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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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   

Initiation of Run-Out Flows on Venus by Oblique Impacts     

Seiji Sugita  Peter H. Schultz 《Icarus》2002,155(2):265-284

A hypervelocity oblique impact results in a downrange-moving vapor cloud, a significant fraction of which is derived from the projectile. Since the vapor cloud expands to great extent and becomes very tenuous quickly on a planet with a thin or no atmosphere, it does not leave a well-defined geologic expression. The thick atmosphere of Venus, however, is sufficient to contain such a rapidly expanding vapor cloud. As a result of atmospheric interactions, impact vapor condenses and contributes to run-out flows around craters on Venus. Previous results of both laboratory experiments and simple semi-analytical calculations indicate that an impact-vapor origin can account for the morphology of run-out flows on Venus most consistently. However, the detailed dynamics and geologic record of downrange-moving impact vapor clouds in Venus's atmosphere are not understood quantitatively. To approach these problems, we carried out two-dimensional hydrocode calculations. Parametric studies of these hydrocode calculations yield simple scaling laws for both the total downrange travel distance and the final temperature of impact vapor clouds under conditions on Venus. Under typical impact conditions, impact vapor clouds travel downrange more than a crater radius prior to the completion of crater formation. Furthermore, the scaling law for the total travel distance is compared with observations for the downrange offset of the source regions of run-out flows around oblique craters. The results of this comparison suggest that energy/momentum-partitioning processes other than pure shock coupling may play important roles in hypervelocity impact at planetary scales. The results of hydrocode calculations also indicate that the terminal temperature of the impact vapor is close to the condensation temperatures of silicates, suggesting that two scenarios are possible for expected range of impact conditions: 1. Impact vapor condenses and forms run-out flows. 2. Impact vapor fails to condense and leaves no run-out flows. Consequently, natural variation in impact angle, velocity, and projectile composition may account for partial occurrence of run-out flows around impact craters on Venus.  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   

Wide-Field Camera for Gravitational Microlensing Survey: MOA-cam2     

Toshifumi Yanagisawa  Yasushi Muraki  Yutaka Matsubara  Fumio Abe  Kimiaki Masuda  Sachiyo Noda  Takahiro Sumi  Yuji Kato  Mitsuaki Fujimoto  Shuji Sato  Ian Bond  Nicholas Rattenbury  Philip Yock  Pam Kilmartin  John Hearnshaw  Micheal Reid  Denis Sullivan  Brian Carter  Richard Dodd  Garry Nankivell  Noiman Rumsey  Morihiro Honda  Maki Sekiguchi  Masanori Yoshizawa  Takashi Nakamura  Humitaka Sato  Seiji Kabe  Makoto Kobayashi  Yoshiyuki Watase  Jun Jugaku  Toshiharu Saito  Barbel Koribalsky 《Experimental Astronomy》2000,10(4):519-535

We have constructed a large, mosaic CCD camera called MOA-cam2 which has 4096 × 6144-pixelsto search for gravitational microlensing events. MOA-cam2 has three4096 × 2048-pixel SITe CCD chips, which have a very high quantum efficiency (nearly 80% in the wave region 500 to 800 nm),and three buttable sides. We have placed the threechips side by side with 100 m dead space. MOA-cam2 has been installed on the 61 cm Boller and Chivens telescope of the MOA collaboration at the Mt. John University Observatory (MJUO) in NewZealand since July 1998. The field coverage is 0.92° × 1.38° per exposure. The technical details of MOA-cam2 and the first images obtained with the Boller and Chivens telescope are presented. MOA-cam2 introduces a second phase of research on gravitational microlensing by the MOA collaboration.  相似文献   

Jointing of two tunnel shields using artificial underground freezing     

Tsutomu Takashi  Shiro Kiriyama  Tetsuji Kato 《Engineering Geology》1979,13(1-4):519-529

Freezing was used in the jointing section of two shields (diameter 3.14 m) which ran across at right angles and at 25-m depth under the crossing of main roads for the construction of a 2.4-m diameter sewer tunnel. The object of freezing was to create a frozen barrier to prevent the inflow of water and fine sand into the area to be excavated.

Thirty-five freeze pipes (length about 7 m) were placed from one shield conically in the direction of the flank of another shield with freeze pipes attached to its inside wall. The cooling unit was placed on unoccupied land at about 60 m distant from the jointing section and the freeze pipes were connected with the cooling unit by supply and return pipelines.

The cooling unit had a cooling capacity of 79,000 kcal/h at an evaporation temperature of −27°C and a condensation temperature of +40°C. Freezing was continued for 180 days and the CaCl₂ brine temperature was −25 to −30°C. These works were accomplished without the sinking of shaft and the use of injection, in complete safety with no traffic restriction on the road surface.  相似文献