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Temporal characteristics of the famous Matsushiro earthquake swarm were investigated quantitatively using point-process analysis. Analysis of the earthquake occurrence rate revealed not only the precise and interesting process of the swarm, but also the relation between pore water pressure and the strength of the epidemic effect, and the modified Omori-type temporal decay of earthquake activity. The occurrence rate function (t) for this swarm is represented well aswhere f(t) represents the contribution of the swarm driver, which was the erupting water from the deep in this case, and the second term represents an epidemic effect of the modified Omori type. Based on changes in the form of f(t), this two-year long swarm was divided into six periods and one short transitional epoch. The form of f(t) in each period revealed the detail of the water erupting process. In the final stage, f (t) decayed according to the modified Omori-formula form, while it decayed exponentially in the brief respite of the water eruption in the fourth period. When an exponential decay of swarm activity is observed, we have to be cautious of a sudden restart of the violent activity. The epidemic effect is stronger when the pressure of the pore water is higher. Even when the pressure is not high, the p value in the epidemic effect is small, when there is plenty of pore water. However, the epidemic effect produced about a quarter of the earthquakes even though there was not much pore water in the rocks. 相似文献
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Daisuke Nishio-Hamane Asa Shimizu Ritsuko Nakahira Ken Niwa Asami Sano-Furukawa Taku Okada Takehiko Yagi Takumi Kikegawa 《Physics and Chemistry of Minerals》2010,37(3):129-136
The stability and equation of state for the cotunnite phase in TiO2 were investigated up to a pressure of about 70 GPa by high-pressure in situ X-ray diffraction measurements using a laser-heated
diamond anvil cell. The transition sequence under high pressure was rutile → α-PbO2 phase → baddeleyite phase → OI phase → cotunnite phase with increasing pressure. The cotunnite phase was the most stable
phase at pressures from 40 GPa to at least 70 GPa. The equation of state parameters for the cotunnite phase were established
on the platinum scale using the volume data at pressures of 37–68 GPa after laser annealing, in which the St value, an indicator of the magnitude of the uniaxial stress component in the samples, indicates that these measurements were
performed under quasi-hydrostatic conditions. The third-order Birch-Murnaghan equation of state at K
0′ = 4.25 yields V
0 = 15.14(5) cm3/mol and K
0 = 294(9), and the second-order Birch-Murnaghan equation of state yields V
0 = 15.11(5) cm3/mol and K
0 = 306(9). Therefore, we conclude that the bulk modulus for the cotunnite phase is not comparable to that of diamond. 相似文献
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