A new typhoon bogussing scheme to obtain the possible maximum typhoon and its application for assessment of impacts of the possible maximum storm surges in Ise and Tokyo Bays in Japan

We developed the new typhoon bogussing scheme to obtain the possible maximum typhoon approaching any region under any climatic conditions by using a potential vorticity inversion method. Numerical simulations with the new typhoon bogussing scheme are conducted for assessment of storm surges by possible maximum typhoons under the present-day and global warming climatic conditions in Ise and Tokyo Bays in Japan. The results suggest that the storm tide higher than the maximum storm tide in recorded history can occur in Ise and Tokyo Bays even for the present-day climate and the storm tide higher than the design sea level can cause severe damage to Nagoya and Tokyo megacities, in particular, airport facilities in Ise Bay for the global warming climate. These results suggest that the new typhoon bogussing scheme we developed is useful for assessment of impacts of storm surge by the possible maximum typhoons.     

Mineralogical study of brown olivine in Northwest Africa 1950 shergottite and implications for the formation mechanism of iron nanoparticles

Martian meteorites, in particular shergottites, contain darkened olivine (so‐called “brown olivine”) whose color is induced by iron nanoparticles formed in olivine during a shock event. The formation process and conditions of brown olivine have been discussed in the Northwest Africa 2737 (NWA 2737) chassignite. However, formation conditions of brown olivine in NWA 2737 cannot be applied to shergottites because NWA 2737 has a different shock history from that of shergottites. Therefore, this study observed brown olivine in the NWA 1950 shergottite and discusses the general formation process and conditions of brown olivine in shergottites. Our observation of NWA 1950 revealed that olivine is heterogeneously darkened between and within grains different from brown olivine in NWA 2737. XANES analysis showed that brown olivine contains small amounts of Fe³⁺ and TEM/STEM observation revealed that there is no SiO‐rich phase around iron metal nanoparticles. These observations indicate that iron nanoparticles were formed by a disproportionation reaction of olivine (3Fe²⁺_olivine → Fe⁰_metal + 2Fe³⁺_olivine + V_olivine, where V_olivine means a vacancy in olivine). Some parts of brown olivine show lamellar textures in SEM observation and Raman peaks in addition to those expected for olivine, implying that brown olivine experienced a phase transition (to e.g., ringwoodite). In order to induce heterogeneous darkening, heterogeneous high temperature of about 1500–1700 K and shock duration of at least ~90 ms are required. This heterogeneous high temperature resulted in high postshock temperature (>900 K) inducing back‐transformation of most high‐pressure phases. Therefore, in spite of lack of high‐pressure phases, NWA 1950 (= Martian meteorites with brown olivine) experienced higher pressure and temperature compared to other highly shocked meteorite groups.     

Distribution of Young Stellar Populations in the Orion Region

Based on the survey of emission-line stars in a wide field of the Orion star forming region, surface distributions of young stellar populations and gaseous clouds are compared as a whole in an attempt to make a speculation on the star formation process in this region. Existence of a primeval molecular cloud is suggested as the birth site of older members of emission-line stars and probably of X-ray detected pre-main sequence stars. This revised version was published online in July 2006 with corrections to the Cover Date.     

Frequency of Be and Ae stars in spectroscopic binaries

The frequency of Be and Ae stars in spectroscopic binaries and Algol binaries is examined based on the available catalogue data, and compared with that of stars in theBright Star Catalogue. It is shown that in binary systems Be and Ae stars reveal different statistical behaviours. The frequency of Be stars in spectroscopic binaries shows a notable peak in its orbital-period distribution in the range of 100–300 days, suggesting a statistical group separated from Algol systems. In contrast, most of Ae stars in spectroscopic binaries belong to the Algol systems.     

Phase relations and P–T conditions of the Ryoke pelitic and psammitic metamorphic rocks in the Ina district, Central Japan

The Ina district of the Ryoke Belt is divided into two mineral zones, based on the mineral parageneses of the pelitic and psammitic rocks at the peak metamorphism. A biotite–muscovite zone (quartz + plagioclase + biotite + muscovite with or without K-feldspar) constitutes the northwestern part, and a biotite–cordierite–K-feldspar zone (quartz + plagioclase + biotite + cordierite + K-feldspar) comprises the central to southern and eastern parts. The isograd reaction between two mineral zones is defined by a divariant reaction: Mg-rich biotite + muscovite + quartz = Fe-rich biotite + cordierite + K-feldspar + H₂O (1), which, in the K₂O–FeO–MgO–Al₂O₃–SiO₂–H₂O (KFMASH) system, occurs at ∼ 590 °C at 0.2 GPa and 660 °C at 0.4 GPa. Fibrolite accompanied by andalusite porphyroblasts in aluminous pelitic rocks of the biotite–muscovite zone and the low-grade part of the biotite–cordierite–K-feldspar zone, suggests that sillimanite was the stable aluminosilicate at the peak metamorphic condition throughout the area. In the high-grade part of the biotite–cordierite–K-feldspar zone, fibrolite mostly occurs as inclusions in cordierite or in plagioclase. The phase relations and the compositional zoning of plagioclase in relation to fibrolite inclusions suggest that fibrolite was formed under relatively high-pressure conditions, and that partial melting took place.     

Optical imaging of impact sites of Comet Shoemaker-Levy 9 at Bisei Astronomical Observatory

The impact sites of the Comet Shoemaker-Levy 9 are observed with the 101-cm telescope at Bisei Astronomical Observatory until the end of August with B, V, R, I, and methane-band (0.89m) filters. The outline of the observation is briefly described.     

Cooperation in astronomy between Indonesia and Japan

The cooperation programme in astronomy between Indonesia and Japan is presented as an example of a well-coordinated bilateral cooperation between Asian countries. This cooperation has started in 1979, in the fields of galactic astronomy and stellar physics. The form of the cooperation is principally the exchange of persons between both countries for the purposes of collaborative works in some specific fields, the training of young astronomers, and technical cooperation. The main subjects of collaborative works are: (1) survey of red giants in the galactic center region, (2) survey of H-emission stars in some areas of the sky, (3) theoretical study of the dynamical evolution of stellar systems, (4) photoelectric observations of southern close binaries, (5) X-ray binaries and pulsars, (6) Be stars, and (7) other topics. The organization and main results of these works are presented, along with a future aspect of the cooperation.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.     

Surface lowering rates of uplifted limestone terraces estimated from the height of pedestals on a subtropical island of Japan

In Kikai‐jima, south‐western Japan, many pedestal rocks have developed on the surface of Holocene raised coral‐reef terraces with known dates of emergence. Pedestals are formed just under boulders, which are considered to have been transported by tsunami and settled on a reef flat before emergence. On the assumption that boulders protect the underlying limestone terrace from rainfall solution, the rate of surface lowering of these limestone terraces was evaluated from the height of pedestals and the period of their formation. The result showed that the mean lowering rate over 6000 years is 205 mm/ky. Copyright © 2007 John Wiley & Sons, Ltd.     

日本东北9.0级地震的同震与震后滑动

大部分强震都发生在海沟,那里是海洋板块向大陆板块俯冲的地方.大量矩震级MW9.0以上的地震发生在若干区域,包括智利,阿拉斯加,堪察加半岛和苏门答腊岛等.位于太平洋板块俯冲鄂霍茨克板块的日本海沟,历史记载上没有发生过MW9.0地震,除了至今震级还有争议的公元869年Jogan大地震[1](可能超过MW9.0).然而,根据...