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中值滤波可用于衰减地震数据中的相干波场,例如在VSP 资料处理中用中值滤波来压制下行波。将滤波器用于沿波场方向的地震道上,再从原始记录中减去滤波后的记录得出最终结果。这种方法被称为“减去法中值滤波”。可将这一方法扩展为自动估算记录中相干波场的慢度,然后根据记录上各点的慢度值,来进行时变、空变滤波。中值滤波属于非线性滤波,与线性滤波相比,它的特性更不易确定。但是,仍然有几种方法可用于分析中值滤波器的特性:(1)拟传输函数以详细说明时间序列的特性;(2)中值滤波器对简单模型的响应;(3)中值滤波器对模拟边界波场的阶跃响应,如叠加剖面上的断层。这些简单的方法对滤波器的性质提供一个直觉的印象,也可以提供一个半定量的测量。道间振幅变化对中值滤波器和线性滤波器有类似的、使其性能变坏的影响。中值滤波器的特性(就信号畸变而言)沿记录的倾斜方向应用时可以改进低通滤波(在t的方向)。中值滤波的阶跃响应受背景噪声大小的控制,中值滤波器造成的阶跃区的畸变在高噪声水平下近似于相应线性滤波器所产生的阶跃畸变
Median filtering can be used to attenuate coherent wavefields in seismic data, for example by using median filtering to suppress the descending wave in VSP data processing. Apply the filter to the traces along the wavefield and subtract the filtered record from the original record to arrive at the final result. This method is called “subtract median filter ”. This method can be extended to automatically estimate the slowness of the coherent wavefield in the recording, and then time-varying and space-variable filtering based on the slowness values of the points recorded. Median filtering is non-linear filtering, which is more difficult to determine than linear filtering. However, there are still several ways to analyze the characteristics of a median filter: (1) the quasi-transfer function to specify the characteristics of the time series; (2) the response of the median filter to the simple model; (3) the median filter A step response to the simulated boundary wave field, such as a fault in a superimposed section. These simple methods provide an intuitive impression of the nature of the filter and can also provide a semi-quantitative measurement. The change in amplitude between channels has a similar effect on the median and linear filters, degrading their performance. The characteristics of the median filter (in the case of signal distortion) improve the low-pass filtering (in the direction of t) when applied in the direction of the recorded tilt. The step response of the median filter is controlled by the magnitude of the background noise. The distortion of the step region caused by the median filter approximates the step distortion caused by the corresponding linear filter at high noise level