The main objective of this study is to examine the NARR (North American Regional Reanalysis Model) high-resolution dataset to understand the last two decades dramatic climate changes in Hudson Bay associated with the ...The main objective of this study is to examine the NARR (North American Regional Reanalysis Model) high-resolution dataset to understand the last two decades dramatic climate changes in Hudson Bay associated with the atmospheric keys by synoptically analysis. The anomalies of the near-surface meteorological parameters such as air temperature, humidity, mean sea level pressure, wind vectors along with cloudiness, precipitation, surface albedo and downward longwave radiation at surface in seasonally based changes have been analysed. The increase in low-level thermal structure leads to changing the near-surface humidity, evaporation, cloudiness, precipitation and downward longwave radiation at the surface. Also, winds have been accelerated associated with anticyclonic curvature development. The results show significant atmospheric changes during the last two decades in Hudson Bay with the highest values mostly during winter and fall seasons in the north, east boundaries and James Bay area. Using the statistical analysis for mean low-level temperature, surface albedo, low-level clouds and evaporation at the surface during nearly recent 2 decades (1998-2018) rather than the normal climatology mean (1981-2010) have revealed the meaningful significant difference for mentioned parameters. The statistical analysis results show that during spring there is a significant positive correlation between low clouds anomaly and 2 m air temperature anomaly rather than other seasons. So, the recent atmospheric changes in the study area as a region located in the Arctic and sub-Arctic can contribute to extra-local and global warming.展开更多
A number of aftershocks of the May 10th 1997, Zirkuh (Ghaen-Birjand) destructive earthquake have been used to investigate the anisotropy in the upper crust by observing shear wave splitting. Particle motion diagram an...A number of aftershocks of the May 10th 1997, Zirkuh (Ghaen-Birjand) destructive earthquake have been used to investigate the anisotropy in the upper crust by observing shear wave splitting. Particle motion diagram and aspect ratio methods were used as two different approaches to obtain splitting parameters. Clear shear wave splitting was observed on the records of the selected aftershocks, indicating that the media in the region was highly anisotropic. By using particle motion method, the direction of fast shear wave was found 22N19E, while the delay time between the fast and slow shear waves was obtained to be (6516) ms. By aspect ratio method, the direction of fast shear wave was determined to be 35N18E and the delay time between fast and slow shear waves was found to be (4910) ms. For a simple horizontal layer with a thickness about 5 km and uniformly distributed anisotropy, a stress aligned cracks model was used and the result was interpreted in terms of vertical aligned cracks in the direc-tion of N22E, having a density about 0.01. It is assumed that cracks are fluid-filled since they are located in the upper crust. Finally, by using Hudson cracks model for three crack densities 0.005, 0.01, 0.03, the velocity curves of shear wave were plotted as a function of angle between the symmetrical axis of cracks and the azimuth of source to receiver. It was concluded that when shear wave was polarized parallel to the crack surface, the velocity was uniform, but the velocity curve varied clearly if shear wave was polarized perpendicular to the crack surface.展开更多
A number of aftershocks of the May 10th 1997, Zirkuh (Ghaen-Birjand) destructive earthquake have been used to investigate the anisotropy in the upper crust by observing shear wave splitting. Particle motion diagram an...A number of aftershocks of the May 10th 1997, Zirkuh (Ghaen-Birjand) destructive earthquake have been used to investigate the anisotropy in the upper crust by observing shear wave splitting. Particle motion diagram and aspect ratio methods were used as two different approaches to obtain splitting parameters. Clear shear wave splitting was observed on the records of the selected aftershocks, indicating that the media in the region was highly anisotropic. By using particle motion method, the direction of fast shear wave was found 22°N±19°E, while the delay time between the fast and slow shear waves was obtained to be (65±16) ms. By aspect ratio method, the direction of fast shear wave was determined to be 35°N±18°E and the delay time between fast and slow shear waves was found to be (49±10) ms. For a simple horizontal layer with a thickness about 5 km and uniformly distributed anisotropy, a stress aligned cracks model was used and the result was interpreted in terms of vertical aligned cracks in the direction of N22°E, having a density about 0.01. It is assumed that cracks are fluid-filled since they are located in the upper crust. Finally, by using Hudson cracks model for three crack densities 0.005, 0.01, 0.03, the velocity curves of shear wave were plotted as a function of angle between the symmetrical axis of cracks and the azimuth of source to receiver. It was concluded that when shear wave was polarized parallel to the crack surface, the velocity was uniform, but the velocity curve varied clearly if shear wave was polarized perpendicular to the crack surface.展开更多
