The birth of sedimentology: Henry Clifton Sorby and Johannes Walther     

Hakuyu Okada  & Alec Kenyon-Smith 《Geology Today》2009,25(6):211-218

Sedimentology is the study of naturally occurring particulate matter with special emphasis on understanding the factors controlling the creation, distribution and accumulation of that matter. Consequently, sedimentology can, and does, embrace geomorphology and climatology, transport mechanisms, depositional environments and lithifaction processes. Its significance lies in the ability of practitioners of the subject—sedimentologists—to determine each and all of the foregoing through the study of samples of sediments and sedimentary rocks. It is, therefore, a basic discipline for the study of past and present environments on Earth, its satellite and its planetary neighbours. The long-standing contributions of two of the nineteenth century founders of the subject, Henry Clifton Sorby (1826–1908) and Johannes Walther (1860–1937), are discussed here.  相似文献   

Methodology for preliminary assessment of Natech risk in urban areas   总被引：1，自引：0，他引：1  

Ana Maria Cruz  Norio Okada 《Natural Hazards》2008,46(2):199-220

Concern for natural hazard-triggered technological disasters (Natech disasters) in densely populated and industrialized areas is growing. Residents living in urban areas subject to high natural hazard risk are often unaware of the potential for secondary disasters such as hazardous materials releases from neighboring industrial facilities, chemical storage warehouses or other establishments housing hazardous materials. Lessons from previous disasters, such as the Natech disaster during the Kocaeli earthquake in Turkey in 1999 call for the need to manage low frequency/high consequence events, particularly in today’s densely populated areas. However, there is little guidance available on how local governments and communities can assess Natech risk. To add to the problem, local governments often do not have the human or economic resources or expertise to carry out detailed risk assessments. In this article, we propose a methodology for preliminary assessment of Natech risk in urban areas. The proposed methodology is intended for use by local government officials in consultation with the public. The methodology considers possible interactions between the various systems in the urban environment: the physical infrastructure (e.g., industrial plants, lifeline systems, critical facilities), the community (e.g., population exposed), the natural environment (e.g., delicate ecosystems, river basins), and the risk and emergency management systems (e.g., structural and nonstructural measures). Factors related to vulnerability and hazard are analyzed and qualitative measures are recommended. Data from hazardous materials releases during the Kocaeli, Turkey earthquake of August 17, 1999 are used as a case study to demonstrate the applicability of the methodology. Limitations of the proposed methodology are discussed as well as future research needs.

Norio OkadaEmail:

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I-1 Wave energy absorption characteristics of circular air chamber for use of light beacon     

Reisaku Inoue  Masami Iwai 《Ocean Engineering》1985,12(6):554-555

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The mineralogy and provenance of deep-sea sediments recovered by gravity corer off Sierra Leone,West Africa     

Hakuyu Okada  Katsutoshi Tomita  E. J. W. Jones 《Journal of Oceanography》1981,37(4):201-211

The mineralogy of eight gravity cores recovered between Sierra Leone and 25°W longitude has been examined in an investigation of the provenance of the recent sediments in the eastern Equatorial Atlantic. X-ray analyses show that the principal mineral components are calcite, quartz, feldspar, kaolinite, illite and montmorillonite. One core taken from the upper continental slope off Freetown also contains gibbsite, a product of intense tropical weathering. Biogenic material forms the dominant component of most sections of the cores but it is clear from the abundance of quartz, kaolinite and freshwater diatoms that an aeolian supply of continental detritus has been important in the formation of the recent sediment cover. A significant contribution from volcanic sources can be recognised to the west of the Sierra Leone Rise. The occurrence of calcareous turbidites in two cores from the St. Paul's Fracture Zone and from the basin west of the Sierra Leone Rise appears to be a reflection of recent tectonic activity.  相似文献   

Dissolution mechanisms of water in depolymerized silicate melts: Constraints from H and Si NMR spectroscopy and ab initio calculations     

Xianyu Xue  Masami Kanzaki 《Geochimica et cosmochimica acta》2004,68(24):5027-5057

