Frequency Shift Processing for the Hypocenter with Short-term Single-frequency Pulse in the Ocean Sub-bottom Profile Data
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摘要: 采用短时单频脉冲震源的浅地层剖面,记录的波形数据空间假频较严重。因其信号具有频率高、频带窄的特征,通常利用Hilbert变换提取瞬时振幅属性(信号包络)供解释使用。但瞬时振幅均为正值,在进行构造解释时不方便使用。本文提出在对浅层剖面资料提取瞬时振幅的基础上,计算瞬时振幅的微分并配合滤波的方法,实现高频窄带浅地层剖面资料的一种频移处理。该方法把高频窄带的多周期信号变为低频带宽的单周期信号,有效扩展了倍频程并消除假频。应用在南海浅地层剖面资料处理中,资料处理后更利于构造解释。Abstract: The spatial aliasing of waveform data which is recorded using the short-term single-frequency pulse in the sub-bottom profile is serious. Usually the instantaneous amplitude attribute(signal envelope) is extracted for interpretation using the Hilbert transform for its signal has a characteristic of high frequency and narrow-band. However, instantaneous amplitude is always positive, so it is not convenient to use when performing structural interpretation. In this paper, on the basis of the extraction of instantaneous amplitude in the sub-bottom profile data, calculating the differential of instantaneous amplitude cooperated the filtering achieve frequency shift processing for high-frequency narrow-band signal in sub-bottom section. This method converts a multi-cycle signal with high-frequency narrow-band to a Single-cycle signal with low-frequency bandwidth, which effectively extends the octave and eliminates aliasing. Application in the South China sea sub-bottom profile data, the data is more conducive to structural interpretation.
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