Weak Localization of Seismic Waves

A group of scientists at the University Joseph Fourier of Grenoble and at the Centre National de la Recherche Scientifique, France believes they have observed the temporary trapping of seismic waves in a natural environment. Years ago the localization of waves was observed under laboratory conditions for electron waves (electrons, acting like waves as they move through a material) and light waves; the waves, traveling in a diffuse medium such as milk or powder, were repeatedly scattered but not absorbed and were, in effect, bottled up or "localized." (For a report on the localization of light waves see Update 356.)

Would such localization of waves be observed at the much larger terrestrial scale and under conditions where very little control could be exercised? The Grenoble scientists sought and found an example of what could be the first step towards a "seismic insulator," a strongly heterogeneous geographic environment which would scatter but not absorb waves in the earth.

Previously the same researchers had found evidence for seismic waves rattling around underground in the wake of some earthquakes (see Physical Review Focus article). Now they are reporting that interference of the seismic waves can be detected and that this method can be used to determine the mean wavelengths of "randomly walking" seismic waves. The waves in this case were propagating inside a volcano located in the French Auvergne and tracked with an array of detectors. (Larose et al., Physical Review Letters, upcoming article; contact Bart van Tiggelen, bart.van-tiggelen@grenoble.cnrs.fr, 33-4-76-88-12-76.)