Dissolution of water in magmas significantly affects phase relations and physical properties. To shed new light on the this issue, we have applied ¹H and ²⁹Si nuclear magnetic resonance (NMR) spectroscopic techniques to hydrous silicate glasses (quenched melts) in the CaO-MgO-SiO₂ (CMS), Na₂O-SiO₂, Na₂O-CaO-SiO₂ and Li₂O-SiO₂ systems. We have also carried out ab initio molecular orbital calculations on representative clusters to gain insight into the experimental results.The most prominent result is the identification of a major peak at ∼1.1 to 1.7 ppm in the ¹H MAS NMR spectra for all the hydrous CMS glasses. On the basis of experimental NMR data for crystalline phases and ab initio calculation results, this peak can be unambiguously attributed to (Ca,Mg)OH groups. Such OH groups, like free oxygens, are only linked to metal cations, but not part of the silicate network, and are thus referred to as free hydroxyls in the paper. This represents the first direct evidence for a substantial proportion (∼13∼29%) of the dissolved water as free hydroxyl groups in quenched hydrous silicate melts. We have found that free hydroxyls are favored by (1) more depolymerized melts and (2) network-modifying cations of higher field strength (Z/R²: Z: charge, R: cation-oxygen bond length) in the order Mg > Ca > Na. Their formation is expected to cause an increase in the melt polymerization, contrary to the effect of SiOH formation. The ²⁹Si MAS NMR results are consistent with such an interpretation. This water dissolution mechanism could be particularly important for ultramafic and mafic magmas.The ¹H MAS NMR spectra for glasses of all the studied compositions contain peaks in the 4 to 17 ppm region, attributable to SiOH of a range of strength of hydrogen bonding and molecular H₂O. The relative population of SiOH with strong hydrogen bonding grows with decreasing field strength of the network-modifying cations. Ab initio calculations confirmed that this trend largely reflects hydrogen bonding with nonbridging oxygens.  相似文献   

Application of AVO Analysis to Seismic Data for Detection of Gas below Methane Hydrate Stability Zone in Nankai Trough Area     

Masami Hato    Takao Inamori    Alfian Bahar  Toshifumi Matsuoka 《Resource Geology》2004,54(1):105-113

Abstract. For the purpose of development of methane hydrate, occurring in the deep marine subsurface, as a resource, the most important issue is to understand the methane hydrate system (generation, migration and accumulation) as well as to delineate the methane hydrate reservoir properties. We have applied the Amplitude Versus Offset (AVO) analysis to the seismic data acquired in the Nankai Trough, offshore Japan, in order to confirm the occurrence of gas just below the methane hydrate-bearing zone, assuming that gas will show a so-called Class-3 AVO response. Knowledge of the amount and occurrence of gas in the sediment below methane hydrate-bearing zone is one of the keys to understand the methane hydrate system.
We have utilized the qualitative analysis of AVO methodology to delineate how gas is located below the BSR, which is thought to be the reflection event from the interface between the methane hydrate-bearing zone and the underlying gas-bearing zone. In the region of MITI Nankai Trough Well PSW-3, we observe two BSRs separated by 25 ms. After AVO modeling using well data, we applied AVO attribute analysis and attribute crossplot analysis to the seismic data. Finally we applied an offset-amplitude analysis to CMP gather data at specific locations to confirm the results of AVO attribute analysis. The AVO analysis shows that there is very little gas located in the underlying sediment below methane hydrate-bearing zone. This result supports the fact that we could not obtain any clear evidence of gas occurrence just below the methane hydrate-bearing zone in the Nankai Trough well drilling.  相似文献   

Detection of Methane Hydrate-Bearing Zones from Seismic Data     

Takao Inamori  Masami Hato 《Resource Geology》2004,54(1):99-104

Abstract. The MITI Nankai Trough wells were drilled offshore Japan in the Tokai area in 1999 and 2000. The occurrence of methane hydrate was confirmed by various indicators in the borehole logs and from core data. These findings have a large impact on potential future Japanese energy resources and other related-scientific interests.
We first tried to find the methane hydrate-bearing zones using interval velocities derived from NMO velocity analysis. However, this analysis produced poor resolution. To achieve a more detailed delineation of the gas hydrate- and gas-bearing zones, we executed a seismic impedance inversion calibrated by the logs from two of the MITI Nankai Trough wells. Although these two wells are only about 90 m apart, we were able to produce an impedance section with fine detail by adopting a simple initial model and incorporating physical properties of the methane hydrate-bearing zones. The locations of the methane hydrate-bearing zones are readily apparent in the final section.  相似文献   

