The origin of precursory signals that precede the P-waves is controversial, as it may be caused by ground effect (seismic nucleation phase) or instrumental effect due to a digitizer. Such signals cause errors in the automatic detection of P-wave arrival times and consequently decrease the accuracy of earthquake parameter estimations. In this paper, we proposed spectral analysis techniques to distinguish between different types of precursory segments, and to find if there is a relation between existence of these precursors and their corresponding earthquakes. These algorithms are applied to 1015 local events recorded by eleven permanent seismic stations belonging to the Egyptian National Seismic Network. Manual inspection of these events reveals the existence of these precursors. The investigations provided evidence that one type of these precursors originated because of an instrumental effect. This study shows the underlying causes of the precursory segment’s appearance prior to P-wave impulses. Many events had similar parameters; however, some of them had such precursors while others did not, in this inspection, multi resolution analysis details of the Discrete Wavelet Transform have been used. When large amplitudes for high frequency P-wave detail exceed ${10}^4$ counts (1 count = 1 nm/s), the appearance percentage for the precursory segment is 100%.

P波之前的前兆信号的起源是有争议的，因为它可能是由于地面效应（地震成核阶段）或数字化仪的仪器效应引起的。这样的信号会导致自动检测P波到达时间时出现错误，从而降低地震参数估计的准确性。在本文中，我们提出了频谱分析技术来区分不同类型的前兆段，并发现这些前兆的存在与其对应的地震之间是否存在关联。这些算法应用于由埃及国家地震台网的11个永久地震台站记录的1015个本地事件。手动检查这些事件揭示了这些前体的存在。调查提供了证据，表明这些前体中的一种是由于工具作用而产生的。这项研究显示了在P波脉冲之前前体部分出现的根本原因。许多事件具有相似的参数。但是，其中一些具有这种前体，而另一些没有，在此检查中，已使用离散小波变换的多分辨率分析详细信息。当高频P波细节的大幅度超过时${10}^4$ 计数（1个计数= 1 nm / s），前段的出现百分比为100％。