Multicomponent seismic polarization analysis
Multicomponent seismic polarization analysis
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多分量地震极化分析
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
R. Stewart
中科院分区：
文献类型：
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作者：
S. Guevara;R. Stewart
在3-C地震方法中，检波器的植物方位和极性应事先已知，以提供正确的振幅信息。原则上，波的线偏振可以用来确定检波器的方向，这样就可以纠正定位中的场误差。为此，本文对两个3-C数据集的极化信息进行了分析。数据来自3C-3D检波器指向性实验和3C-2D高分辨率数据集。偏振分析采用两个参数：水平接收机的方位角和线性度。在3d情况下，使用了第一个破窗。在二维情况下，分析了第一次断裂和第二次事件。对于第一次断裂，极化与源接收机方向之间存在一定的关系，但受多种因素的影响，无法准确推断出方向信息。观察到响应随检波器方向的差异等效应。对二维数据分析的第二个事件，解释为S折射，呈现出更明确的线偏振。受弹性波影响的颗粒位移显示出一个优先的极化方向，这取决于引起颗粒运动的地震事件和介质的弹性特性。这一事实在理论上和许多实验中都得到了证明。偏振与发射方向和介质的弹性特性有关。为了利用波的偏振特性，人们做了很多努力。一些方法已经成功地应用，主要是在地震地震学和VSP中。然而，在地面地震勘探中却不那么容易应用。这归因于近地表的非均匀性（Gal’perin, 1977），可能是3-C检波器的耦合和响应。极化分析的一个缺点是难以区分，因为地震事件通常是混合的。在常规地震方法中，只测量垂直地面运动，地震事件的极化不是一个问题，但在多分量地震方法中应该考虑到这一点。在三维地震处理中，检波器信息应旋转到震源-接收方向进行第一次极化校正。可以进行另一次旋转，从与双折射性质有关的“自然坐标”角度获得各向异性的信息（Cary, 1994）。图1显示了多分量二维和三维地震采集的极化特征。在二维中，组件沿源和接收器定义的线定向。在3-D中，相对于接收器，光源可以位于任何方向，因此能量可以来自任何方向。
In the 3-C seismic method, the plant orientation and polarity of geophones should be previously known to provide correct amplitude information. In principle the linear polarization of waves can be used to determine the direction of the geophones and in that way field errors in location can be corrected. In this work, polarization information of two 3-C data set is analyzed with that purpose. The data are from a 3C-3D geophone directivity experiment and from a 3C-2D high-resolution data set. Two parameters were used to analyze polarization: the azimuth of horizontal receivers and the linearity. In the 3-D case, a first break window was used. In the 2-D case, first breaks and a second event were analyzed. For the first breaks, a relationship was found between polarization and direction source-to-receiver, but it is affected by many factors and the directional information cannot be inferred accurately from it. Effects like difference in response with the direction of the geophone were observed. The second event analyzed for the 2-D data, interpreted as an S refraction, presents much more definite linear polarization. INTRODUCTION The displacement of particles effected by elastic waves shows a preferred direction of polarization, depending on the seismic event that is causing the particle motion and on the elastic properties of the medium. This fact has been shown both theoretically and in many experiments. Polarization is related to shot-to-receiver orientation and to elastic properties of the medium. Much effort has been devoted to take advantage of the polarization properties of waves. Some methods have been used successfully, mainly in earthquake seismology and in VSP. However in surface seismic exploration it is not so easily applied. This has been attributed to the heterogeneity of the near surface layers (Gal’perin, 1977) and likely the coupling and response of the 3-C geophone. A drawback of polarization analysis is that it is difficult to discriminate because the seismic events usually are mixed. Polarization of seismic events is not an issue in the conventional seismic method, where only vertical ground motion is measured, but should be taken in account in multicomponent seismic method. In 3C-3D seismic processing geophone information should be rotated to the source-receiver direction to have a first polarization correction. Another rotation can be carried out to get information about anisotropy from the angles of the “natural coordinates”, which are related to birefringence properties (Cary, 1994). Figure 1 illustrates the polarization characteristics in multicomponent 2-D and 3-D seismic acquisition. In 2-D, the components are oriented along the line defined by source and receiver. In 3-D, sources can be located at any direction with respect to receivers and so the energy can come from any direction.