Crustal shear-wave velocity structure beneath Anhui Province revealed by receiver function inversions
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摘要: 根据安徽台网25个台站记录到的远震波形资料，运用频率域反褶积的方法提取接收函数，并采用H-Kappa扫描法反演得到安徽地区各个台站下方的地壳厚度与纵横波速度比。结果显示，安徽地区台站下方地壳厚度大致可分为3个区域：皖西南大别山地区、皖南山区和淮河以北的皖北平原地区，其中大别山地区台站下方的地壳厚度位于35—39 km范围内，相对较厚；皖南地区位于33—36 km范围内；皖北以平原为主，地壳厚度位于30—33 km范围内。这一研究结果与安徽地区的地质构造背景具有较好的相关性。同时，H-K扫描结果显示，安徽地区台站下方波速比基本处于1.70—1.80范围内，变化不大。在界面倾斜角度不大的前提下，利用横向均匀分层模型的波形反演实现接收函数的波形拟合，得到台站下方地壳上地幔S波速度结构，计算结果显示，安徽地震监测台站下莫霍面上表面S波速度一般为3.6—3.9 km/s，而界面底部大约为4.3—4.6 km/s，莫霍面处的速度起伏变化并不十分明显。Abstract: According to the teleseism recorded by twenty-five stations of Anhui Network, this paper has used the method of frequency domain deconvolution to extract receiver functions, and the H-Kappa scanning method to invert the crust thickness and vP/vS ratio under the stations in Anhui area. The results show that the crust thickness of Anhui area can be divided into three regions, including the Dabie Mountains in the southwest of Anhui, the mountains in southern Anhui, and the plains in northern Anhui. The crustal thickness is in the range of 35—39 km beneath the stations in the Dabie Mountain area, in the range of 33—36 km in southern Anhui, and in the range of 30—33 km for plains in northern Anhui. The results of this study have a good correlation with the geological tectonic setting of Anhui. Meanwhile, the H-K results show that the ratio of velocity beneath the stations in Anhui is basically from 1.7 to 1.8 with little change. Under the premise that the inclined angle of the interface is not large, the S-wave velocity structure is obtained by waveform fitting of the receiver functions which are implemented using the waveform inversion of horizontal uniform stratified model. And the calculation results show that the S-wave velocity on the surface of Moho is within the range of 3.6—3.9 km/s, while that is about 4.3—4.6 km/s at the bottom of Moho. The velocity fluctuation of Moho beneath stations in Anhui is not extremely obvious.
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Key words:
- Anhui area /
- receiver functions /
- H-K stacking /
- shear-wave velocity structure /
- Moho
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表 1 安徽地区台站下方莫霍面厚度、波速比和泊松比
台站名 代号 莫霍面深度/km 波速比vP/vS 泊松比 安庆台 ANQ 36.2 1.79 0.27 白山台 BAS 31.4 1.72 0.24 蚌埠台 BEB 32.2 1.68 0.23 滁州台 CHZ 31.2 1.74 0.25 淮北台 HBE 31.5 1.73 0.25 合肥台 HEF 33.2 1.77 0.27 淮南台 HNA 33.5 1.75 0.26 黄山台 HUS 33.6 1.77 0.27 嘉山台 JAS 30.3 1.74 0.25 泾县台 JIX 33.2 1.72 0.24 马鞍山台 MAS 32.7 1.75 0.26 蒙城台 MCG 31.8 1.74 0.25 泗县台 SIX 32.8 1.73 0.25 舒城台 SCH 32.4 1.76 0.26 金寨台 JZA 35.5 1.72 0.24 六安台 LAN 33.4 1.76 0.26 豹子崖台 BZY 36.8 1.73 0.25 佛子岭台 FZL 38.9 1.74 0.25 
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