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Tadashi Akamatsu Kiyoshi Fujino Mineo Kumazawa Akio Fujimura Manabu Kato Hiroshi Sawamoto Takamitsu Yamanaka 《Physics and Chemistry of Minerals》1988,16(2):105-113
Synthetic (Mg0.51, Mn0.49)2SiO4 olivine samples are heat-treated at three different pressures; 0, 8 and 12 GPa, all at the same temperature (~500° C). X-ray structure analyses on these single crystals are made in order to see the pressure effect on cation distribution. The intersite distribution coefficient of Mg and Mn in M1 and M2 sites, K D = (Mn/Mg) M1/(Mn/Mg) M2, of these samples are 0.192 (0 GPa), 0.246 (8 GPa) and 0.281 (12 GPa), indicating cationic disordering with pressure. The small differences of cell dimensions between these samples are determined by powder X-ray diffraction. Cell dimensions b and c decrease, whereas a increases with pressure of equilibration. Cell volume decreases with pressure as a result of a large contraction of the b cell dimension. The effect of pressure on the free energy of the cation exchange reaction is evaluated by the observed relation between the cell volume and the site occupancy numbers. The magnitude of the pressure effect on cation distribution is only a fifth of that predicted from the observed change in volume combined with thermodynamic theory. This phenomenon is attributed to nonideality in this solid solution, and nonideal parameters are required to describe cation distribution determined in the present and previous experiments. We use a five-parameter equation to specify the cationic equilibrium on the basic of thermodynamic theory. It includes one energy parameter of ideal mixing, two parameters for nonideal effects, one volume parameter, and one thermal parameter originated from the lattice vibrational energy. The present data combined with some of the existing data are used to determine the five parameters, and the cation distribution in Mg-Mn olivine is described as a function of temperature, pressure, and composition. The basic framework of describing the cationic behavior in olivine-type mineral is worked out, although the result is preliminary: each of the determined parameters is not accurate enough to enable us to make a reliable prediction. 相似文献
14.
Antiphase domains (APD's) of pigeonite lamellae in natural and heated augite crystals from the Hakonetoge andesite have been examined by a transmission electron microscope (TEM). Antiphase boundaries (APB's) of the pigeonite lamellae in natural specimens have a sigmoidal shape cutting the c axis in (010) sections. APB's in specimens heated at temperatures above the high-low inversion and then quenched are nearly parallel to the c axis with almost straight boundaries. These observations indicate that the preferred orientation of APB's in (010) sections depends on cooling rate; at fast colling rates the APB's are nearly parallel to the c axis, whereas at slower cooling rates they are inclined to the c axis. The cooling rate of the natural augite specimen from Hakonetoge is estimated to be about 0.01 °C/h from the experimentally determined time-temperature-transformation (TTT) diagram for the APB orientations. APD sizes are large in specimens quenched from above the inversion temperature; they are at a minimum after cooling rates of around 1–0.1 °C/h, and then become larger with slower cooling rates. 相似文献
15.
Detection of anomalous seismic phases by the wavelet transform 总被引:1,自引:0,他引:1
Kiyoshi Yomogida 《Geophysical Journal International》1994,116(1):119-130
16.
The optical interference phenomenon of an iridescent grandite garnet was examined by using white light and laser light on the analogy of the X-ray diffraction method. A kinematical interpretation was also made for the observed angle and intensity of interference light. The regularly stratified layers which cause iridescence are deduced to be periodic twins oriented parallel to the growth layers in each sector with a periodicity of about 1,000 Å. 相似文献
17.
Hideko Takayanagi Yasufumi Iryu Tsutomu Yamada Motoyoshi Oda Kazuyuki Yamamoto Tokiyuki Sato Shun Chiyonobu Akira Nishimura Tsutomu Nakazawa Satoshi Shiokawa 《Island Arc》2007,16(3):394-419
Abstract The lithology of shallow-water carbonates collected from 19 sites on 16 seamounts in six areas of the northwestern Pacific Ocean using the Deep-sea Boring Machine System are described. The areas include the Amami Plateau, Daito Ridge, Oki-Daito Ridge, Urdaneta Plateau, Kyushu-Palau Ridge and Ogasawara Plateau. Chronological constraint is provided by calcareous nannofossil biostratigraphy, planktonic foraminiferal biostratigraphy, larger foraminiferal biostratigraphy and strontium (Sr) isotope stratigraphy. Large amounts of shallow-water carbonates accumulated on the seamounts during the Oligocene, a relatively cool period, whereas limited carbonate deposits formed during the Early Miocene, a relatively warm period. This might indicate that deposition of shallow-water carbonates on seamounts in the northwestern Pacific Ocean was not necessarily controlled by climatic conditions, but was related to volcanism and tectonics that served as foundations for reef/carbonate-platform formation. Remarkable differences in biotic composition exist between Cretaceous and Cenozoic shallow-water carbonates. Late Cretaceous shallow-water carbonates are distinguished by the occurrence of rudists, solenoporacean algae and microencrusters. Middle Eocene to Early Oligocene shallow-water carbonates are dominated by Halimeda or nummulitid and discocyclinid larger foraminifers. Scleractinian corals became common from the Oligocene onward. Nongeniculate coralline algae and larger foraminifers were common to abundant throughout the Eocene to the Pleistocene. The replacement of major carbonate producers in the shallow-water carbonate factory during post-Cretaceous time is in accordance with previous studies and is considered to reflect a shift in seawater chemistry. 相似文献
18.
