Seismic velocities in rock subjected to axial loading up to shear fracture
Seismic velocities in rock subjected to axial loading up to shear fracture
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DOI：
10.1029/jb078i029p06936
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发表时间：
1973-10
影响因子：
--
通讯作者：
I. Gupta
中科院分区：
文献类型：
--
作者：
I. Gupta
在印第安纳州石灰岩试样上测量了沿沿着三个相互垂直方向的P和S速度随轴向载荷的变化。试件为矩形棱柱体，在平行于长尺寸（Z轴）的垂直方向上施加可变轴向载荷。夹具用于沿着横向（Y轴）牢固地保持试样。压缩型和剪切型压电换能器用于发送和接收地震信号，并安装在样品的相对面上，以便可以沿沿着三个正交方向（Z、Y和X轴）测量地震速度。当轴向载荷以小的增量增加直到剪切破裂发生时，得到了显示P波和S波到达的地震图。对地震图的检查表明，在破裂之前，P和S速度在所有三个方向上都减小，但减小的量完全不同。P速度与S速度之比沿Z轴沿着几乎保持不变，沿Y轴沿着略有减小，沿X轴沿着显著下降。这些结果被解释为由于破坏前的不稳定性，提供了定性信息的各向异性行为的不稳定性，地震的一个重要的前兆指标。
The P and S velocities along three mutually perpendicular directions are measured as a function of the axial load on specimens of Indiana limestone. The specimens are rectangular prisms, and variable axial load is applied in the vertical direction parallel to the long dimension (Z axis). A clamp is used to hold the specimen firmly along a transverse direction (Y axis). Piezoelectric transducers of the compressional and shear type are used for both transmitting and receiving the seismic signal and are mounted on opposite faces of the specimen so that seismic velocities can be measured along the three orthogonal directions (Z, Y, and X axes). Seismograms showing the arrivals of P and S waves are obtained while the axial load is increased in small increments until shear fracture takes place. An examination of seismograms shows that prior to rupture both P and S velocities decrease in all three directions but by quite different amounts. The ratio of P to S velocities, ξ, remains nearly constant along the Z axis, decreases somewhat along the Y axis, and drops considerably along the X axis. These results, interpreted as being due to prefailure dilatancy, provide qualitative information on the anisotropic behavior of ξ, an important premonitory indicator of earthquakes.