Using pure S wave fitting method, we studied the shear wave velocity structures under the Ordos block and its eastern and southern marginal areas. The results show that the velocity structure beneath Yulin station in ...Using pure S wave fitting method, we studied the shear wave velocity structures under the Ordos block and its eastern and southern marginal areas. The results show that the velocity structure beneath Yulin station in the interior of Ordos block is relatively stable, where no apparent change between high and low velocity layers exists and the shear wave velocity increases steadily with the depth. There is a 12km thick layer at the depth of 25km under this station, with an S wave velocity (V S=3.90km/s) lower than that at the same depth in its eastern and southern areas (V S≥4.00km/s). The crust under the eastern margin of Ordos block is thicker than that of the Yulin station, and the velocity structures alternate between the high and low velocity layers, with more low velocity layers. It has the same characteristic as having a 10km-thick low velocity layer (V S=3.80km/s) in the lower crust but buried at a depth of about 35km. Moreover, we studied the V P/V S ratio under each station in combination with the result of P wave velocity inversion. The results show that, the average velocity ratio of the Yulin station at the interior of Ordos block is only 1.68, with a very low ratio (about 1.60) in the upper crust and a stable ratio of about 1.73 in the mid and lower crust, which indicates the media under this station is homogenous and stable, being in a state of rigidity. But at the stations in the eastern and southern margins of the Ordos block, several layers of high velocity ratio (about 1.80) have been found, in which the average velocity ratio under Kelan and Lishi stations at the eastern margin is systemically higher than that of the general elastical body waves (1.732). This reflects that the crust under the marginal areas is more active relatively, and other materials may exist in these layers. Finally, we discussed the relationship among earthquakes, velocity structures beneath stations and faults.展开更多
Beijing has been severely affected by SARS, and SARS-associated coronavirus has been confirmed as its cause. However, clinical and experimental evidence implicates the possibility of co-infection. In this report, reov...Beijing has been severely affected by SARS, and SARS-associated coronavirus has been confirmed as its cause. However, clinical and experimental evidence implicates the possibility of co-infection. In this report, reovirus was isolated from throat swabs of SARS patients, including the first case in Beijing and her mother. Identification with the electron microscopy revealed the characteristic features of reovirus. 24 of 38 samples from other SARS cases were found to have serologic responses to the reovirus. Primers designed for reovirus have amplified several fragments of DNA, one of which was sequenced (S2 gene fragment), which indicates it as a unique reovirus (orthoreovirus). Preliminary animal experiment showed that inoculation of the reovirus in mice caused death with atypical pneumonia. Nevertheless, the association of reovirus with SARS outbreak requires to be further investigated.展开更多
文摘Using pure S wave fitting method, we studied the shear wave velocity structures under the Ordos block and its eastern and southern marginal areas. The results show that the velocity structure beneath Yulin station in the interior of Ordos block is relatively stable, where no apparent change between high and low velocity layers exists and the shear wave velocity increases steadily with the depth. There is a 12km thick layer at the depth of 25km under this station, with an S wave velocity (V S=3.90km/s) lower than that at the same depth in its eastern and southern areas (V S≥4.00km/s). The crust under the eastern margin of Ordos block is thicker than that of the Yulin station, and the velocity structures alternate between the high and low velocity layers, with more low velocity layers. It has the same characteristic as having a 10km-thick low velocity layer (V S=3.80km/s) in the lower crust but buried at a depth of about 35km. Moreover, we studied the V P/V S ratio under each station in combination with the result of P wave velocity inversion. The results show that, the average velocity ratio of the Yulin station at the interior of Ordos block is only 1.68, with a very low ratio (about 1.60) in the upper crust and a stable ratio of about 1.73 in the mid and lower crust, which indicates the media under this station is homogenous and stable, being in a state of rigidity. But at the stations in the eastern and southern margins of the Ordos block, several layers of high velocity ratio (about 1.80) have been found, in which the average velocity ratio under Kelan and Lishi stations at the eastern margin is systemically higher than that of the general elastical body waves (1.732). This reflects that the crust under the marginal areas is more active relatively, and other materials may exist in these layers. Finally, we discussed the relationship among earthquakes, velocity structures beneath stations and faults.
基金supported by the National High Technology Research and Development Program of China(Grant No.2001AA233041).
文摘Beijing has been severely affected by SARS, and SARS-associated coronavirus has been confirmed as its cause. However, clinical and experimental evidence implicates the possibility of co-infection. In this report, reovirus was isolated from throat swabs of SARS patients, including the first case in Beijing and her mother. Identification with the electron microscopy revealed the characteristic features of reovirus. 24 of 38 samples from other SARS cases were found to have serologic responses to the reovirus. Primers designed for reovirus have amplified several fragments of DNA, one of which was sequenced (S2 gene fragment), which indicates it as a unique reovirus (orthoreovirus). Preliminary animal experiment showed that inoculation of the reovirus in mice caused death with atypical pneumonia. Nevertheless, the association of reovirus with SARS outbreak requires to be further investigated.
