Boundary-reflected waves and ultrasonic coda waves in rock physics experiments
Fu Bo-Ye1,2, Fu Li-Yun1, Wei Wei1, and Zhang Yan1
1. Key Laboratory of Petroleum Resource Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China.
2. University of Chinese Academy of Sciences, Beijing 100049, China.
Abstract：
Ultrasonic coda waves are widely used to study high-frequency scattering. However, ultrasonic coda waves are strongly affected by interference from by boundary-reflected waves. To understand the effect of boundary-reflected waves, we performed ultrasonic experiments using aluminum and shale samples, and the rotating staggered-mesh finite-difference method to simulate the wavefield. We analyzed the wavefield characteristics at the different receiving points and the interference characteristics of the boundary-reflected waves with the ultrasonic coda wave, and the effect of sample geometry on the ultrasonic coda waves. The increase in the aspect ratio of the samples delays the interference effect of the laterally reflected waves and reduces the effect on the ultrasonic coda waves. The main waves interfering with the ultrasonic coda waves are laterally reflected PP-, PS-, PPP-, and PPS-waves. The scattering and attenuation of the high-frequency energy in actual rocks can weaken the interference of laterally reflected waves with the ultrasonic coda waves.
. Boundary-reflected waves and ultrasonic coda waves in rock physics experiments[J]. APPLIED GEOPHYSICS, 2016, 13(4): 667-682.
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2016, Vol. 13 
