Tokyo Bay Area Research Articles

Soil liquefaction in Tokyo Bay area due to the 2011 Tohoku (Japan) earthquake

A devastating earthquake hit the Tohoku and Kanto regions of Japan on 11 March 2011, causing extensive damage to life and property as a result of a large-scale tsunami and damage to nuclear power plants. Although located about 400 km away from the epicentre, many residential and commercial buildings and lifeline facilities in Tokyo Bay area suffered extensive damage due to soil liquefaction and associated ground deformation. This paper discusses the results of the damage investigation conducted in the area after the earthquake, with emphasis on liquefaction-induced damage to buildings, roads, lifelines and other infrastructure. In addition, the performance of ground improved by various remediation techniques is discussed. Finally, lessons learned from the event are summarised.

Stable carbon isotope behaviour of natural seepage of deep underground 13C-rich methane detected along a fault zone and adsorbed in mudstone: Tokyo Bay area, Japan

Abstract Gas was sampled regionally, including by drilling into faults, in the South Kanto gas-field around Tokyo Bay, Japan. Gas samples were collected from cores in a gas sampling container immediately after drilling. A value of δ13C1 = −44.3‰ was obtained for gas in the container and δ13C1 = −36.3‰ for seeping gas in a fault zone. However, typical CH4 in this dissolved-in-water gas-field is mainly depleted in 13C, and δ13C1 values range from −66‰ to −68‰ owing to microbial degradation of organic material. 13C-rich CH4 is so far uncommon in the South Kanto gas-field. Seepages were observed from the surface along the north–south fault zone. The natural gas is stored below the sandstone layer by impermeable mudstone underlying the boundary at a depth of 30 m. Gas seepages were not observed below a depth of 40 m. Gas rises along the fault zone dissolved-in-groundwater up to the shallow region and then separates from the groundwater. 13C-rich CH4 (adsorbed CH4) was found to have desorbed from drilled mudstone core samples taken at depths of 1400–1900 m in the main gas-production strata. Similarly, 13C-rich CH4 was found in black shale overlying the oceanic crust forming part of a sedimentary accretionary prism underling the Tokyo region. It also appears in the spring-water of spa wells, originating at a depth of 1200–1500 m along a tectonic line. Methane generated by microbial degradation of organic material through CO2 reduction in the South Kanto gas-field mainly originates as biogenic gas mixed with a small amount of 13C-rich CH4, derived from thermogenic gas without oil components in strata. It is assumed that 12C-rich CH4 is easily detached from core or pore water through gas production, whereas 13C-rich CH4 is strongly adsorbed on the surfaces of particles. The 13C-rich CH4 rises along the major tectonic line or up the 50 m wide normal fault zone from relatively deep sources in the Kanto region.

東京湾沿岸部埋立地における緑被分布とバッタ類の生息分布との関係について

東京湾沿岸部埋立地における緑被分布とバッタ類の生息分布との関係について

S101012 東日本大震災における関東の地盤被害状況

The 2011 Great East Japan earthquake caused severe liquefaction in Tohoku and Kanto districts. About 27,000 timber houses, a lot of buried sewage pipes and roads were damaged due to liquefaction. In Tokyo Bay area, liquefaction occurred in a wide area from Shinkiba in Tokyo through Urayasu, Ichikawa and Narashino cities to Chiba City Dredged and filled soils must have been liquefied by the earthquake. The very long duration of the main shock and an aftershock 29 minutes later probably induced the severe liquefaction Sidewalks and alleys buckled at several sites, probably due to a kind of sloshing of liquefied ground Moreover, much sand boiled from the ground and the ground subsided significantly because the liquefied soils were very fine Many houses settled notably and tilted. Sewage pipes meandered or were broken, their joints were extruded from the ground, and many manholes were sheared horizontally. This remarkable damage might have occurred due to the sloshing of liquefied ground. In reclaimed land along Pacific Ocean, many facilities were damaged as well as Tokyo Bay area due to liquefaction. In an industry facility, oil fences tilted and machinery rooms sunk.

