Seismic interferometry in the presence of an isolated noise source

Feb 13, 2023 | CWP Blog

Posted by Roel Snieder

Seismic interferometry is a technique to extract the waves that propagate between seismic sensors from noise that is recorded at these sensors. In a collaborative project with Sven Schippkus and Celine Hadziioannou from the University of Hamburg, I studied the properties of seismic noise recorded at 4907 seismic stations in Austria shown below.

The cross-correlation of the noise recorded at a master station at location rM with all other stations is shown in the left panel below. The retrieved waveforms show a wavefront that is centered at the master station at rM. This panel shows a surface wave that propagates between the master station and all other stations, this surface wave is usually retrieved in seismic interferometry. But in addition, the retrieved cross-correlation in the left panel also shows a circular wavefront that is centered at the red cross. This raises the question what is special about this location?

It turns out that there is a park of wind turbines at the location of the red cross that gives the second circular wavefront. The authors of this study show that the two wavefronts touch for all values of the lag time of the cross-correlation, as is also shown in the numerical simulation in the right panel. Both wavefronts carry information about the subsurface. More examples and details can be found in a recent article in the new journal Seismica.

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