Alexander Pavelyev Yuei-An Liou Christoph Reigber Jens Wickert Kiyoshi Igarashi Klemens Hocke Cheng-Yung Huang 《GPS Solutions》2002,6(1-2):100-108
GPS radio occultation (RO) signals are highly coherent and precise, and thus sufficient for holographic investigation of
the atmosphere, ionosphere, and the Earth's surface from space. In principle, three-dimensional radio-holographic remote sensing
is possible by using new radio holographic equations to retrieve the radio field within the atmosphere from a radio field
known at some interface outside the atmosphere. A simplified two-dimensional form of the radio-holographic equations which
are developed under an assumption of local spherical symmetry can be used to obtain two-dimensional radio images of the atmosphere
and terrestrial surface. To achieve this, radio holograms recorded by a GPS receiver onboard a low earth orbit (LEO) satellite
at two GPS frequencies can be used and focused synthetic aperture principle applied. Analysis of GPS/MET RO data is presented
to show the effectiveness of a radio-holographic approach. It is shown that the amplitude of GPS radio signals (in addition
to phase data) can be used to obtain detailed altitude profiles of the vertical gradient of refractivity in the atmosphere
and electron density in the mesosphere. The results demonstrate the applicability of GPS radio holography for a detailed global
study of the natural processes in the atmosphere and mesosphere.
Electronic Publication 相似文献
19.
Takeshi Ohmura Takeo Moriya Chengshi Piao Takaya Iwasaki Toshikastu Yoshi Shin'ichi Sakai Tetsuya Takeda Kaoru Miyashita Humihito Yamazaki Kiyoshi Ito Akira Yamazaki Yoji Shimada Katsuya Tashiro Hiroki Miyamachi 《Island Arc》2001,10(3-4):215-227
Abstract The 1995 Kobe (Hyogo-ken Nanbu) earthquake (MJMA 7.2, Mw 6.9) occurred on Jan. 17, 1995, at a depth of 17 km, beneath the areas of southern part of Hyogo prefecture and Awaji Island. To investigate P-wave velocity distribution and seismological characteristics in the aftershock area of this great earthquake, a wide-angle and refraction seismic exploration was carried out by the Research Group for Explosion Seismology (RGES) . The profile including 6 shot points and 205 observations was 135 km in length, extending from Keihoku, Northern Kyoto prefecture, through Kobe, to Seidan on Awaji Island. The charge of each shot was 350–700 kg. The P-wave velocity structure model showed a complicated sedimentary layer which is shallower than 2.5 km, a 2.5 km-thick basement layer whose velocity is 5.5 km/s, overlying the crystalline upper crust, and the boundary between the upper and lower crust.
Almost all aftershock hypocenters were located in the upper crust. However, the structure model suggests that the hypocenters of the main shock and some aftershock clusters were situated deeper than the boundary between the upper and lower crust. We found that the P-velocity in the upper crust beneath the northern part of Awaji Island is 5.64 km/s which is 3% lower than that of the surrounding area. The low-velocity zone coincides with the region where the high stress moment release was observed. 相似文献
Almost all aftershock hypocenters were located in the upper crust. However, the structure model suggests that the hypocenters of the main shock and some aftershock clusters were situated deeper than the boundary between the upper and lower crust. We found that the P-velocity in the upper crust beneath the northern part of Awaji Island is 5.64 km/s which is 3% lower than that of the surrounding area. The low-velocity zone coincides with the region where the high stress moment release was observed. 相似文献
20.
Numerical modelling ofSH wave seismograms in media whose material properties are prescribed by a random distribution of many perfectly elastic cavities and by intrinsic absorption of seismic energy (anelasticity) demonstrates that the main characteristics of the coda waves, namely amplitude decay and duration, are well described by singly scattered waves in anelastic media rather than by multiply scattered waves in either elastic or anelastic media. We use the Boundary Integral scheme developed byBenites
et al. (1992) to compute the complete wave field and measure the values of the direct waveQ and coda wavesQ in a wide range of frequencies, determining the spatial decay of the direct wave log-amplitude relation and the temporal decay of the coda envelope, respectively. The effects of both intrinsic absorption and pure scattering on the overall attenuation can be quantified separately by computing theQ values for corresponding models with (anelastic) and without (elastic) absorption. For the models considered in this study, the values of codaQ
–1 in anelastic media are in good agreement with the sum of the corresponding scatteringQ
–1 and intrinsicQ
–1 values, as established by the single-scattering model ofAki andChouet (1975). Also, for the same random model with intrinsic absorption it appears that the singly scattered waves propagate without significant loss of energy as compared with the multiply scattered waves, which are strongly affected by absorption, suggesting its dominant role in the attenuation of coda waves. 相似文献