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Earthquake-source parameters related to magnitude 总被引：1，自引：0，他引：1
Mitiyasu Ohnaka 《Geophysical Journal International》1978,55(1):45-66
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Mitiyasu Ohnaka 《Pure and Applied Geophysics》2004,161(9-10):1915-1929
It is shown that the rupture nucleation length increases up to the critical length with time according to a power law, and that the accelerating phase of nucleation leading up to the critical point is scaled in the framework of fracture mechanics based on slip-dependent constitutive formulation. Geometric irregularity of the rupturing surfaces plays a fundamental role in scaling the accelerating phase of nucleation up to the critical point. A power-law scaling relation between the rupture growth length and the nucleation time to the critical point is derived from theoretical consideration based on laboratory data. This power-law scaling relation has no singularity, and hence it may be useful for the predictive purpose of an imminent, large earthquake. 相似文献
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Aitaro Kato Shingo Yoshida Mitiyasu Ohnaka Hiromine Mochizuki 《Pure and Applied Geophysics》2004,161(9-10):1895-1913
— We have evaluated how the parameters prescribing the slip-dependent constitutive law are affected by temperature and effective normal stress, by conducting the triaxial fracture experiments on Tsukuba-granite samples in seismogenic environments, which correspond to a depth range to 15 km. The normalized critical slip displacement D c almost remains constant below 300oC (insensitive to both temperature and effective normal stress σ n eff); D c increases with increasing temperature above 300 °C, and the rate of D c increase with temperature tends to be largest at higher σ n eff. The breakdown stress drop Δτ b for the granite at constant σ n eff is roughly 80 MPa below 300 °C, and does not depend on σ n eff. Above 300 °C, Δτ b decreases gradually with increasing temperature, and the rate of Δτ b reduction with temperature increases at higher σ n eff. The peak shear strength τ p increases nearly linearly with increasing σ n eff below 300 °C. However, τ p becomes lower above 300 °C, deviating from the linear relation extrapolated from below 300 °C. This is consistent with the onset of crystal plastic deformation mechanisms of Tsukuba granite. 相似文献
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Mitiyasu Ohnaka 《Pure and Applied Geophysics》1984,122(6):848-862
The Kanto earthquake (M=7.9) that occurred along the Sagami Trough in the Sagami Bay on 1 September 1923 was one of the most disastrous earthquakes in Japanese history. The Kanto area includes Metropolitan Tokyo and Yokohama which are densely populated, and hence it has been a matter of great concern, from the viewpoints of earthquake prediction and disaster prevention, whether or not the 1923 Kanto earthquake was preceded by precursory seismicity. A study using the most complete lists of earthquakes catalogued recently by Utsu and the Japan Meteorological Agency reveals that seismic activity in the Kanto area was appreciably higher before and after the Kanto earthquake, and that the Kanto earthquake was preceded by a sequence of anomalous seismic activity, quiescence, and foreshocks. Such higher activity before and after the Kanto earthquake is contrasted with low seismicity during the recent 30-year period. A model is proposed to explain the precursory seismic activity, subsequent quiescence, and foreshocks for the Kanto earthquake. In the model, the transition from precursory seismic activity to quiescence is ascribed to time-dependent fracture due to stress-aided corrosion. Foreshocks are related to an acceleration of premonitory slip shortly before the mainshock slip. 相似文献
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Overall SEDs based on ISO SWS observations show fair agreement with photospheric model predictions for red (super)giant stars.
However, some details of molecular spectra cannot be explained by a photospheric origin. In particular, fine structure in
the H2O 2.7 μm band can be clearly resolved by the SWS and is identified in an early M giant, whose photosphere will never
produce H2O. This is definite evidence for H2O of non-photospheric origin in an early M giant. Also, the observed H2O and
CO2 bands in a late M giant are too strong to be explained by a photospheric origin alone. Further, the H2O 2.7 μm band is
found in four early M supergiants in the h + χ Persei clusters (three of which show UIRs) and is especially strong in the
M4 supergiant S Per (which also shows a highly peculiar SED). Thus, against a belief that H2O is found only in the latest
M giants such as Miras, the SWS has revealed the presence of H2O in a wider region of the HR diagram. The origin of this H2O
is unknown but is probably in a non-photospheric extra envelope. Such a H2O envelope appears to be a general feature through
early M (super)giants to cool supergiants such as S Per, where the envelope has finally developed to be optically thick.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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M. D. Gray M. Wittkowski M. Scholz E. M. L. Humphreys K. Ohnaka D. Boboltz 《Monthly notices of the Royal Astronomical Society》2009,394(1):51-66
We describe a combined dynamic atmosphere and maser propagation model of SiO maser emission in Mira variables. This model rectifies many of the defects of an earlier model of this type, particularly in relation to the infrared (IR) radiation field generated by dust and various wavelength-dependent, optically thick layers. Modelled masers form in rings with radii consistent with those found in very long baseline interferometry (VLBI) observations and with earlier models. This agreement requires the adoption of a radio photosphere of radius approximately twice that of the stellar photosphere, in agreement with observations. A radio photosphere of this size renders invisible certain maser sites with high amplification at low radii, and conceals high-velocity shocks, which are absent in radio continuum observations. The SiO masers are brightest at an optical phase of 0.1–0.25, which is consistent with observed phase lags. Dust can have both mild and profound effects on the maser emission. Maser rings, a shock and the optically thick layer in the SiO pumping band at 8.13 μm appear to be closely associated in three out of four phase samples. 相似文献
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Mitiyasu Ohnaka 《Geophysical Journal International》1978,53(2):311-318
Summary . Quantitative comparison of dynamic parameters is made between stick—slip in the laboratory and earthquakes in the Earth. It is shown that the same theory is successfully applied for both earthquakes and stick—slip for rock samples for which slip occurs over the entire pre-existing fault, in so far as the physical processes of earthquakes are explained by the elastic rebound theory. 相似文献
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