東北地方太平洋沖地震及びその前震・余震で観測された東京湾岸の長周期地震動

2011年東北地方太平洋沖地震の本震及び前震・余震による記録を用いて、東京湾岸における長周期地震動の検討を行った。本震の速度波形・変位波形には周期約20秒のパルス状の波が認められる。本震の速度応答スペクトル形状には、地点毎の差異は認められるが、周期5～10秒の範囲で顕著なピークは見られない。宮城県沖～茨城県沖で発生した前震・余震でも同様な傾向である。一方、長野県北部の地震では周期5～7秒の卓越が見られ、震源位置により長周期地震動の励起が異なることが確認された。また、本震の周期７～8秒の位相速度は、応答スペクトルに顕著なピークがみられた2007年新潟県中越沖地震の位相速度より早く、周期7～8秒の卓越性状と波動成分の関係が示唆される。

Occurrence of canker of chestnut tree at Ariake of the Tokyo Bay Area in summer of 2010

Occurrence of canker of chestnut tree at Ariake of the Tokyo Bay Area in summer of 2010

Liquefaction of soil in the Tokyo Bay area from the 2011 Tohoku (Japan) earthquake

Immediately following the 11th March 2011 M w 9.0 Tohoku (Japan) earthquake, a field investigation was carried out around the Tokyo Bay area. This paper provides first-hand observations (before or just at the onset of repair) of widespread liquefaction and the associated effects. Observations related to uplift of manholes, settlement of ground, performance of buildings and bridges and the effects of ground improvements are also presented. Recorded ground motions near the Tokyo Bay area were analysed to understand their key characteristics (large amplitude and long duration). Lessons learnt are also presented.

東京都心湾岸部における住宅取得の新たな展開<br>——江東区豊洲地区の超高層マンションを事例として——

東京都心湾岸部における住宅取得の新たな展開<br>——江東区豊洲地区の超高層マンションを事例として——

Down-hole seismometer arrays near Tokyo Bay Area

Down-hole seismometer arrays near Tokyo Bay Area

Numerical simulation on the long-term behavior of CO2 injected into a deep saline aquifer composed of alternating layers

Abstract In this study, numerical simulations are conducted to predict the long-term behavior of CO2 injected into a deep saline aquifer composed of alternating sandstone and shale layers. We carried out a base-case simulation with a conceptual model broadly based on the geological structure underlying the Tokyo Bay area and sensitivity analyses of key parameters. The results show that alternating layers of moderate permeability and capillary pressure without a structural trapping also has considerable capacity of CO2 storage and seal.

Urban‐scale CFD analysis in support of a climate‐sensitive design for the Tokyo Bay area

AbstractRecently, countermeasures against the urban heat island effect have become increasingly important in Tokyo. Such countermeasures include reduction of anthropogenic heat release and enhancement of urban ventilation. Evaluations of urban ventilation require construction of a high‐resolution computational fluid dynamics (CFD) model, which takes into account complex urban morphology. The morphological complexity arises from multi‐scale geometry consisting of buildings, forests, and rivers, which is superimposed on varying topography. Given this background, airflow and temperature fields over the 23 wards of Tokyo were simulated with a CFD technique using a total of approximately 5 billion computational grid cells with a horizontal grid spacing of 5 m. The root mean square (RMS) error of the air temperature between the simulation and observation results at 127 points was 1.1 °C. Using the developed model, an urban redevelopment plan for two districts in metropolitan Tokyo was examined from the viewpoint of air temperature mitigation. Numerical results showed that a reduction by 1 ha in the area covered by buildings increases the area with temperatures below 30 °C by 12 ha. Copyright © 2010 Royal Meteorological Society

Propagation Characteristics of Ulva sp. and Laver in the Yatsu Tidal Flats in Inner Tokyo Bay

The Yatsu Higata wetland is one of the most significant tidal flat areas remaining in Japan. Although the site was officially recognized as an important wetland for migratory bird species in 1993 when it was registered as the Ramsar Convention, the extraordinary growth of Ulva sp. (sea lettuce) in recent years has severely impacted the ecology of the area and has resulted in the widespread death of benthic organisms such as clams and sandworms. Conversely, the crop of laver has decreased along the periphery of the tidal flat area.. This study examined the underlying causes of the increase and decrease in the crops of Ulva sp. and laver populations in the field, respectively. In addition, numerical simulations were performed to estimate the flow movement of Ulva sp. circulating in the inner Tokyo Bay area.

