利用接收函数研究郯庐断裂带鲁苏皖段及邻区地壳结构特征

利用郯庐断裂带鲁苏皖段及邻区的261个宽频带地震台站5年记录的763个远震波形数据，计算并筛选得到了10846条远震P波接收函数.采用P波接收函数H-κ法得到了该区的地壳厚度和壳内平均泊松比值，并采用共转换点叠加法进一步揭示台站下方Moho界面的起伏形态.研究发现：⑴研究区Moho界面埋深在27~40 km范围内变化，平均深度在~34 km，总体上以郯庐断裂带为界呈现出东薄西厚的特征.地壳厚度在不同块体之间或者是块体内部存在着明显差异，表明不同的地质构造单元经历了不同的构造演化过程.⑵研究区地壳泊松比在0.15~0.32之间变化，平均泊松比为0.24，略低于全球陆壳和中国陆壳平均泊松比值；然而，较大的泊松比浮动范围却意味着研究区内地壳物质具有强烈的横向非均匀性及物质组成的复杂性.沿郯庐断裂带展布着一条NNE-SSW方向的泊松比高值异常带，推测是镁铁质基性岩沿郯庐断裂带上涌至地壳所致，亦或是高温高压的幔源热物质底侵至下地壳所致.⑶研究区的地壳厚度和壳内平均泊松比存在着反相关的关系；地壳厚度和地表地貌特征呈镜向关系，即造山隆起区Moho界面埋藏较深，而平原盆地区Moho界面埋藏较浅.Moho埋深等值线分布图和研究区布格重力异常特征对应良好.⑷共转换点（Common Conversion Point，CCP）叠加法对Moho界面的刻画与H-κ叠加法求得的地壳厚度结果具有较好的一致性.CCP剖面表明郯庐断裂带不仅是扬子断块区和华北块体的分界断裂，更是一条切割Moho面、深抵上地幔的深大超壳断裂带，错距达4~7 km.⑸研究区内部分台站下方存在壳内分界面，仍能通过改变壳内速度后采用H-κ法获得其埋藏深度.

Crustal structure characteristics beneath the Shandong-Jiangsu-Anhui segment of the Tan-Lu fault zone and its adjacent regions using receiver functions

Using 763 teleseismic waveform data recorded in 5 years by 261 broadband seismic stations in the Shandong-Jiangsu-Anhui segment of the Tan-Lu fault zone and adjacent areas, 10846 teleseismic P-wave receiver functions were calculated and filtered. The P-wave receiver function H-κ method was used to obtain the crustal thickness and the average Poisson's ratio in the crust, and the CCP (Common Conversion Point) method was used to further reveal the undulation pattern of the Moho interface below the station. The comparison shows that the crustal thickness distribution characteristics obtained by the two different methods have good consistency. The research found that: (1) The Moho interface burial depth in the study area varies in the range of 27~40 km, with an average depth of ~34 km, and generally shows the characteristics of thinness in the east and thickness in the west with the Tan-Lu fault zone as the boundary. The thickness of the crust varies significantly between or within blocks, indicating that different geological units have undergone different tectonic evolutionary processes. (2) The Poisson's ratio of the crust in the study area varies between 0.15 and 0.32, and the average Poisson's ratio is 0.24, which is slightly lower than the average Poisson's ratio of the global continental crust and the Chinese continental crust; however, the larger floating range of Poisson's ratio means that the crustal material in the study area has strong lateral heterogeneity and complex material composition. There is an anomalous zone of high Poisson's ratio in the NNE-SSW direction along the Tan-Lu fault zone, which is presumed to be caused by the upwelling of ferromagnesian basal rocks to the crust along the Tan-Lu fault zone, or the bottom intrusion of high temperature and high pressure mantle-derived thermal material into the lower crust. (3) There is an inverse correlation between the crustal thickness and the average Poisson's ratio within the crust in the study area; the crustal thickness and the surface geomorphic features show a mirror relationship, i.e., the Moho interface is buried deeper in the orogenic uplift area and shallower in the plain basin area. The Moho burial depth contour distribution map and the Bouguer gravity anomaly feature in the study area correspond well. (4) The CCP stacking method for the Moho interface is in good agreement with the crustal thickness results obtained by the H-κ stacking method, and the CCP section shows that the Tan-Lu Fracture Zone is not only a divisional fracture between the Yangzi fault block area and the North China block, but also a deep and large ultracrustal fracture zone cutting through the Moho surface and reaching the upper mantle with a misalignment of 4~7 km. (5) Some of the stations in the study area have intracrustal interfaces below them, and their burial depths can still be obtained by the H-κ method after changing the intracrustal velocity.