Japan’s <Emphasis Type="Italic">Jishu-bosai-soshiki</Emphasis> community activities: analysis of its role in participatory community disaster risk management

Jishu-bosai-soshiki, or Jishubo for short, with a literal meaning of “autonomous organization for disaster reduction”, is a neighborhood association for disaster preparedness and rescue activity. In this paper, the role of Jishubo in the context of participatory disaster management in Japan is discussed. Although the formation of Jishubo is not legally mandated, local governments exercise a great deal of persuasion on the inhabitants of their community to organize and participate in disaster management activities. Therefore, participants in Jishubo activities tend to be guided and mobilized with a soft touch by local governments rather than being truly self-motivated, with the objective of reducing disaster risks in their residential areas. There have been several studies on community participatory management conducted in a number of countries, including New Zealand, the USA and Europe, which will serve as a reference in our study. However interesting, the cultural comparison of the “Western” and “Japanese” approaches to community disaster management, is beyond the scope of this paper, the aim of which is to determine a case of community disaster management in Japan. This paper addresses the background behind the development of Jishubo and discusses the uniqueness and limits of this softly mobilized participatory movement in Japan. Based on a case study in Kishiwada City, Osaka, the motivations driving people to participate in disaster management activities organized for Jishubo members is examined. In conclusion, we derive some policy implications and suggest possible approaches for improving the effectiveness of Jishubo and increasing the motivation of people to participate. We also propose that the roles of administrative bodies in Japan, such as non-profit organizations, be better incorporated into community’s participatory disaster reduction activities.     

Semi-brittle behavior of wet olivine aggregates: the role of aqueous fluid in faulting at upper mantle pressures

The role of aqueous fluid in fracturing in subducting slabs was investigated through a series of deformation experiments on dunite that was undersaturated (i.e., fluid-free) or saturated with water (i.e., aqueous-fluid bearing) at pressures of 1.0–1.8 GPa and temperatures of 670–1250 K, corresponding to the conditions of the shallower regions of the double seismic zone in slabs. In situ X-ray diffraction, radiography, and acoustic emissions (AEs) monitoring demonstrated that semi-brittle flow associated with AEs was dominant and the creep/failure strength of dunite was insensitive to the dissolved water content in olivine. In contrast, aqueous fluid drastically decreased the creep/failure strength of dunite (up to ~?1 GPa of weakening) over a wide range of temperatures in the semi-brittle regime. Weakening of the dunite by the aqueous fluid resulted in the reduction of the number of AE events (i.e., suppression of microcracking) and shortening of time to failure. The AE hypocenters were located at the margin of the deforming sample while the interior of the faulted sample was aseismic (i.e., aseismic semi-brittle flow) under water-saturated conditions. A faulting (slip rate of ~?10^?3 to 10^?4 s^?1) associated with a large drop of stress (Δσ?~?0.5 to 1 GPa) and/or pressure (ΔP?~?0.5 GPa) was dominant in fluid-free dunite, while a slow faulting (slip rate?<?8?×?10^?5 s^?1) without any stress/pressure drop was common in water-saturated dunite. Aseismic semi-brittle flow may mimic silent ductile flow under water-saturated conditions in subducting slabs.     

Applicability to Korean Marine Clay of the Mobilized Undrained Vane Shear Strength Using Correction Factors

The undrained shear strength normalized by the yield consolidation pressure, su/pc', is presented for four coastal sites: Busan/Gwangyang and Incheon/Gunsan, having the characteristics of high and low plasticity, respectively. The field vane shear strengths, su(FVT), were compared with unconfined compressive strength, qu/2 which has been used as a representative testing method in Korea. Many researchers have suggested that the undrained shear strength normalized by the yield consolidation pressure, su/pc', depends on Ip. However, the undrained shear strength normalized by the yield consolidation pressure, su/pc' is in the range of 0.25–0.35, independently of the plasticity index, Ip except for su/pc' using qu/2 values in the case of soils having a low plasticity, such as Incheon and Gunsan intermediate soils.

Bjerrum's correction factor has been commonly applied to evaluate mobilized undrained shear strength using the field vane test in Korea. However, the corrected undrained shear strengths using Bjerrum's correction factor, including Morris and Williams' method, were considerably underestimated for Korean marine clay when compared with the qu/2 values that have been used as the mobilized undrained shear strength for practical design in Korea.     