In fractured reservoir beds, fracture characteristics affect seismic wave response. Fractured models based on the Hudson＇s fractured medium theory were constructed in our laboratory by a backfilling technique. For th...In fractured reservoir beds, fracture characteristics affect seismic wave response. Fractured models based on the Hudson＇s fractured medium theory were constructed in our laboratory by a backfilling technique. For the same fracture density, the variations of the velocity and amplitude of the primary wave and shear wave parallel and perpendicular to the fracture were observed by altering the diameter （scale） of the penny-shaped fracture disk. The model test indicated that an increase of fracture scale increased the velocity and amplitude of the primary wave by about 2%. When the shear wave propagated parallel to the fracture, the velocity of the fast shear wave hardly changed, while the velocity of slow shear wave increased by 2.6% with increasing fracture scale. The results indicated that an increase of fracture scale would reduce the degree of anisotropy of the shear wave. The amplitudes of slow shear waves propagating parallel and perpendicular to fractures decreased with increasing fracture scale.展开更多
Based on Hudson’s theoretical hypothesis of equivalent fracture model,inserting aligned round chips in solid model can simulate fractured media. The effect of fractures on the propagation of P and S waves can be obse...Based on Hudson’s theoretical hypothesis of equivalent fracture model,inserting aligned round chips in solid model can simulate fractured media. The effect of fractures on the propagation of P and S waves can be observed by changing the fracture thickness. The base model is made of epoxy resin,and the material of fractures is a kind of low-velocity mixture containing silicon rubber. With constant diameter and number of fractures in each model,one group of models can be formed through changing the thickness of fracture. These models have the same fracture density. By using the ultrasonic pulse transmission method,the experiment records time and waveform of P and S waves in the direction parallel and perpendicular to the fracture orientation. The result shows that,with the same fracture density,changing fracture aperture will affect both velocity and amplitude of P and S waves,and the effect on P-wave amplitude is much greater than that on the velocity. Moreover,the variation in velocity of S wave is more obvious in the slow shear wave (S2),while the variation in amplitude is more obvious in the fast shear wave (S1). These properties of wave propagation are useful for seismic data processing and interpretation.展开更多
文摘The main objective of this study is to examine the NARR (North American Regional Reanalysis Model) high-resolution dataset to understand the last two decades dramatic climate changes in Hudson Bay associated with the atmospheric keys by synoptically analysis. The anomalies of the near-surface meteorological parameters such as air temperature, humidity, mean sea level pressure, wind vectors along with cloudiness, precipitation, surface albedo and downward longwave radiation at surface in seasonally based changes have been analysed. The increase in low-level thermal structure leads to changing the near-surface humidity, evaporation, cloudiness, precipitation and downward longwave radiation at the surface. Also, winds have been accelerated associated with anticyclonic curvature development. The results show significant atmospheric changes during the last two decades in Hudson Bay with the highest values mostly during winter and fall seasons in the north, east boundaries and James Bay area. Using the statistical analysis for mean low-level temperature, surface albedo, low-level clouds and evaporation at the surface during nearly recent 2 decades (1998-2018) rather than the normal climatology mean (1981-2010) have revealed the meaningful significant difference for mentioned parameters. The statistical analysis results show that during spring there is a significant positive correlation between low clouds anomaly and 2 m air temperature anomaly rather than other seasons. So, the recent atmospheric changes in the study area as a region located in the Arctic and sub-Arctic can contribute to extra-local and global warming.
