首页|期刊导航|中国地震研究（英文版）|Study on Shear Wave Velocity Structure and Velocity Ratio Beneath Ordos Block and Its Eastern and Southern Margins
中国地震研究（英文版）2004，Vol.18Issue(3)：242-252,11.
Study on Shear Wave Velocity Structure and Velocity Ratio Beneath Ordos Block and Its Eastern and Southern Margins
Study on Shear Wave Velocity Structure and Velocity Ratio Beneath Ordos Block and Its Eastern and Southern Margins
摘要
Abstract
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 Iow 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 about 35km. Moreover, we studied the Vi/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.关键词
Ordos block/S wave/Velocity structure/Velocity ratioKey words
Ordos block/S wave/Velocity structure/Velocity ratio分类
天文与地球科学引用本文复制引用
Zhang Xuemin,Diao Guiling ,Shu Peiyi..Study on Shear Wave Velocity Structure and Velocity Ratio Beneath Ordos Block and Its Eastern and Southern Margins[J].中国地震研究（英文版）,2004,18(3):242-252,11.基金项目
The project of Continental Strong Earthquake Mechanism and Forecast is under the National Key Basic Research and Development Programs (Foundation Item: G1998040704),China. （Foundation Item: G1998040704）
