大容量气枪震源陆地反射地震探测——以长江中下游铜陵地区为例

The Seismic Reflection Survey Using Large Capacity Air-gun Source—A Case Study of Tongling Area in Mid-lower Reaches of the Yangtze River

摘要:

为了实验大容量气枪震源陆地水体流动激发反射地震探测效果，在长江中下游安徽省铜陵段，采用气枪船长江航道流动激发、沿江岸布设反射地震仪器接收的非纵弯线工作方式，得到了反映测线经过地区地壳深部结构和构造特征的反射地震数据。原始资料信噪比较低，但部分资料不同部位仍可辨认出来自地壳及莫霍面反射波组。就传播距离而言，地震波传播的水平距离最大可达21km，垂直深度可达30km以上。在数据处理中，根据原始资料特点，针对性采用了非纵弯线面元定义、三维层析静校正、叠前多域去噪及组合反褶积技术，最终得到的叠加时间剖面上具有丰富的壳内反射波组。结果显示，测线经过地区的地壳结构为双层结构，总厚度为30.0~36.0km。上地壳呈现隆坳相间的反射特征，下地壳存在多组叠层状弧型反射波组，莫霍面反射特征清晰，由2~3个反射同相轴组成，呈现SW端向NE段抬升的形态。剖面经过地区存在一个切穿下地壳和莫霍面的深部断裂，应该是长江深断裂的反映。研究结果充分说明，大容量气枪震源可应用于陆地流动水体地壳精细结构的深地震反射探测。

Abstract:

In order to verify the reflection seismic detection effect of large capacity air-gun on land flow water,we adopted the working mode of non-longitudinal and bending line which air gun ship excitated in the Tongling area of Yangtze river and the reflective seismic instrument received along the river bank. We obtained the reflection seismic data of the deep structure and tectonic features in the area. Although the original record has lower signal noise,the reflected wave group of upper crust and the Moho can be recognized in different parts of the record. The maximum horizontal distance of seismic wave propagation reaches as far as 21km,and the vertical depth of seismic wave propagation can reach more than 30km. Based on the characteristics of original data,we applied the combined methods such as non-longitudinal and bending line bin definition,3d tomographic static correction,pre-stack multi-domain denoising and combined deconvolution. The abundant crustal reflections are in the stack time section. The results show that the crustal structure in the area are of double layer structure,with a total thickness of 30.0~36.0km. The reflection features of uplift and depression interphase was showed in the upper crust,and there are multiple groups of laminated arc-shaped reflection waves in the lower crust. The Moho is clearly observed by reflection features,which are composed of 2~3 reflection events,showing the raise from SW end to NE. There is a deep fault cutting through the lower crust and the Moho in the area,which is caused by the Yangtze river deep fault. The above results indicate that the large capacity air-gun can be used for deep reflection seismic detection of crustal fine structure in land flowing water.