Multifaceted potentials of tire-derived three dimensional geosynthetics in geotechnical applications and their evaluation

Scrapped tire-derived materials, such as tire chips and tire shreds, can be categorized as three dimensional geosynthetics. This paper introduces recent Japanese experience in geotechnical related applications of geosynthetics that focus mainly on tire chips and tire shreds. Three specific applications of tire chips and tire shreds are introduced here. They are: (1) tire shreds to improve drainage; (2) sand-mixed tire chips to mitigate earthquake damage; and (3) tire chips mixed with cement-treated clay to improve toughness and ductility. The developed techniques related to these applications, verification through model testing, as well as element testing and the field applications are presented. It was observed that tire shreds can maintain high permeability even under a high compressive load. When tire chips and/or sand-mixed tire chips are used as a compressible cushion, not only the dynamic load against a structure but also the dynamically induced permanent structural displacement could also be significantly reduced. On the other hand, mixing tire chips with cement-treated clay gives toughness to the geomaterial, and thus provides resistance against the development of cracks during deformation. In addition, an X-ray CT investigation of deformation behavior of such materials demonstrated the success of using cement-treated clay with tire chips as a sealing material to protect leakage of contaminated materials at a waste disposal site in Tokyo bay area.

Geochemical CO2 trapping in open aquifer storage — the Tokyo Bay model

Abstract Numerical simulation using TOUGHREACT software has shown that more than 20Mt of CO 2 can be stored for a period up to 10,000 years in a 2-D model system taking from the geology of the Tokyo Bay area. Carbonate precipitation occurs extensively in the front of enlarging plume, forming a shell enclosing CO 2 . The distribution of dawsonite is predicted to be dependent on the dissolution of plagioclase which presents abundantly in sandstones of the Tokyo Bay area as well as those in young sedimentary strata of Japanese Islands, suggesting its potential importance in the mineral trapping of CO 2 .

東京湾岸地域における地質工学

東京湾沿岸の地域開発/自然の人工改変の変遷の50年を振り返り, この人工改変に地質工学がどのように対応してきたか,基盤の科学・技術である地球科学と地盤工学の論理と知見を取り込み, どのように地質工学の論理体系を作り上げてきたのかを示した. すなわち, 地盤図を地盤地質図にするための論理の転換を行ったこと, ナチュラルアナログの論理を用いて地盤物性を求める手法を示したこと, 地層への物性の組み込みや地盤物性の劣化の論理を展開してきたことなどを, 事例を挙げて示した. これまでの50年の成果を踏まえ, 今後は, 自然の現象論・地盤の物性論・方法論の3つの基本論理とそれらを統合した地質工学を発展させていくことが重要である. 具体的には, シークェンスやナチュラルアナログの論理や手法の展開, また, 地層への4次元物性組み込みの論理の展開, すなわち地盤スケールの物性を求めること, 広域かつ長期の時系列データから自然の地盤特性を評価すること, そして人工改変の自然への影響を予測するために, 自然現象の変化を, 広域かつ同時に把握するツールの開発などがある.

東京港港湾区域内埋立地の生成過程に関する調査と形態学的考察

東京港港湾区域内埋立地の生成過程に関する調査と形態学的考察

地化学・貯留層シミュレーションによる二酸化炭素の地化学トラッピングの検討：東京湾岸モデル

Two dimensional numerical simulation was performed using reactive geochemical transport code TOUGHREACT based on the geology of the Tokyo Bay area to understand long-term geochemical evolution of aqueous and mineral phases after CO2 injection and to elucidate key issues affecting CO2 mineral trapping. The injected CO2 migrates upward in the reservoir (the Umegase Formation) towards the cap rock (the Kokumoto Formation) driven by buoyant force. In the CO2 plume, water pH drops from 7.8 (initial) to 4.9 by dissolution and dissociation of CO2. The acidified water containing CO2 and related species induces mineral dissolution and promotes complexing of dissolved ions, which increase the water density and cause its downward movement to the bottom of the reservoir. This process gives rise to convective mixing which further promotes CO2 solubility trapping. In the peripheral zone of the CO2 plume, the acidified water comes in contact with intact reservoir water, giving rise to the precipitation of calcite (and siderite, in lesser amount). The precipitation of calcite and other carbonates might form a low permeability barrier surrounding the CO2 plume, and is expected to increase the storage security with time. Among newly formed carbonates, calcite becomes the most dominant in a long period after injection cease. Dawsonite, which is occasionally considered to be important in trapping CO2, is found to have limited stability that requires high CO2 partial pressure at the conditions of saline aquifer storage. Our study also finds that the formation of dawsonite is in a close relation to the dissolution of plagioclase, and that its precipitation is strongly suppressed by the formation of kaolinite. After reviewing rates of dissolution of carbonates and feldspars, we conclude that the precipitation of dawsonite is controlled by plagioclase dissolution kinetics which determines the supply of Al as a major constituent of dawsonite. Plagioclase is a dominant clastic mineral in sandstones in geologically young formations of the Japanese Islands. Its dissolution could be a key issue in geochemical modeling of CO2 aquifer storage.

