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Strong-motion recordings at 87 sites from 56 different intraplate earthquakes from North America, Europe, China and Australia have been used through a two-step regression analysis to develop new attenuation models for peak ground acceleration, and for pseudo-relative velocity for frequencies of 0.25, 0.5, 1.0, 2.0, 5.0 and 10.0 Hz, all for 5 per cent of critical damping. The estimates are obtained along with an analysis of residuals and scatter. A similar regression analysis has been performed also for Fourier spectra of acceleration, in which case the coefficient for the anelastic term has been interpreted in terms of a frequency dependent quality factor Q. The resulting Q-model shows a strong frequency sensitivity with values around 600–700 at 1 Hz, around 2000 at 10 Hz and around 5200 at 25 Hz. These PGA, PSV and Q results depend, however, on the underlying assumption for geometrical spreading, in particular for low frequencies. 相似文献
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Radiocarbon dating of thin palaeopodsols buried beneath turf-banked gelifluction lobes at four localities in the low alpine mountain zone in the Jostedalsbreen region, western Norway, show that gelifluction processes were initiated subsequent to the late Subboreal Chronozone. Although large age-depth gradients have been demonstrated from buried palaeosols in southern Norway, evidence is presented that the palaeosols in this study show only moderate age-depth gradients. The age estimates from these buried palaeosols give maximum dates of burial, but the error is not thought to be large. Gelifluction processes were probably initiated close to the time of the climatic deterioration, which led to the formation of the present glaciers during the Subatlantic Chronozone. The processes may have been most active during the peak of the Little Ice Age, during which a periglacial climate was established to low levels in this mountainous region. 相似文献
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An analysis of the attenuation of seismic waves as measured by the quality factorQc (for coda waves) has been performed for the volcanic Jan Mayen island in the Norwegian Sea, using earthquakes near the Jan
Mayen Fracture Zone and local seismic stations on the Jan Mayen island.Qc values of the order of 100 at a frequency of 1 Hz are found, increasing to about 300 at 10 Hz. These values are typical of
what usually is observed in tectonically influenced areas near oceanic/continental plate boundaries. It is considered likely
that these results are influenced by the fact that the Jan Mayen island, in spite of its proximity to a fracture zone, is
located in the northern end of the Jan Mayen Ridge, which now is accepted as being a micro-continent. The presence of the
active Beerenberg volcano on the Jan Mayen island does give rise to a somewhat stronger attenuation for waves traversing that
area, but this effect is weak and quite limited in spatial extent. There is also a slight increase in attenuation as a function
of depth, but less than what is observed in terms of lateral variations. This is reasonable in view of the very strong lateral
variations in lithospheric structure exhibited in this area. 相似文献
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Simulation of CO<Subscript>2</Subscript> hydrate formation in cold aquifers: nonequilibrium approach
Khaled Jemai Mohammad Taghi Vafaei Bjørn Kvamme Ashok Chejara 《Arabian Journal of Geosciences》2017,10(5):113
In this paper, we focus on the geological storage of CO2 in reservoirs with zones that are cold enough to facilitate CO2 hydrate formation at local pressures. A 2D hydro-chemical mechanical model which has five layers (three layers with aquifers and two layers with cap rock in which we introduced two fractures) is created. We apply a reactive transport reservoir simulator, RetrasoCodeBright (RCB), in which hydrate is treated as a pseudo mineral. Following the recent modifications to account for hydrate dynamics in the code through a kinetic approach (Kvamme et al., Proceedings of the 7th International Conference on Gas Hydrates (ICGH 2011), 2011b), we have further improved the simulator to implement the nonequilibrium thermodynamic calculations. In the present study, we spot the light on the hydrate formation effects on porosity in different regions, as well as on the flow pattern. These simulations are based on classical relationships between porosity and permeability, but the outline of ongoing modifications is presented as well. A critical question in such systems is whether hydrate formation can contribute to stabilizing the storage, given that hydrates are pore filling and cannot be stable toward mineral surfaces. The implications of hydrate formation on the geo-mechanical properties of the model reservoir are other aspects addressed in this study. 相似文献
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This paper presents detailed analyses of a bottom-hole pressure record observed at the Gullfaks oil field in the northern North Sea. The series contains variability which is superimposed on the large-scale reservoir pressure. This variability can lead to a misinterpretation of the gradients coupled with short-term pressure tests.The presents analysis has revealed that the mechanism behind these fluctuations is mainly the loading from the sea tides. A number of tidal constituents have been recovered from the observations. These are in phase with the local sea tidal oscillations, however the amplitudes are reduced by a factor of 3–4. Earth tides cannot be detected. A model has been constructed to describe the tidal influence on the reservoir pressure at the specific location. The model is able to resolve the reservoir tide with satisfactory accuracy and may be used to correct for or remove the tidal influences during pressure tests.The effect of atmospherically induced sea-surface displacement on the reservoir pressure has also been studied. 相似文献
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