Yao Yanji, Xu Xin, Wang Jing, Liu Lintao, Ma Zifei
School of Water Conservancy, Yunnan Agricultural University, Kunming 650201, China.
State Key Laboratory of Precision Geodesy, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430077, China.
Sensors (Basel). 2025 Jul 3;25(13):4157. doi: 10.3390/s25134157.
P-wave first-motion polarity is a critical parameter for determining earthquake focal mechanisms. Extracting relative P-wave arrival times and polarity information using waveform cross-correlation techniques can enhance the accuracy of earthquake location and focal mechanism inversion. However, seismic noise severely hampers the reliable detection of P-wave onsets and their first-motion polarities. To address this issue, we propose a noise-resistant polarity detection method based on the normal time-frequency transform (NTFT), termed the time-frequency similarity coefficient (TFSC). The TFSC method computes relative delays and similarity coefficients by calculating the real part of the NTFT coefficients between two seismic signals. We validated the proposed approach using both synthetic and real earthquake data. Without any filtering or preprocessing, the TFSC method demonstrated significantly greater robustness and reliability compared to the conventional time-domain normalized cross-correlation (NCC) method. These results indicate that the TFSC method has strong potential for practical application and provides a novel perspective for accurate detection of P-wave first-motion polarity in noisy seismic environments.
P波初动极性是确定地震震源机制的关键参数。利用波形互相关技术提取相对P波到时和极性信息，可以提高地震定位和震源机制反演的精度。然而，地震噪声严重阻碍了P波震相及其初动极性的可靠检测。为了解决这个问题，我们提出了一种基于常规时频变换（NTFT）的抗噪声极性检测方法，称为时频相似系数（TFSC）。TFSC方法通过计算两个地震信号之间NTFT系数的实部来计算相对延迟和相似系数。我们使用合成地震数据和实际地震数据对提出的方法进行了验证。在没有任何滤波或预处理的情况下，与传统的时域归一化互相关（NCC）方法相比，TFSC方法表现出显著更强的稳健性和可靠性。这些结果表明，TFSC方法具有很强的实际应用潜力，并为在噪声地震环境中准确检测P波初动极性提供了新的视角。
