Extraction of High-Rate GPS Seismic Wave Signals with Wavelet Packets Decomposition
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摘要: 随着高采样率GPS接收机的出现、高精度的定轨以及数据处理技术的发展, 利用GPS观测高频率、瞬态的地震波信号成为可能.但如何消除混叠在地震波信号中的多路径、随机噪声等误差, 有效地提取地震波信号, 仍然是制约高采样率GPS及其地球物理应用的重要因素.提出一种基于小波包分解的方法, 对动态位移序列中的多路径误差进行消除, 同时去除高频率随机噪声, 提取地震波信号.通过结合SCIGN的19个GPS测站的1Hz采样GPS观测数据, 对2010年墨西哥M7.2地震的地震波引起的地表动态位移进行解算, 采用小波包分解有效地提取地震波信号并对其进行谱分析.结果表明, 该方法提取的地震波信号能较好地反映出地震波的传播及其特性, 具有无需多天重复观测、处理精度高等特点.Abstract: With the development of high-rate GPS receivers, precise orbit and processing technology of GPS data, it is possible to observe the high frequency, transient dynamic displacement by GPS. However, it remains a problem as how to mitigate the error such as multipath errors, and random noise aliasing in geophysical signals so as to extract seismic signals, which in turn limits the high-rate GPS and its geophysical applications. In this paper, an approach based on wavelet packets decomposition (WPD) is presented to extract seismic signals through mitigating the multipath error and random noise of dynamic displacement series from high-rate GPS. With the 1 Hz observation data from 19 stations in Southern California Integrated GPS Network (SCIGN) during the Mexico M7.2 earthquake in 2010, the ground displacement is calculated. Meanwhile, the approach based on WPD is introduced for seismic signal extraction and spectrum analysis. As is shown in results, the approach is accurate and effective in seismic signal extraction to reflect the characteristics of seismic wave propagations and it enjoys an advantage that it does not necessarily involve multiple-day observation.
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表 1 19个测站的震中距及其由1 Hz采样观测值解算的E、N方向坐标的参考误差
Table 1. Epicentral distance, north and east coordinates reference error based on 1 Hz observation of 19 stations
站名 震中距(km) 处理前误差(mm) 处理后误差(mm) 站名 震中距(km) 处理前误差(mm) 处理后误差(mm) N E N E N E N E BILL 215 10.8 8.3 5.0 3.3 PIN1 183 7.4 7.9 4.5 3.1 CCCS 301 11.5 7.5 4.7 3.2 SIO5 195 12.0 7.2 4.4 2.9 CIT1 334 26.3 7.3 5.3 3.6 TABL 320 17.1 20.1 4.8 3.5 CRBT 638 18.3 10.2 5.2 3.3 TRAK 278 18.9 18.9 4.3 2.9 CSDH 328 23.3 6.0 4.8 3.1 USGC 110 11.9 12.1 5.5 3.5 DHLG 130 13.4 7.4 4.0 2.7 WIDC 208 25.8 11.2 4.7 3.2 EWPP 290 11.7 6.5 5.3 3.5 AZRY 184 51.4 171.0 10.3 8.8 GLRS 110 18.7 8.8 4.9 3.3 CSN1 371 580.1 305.7 10.8 7.8 MASW 615 10.1 7.0 4.9 3.1 LOWS 627 - - - - MONP 109 18.1 9.3 4.3 2.9 - - - - - - -
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