Sensitivity of seismic velocity towards tidal induced stress changes

岩石不是线性弹性材料，因为地震波的速度也取决于外加应力。通过测量地震波速度的变化，就可以得出关于外加应力的结论，这对于理解地震具有根本的重要性。观测潮汐引起的应力和速度变化是校准这些测量的一个好方法。速度变化是通过测量定期计算的地震环境噪声的互函数和自相关函数的相位的微小变化来确定的。该项目旨在研究地震速度随固体潮的变化。除了以前不经常进行的观测外，还将提供更多的地震速度应力敏感性数据点，此外，在项目的第一部分，将借助地震台阵调查由于上覆岩石的加载而引起的敏感性对深度的预期依赖性。在该项目的第二部分，将调查所测得的灵敏度是否允许通过观测地震速度的变化来探测地震引起的静态应力变化，有助于对地震的一般了解的一个可能的未来应用是监测地壳的应力状态。

Rocks are not linear-elastic materials, because the seismic velocity also depends on the applied stress. By measuring the changes in the seismic velocity, it is therefore possible to draw conclusions about the applied stress, which is of fundamental importance for the understanding of earthquakes.Observing tidal-induced stresses and velocity changes is a good way to calibrate these measurements.The velocity changes are determined by measuring small changes in the phase of regularly calculated cross- and autocorrelation functions of the seismic ambient noise. The project aims at investigating the change of seismic velocity with Earth tides. Previous infrequent observations are to be complemented with more data points of the stress sensitivity of seismic velocity.Additionally, in the first part of the project, the expected depth dependence of the sensitivity due to the loading of overlying rocks will be investigated with the help of seismic arrays. In the second part of the project, it will be investigated whether the measured sensitivities allow to detect static stress changes caused by earthquakes by means of observations of the change of the seismic velocity.One possible future application that could contribute to the general understanding of earthquakes is the monitoring of the stress state of the Earth's crust.