利用背景噪声反演鄂尔多斯块体及其南缘地区地壳速度结构

摘要

Using the dispersion curves of Rayleigh waves that were extracted from the seismic noise of 53 broad-band stations recorded in the Ordos Block and its southern Edge by two seismic stations cross correlation, we have obtained the average dispersion curve of the Fen-Wei graben system, the Northern edge of Qinling, the Ordos Block and the Liupan Mountains, and extracted the crustal and upper mantle structures of the four regions. The results show that the depth of the crust in the Fen-Wei graben system, the northern edge of Qinling and the Ordos Block, and the Liupan Mountains is 34 km,~40 km, and 49~50 km, respectively. The velocity of S wave in the uppermost mantle of the corresponding region is 4.20 km/s, 4.25 km/s, 4.30 km/s, and 4.15 km/s. The most obvious difference of velocity structure appears in the upper crust. The Liupan Mountains has a low velocity in the middle crust. The characteristics of velocity are almost the same for the lower crust.%文中利用分布在鄂尔多斯块体及其南部周缘地区的53个宽频带地震固定台站的连续波形记录，采用双台互相关计算方法由背景噪声提取瑞利波格林函数，经时频分析获得相速度和群速度频散曲线，并分别计算了汾渭地堑、秦岭北缘、鄂尔多斯块体内部和六盘山地区4个不同构造区的平均频散曲线，进而反演了各构造区的地壳上地幔一维横波速度结构。结果显示：地壳厚度在汾渭地堑为34 km，在秦岭北缘地区和鄂尔多斯块体均为40 km，在六盘山地区最厚，达49~50 km；相应的上地幔顶部横波速度分别为4.20，4.2，4.30和4.15 km/s；地壳内结构浅部特征差异最大，在地壳中部六盘山地区的速度较低，下部地壳不同地区的波速较一致。