Characteristics and climatic sensitivities of runoff from a cold‐type glacier on the Tibetan Plateau

Model calculations are made in order to understand the characteristics and response to climate change of runoff from a cold glacier on the Tibetan Plateau. Some 20% of meltwater is preserved at the snow–ice boundary due to refreezing, since the glaciers in mid to northern Tibet are sufficiently cooled during the previous winter. Sensitivity to alterations in meteorological parameters has revealed that a change in air temperature would cause not only an increase in melting by sensible heat, but also a drastic increase in melting due to lowering of the albedo, since some of the snowfall changes to rainfall. In addition, it was suggested that a decrease in precipitation would cause a lowering of the surface albedo, with a resulting increase in the contribution of glacier runoff to the total runoff of river water. This study shows the first quantitative evaluation of the above effects, though they have been suggested qualitatively. The seasonal sensitivity of glacier runoff was examined by changing the dates given for a meteorological perturbation for a period of only 5 days. It was revealed that changes in both air temperature and precipitation during the melting season strongly affected glacier runoff by changing the surface albedo, though these perturbations only slightly altered the annual averages. Copyright © 2006 John Wiley & Sons, Ltd.     

The comoving-frame equation of radiative transfer in relativistic flows

The comoving-frame equations of radiative transfer and moment equations to accurate terms of all orders inv/c are derived in the modified Lagrangian form. The equations exactly describe the interaction of radiation with matter in a relativistically moving medium in flat or curved spacetime. Two specialized sets of equations are presented: (1) the equation of radiative transfer and moment equations accurate to terms of second order (v ²/c ²), and (2) the transfer equation and moment equations for a radial flow in curved spacetime with the Schwarzschild-type metric.     

Basic theory of three-dimensional landslide modeling based on the logical model of geologic structure

Dynamic visualization of landslide cross-sections is important for understanding the structure and mechanism of landslide formation. Moreover, the modeling of geologic information plays an effective role in geo-hazard assessment and their mitigation. In this study, we developed the basic theory of a three-dimensional landslide modeling and applied it to the Nigawa landslide of the Hyogo Prefecture in central Japan. The construction of this model is based on the boundary surfaces of slump blocks and geologic units, and the hierarchical relationships between these surfaces. An application algorithm was validated and the model proved efficient in depicting the nature of landslides in the Nigawa area.     

Heating experiments of the Tagish Lake meteorite: Investigation of the effects of short‐term heating on chondritic organics

We present in this study the effects of short‐term heating on organics in the Tagish Lake meteorite and how the difference in the heating conditions can modify the organic matter (OM) in a way that complicates the interpretation of a parent body's heating extent with common cosmothermometers. The kinetics of short‐term heating and its influence on the organic structure are not well understood, and any study of OM is further complicated by the complex alteration processes of the thermally metamorphosed carbonaceous chondrites—potential analogues of the target asteroid Ryugu of the Hayabusa2 mission—which had experienced posthydration, short‐duration local heating. In an attempt to understand the effects of short‐term heating on chondritic OM, we investigated the change in the OM contents of the experimentally heated Tagish Lake meteorite samples using Raman spectroscopy, scanning transmission X‐ray microscopy utilizing X‐ray absorption near edge structure spectroscopy, and ultraperformance liquid chromatography fluorescence detection and quadrupole time of flight hybrid mass spectrometry. Our experiment suggests that graphitization of OM did not take place despite the samples being heated to 900 °C for 96 h, as the OM maturity trend was influenced by the heating conditions, kinetics, and the nature of the OM precursor, such as the presence of abundant oxygenated moieties. Although both the intensity of the 1s?σ* exciton cannot be used to accurately interpret the peak metamorphic temperature of the experimentally heated Tagish Lake sample, the Raman graphite band widths of the heated products significantly differ from that of chondritic OM modified by long‐term internal heating.     

Small-Amplitude Disturbances in a Radiating and ScatteringGrey MediumI. Solutions of Given Real Frequency ω

We reanalyze the propagation of one-dimensional small-amplitude disturbances of given real frequency ω in a radiating and scattering grey medium using the Eddington approximation, which has been studied previously by us (Kaneko et al., 1976). Numerical results reveals three frequency regimes to be distinguished, and two wave modes always appear in each frequency regime. The governing equations and analytic solutions are derived for all wave modes using Whitham's method modified into quadratic form and approximate methods based on radiation thermodynamics. In the high-frequency regime appear the radiation-wave and adiabatic sound modes, which are damped by opacity and radiative cooling, respectively. Wave patterns in the intermediate-frequency and low-frequency regimes depend critically on the importance of radiation, for which the criterion is given in terms of the ratio of total specific heats at constant pressure and constant volume. When the radition overwhelms the matter (radiation-dominated case), the radiative mode in the intermediate-frequency regime is the constant-volume diffusion mode. When the matter overwhelms the radiation (matter-dominated case), damped radiation-wave and damped radiation-diffusion modes newly appear between the radiation-wave and constant-volume diffusion modes. The acoustic mode in the intermediate-frequency regime is the isothermal sound mode,which is damped by radiative cooling at higher frequencies and by radiation-thermal drag force at lower frequencies. Two modes appearing in the low-frequency regime are the isentropic radiation-acoustic and constant-pressure diffusion modes. The absorption coefficient derived for the former is shown to be a radiation-thermodynamic extension of that of Landau and Lifshitz (1987). The transition frequencies between all adjacent two modes are also derived to discuss the implications of them. This revised version was published online in July 2006 with corrections to the Cover Date.     

