单裂缝不同传播方向Krauklis波振幅变化的实验研究

裂缝广泛分布于地壳岩石中并具有多尺度的特点，研究地震波在裂缝介质中的传播规律具有重要的科学意义和应用价值.含流体的裂缝中传播的Krauklis波（也曾被称为慢流体波、裂缝波、斯通利导波等）近年来逐渐成为地球物理学界的研究热点之一.本研究利用地震物理模型技术研究横波在单裂缝样品中传播时随传播方向变化的响应特征，在实验室用环氧树脂为基质构建模型样品，一个为不含裂缝的参考样品，一个为含直径30 mm、厚度0.2 mm的薄币状单裂缝的模型，利用0.5 MHz换能器测试了横波在模型中传播时透射信号的特征.实验结果显示在单裂缝样品中透射横波发生了波形的畸变和振幅降低，振幅谱显示透射信号的主频明显降低，在初至横波之后为具有一定能量的尾波.对尾波进行时频分析，发现在方位角较小时尾波能量较弱而方位角较大时尾波能量较强，尾波中信号的主频在0.1 MHz左右，与前人理论和实验研究结果一致.

Experimental observation of Krauklis wave amplitude variation based on single fracture physical model

Fractures widely develop in crustal rocks and have multi-scale characteristics. It is of great scientific significance and application value to study the properties of seismic wave propagation in fractured media. Krauklis wave (also-called Stoneley-guided wave, slow Stoneley wave or crack wave) is a unique wave mode propagating along fluid filled fractures. Krauklis wave has recently become a research hot spot in the field of geophysics. In this research, we study propagation properties of Krauklis wave varying with S wave propagation direction. We design two epoxy samples:one reference sample and one sample contains an air-filled single fracture with a diameter 30 mm and a thickness 0.2 mm. We use a transducer with a central frequency 0.5 MHz to initiate S wave and record the transmitted wave using a transducer with a central frequency 0.8 MHz. For transmitted S wave of the single fracture sample, when the azimuthal angle varies from 0 degree to 90 degree, the waveform distorts, the amplitude is attenuated, and the central frequency of spectrum decreases. Besides, there is apparent coda after transmitted S wave. Then we implement time frequency analysis on the coda wave. Amplitude of the coda wave is strengthened as the azimuthal angle increases. In our study, the central frequency of the coda wave is nearly 0.1 MHz, which agrees with previous research results.