文摘A number of aftershocks of the May 10th 1997, Zirkuh (Ghaen-Birjand) destructive earthquake have been used to investigate the anisotropy in the upper crust by observing shear wave splitting. Particle motion diagram and aspect ratio methods were used as two different approaches to obtain splitting parameters. Clear shear wave splitting was observed on the records of the selected aftershocks, indicating that the media in the region was highly anisotropic. By using particle motion method, the direction of fast shear wave was found 22N19E, while the delay time between the fast and slow shear waves was obtained to be (6516) ms. By aspect ratio method, the direction of fast shear wave was determined to be 35N18E and the delay time between fast and slow shear waves was found to be (4910) ms. For a simple horizontal layer with a thickness about 5 km and uniformly distributed anisotropy, a stress aligned cracks model was used and the result was interpreted in terms of vertical aligned cracks in the direc-tion of N22E, having a density about 0.01. It is assumed that cracks are fluid-filled since they are located in the upper crust. Finally, by using Hudson cracks model for three crack densities 0.005, 0.01, 0.03, the velocity curves of shear wave were plotted as a function of angle between the symmetrical axis of cracks and the azimuth of source to receiver. It was concluded that when shear wave was polarized parallel to the crack surface, the velocity was uniform, but the velocity curve varied clearly if shear wave was polarized perpendicular to the crack surface.
文摘A number of aftershocks of the May 10th 1997, Zirkuh (Ghaen-Birjand) destructive earthquake have been used to investigate the anisotropy in the upper crust by observing shear wave splitting. Particle motion diagram and aspect ratio methods were used as two different approaches to obtain splitting parameters. Clear shear wave splitting was observed on the records of the selected aftershocks, indicating that the media in the region was highly anisotropic. By using particle motion method, the direction of fast shear wave was found 22°N±19°E, while the delay time between the fast and slow shear waves was obtained to be (65±16) ms. By aspect ratio method, the direction of fast shear wave was determined to be 35°N±18°E and the delay time between fast and slow shear waves was found to be (49±10) ms. For a simple horizontal layer with a thickness about 5 km and uniformly distributed anisotropy, a stress aligned cracks model was used and the result was interpreted in terms of vertical aligned cracks in the direction of N22°E, having a density about 0.01. It is assumed that cracks are fluid-filled since they are located in the upper crust. Finally, by using Hudson cracks model for three crack densities 0.005, 0.01, 0.03, the velocity curves of shear wave were plotted as a function of angle between the symmetrical axis of cracks and the azimuth of source to receiver. It was concluded that when shear wave was polarized parallel to the crack surface, the velocity was uniform, but the velocity curve varied clearly if shear wave was polarized perpendicular to the crack surface.
文摘In fractured reservoir beds, fracture characteristics affect seismic wave response. Fractured models based on the Hudson＇s fractured medium theory were constructed in our laboratory by a backfilling technique. For the same fracture density, the variations of the velocity and amplitude of the primary wave and shear wave parallel and perpendicular to the fracture were observed by altering the diameter （scale） of the penny-shaped fracture disk. The model test indicated that an increase of fracture scale increased the velocity and amplitude of the primary wave by about 2%. When the shear wave propagated parallel to the fracture, the velocity of the fast shear wave hardly changed, while the velocity of slow shear wave increased by 2.6% with increasing fracture scale. The results indicated that an increase of fracture scale would reduce the degree of anisotropy of the shear wave. The amplitudes of slow shear waves propagating parallel and perpendicular to fractures decreased with increasing fracture scale.
基金Supported by the Major State Basic Research Development Program of China (973 Project) (Grant No.2006CB202306)the Applied Basic Project of China National Petroleum Corporation (Grant No.200510101)
文摘Based on Hudson’s theoretical hypothesis of equivalent fracture model,inserting aligned round chips in solid model can simulate fractured media. The effect of fractures on the propagation of P and S waves can be observed by changing the fracture thickness. The base model is made of epoxy resin,and the material of fractures is a kind of low-velocity mixture containing silicon rubber. With constant diameter and number of fractures in each model,one group of models can be formed through changing the thickness of fracture. These models have the same fracture density. By using the ultrasonic pulse transmission method,the experiment records time and waveform of P and S waves in the direction parallel and perpendicular to the fracture orientation. The result shows that,with the same fracture density,changing fracture aperture will affect both velocity and amplitude of P and S waves,and the effect on P-wave amplitude is much greater than that on the velocity. Moreover,the variation in velocity of S wave is more obvious in the slow shear wave (S2),while the variation in amplitude is more obvious in the fast shear wave (S1). These properties of wave propagation are useful for seismic data processing and interpretation.
