods for which the assumption of 2D propagation holds, which we propose to determine through a principal component analysis. A linearized iterative inversion analysis for the selected Love wave segments filtered for periods of 1 s each allows a detailed estimation of the boundary shapes of interfaces over the seismic bedrock with an S-wave velocity of approximately 3 km/s. We demonstrate the effectiveness of the technique with applications to observed seismograms in the Kanto Plain, Japan. The differences between the estimated and existing velocity structure models are remarkable at the basin edges. Our results show remarkable differences from previous existing structural models, particularly near the basin edges while being in good agreement with the surface geology. Since a subsurface structure at a basin edge strongly affects the earthquake ground motions in a basin with the generation of surface waves, our method can provide a detailed model of a complex S-wave velocity structure at an edge part for strong ground motion prediction.