Damage Evaluation of Agro-meteorological Hazards in the Maize-Growing Region of Songliao Plain,China: Case Study of Lishu County of Jilin Province     

Zhang  Jiquan  Okada  Norio  Tatano  Hirokazu  Hayakawa  Seiji 《Natural Hazards》2004,31(1):209-232

Agro-meteorological hazards such as drought, waterlogging and cool summer occur with very high frequency and affect maize production and social-economic development in the maize-growing region of Songliao Plain, China. Moreover, both the frequency of these hazards and loss from them are considered to be increasing with global warming. The purpose of this paper is to quantitatively analyze the relationships between the fluctuation of maize yield and drought, waterlogging and cool summer, and to evaluate the consequences of these hazards in the maize-growing area of Songliao Plain, taking Lishu county as a case study area based on GIS (Geographic Information System). Crop yield-climate analysis and regression analysis were employed to analyze and quantify relationships between the fluctuation of maize yield and drought, waterlogging and cool summer, and to evaluate the consequences of these hazards. The parameters and model of damage evaluation were presented using weighted comprehensive analysis, and the degree of damage of drought, waterlogging and cool summer to maize production was comprehensively evaluated and regionalized. It is shown that from 1949 to 1990, the negative value years of the fluctuation of maize yield due to meteorological hazards accounted for 55% of seasons, of which 14% was caused by drought, 30% by waterlogging, 4% by cool summer and drought, 9% by cool summer and waterlogging, 13% by drought and waterlogging, 30% by drought, waterlogging and cool summer. Studies on the instability and spatial variation of the fluctuations in maize yield in Lishu county showed that the middle plains are stable areas to climatic influence, while southeastern hills and low mountains, the low lands of the plains along the East Liao River and the western plain are unstable areas in terms of areas in maize yield. The synthetic index of the degree of damage to maize of drought, waterlogging and cool summer showed a strong positive correlation with the ratio of the amount damaged to the normal yield of maize. This suggests that this index can be used to evaluate such damage. The degree of damage of drought, waterlogging and cool summer to maize in Lishu county shows the regional characteristics, which increase gradually from the center to the west and east, this being almost identical with the spatial distribution of the fluctuation of maize yield due to these hazards. This study can be expected to provide the basis for developing strategies to mitigate agro-meteorological hazards and reducing the losses from them, and adjust the medium and long-term distribution of agricultural activities so as to adapt to environmental changes.  相似文献   

Contribution of sea-surface wind curl to the maintenance of the SST gradient along the upstream Kuroshio Extension in early summer     

Naoki Sato  Masami Nonaka  Yoshikazu Sasai  Hideharu Sasaki  Youichi Tanimoto  Ryuichi Shirooka 《Journal of Oceanography》2016,72(5):697-705

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The influence of aerosol particle composition on cloud droplet formation     

A. Hallberg  J. A. Ogren  K. J. Noone  K. Okada  J. Heintzenberg  I. B. Svenningsson 《Journal of Atmospheric Chemistry》1994,19(1-2):153-171

A difference in partitioning between cloud droplets and interstitial air for two chemical species (elemental carbon and sulphur) with different expected behaviour in nucleation scavenging was observed in clouds at Mt. Kleiner Feldberg (825 m asl), near Frankfurt, Germany. The fraction of sulphur incorporated in cloud droplets was always higher than the fraction of elemental carbon. This difference in partitioning has also been observed in fog but under different pollution conditions in the Po Valley, Italy. Both these studies were based on bulk samples. In the present study at Kleiner Feldberg, impactor samples of the particles in the interstitial air and the cloud droplet residuals were taken and a single particle analysis was done on the samples. It was found that, for a given particle size, the majority of particles forming cloud droplets were soluble and that insoluble particles preferentially remained in the interstitial air.  相似文献