High time resolution monitoring of tropospheric temperature with a Radio Acoustic Sounding System (RASS)     

T. Tsuda  Y. Masuda  H. Inuki  K. Takahashi  T. Takami  T. Sato  S. Fukao  S. Kato 《Pure and Applied Geophysics》1989,130(2-3):497-507

We have observed the time-height variation of the temperature field in the upper troposphere using a Radio Acoustic Sounding System (RASS) which consists of the MU radar and a high-power acoustic transmitter. The fast beam steerability of the MU radar has made it possible to measure temperature profiles in a fairly wide height range in the upper troposphere (5–11 km), even under intense wind conditions. Observations were continued for about 32 hr on 24–26 December, 1986 with a time-height resolution of 30 min and 150 m. During the observation period, the tropospheric jet was so intense that the acoustic wavefronts were severely distorted. Using wind velocity profiles observed by the MU radar we have numerically estimated the propagation of acoustic wavefronts, and further determined favorable pointing directions for the MU radar to receive significant backscattering from refractive index fluctuations produced by the acoustic waves. Conventional radiosonde soundings were carried out every 6 hr, which showed a temperature decrease of 4 K/day in the upper troposphere during the observation period. Temperature profiles taken by RASS agree well with the radiosonde results.  相似文献   

Melting relationships in the system Fe-Feo at high pressures: Implications for the composition and formation of the earth's core     

Takumi Kato  A. E. Ringwood 《Physics and Chemistry of Minerals》1989,16(6):524-538

A reconnaissance investigation has been carried out on melting relationships in the system Fe-FeO at pressures up to 25 GPa and temperatures up to 2200° C using an MA-8 apparatus. Limited studies were also made of the Co-CoO and Ni-NiO systems. In the system FeFeO, the rapid exsolution of FeO from liquids during quenching causes some difficulties in interpretation of textures and phase relationships. The Co-CoO and Ni-NiO systems are more tractable experimentally and provide useful analogues to the Fe-FeO system. It was found that the broad field of liquid immiscibility present at ambient pressure in the Co-CoO system had disappeared at 18 GPa, 2200° C and that the system displayed complete miscibility between molten Co and CoO, analogous to the behaviour of the Ni-NiO system at ambient pressure. The phase diagram of the system Fe-FeO at 16 GPa and from 1600–2200° C was constructed from interpretations based on the textures of quenched run products. The solubility of FeO in molten iron is considerably enhanced by high pressures. At 16 GPa, the Fe-FeO eutectic contains about 10–15 mol percent FeO and the eutectic temperature in this iron-rich region of the system occurs at 1700±25° C, some 350° C below the melting point of pure iron at the same pressure. The solubility of FeO in molten Fe increases rapidly as temperature increases from 1700 to 2200° C. A relatively small liquid immiscibility field is present above 1900° C but is believed to be eliminated above 2200° C. This inference is supported by thermodynamic calculations on the positions of key phase boundaries. A single run carried out on an Fe₅₀ FeO₅₀ composition at 25 GPa and 2200° C demonstrated extensive and probably complete miscibility between Fe and FeO liquids under these conditions. The melting point of iron is decreased considerably by solution of FeO at high pressures; moreover, the melting point gradient (dP/dT) of the Fe-FeO eutectic is much smaller than that of pure iron and is also smaller than that of mantle pyrolite under the P, T conditions studied. These characteristics make it possible for melting of metal phase and segregation of the core to proceed within the Earth under conditions where most of the mantle remains below solidus temperatures. Under these conditions, the core would inevitably contain a large proportion of dissolved FeO. It is concluded therefore, that oxygen is likely to be the principal light element in the core. The inner core may not be composed of pure iron, as often proposed. Instead, it may consist of a crystalline oxide solid solution (Ni, Fe)₂O.  相似文献   

Geomorphological study on a clastic accretionary prism: The Nankai Trough     

Kyoko  Okino Yukihiro  Kato 《Island Arc》1995,4(3):182-198

Abstract The Nankai Trough, off southwest Japan, is one of the best sites for the study of geomorphic characteristics of a clastic accretionary prism. A recent multibeam survey over the central and eastern parts of the Nankai accretionary prism has revealed a large variation of the topography along the trough axis. Analysis of the bathymetric data suggests the existence of prism deformational features of different scales, such as depressions, embayment structures and cusps. These structures are the results of slope instability caused by basement relief of subducted oceanic plate. Unstable slopes recover by new accretion and development of a low angle thrust. Small-scale deformation due to the subduction of a small isolated seamount is then adjusted to the regional trend. By contrast, a 30 km indentation of the wedge observed in the eastern part of the Nankai Trough, the Tenryu Cusp, has seemed to retain its geometry. The subducted Philippine Sea plate has deformed greatly near the eastern end of the Nankai Trough, because of the collision between the Izu-Ogasawara (Bonin) arc and central Japan. Therefore, the indentation may be the result of the continuous subduction of a basement high, such as the Zenisu Ridge, which has been formed under north-south compression due to the arc-arc collision.  相似文献   

High-angle reverse faulting associated with the 1946 Nankaido earthquake     

Teruyuki Kato   《Tectonophysics》1983,96(1-2)