Horizontal displacements in Japan

Recent horizontal displacements in Japan are discussed by using the results of the first-order triangulation surveys. Large horizontal displacements are found in East Hokkaido, Tohoku, South Kanto, Tokai and Nankai districts (Fig.1). Crustal activity in these districts is also briefly discussed. The original triangulation survey in Japan neglected Laplace (azimuth) observations and consequently rotation and divergence around the assumed fixed point often appear as horizontal displacements. This is especially true in the central Japan where horizontal displacements result from cancelling the apparent rotation and divergence around the assumed fixed point (Fig.2).On the other hand, strain measurements avoid such shortcoming. Considering with the results of the first triangulation, the horizontal earth-strain can be calculated for every subsequent triangulation net. It is interesting that the velocity of the maximum shear strain is almost 2–3 · 10^/t7/year throughout Japan (Fig.3), even though the seismic activities show large regional discrepancies.     

Theoretical and experimental dynamic behaviour of a curved model bridge structure

Correlations between analytical and experimental seismic responses of a curved model bridge structure, which was constructed to have the same features as a typical full-scale high curved highway bridge structure, are presented. Dynamic behaviour and seismic response of the experimental bridge model are examined with particular emphasis on the discontinuous behaviour of expansion joints. Modelling of Coulomb type friction with slippages and impacting at the expansion joints is described. Correlations of displacement response of the bridge model carried out for three seismic excitations are presented. Parameter studies conducted to assist in the interpretation of correlation results are presented and the characteristics of the dynamic behaviour of the bridge model are discussed.     

Latitudinal changes in larger benthic foraminiferal assemblages in shallow-water reef sediments along the Ryukyu Islands, Japan

Abstract The taxonomic diversity of hermatypic corals decreases with increasing latitude, which correlates with sea‐surface temperatures. However, little is known about latitudinal changes in the taxonomic diversity and biogeographic patterns of larger benthic foraminifera, although their physiological requirements are similar to those of hermatypic corals because of their symbiotic relationships with microalgae. The present study examined how the abundance and taxonomic composition of larger foraminiferal assemblages in shallow‐water reef sediments change with latitude along the Ryukyu Islands (Ryukyus), which are located near the northern limit of coral‐reef distributions in the western Pacific Ocean. Three islands from different latitudes in the Ryukyus were selected to investigate latitudinal changes in larger foraminiferal assemblages: Ishigaki Island (24°20′N, 124°10′E), Kudaka Island (26°09′N, 127°54′E) and Tane‐ga‐shima Island (30°20′N, 131°E). Four sediment samples were taken at each of three topographic sites (beach, shallow lagoon and reef crest) on the reef flat of each island. Foraminiferal tests of a 2.0‐ to 0.5‐mm size fraction were selected, identified and counted. The variations in foraminiferal abundance in reef sediments from three latitudinally different islands exhibit two contrasting trends along reef flats: a shoreward decrease on Ishigaki and Tane‐ga‐shima Islands and a shoreward increase on Kudaka Island. A total of 25, 24 and 13 foraminiferal taxa were identified in Ishigaki, Kudaka and Tane‐ga‐shima Islands, respectively. Baculogypsina sphaerulata, Neorotalia calcar and Amphistegina spp. were dominant (i.e. >3% of foraminiferal assemblages) in the three islands. Calcarina gaudichaudii and Calcarina hispida were common on Ishigaki and Kudaka Islands but were absent on Tane‐ga‐shima Island. Larger foraminiferal assemblages from three different reef‐flat environments on Ishigaki Island can be distinguished, whereas those from the three environments on Kudaka and Tane‐ga‐shima Islands are similar in composition. These latitudinal changes in larger foraminiferal assemblages in reef sediments may possibly be caused by variations in the topography of reef flats, distributions and standing crops of living foraminifers on reef flats, and the northern limit of some calcarinid species in the northern Ryukyus.     

Seismicity and tectonics of the far Western Aleutian Islands

Study of focal mechanisms of earthquakes in the Near and Komandorsky Islands indicate that there are several distinct zones of tectonic activity. South of the Near Islands, normal faulting occurs in the trench east of 172°E and low-angle thrusting dominates the Aleutian ridge. Mechanisms indicate underthrusting as far west as Mednyy Island with strike-slip faulting restricted to the south and west of Beringa Island. A zone of northeast striking left-lateral faulting near 1645.°E is proposed to separate the Aleutian Ridge from Kamchatka Peninsula. This motion, as well as faulting north of the Komandorsky Islands, may be related to the existance of a buffer plate comprising the Aleutian Ridge in the Komandorsky Islands. Active subduction terminates near 173°E and the faulting north of the Komandorsky Islands may, in part, be due to the bouyancy of a remnant slab. Depth phase modelling indicates bulletin-reported depths are overestimated due to a misidentification of depth phases.     

Earthquake response spectra taking account of number of response cycles

Proposed is a new definition of earthquake response spectra, which takes account of the number of response cycles N. The Nth largest amplitude of absolute acceleration response of a linear oscilator with natural period T and damping ratio h, which is subjected to ground motion at its base, is defined as S_A(T, h, N). By defining a reduction factor η(T, h, N) as S_A(T, h, N)/S_A(T, h, 1), characteristics of η(T, h, N) were investigated based on 394 components of strong motion records obtained in Japan. Two practical empirical formulae to assess the reduction factor η(T, h, N) are proposed.