Imposing Active Sources during High-Frequency Passive Surface-Wave Measurement

• Published in: Engineering (Beijing, China) China), 2018-10, Vol.4 (5), p.685-693
• Main Authors: Cheng, Feng, Xia, Jianghai, Shen, Chao, Hu, Yue, Xu, Zongbo, Mi, Binbin
• Format: Article
• Language: English
• Subjects: Active surface wave; High frequency; Mixed-source surface wave; Multichannel analysis of passive surface waves; Passive surface wave; Spatial autocorrelation
• ISSN: 2095-8099
• DOI: 10.1016/j.eng.2018.08.003

Passive surface-wave utilization has been intensively studied as a means of compensating for the shortage of low-frequency information in active surface-wave measurement. In general, passive surface-wave methods cannot provide phase velocities up to several tens of hertz; thus, active surface-wave methods are often required in order to increase the frequency range. To reduce the amount of field work, we propose a strategy for a high-frequency passive surface-wave survey that imposes active sources during continuous passive surface-wave observation; we call our strategy “mixed-source surface-wave (MSW) measurement.” Short-duration (within 10 min) passive surface waves and mixed-source surface waves were recorded at three sites with different noise levels: namely, inside a school, along a road, and along a railway. Spectral analysis indicates that the high-frequency energy is improved by imposing active sources during continuous passive surface-wave observation. The spatial autocorrelation (SPAC) method and the multichannel analysis of passive surface waves (MAPS) method based on cross-correlations were performed on the recorded time sequences. The results demonstrate the flexibility and applicability of the proposed method for high-frequency phase velocity analysis. We suggest that it will be constructive to perform MSW measurement in a seismic investigation, rather than exclusively performing either active surface-wave measurement or passive surface-wave measurement.