Effects of dust abundance on the far-infrared colours of blue compact dwarf galaxies

We investigate the far-infrared (FIR) properties of a sample of blue compact dwarf galaxies (BCDs) observed by AKARI . By utilizing the data at wavelengths of  λ= 65  , 90 and 140 μm, we find that the FIR colours of the BCDs are located at the natural high-temperature extension of those of the Milky Way and the Magellanic Clouds. This implies that the optical properties of dust in BCDs are similar to those in the Milky Way. Indeed, we explain the FIR colours by assuming the same grain optical properties, which may be appropriate for amorphous dust grains, and the same size distribution as those adopted for the Milky Way dust. Since both interstellar radiation field and dust optical depth affect the dust temperature, it is difficult to distinguish which of these two physical properties is responsible for the change of FIR colours. Then, in order to examine if the dust optical depth plays an important role in determining the dust temperature, we investigate the correlation between FIR colour (dust temperature) and dust-to-gas ratio. We find that the dust temperature tends to be high as the dust-to-gas ratio decreases but that this trend cannot be explained by the effect of dust optical depth. Rather, it indicates a correlation between dust-to-gas ratio and interstellar radiation field. Although the metallicity may also play a role in this correlation, we suggest that the dust optical depth could regulate the star formation activities, which govern the interstellar radiation field. We also mention the importance of submillimetre data in tracing the emission from highly shielded low-temperature dust.     

Computer simulations of gas flow around close binary systems

A gas-dynamical model of gas streams around close binary systems is given. The velocity feld and the density distribution are determined for different parameter ranges. The results succeed in explaining the formation of a ring and a disk around the accreting component. The models furthermore reveal the existence of a tongue of matter extending from the inner Lagrangian point and a jet perpendicular to the system axis.     

On the formation of large-scale shock waves in barre galaxies

The behavior of the gaseous phase in a barred galaxy is followed by computer simulations of the gas flow in a fixed potential formed by a bar and a disk. The results support a hypothesis that the dark lanes observed on the leading side of the bar in many SB galaxies are coinciding with the shock waves. Furthermore the results reject an outflow explanation of the arms but suggest these to be formed mechanically by the bar. Ring-shaped features were not reproduced but double arms were occasionally detected.     

Two surveys for taking measures to cope with the coming earthquake to the Tokyo Metropolis

Although Tokyo City has frequently suffered from earthquake disasters, more than 70 years have passed since the last catastrophe of 1923. Because Tokyo has a greater probability now than ever of being hit by another major earthquake, the Tokyo Metropolitan Government has carried out two surveys for taking measures to cope with it; earthquake vulnerability assessment and earthquake damage prediction. The former assesses earthquake vulnerability regionally and is used for disaster-proof city planning. Damage due to the expected earthquake is quantitatively estimated in the latter. The results are used for making a regional disaster prevention plan in an emergency. Both physical and human geographers participate in these interdisciplinary surveys effectively.     

Degradation ofn-paraffin mixture by marine microorganisms in enriched seawater medium

The ability to degraden-paraffin mixture of two bacterial strains,Caulobacter sp. andFlavobacterium sp., isolated from sea water of Tokyo Bay was studied experimentally in the enriched seawater (ESW) medium. These bacteria degraded actively the mixture ofn-tridecane,n-tetradecane,n-pentadecane andn-hexadecane. The maximum rate of degradation was observed after a lag period of 2 to 8 day and these bacteria were found to degrade then-paraffin mixture at rates calculated to be in a range from 3.3×10^?12 to 3.4×10^?11 mg-oil cell^?1 h^?1 at 20°C. The maximum degradation rate,r _m mg-oil l^?1 h^?1, was correlated with the amount of the initial totaln-paraffin,S mg-oil l^?1, as expressed by the following equation: $$rm = (rm)\max \left( {\frac{S}{{S + Km}}} \right)$$ where (r _m )_max denotes the largest value ofr _m whenn-paraffin exists in large excess andK _m is a constant and represents the amount ofn-paraffin at which the degradation rate,r _m , reaches 1/2 of its largest value, (r _m )_max. The values of (r _m )_max andK _m were calculated to be as follows: In the case ofCaulobacter sp. (strain KM-1), (r _m )_max=6.0 mg-oil l^?1 h^?1 andK _m =191 mg-oillesw ^?1; in the case ofFlavobacterium sp., (r _m )_max=5.47 mg-oil l^?1 h^?1 andK _m =152 mg-oillesw ^?1.     

