Cracks that develop during brittle deformation easily modify rocks' physical properties; therefore, understanding of seismic properties of oceanic rocks during deformation is essential for interpretation of the seismic observations of the oceanic lithosphere. Here we measured elastic wave velocities of gabbro and peridotite during triaxial deformation experiments at room temperature, a confining pressure of 20 MPa, and a strain rate of ∼10⁻⁶ s⁻¹. Gabbroic rocks showed significant decrease in elastic wave velocities approaching the maximum stress, which is comparable to that of typical crystalline rocks. On the other hand, peridotite showed relatively sudden and small decrease in elastic wave velocities close to the maximum stress. We inverted the observed velocities to crack density tensor based on an effective medium theory. The different changes in elastic wave velocities between gabbroic rocks and peridotites were interpreted by different characteristics of crack development, where limited number of cracks were opened in peridotite than in gabbroic rocks. The calculated reflection coefficient of the interface between the gabbro and peridotite increases from <0.1 to ∼0.25 as approaching the maximum stress. Synthetic seismograms computed from the crack-dependent velocity structures of the oceanic lithosphere indicate that the Moho reflectivity is highly sensitive to the contrast of crack-damage across the crust-mantle boundary. The existence of a heterogeneous crack-damaged zone in the oceanic lithosphere, which is likely related to intra-plate earthquakes, may result in the spatial variations of Moho reflection.

脆性变形过程中产生的裂缝很容易改变岩石的物理性质；因此，了解大洋岩石在变形过程中的地震特性对于解释大洋岩石圈的地震观测至关重要。在这里，我们在室温、20 MPa 的围压和~10 ^-6 s ^-1的应变速率下，在三轴变形实验中测量了辉长岩和橄榄岩的弹性波速度. 辉长岩在接近最大应力时弹性波速度显着降低，这与典型的结晶岩相当。另一方面，橄榄岩在接近最大应力时表现出相对突然和较小的弹性波速度下降。我们根据有效介质理论将观测到的速度反演为裂纹密度张量。辉长岩和橄榄岩之间弹性波速度的不同变化可以用不同的裂缝发展特征来解释，其中橄榄岩比辉长岩打开的裂缝数量有限。随着接近最大应力，辉长岩和橄榄岩之间界面的计算反射系数从<0.1增加到~0.25。根据海洋岩石圈裂缝相关速度结构计算的合成地震图表明，莫霍面反射率对跨壳幔边界的裂缝损伤对比高度敏感。大洋岩石圈存在异质裂隙破坏带，可能与板内地震有关，可能导致莫霍面反射的空间变化。