利用接收函数研究重庆及周边地区地壳结构

Crustal structure in Chongqing and adjacent region determined by receiver functions

利用中国地震台网33个台站记录的远震资料,采用接收函数扫描法和线性反演方法,对重庆及其邻区的壳幔速度结构进行了研究,获得了研究区内地壳厚度、Vp/Vs以及壳幔速度的分布特征。研究结果表明:重庆区域地壳厚度最厚为CHK台站,为50.4km;最薄为ROC台站,为38.5km;中部地区厚度为41～45km。在所设定测线A—A'上,莫霍面有一定起伏,四川盆地处浅层速度偏低,在WUL台处发现台站下方8～10km处有低速异常,推断这个很薄的低速区很可能是导致川东薄皮褶皱构造的滑脱面。

We select broadband teleseismic waveform data recorded by the CDSN and study the crustal structure in Chongqing and its adjacent region.The crustal thickness and Vp/V s ratio are estimated by the grid-search method using crustal conversion and multiples,assuming an average P-wave velocity in the crust.Teleseismic P waveform is carried out to investigate the S-wave velocity structure,assuming the fixed Vp/Vs value inferred from the grid-search method.The results also indicate that the crustal thickness is the thickest beneath CHK station,which is 50.4 km,the thinnest crustal thickness is beneath ROC station,which is 38.5 km,and the crustal thickness beneath central area is 41-45 km.On the line A-A',the crust shallow velocity beneath the Sichuan basin is low.At the WUL station,there is a low-velocity anomaly at 8-10 km below the station.We infer that this thin low-velocity zone likely to be the detachment surface which caused the eastern Sichuan thin-skin fold structure.