Interannual variations of the occurrence of epipelagic fish in the diets of the seabirds breeding on Teuri Island, northern Hokkaido, Japan

The diets of breeding seabirds can be a good monitor of marine environmental changes. From 1984 to 2001 we monitored the diets of black-tailed gulls (Larus crassirostris) (“surface foragers”), rhinoceros auklets (Cerorhinca monocerata) (“epipelagic divers”), and Japanese cormorants (Phalacrocorax filamentotus) (“bottom divers”) that breed on Teuri Island at the northern boundary of the Tsushima Warm current in the Sea of Japan/East Sea. Between 1984 and 1987, both the gulls and the auklets foraged on the sardine (Sardinops melanostictus), but after 1992, they switched to the anchovy (Engraulis japonica). This change might reflect the collapse of the sardine stock in the late 1980s. In the 1990s, the year-to-year variations of the percentage of anchovy in the diets of the three seabird species showed similar trends: High in 1994 and 1998–2001; and low in 1992–1993 and 1995–1997. The estimated stock size of the anchovy population in the Tsushima Current area was positively correlated with the percentage of mass of anchovy in the seabirds’ diets. Thus, the short-term annual changes of the total anchovy availability, which might reflect SST or the volume transport of Tsushima Current, possibly affected the seabirds diets on this island.     

Fracture-zone conditions on a recently active fault: insights from mineralogical and geochemical analyses of the Hirabayashi NIED drill core on the Nojima fault, southwest Japan, which ruptured in the 1995 Kobe earthquake

An 1800-m-deep borehole into the Nojima fault zone was drilled at Nojima-Hirabayashi, Japan, after the 1995 Hyogo-ken Nanbu (Kobe) earthquake. Three possible fracture zones were detected at depths of about 1140, 1300, and 1800 m. To assess these fracture zones in this recently active fault, we analyzed the distributions of fault rocks, minerals, and chemical elements in these zones. The central fault plane in the shallowest fracture zone was identified by foliated blue-gray gouge at a depth of 1140 m. The degree of fracturing was evidently greater in the hanging wall than in the footwall. Minerals detected in this zone were quartz, orthoclase, plagioclase, and biotite, as in the parent rock (granodiorite), and also kaolinite, smectite, laumontite, stilbite, calcite, ankerite, and siderite, which are related to hydrothermal alteration. Biotite was absent in both the hanging wall and footwall across the central fault plane, but it was absent over a greater distance from the central fault plane in the hanging wall than in the footwall. Major element compositions across this zone suggested that hydrothermal alteration minerals such as kaolinite and smectite occurred across the central fault plane for a greater distance in the hanging wall than in the footwall. Similarly, H₂O+ and CO₂ had higher concentrations in the hanging wall than in the footwall. This asymmetrical distribution pattern is probably due to the greater degree of wall–rock fracturing and associated alteration in the hanging wall. We attributed the characteristics of this zone to fault activity and fluid–rock interactions. We analyzed the other fracture zones along this fault in the same way. In the fracture zone at about 1300 m depth, we detected the same kinds of hydrothermal alteration minerals as in the shallower zone, but they were in fewer samples. We detected relatively little H₂O+ and CO₂, and little evidence for movement of the major chemical elements, indicating little past fluid–rock interaction. In the fracture zone at about 1800 m depth, H₂O+ and CO₂ were very enriched throughout the interval, as in the fracture zone at about 1140 m depth. However, smectite was absent and chlorite was present, indicating the occurrence of chloritization, which requires a temperature of more than 200 °C. Only smectite can form under the present conditions in these fracture zones. The chloritization probably occurred in the past when the fracture zone was deeper than it is now. These observations suggest that among the three fracture zones, that at about 1140 m depth was the most activated at the time of the 1995 Hyogo-ken Nanbu (Kobe) earthquake.