Orthopyroxene–cordierite mafic gneiss from the Nomamisaki metamorphic rocks,Southern Kyushu,Japan: Implication for western continuation of the Usuki–Yatsushiro Tectonic Line     

Takeshi Ikeda  Aya Hiramine  Tetsuji Onoue 《Island Arc》2010,19(2):230-242

We describe an orthopyroxene–cordierite mafic gneiss from the Nomamisaki metamorphic rocks in the Noma Peninsula, southern Kyushu, Japan. The mineral assemblage of the gneiss is orthopyroxene, cordierite, biotite, plagioclase, and ilmenite. Thermometry based on the Fe–Mg exchange reaction between orthopyroxene and biotite yields a peak metamorphic temperature of 680°C. The stability of cordierite relative to garnet, quartz, and sillimanite defines the upper limit of the peak metamorphic pressure as 4.4 kbar. These features indicate that the Nomamisaki metamorphic rocks underwent low‐pressure high‐temperature type metamorphism. Although a chronological problem still remains, the Nomamisaki metamorphic rocks can be regarded as a western continuation of the Higo Belt. The Usuki–Yatsushiro Tectonic Line, which delineates the southern border of the Higo Belt, is therefore located on the east of the Nomamisaki metamorphic rocks in southern Kyushu.  相似文献   

Inaugural Address 25:1          下载免费PDF全文

Tetsuji Muto  Yoshihiko Tamura 《Island Arc》2016,25(1):3-3

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The impact of the Wangara experiment   总被引：1，自引：0，他引：1  

G. D. Hess  B. B. Hicks  Tetsuji Yamada 《Boundary-Layer Meteorology》1981,20(2):135-174

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PBL similarity profiles determined from a level-2 turbulence-closure model     

Tetsuji Yamada 《Boundary-Layer Meteorology》1979,17(3):333-351

A diagnostic model for the determination of similarity profiles of turbulence and mean-wind gradient in the planetary boundary layer is developed. Vertical profiles of a turbulence length scale and the flux Richardson number are formulated through the extension of the relationships for the constant flux layer. These profiles together with a turbulence energy equation and a similarity profile empirically determined for heat or momentum flux are used to compute the turbulence energy. Relationships previously derived from a turbulence closure model are used to compute second moments of turbulence.  相似文献   

Infrared device for simultaneous measurement of fluctuations of atmospheric carbon dioxide and water vapor   总被引：3，自引：0，他引：3  

Eiji Ohtaki  Tetsuji Matsui 《Boundary-Layer Meteorology》1982,24(1):109-119

An infrared device designed to measure simultaneous fluctuations of atmospheric CO₂ and water vapor concentrations is described. The measuring frequency is 30 Hz. The sensing path length is 20 cm. It is compatible with the path length of the standard type of a sonic anemometer. The noise level of the device is equivalent to fluctuations of about 0.8 ppm peak-to-peak for CO₂ and 0.02 g kg^-1 peak-to-peak for water vapor. Field tests have showed that the device is suitable for simultaneous measurement of turbulent fluxes of CO₂ and water vapor in conjunction with a sonic anemometer.  相似文献   

Two-dimensional effective stress analysis of liquefaction of irregular ground including soil–structure interaction     

Akira Ohtsuki  Tetsuji Itoh 《地震工程与结构动力学》1987,15(3):345-366

An effective stress method is presented for analysis of seismic response and liquefaction of irregular ground including soil–structure interaction, based on an implicit–explicit finite element method. A pore water pressure is computed with iteration from the total stress considering an undrained condition. The simulated pore water pressure is in reasonably good agreement with the experimental data. The proposed method of analysis is compared with other well-known methods for a one-dimensional model, which is in good agreement. The present effective stress method is also applied to liquefaction problems involving a two-dimensional soil–structure model. The structure is modelled by not only a rigid model but also as a multi-degree-of-freedom system with bi-linear springs. The numerical results are considered to be significant from the viewpoint of earthquake engineering.  相似文献   

Autostratigraphic modelling of the growth of alluvial‐shelf systems during steady base‐level cycles: Two‐dimensional tank experiments     

Junhui Wang  Tetsuji Muto 《Sedimentology》2021,68(1):135-167

Autostratigraphy is the stratigraphy generated by large‐scale autogenesis, developed based on the full recognition of the non‐equilibrium behaviour of depositional systems in response to steady external forcing. The existing autostratigraphic concepts were derived mostly from studies of river deltas growing during a single rise or fall of base level (or relative sea level). The present study challenges to extend the autostratigraphic framework to the alluvial‐shelf system growing through steady base‐level cycles by two‐dimensional tank experiments. During each experimental run, the base level was changed symmetrically, wherein through cycles, the rise and fall had the same constant rate (|R_bl|) and period (T_bl), and thus the same constant amplitude (A_bl), but with no basin tectonism. In total, nine runs with different combinations of |R_bl| and A_bl were performed. The experimental results brought the following implications. (i) The shelf‐transiting active depositional system takes non‐equilibrium responses in earlier base‐level cycles, during each of which the system experiences episodes of degradation with base‐level fall. (ii) After the system has sufficiently grown through cycles, non‐equilibrium responses change into equilibrium responses, whereby the shelf‐transiting alluvial system, whether retrogradational or progradational, is free from degradation and continues to aggrade but with a gradually decreasing rate of aggradation. (iii) The alluvial topset river tentatively but autogenically attains a graded state during the falling limb of an intermediate cycle, which separates the earlier degradation‐inclusive and later aggradation‐sustainable cycles. (iv) The number (or duration) of cycles elapsed prior to this phase‐transition is linearly proportional to the amplitude (or the square of the period) of base‐level cycles, with a coefficient defined by the rates of base‐level change and sediment supply. Such a growth pattern does not necessarily hold when considering long‐term tectonic subsidence or uplift. These notions help to understand the stratigraphic architectures of natural alluvial‐shelf systems evolved through base level cycles.  相似文献   

