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Abstract

Mathematical developments summarized as seismic interferometry provide the basis for a multitude of methods to analyze ambient vibrations in seismology. Usually called seismic noise these vibrations are seismic waves excited by wave motion in the oceans, wind, and anthropogenic activity. An intriguing benefit of ambient noise as seismological signal is its permanent availability that allows for a continuous monitoring of wave propagation. Here we present two applications to different environments that investigate dynamic processes in the subsurface. The first application uses the simplicity of a rather exotic environment – the Moon – to relate variations of the seismic velocity in the lunar crust to material change caused by the strong temperature differences between day and night. On Earth the situation is more complex as atmospheric effects and active tectonics also affect the material as demonstrated in the investigation in northern Chile. Here, co-seismic velocity reductions are superimposed on environmental changes of annual periodicity.