Sensitivity of seismic velocity towards tidal induced stress changes

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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.