Analysis of vertical crustal deformation data in the southwestern part of Shikoku, southwest Japan, suggests that the Nankaido earthquake of 1946 (M_w = 8.1), which is a principal interplate thrust earthquake, was accompanied by subsidiary faulting on a splay fault adjacent to the coast of Shikoku. Discarding crustal movement resulting from the main thrusting of the Nankaido earthquake, local leveling data are explained by slip on a simple rectangular thrust fault located just offshore of Shikoku. Although it is difficult to constrain the fault location, a possible result is a high-angle thrust dipping landward at an angle of about 70°, with a dislocation of about 1.5 m, and source dimensions of 30 × 13 km along strike and dip. respectively. This result indicates that the fault may be one of the steeply dipping subsidiary faults branching from the main low-angle thrust, as was the case in the Alaska earthquake of 1964. Although several lines of evidence suggest that this faulting occurred as slow aseismic slip, its discrimination from the main seismic event is extremely difficult. This kind of high-angle thrusting just offshore of the coast would play an important role for the formation of the marine terraces during the late Quaternary period.  相似文献   

Expansion of aftershock areas caused by propagating post-seismic sliding   总被引：1，自引：0，他引：1  

Naoyuki Kato 《Geophysical Journal International》2007,168(2):797-808

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ACTIVE system for monitoring volcanic activity: A case study of the Izu-Oshima Volcano,Central Japan     

Hisashi Utada  Yuji Takahashi  Yuichi Morita  Takao Koyama  Tsuneomi Kagiyama 《Journal of Volcanology and Geothermal Research》2007

A system is proposed for the monitoring of changes in the underground structure of an active volcano over time by applying a transient electromagnetic method. The monitoring system is named ACTIVE, which stands for Array of Controlled Transient-electromagnetics for Imaging Volcano Edifice. The system consists of a transmitter dipole used to generate a controlled transient electromagnetic (EM) field and an array of receivers used to measure the vertical component of the transient magnetic field at various distances, with automatic operation of both units. In order to verify the performance of the proposed system, numerical and field experiments were carried out by application of the system to the Izu-Oshima volcano, where a remarkable change in the apparent DC resistivity over time had been detected in association with the eruption in 1986.  相似文献   

Effect of frictional heating on pre-seismic sliding: a numerical simulation using a rate-, state- and temperature-dependent friction law   总被引：1，自引：0，他引：1  

Naoyuki Kato 《Geophysical Journal International》2001,147(1):183-188

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The use of sintered diamond anvils in the MA8 type high-pressure apparatus     

Tadashi Kondo  Hiroshi Sawamoto  Akira Yoneda  Manabu Kato  Akihito Matsumuro  Takehiko Yagi  Takumi Kikegawa 《Pure and Applied Geophysics》1993,141(2-4):601-611

A new multi-anvil type high-presure apparatus has been developed using sintered diamond anvils to generate pressures over 30 GPa and temperatures up to about 2000°C. A maximum sample volume of about 1 mm³ is available in this system. The pressure was confirmed by dissociation of forsterite into Mg-perovskite and periclase. The basic techniques and problems in utilizing sintered diamond in the MA8 type high-pressure apparatus are discussed with an emphasis on the future prospect of incorporating simultancous X-ray diffraction observation.  相似文献   

Convective instability and overstability in the sunspot umbra     

Mamoru Saitō  Shoji Kato 《Solar physics》1968,3(4):531-542

Convective instability and overstability of a plane-parallel medium in the presence of a uniform vertical magnetic field is studied. We take into account both the effect of penetration of disturbances into sub-adiabatically stratified semi-infinite upper and lower layers, and the effect of thermal damping of disturbances introduced by the compressibility of the medium. If the degree of super-adiabaticity in temperature stratification in the middle layer is relatively large compared with that of sub-adiabaticity in the upper and lower layers, the range of physical conditions in which overstable convection occurs is very narrow. However, if it is not the case the range is rather wide. In the normal sunspot umbra, only disturbances with selected sizes in vertical dimension will be able to become overstable. The overstable convection might be a cause of some dynamical features (such as dots) in the sunspot umbra, but will not be the main contributor for transporting mechanical energy in the sunspot region.  相似文献   

A Model for the Quiescent Phase of the Recurrent Nova U Scorpii     

Hachisu I  Kato M  Kato T  Matsumoto K  Nomoto K 《The Astrophysical journal》2000,534(2):L189-L192

A theoretical light curve is constructed for the quiescent phase of the recurrent nova U Scorpii in order to resolve the existing distance discrepancy between the outbursts (d approximately 6 kpc) and the quiescences (d approximately 14 kpc). Our U Sco model consists of a very massive white dwarf (WD), an accretion disk (ACDK) with a flaring-up rim, and a lobe-filling, slightly evolved, main-sequence star (MS). The model properly includes an accretion luminosity of the WD, a viscous luminosity of the ACDK, and a reflection effect of the MS and the ACDK irradiated by the WD photosphere. The B light curve is well reproduced by a model of 1.37 M middle dot in circle WD + 1.5 M middle dot in circle MS (0.8-2.0 M middle dot in circle MS is acceptable) with an ACDK having a flaring-up rim and the inclination angle of the orbit i approximately 80&j0;. The calculated color is rather blue (B-V approximately 0.0) for a suggested mass accretion rate of 2.5x10-7 M middle dot in circle yr-1, thus indicating a large color excess of E(B-V) approximately 0.56 with the observational color of B-V=0.56 in quiescence. Such a large color excess corresponds to an absorption of AV approximately 1.8 and AB approximately 2.3, which reduces the distance to 6-8 kpc. This is in good agreement with the distance estimation of 4-6 kpc for the latest outburst. Such a large intrinsic absorption is very consistent with the recently detected period change of U Sco, which is indicating a mass outflow of approximately 3x10-7 M middle dot in circle yr-1 through the outer Lagrangian points in quiescence.  相似文献