Nakagawa Seiji, Korneev Valeri A
Earth Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS74R120, Berkeley, California 94720.
J Acoust Soc Am. 2014 Jun;135(6):3186-97. doi: 10.1121/1.4875333.
Open and partially closed fractures can trap seismic waves. Waves propagating primarily within fluid in a fracture are sometimes called Krauklis waves, which are strongly dispersive at low frequencies. The behavior of Krauklis waves has previously been examined for an open, fluid-filled channel (fracture), but the impact of finite fracture compliance resulting from contacting asperities and porous fillings in the fracture (e.g., debris, proppants) has not been fully investigated. In this paper, a dispersion equation is derived for Krauklis wave propagation in a fracture with finite fracture compliance, using a modified linear-slip-interface model (seismic displacement-discontinuity model). The resulting equation is formally identical to the dispersion equation for the symmetric fracture interface wave, another type of guided wave along a fracture. The low-frequency solutions of the newly derived dispersion equations are in good agreement with the exact solutions available for an open fracture. The primary effect of finite fracture compliance on Krauklis wave propagation is to increase wave velocity and attenuation at low frequencies. These effects can be used to monitor changes in the mechanical properties of a fracture.
开放性骨折和部分闭合性骨折能够捕获地震波。主要在骨折缝隙内的流体中传播的波有时被称为克劳克利斯波，这种波在低频时具有很强的色散性。此前已经对开放的、充满流体的通道（骨折缝隙）中的克劳克利斯波行为进行了研究，但骨折中由于接触粗糙面和多孔填充物（例如碎片、支撑剂）而产生的有限骨折柔度的影响尚未得到充分研究。在本文中，使用改进的线性滑动界面模型（地震位移不连续模型），推导了克劳克利斯波在具有有限骨折柔度的骨折缝隙中传播的色散方程。所得方程在形式上与对称骨折界面波（另一种沿骨折传播的导波）的色散方程相同。新推导的色散方程的低频解与开放骨折的精确解吻合良好。有限骨折柔度对克劳克利斯波传播的主要影响是在低频时增加波速和衰减。这些影响可用于监测骨折力学性能的变化。