The Kolmogorov model of bed-thickness distribution: an assessment based on numerical simulation and field-data analysis     

Tetsuji Muto 《地学学报》1995,7(4):417-423

Kolmogorov's model of the distribution of bed thicknesses is assessed by numerical simulations of a sedimentation process, assumed to be a random time-series of alternating depositional and erosional episodes conformable with a stationary Markov process in a state of equilibrium. The study supports the validity of the main point of the model. The random time-series process generates a succession of beds with 'positive' (preserved) and 'negative' (eroded) thicknesses, the frequency distribution of which, f(x), spans the range of positive to negative x -values. The beds with negative thicknesses are absent in the stratigraphic record, whereby the measured bed thicknesses show a frequency distribution, f*( x | x > 0), that is left-side truncated, cut off at the zero thickness value. The numerical simulations further indicate that f( x ) is a 'composite' geometrical distribution, whose actual form changes progressively with p _d, the probability of sediment deposition relative to erosion. The distribution f( x ) invariably has a maximum at x ≤0, such that the truncated distribution f*( x ) for p _d≥0.5 is a simple geometrical distribution regardless of p _d value. The f*( x ) distribution will appear to be a negative exponential distribution when based on the bed-thickness data measured in a conventional metric scale. Data sets from four different turbidite successions in the Cenozoic of Japan, each comprising a few thousand beds, show this type of distribution. However, the sandstone-capping shales in one of the turbidite successions show a truncated Gaussian distribution, attributed to a significant component of non-turbiditic mud. No universal form of bed-thickness distribution can be assumed for the Kolmogorov model. The form of bed-thickness distribution may vary with the type of the depositional process and the character of the sedimentary environment.  相似文献   

Role of autoretreat and A/S changes in the understanding of deltaic shoreline trajectory: a semi-quantitative approach     

Tetsuji Muto  Ron J. Steel 《Basin Research》2002,14(3):303-318

ABSTRACT There is continued interest in how the rate of relative sea‐level rise [A ( > 0)] and the rate of sediment supply [S] function during the growth and evolution of deltaic shorelines. The theory of shoreline autoretreat, recently corroborated in flume experiments, claims that (1) A( > 0) and S can never be in equilibrium, and (2) shoreline or shelf‐edge progradation inevitably turns to retrogradation, when relative sea level is rising even modestly and even if A/S = const (> 0). Autoretreat arises because the area of the clinoform surface of the delta (or shelf edge) per kilometer of shoreline must increase as the relative sea level rises, and the delta (or shelf edge) progrades into deeper water. A finite sediment supply rate is thus liable to become inadequate to sustain progradation. The problem increases further as a rising sea level also greatly increases the delta‐plain volume that needs to be filled, further limiting the progradation of the system. The fundamental trajectory of shoreline migration is thus one characterized by a concave‐landward shape, even under the steady forcing of the basin. The magnitudes of A (> 0) and S, or A/S do not determine whether the landward turnaround of the shoreline is realized or not, but affect merely the length and height of the fundamental trajectory curve. Thus, any attempt to detect and interpret temporal changes in A and S from the observed stratigraphic record of shoreline trajectory needs first to take full account of the inbuilt autoretreat mechanism. We develop here a simple, semi‐quantitative method of reconstructing the basin conditions (A and S) from the stratigraphic record of prograding deltaic shorelines (or prograding shelf‐margin clinoforms) on the basis of the theory of shoreline autoretreat. The deterministic nature of the autoretreat theory is advantageous in managing this latter issue, because any expected or unexpected change emerges as some discrepancy from a trajectory that was predicted for the initial conditions. The autoretreat theory also provides a convenient graphical method of dealing with the uncertainty of the field data, and with evaluating the accuracy of any reconstruction. Our methodology has been developed to deal with the behaviour of deltaic shorelines, but is basically applicable to any clinoform system, the development of which is affected by relative sea level. The suggested method is applied to an Early Eocene (Ypresian) regressive shoreline succession in the Central Tertiary Basin on Spitsbergen. The studied regressive wedge developed as a delta‐driven, progradational shelf‐margin system under a regime of overall (i.e. long‐term) rise of relative sea level, but also suffered short‐term sea‐level falls associated with valley incisions on the coastal plain and shelf. On the assumption that S was constant or was steadily decreasing, the analysis of field data obtained from three sites within the basin suggests that the initial water depth in the basin was around 0.45 km, and that the overall relative sea‐level rise (c. 0.80 km) happened largely during an early time period and was followed by a longer period of much lower rate of rise. This pattern of relative sea‐level rise is consistent with the Palaeogene tectonic subsidence trend of the basin which was determined independently through a geohistory analysis. The uncertainty of the field data does not negate our reconstruction. The combined effects of autoretreat and A/S changes on a deltaic shoreline trajectory are confirmed through the development of an autoretreat‐based methodology. Conventional sequence stratigraphic models that assume a possible equilibrium condition between A and S are both conceptually misleading and insufficient to analyse basin conditions quantitatively. Sequence stratigraphic analyses of shorelines need to incorporate the autoretreat concept.  相似文献   

Landslide detection based on height and amplitude differences using pre- and post-event airborne X-band SAR data     

Uemoto  Jyunpei  Moriyama  Toshifumi  Nadai  Akitsugu  Kojima  Shoichiro  Umehara  Toshihiko 《Natural Hazards》2019,95(3):485-503

Natural Hazards - The recognition of landslides and making their inventory map are considered to be urgent tasks not only for damage estimation but also for planning rescue and restoration...  相似文献