井下地震计的P波接收函数正演计算及其稳定性研究——以首都圈地区为例

井下地震计波形记录的P波垂向分量存在频谱极小（spectrum null）现象，导致接收函数的结果不稳定.本文以首都圈地区为例，基于平面波入射的传播矩阵理论，发展了用于计算井下地震计的接收函数正演方法.在此基础上，分析了井下地震计波形垂向分量频谱极小现象，研究其对接收函数稳定性的影响.结果表明，井下地震计波形记录垂向分量的频谱极小开始出现的频率和地震计的埋深相关.该现象可造成反卷积提取的接收函数不稳定，且不稳定情况出现在频谱极小附近的频段，可通过选择合适的高斯因子压制其对接收函数的影响.

Stability of receiver function from borehole seismometer from forward modeling and case study of waveform data in China Capital Region

The vertical component P waves recorded by borehole seismometers features the phenomenon of spectrum null, which makes the receiver function unstable. Taking China Capital region as an example, we develop a method to forward modeling receiver functions based on the propagation matrix theory. We analyze the phenomenon of spectrum null on vertical component waveforms and study its influence on the stability of retrieving receiver functions. The result shows that the spectrum null of vertical component waveforms recorded at borehole seismometers is related to the burial depth of the seismometer. This phenomenon leads to the instability of receiver functions retrieved via deconvolution method, and this instability occurs near the period of spectrum null. A suitable Gaussian factor can be selected to reduce the influence of spectrum null when applying the deconvolution method.