An impulsive solar X-ray burst in the energy range 90–400 keV

A hard solar X-ray burst in the energy range 90–400 keV was observed at about 0528:30 UT on 13 April 1974. This event is peculiar in the sense that the X-ray flux is considerably high whereas the corresponding radio and optical flares are of moderate sizes, that the duration of the X-ray burst is very short, and that the X-ray peak is delayed by about 2.5 min relative to the first radio peak.     

Deformation mechanisms and fluid behavior in a shallow, brittle fault zone during coseismic and interseismic periods: Results from drill core penetrating the Nojima Fault, Japan

Abstract This paper describes the results of petrographical and meso- to microstructural observations of brittle fault rocks in cores obtained by drilling through the Nojima Fault at a drilling depth of 389.52 m. The zonation of deformation and alteration in the central zone of the fault is clearly seen in cores of granite from the hanging wall, in the following order: (i) host rock, which is characterized by some intragranular microcracks and in situ alteration of mafic minerals and feldspars; (ii) weakly deformed and altered rocks, which are characterized by transgranular cracks and the dissolution of mafic minerals, and by the precipitation of zeolites and iron hydroxide materials; (iii) random fabric fault breccia, which is characterized by fragmentation, by anastomosing networks of transgranular cracks, and by the precipitation of zeolites and iron hydroxide materials; and (iv) fault gouge, which is characterized by the precipitation of smectite and localized cataclastic flow. This zonation implies that the fault has been weakened gradually by fluid-related fracturing over time. In the footwall, a gouge layer measuring only 15 mm thick is present just below the surface of the Nojima Fault. These observations are the basis for a model of fluid behavior along the Nojima Fault. The model invokes the percolation of meteoric fluids through cracks in the hanging wall fault zone during interseismic periods, resulting in chemical reactions in the fault gouge layer to form smectite. The low permeability clay-rich gouge layer sealed the footwall. The fault gouge was brecciated during coseismic or postseismic periods, breaking the seal and allowing fluids to readily flow into the footwall, thus causing a slight alteration. Chemical reactions between fluids and the fault breccia and gouge generated new fault gouge, which resealed the footwall, resulting in a low fluid condition in the footwall during interseismic periods.     

Internal structure of the Nojima Fault zone from the Hirabayashi GSJ drill core

Abstract The internal structures of the Nojima Fault, south-west Japan, are examined from mesoscopic observations of continuous core samples from the Hirabayashi Geological Survey of Japan (GSJ) drilling. The drilling penetrated the central part of the Nojima Fault, which ruptured during the 1995 Kobe earthquake (Hyogo-ken Nanbu earthquake) ( M 7.2). It intersected a 0.3 m-thick layer of fault gouge, which is presumed to constitute the fault core (defined as a narrow zone of extremely concentrated deformation) of the Nojima Fault Zone. The rocks obtained from the Hirabayashi GSJ drilling were divided into five types based on the intensities of deformation and alteration: host rock, weakly deformed and altered granodiorite, fault breccia, cataclasite, and fault gouge. Weakly deformed and altered granodiorite is distributed widely in the fault zone. Fault breccia appears mostly just above the fault core. Cataclasite is distributed mainly in a narrow (≈1 m wide) zone in between the fault core and a smaller gouge zone encountered lower down from the drilling. Fault gouge in the fault core is divided into three types based on their color and textures. From their cross-cutting relationships and vein development, the lowest fault gouge in the fault core is judged to be newer than the other two. The fault zone characterized by the deformation and alteration is assumed to be deeper than 426.2 m and its net thickness is > 46.5 m. The fault rocks in the hanging wall (above the fault core) are deformed and altered more intensely than those in the footwall (below the fault core). Furthermore, the intensities of deformation and alteration increase progressively towards the fault core in the hanging wall, but not in the footwall. The difference in the fault rock distribution between the hanging wall and the footwall might be related to the offset of the Nojima Fault and/or the asymmetrical ground motion during earthquakes.     

