| Study on Shear Wave Velocity Structure and Velocity Ratio Beneath Ordos Block and Its Eastern and Southern Margins |
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| 作者姓名： | Zhang Xuemin |
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| 作者单位： | [1]SchoolofGeophysicsandInformationTechnology,ChinaUniversityofGeosciences,Beijing100083,China [2]EarthquakeAdministrationofHebeiProvince,Shijiazhuang050021,China [3]InstituteofGeologyandGeophysics,ChineseAcademyofSciences,Beijing100029,China |
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| 基金项目： | TheprojectofContinentalStrongEarthquakeMechanismandForecastisundertheNationalKeyBasicResearchandDevelopmentPrograms (FoundationItem :G19980 4 0 70 4 ) ,China |
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| 摘 要： | 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 (Vs=3.90km/s) lower than that at the same depth in its eastern and southern areas (Vs≥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 (Vs=3.80km/s) in the lower crust but buried at a depth of aout 35km. Moreover, we studied the Vp/Vs 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.
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| 关 键 词： | 鄂尔多斯板块 S波 速度结构 地质运动 地震 |
Study on Shear Wave Velocity Structure and Velocity Ratio Beneath Ordos Block and Its Eastern and Southern Margins |
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| Zhang Xuemin.Study on Shear Wave Velocity Structure and Velocity Ratio Beneath Ordos Block and Its Eastern and Southern Margins[J].Earthquake Research in China,2004,18(3):242-252. |
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| Authors: | Zhang Xuemin |
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| Institution: | Zhang Xuemin 1,2),Diao Guiling 2) and Shu Peiyi 3) 1)School of Geophysics and Information Technology,China University of Geosciences,Beijing 100083,China 2)Earthquake Administration of Hebei Province,Shijiazhuang 050021,China 3)Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China |
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| Abstract: | |
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| Keywords: | Ordos block S wave Velocity structure Velocity ratio |
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