江西九江—福建宁化接收函数剖面研究

Study of the receiver function profile from Jiujiang, Jiangxi Province to Ninghua, Fujian Province

  • 摘要: 江西九江—福建宁化剖面沿NW--SE方向穿过华南大陆东部的扬子地块和华夏地块两个地质单元. 通过收集沿该剖面布设的35个流动宽频带地震台站2012—2014年记录的远震波形资料, 采用P波接收函数H-k扫描叠加和CCP叠加两种方法, 对该剖面下方的地壳厚度和泊松比分布进行了研究. 结果表明: 沿剖面地壳厚度为29—33 km, 扬子地块东南边缘与华夏地块的莫霍形态差异明显, 萍乡—广丰断裂北侧的萍乐凹陷带深部存在明显的莫霍面上隆现象, 为研究区域中地壳最薄处; 研究区大部分台站下方的泊松比值相对较低, 介于0.21—0.24之间, 萍乡—广丰断裂两侧泊松比值稍高, 可达0.26, 表明不同构造单元地壳深部岩石组成存在差异; 萍乡—广丰断裂可作为江绍拼合带的自然西延, 是扬子地块与华夏地块在赣北地区的拼合界线, 推测其深部的物质组成有相似之处.

     

    Abstract: The profile from Jiujiang, Jiangxi Province to Ninghua, Fujian Province, passes through the Yangtze block and the Cathaysia block from northwest to southeast in the east of South China continent. This paper selected teleseismic records from 35 temporary broadband stations along the profile from June 2012 to June 2014 so as to obtain the crustal thickness and Poisson's ratio by the H-k stacking method and common conversion point (CCP) stacking method. The results show that the crustal thickness of the studied area ranges 29-33 km. The depth of Moho of the southeast edge of the Yangtze block has an obvious difference from that of the Cathaysia block. The depth of the Ping-xiang--Leping depression zone to the north of Pingxiang--Guangfeng fault exhi-bits obvious uplift of Moho in the deep, being the thinnest part of the studied area. The average value of Poisson's ratio obtained from H-k stacking method shows that the Poisson's ratios are as low as 0.21-0.24 beneath crust of most of the studied area. At the two sides of the Pingxiang--Guangfeng fault, the Poisson's ratio value is higher, reaching about 0.26, which means the different constitution of the rock in the deep for the disparate tectonic units. All above evidences suggest that the Pingxiang--Guangfeng fault can be considered as the extension of Jiangshan-Shaoxing coherence belt, meanwhile it is the convergent boundary of Yangtze block and Cathaysia block in the north of Jiangxi Province, therefore it is inferred that the two blocks are composed of similar material in the deep.

     

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