Electric imaging and laboratory resistivity testing for geotechnical investigation of Pusan clay deposits

Large-scale reclamation works for new land development in the Nakdong River plain have been extensively carried out on soft clays. Several geotechnical characteristics of the clays could not be well evaluated, partly due to easy disturbance during drilling and sampling. Consequently, geophysical methods, seen as nondestructive testing tools, have been applied in geotechnical investigation of Pusan clays for the first time. In this study, the 2D electric imaging technique was employed to map the thick soft clay deposits in four reclamation sites. The Pusan clay deposit was very well mapped. Electric resistivity of Pusan clays was measured on over 50 core samples in the laboratory, and then correlated with other geotechnical parameters such as salinity, organic content, water content, plasticity, unit weight and sampling depth. Additionally, electric resistivity of about 20 natural clays collected worldwide was measured and compared to that of the Pusan clays as an initial effort in creating a database of clay electric resistivity to help further application of electric imaging in geotechnical investigation of clayey soils.     

Building Damage and Casualties after an Earthquake

The relationship between building damage patterns and human casualties in Nishinomiya City – one of the most heavily damaged cities in the 1995 Hanshin-Awaji Earthquake Disaster – was investigated using photographs of damaged buildings. First, the photographs of buildings in which casualties occurred were identified, and the building damage patterns were judged based on the photographs considering the existence of survival space. Then the relationship between the building damage pattern and casualty occurrence, and the characteristics of casualty distribution, were investigated. The main findings were as follows: Most casualties occurred in relatively old two-story wooden buildings in which the ground floor completely collapsed without survival space; casualties occurred at all building damage levels including ``no damage', and it can be seen that building damage is the major, but not the sole cause, of casualties in an earthquake; in Nishinomiya City, the regional distributions of casualties due to the collapse of buildings that left no survival space is similar to that of casualties due to other types of building damage.     

Temporal changes in the phytoplankton community of the southern basin of Lake Baikal over the last 24,000 years recorded by photosynthetic pigments in a sediment core

Photosynthetic pigments and other indicators of phytoplankton were analyzed in a dated undisturbed sediment core obtained from the southern basin of Lake Baikal to reveal temporal changes in the phytoplankton community in the lake through the last glacial/post-glacial transition. The sedimentation age of the core spans the last 24 ¹⁴C ka. Chlorophyll a, its derivatives, carotenoids and total organic carbon (TOC) started to increase after 15 ¹⁴C ka, and the onset of biogenic silica occurred at 10 ¹⁴C ka. This indicated that the post-glacial growth of diatoms was preceded by that of other phytoplankton groups. In the record of the pigments and TOC, a temporary decrease was observed in the period 11.5–10.5 ¹⁴C ka, corresponding to the Younger Dryas cold period. The similarity found between the depth profiles of pyropheophytin a and steryl chlorin esters formed through predation of phytoplankton by zooplankton and that of TOC suggested the important contribution of fecal pellets to sedimentary organic matter in the lake.     

Stress-strain behaviour of reconstituted illitic clay at different temperatures

Tests on specimens of reconstituted illitic clay have examined the influence of temperature on the mechanical behaviour of clay soils. The program involved consolidation to effective confining pressures up to 1.5 MPa, heating to 100°C, and tests on normally consolidated and overconsolidated specimens with OCR = 2. The tests included isotropic consolidation, undrained triaxial compression with pore water pressure measurement, drained tests along controlled stress paths to investigate yielding behaviour, and undrained tests which involved heating and measurement of the resulting induced pore water pressures. The large strain strength envelope is independent of temperature. However, peak undrained strengths increase with temperature because smaller pore water pressures are generated during shearing. An important contribution from the study is a series of results for the yielding of illitic clay at three different temperatures. For the first time, there is clear evidence of yield loci decreasing in size with increasing temperature. An associated flow rule can be assumed without serious error. The results contribute to the confirmation of a thermal elastic-plastic soil model developed by the authors from cam clay following the addition of a small number of extra assumptions. Depending on the initial stress state, heating under undrained conditions may produce shear failure.     

网点再现与油墨流动性及纸张表面的关系

分数维Ｄ值能够表示印刷网点与底片上网点的相似性关系，本文用分数维法定量评价了印刷网点的再现性，主要分析了网点再现与网屏线数、网点面积率、纸张表面粗度及油墨物性的关系。