東京都千代田区日比谷公園と江東区新砂における珪藻化石による完新世の古環境復元

We analyzed core samples from two sites in the Tokyo lowland to clarify paleoenvironmental changes that occurred during the Holocene in the northern Tokyo Bay area. The samples are from (1) Core HK, which was bored at Hibiya Park, Chiyoda Ward, Tokyo, and from (2) Core DK, which was bored at Civil Engineering Center Tokyo Metropolitan Government in Koto Ward, Tokyo. Both cores belong to Civil Engineering Center Tokyo Metropolitan Government. Analyses of both lithofacies and diatom assemblages of the cored samples found the following paleoenvironmental changes. The first distinct regression occurred in the early Holocene (11,450-10,600 cal. yrBP) and was followed by one in the high-stand relative sea-level stage at 7,300-6,250 cal. yrBP. Subsequently, two small-scale regressions occurred at 3,600-1,200 cal. yrBP and 1,000 cal. yrBP, respectively. These two regressions were documented by temporal variations in diatom assemblages from marine to brackish-water diatoms to brackish and fresh-water diatoms. During the high-stand stage (7,300-6,250 cal. yrBP), the Hibiya embayment area was inundated with seawater and became part of Paleo-Okutokyo Bay. The marine transgressions and regressions inferred from diatom assemblages in both cores might be correlated with small-scale sea-level fluctuations at one- or two-thousand-year intervals during the Holocene, such as a minor regression during the middle Jomon period, Yayoi regression, and Heian transgression.

A 45-Year Wave Hindcast System in the Inner Bay Areas and Inland Sea of Japan Using SDP Measurements-Based Winds -Tokyo Bay Case-

A long-term wave hindcast system applicable for the wave computations over a 45-year period at an arbitrary location of Tokyo Bay area is reconstructed. Hourly sea wind distributions estimated by making use of an analogy between land-based SDP wind measurement data and coast- and sea-based wind measurement data are given on the coastal sea area and those made by recompiling the NCEP/NCAR reanalysis surface wind product on the open ocean. Wave computation is based on a backward ray tracing model on a nested grid with very high space resolution. Comparison between hindcasts and measurements for wave height over a long period of 10 to 23 years at 5 stations situated inside and outside of Tokyo Bay verified a reasonable performance of the system.

Wet and dry deposition fluxes of trace elements in Tokyo Bay

The annual wet and dry deposition fluxes of As, Cd, Cr, Cu, Hg, Mn, Ni, Pb and V were measured on the basis of data obtained from 2 years of observation (December 2003–November 2005) at three sites in the Tokyo Bay area, which is highly affected by anthropogenic sources. Moreover, the concentrations of these trace elements in the air and bay sediments were determined concurrently. Using these data, we evaluated the factors affecting wet and dry deposition fluxes and the contribution of the atmospheric input of each element to the supply of trace elements to the bay. The order of the average ratios of dry/wet deposition fluxes at three sites was Cr, 6.9>As, 5.9>Mn, 4.7>V, 4.5>Cu, 4.4>Ni, 3.7>Cd, 2.9>Pb, 2.0>Hg, 1.0. Thus, the atmospheric deposition of the trace elements except Hg in Tokyo Bay is predominantly dry deposition. For such trace elements, the wet and dry deposition fluxes within the bay were higher than those inland. Except in the case of some elements, the differences in wet and dry deposition fluxes between these sites were primarily due to the differences in scavenging ratio (=concentration in precipitation/concentration in air) and dry deposition velocity (=deposition flux/concentration in air), respectively, rather than in atmospheric concentration. Also, a significant correlation ( r 2=0.76, P<0.001) was observed between the scavenging ratios and dry deposition velocities of the trace elements. These suggest that large particles from sources in the coastal regions contribute largely to the wet and dry depositions of trace elements to the bay. The contributions of the atmospheric input of the trace elements to the bay ranged from 5% to 26%. Atmospheric deposition seems to have no significant role in the supply of trace elements to Tokyo Bay, suggesting the importance of river and effluent discharges.