Time‐reversal in seismology.

This talk is a review of the use and history of time‐reversal in seismology. time‐reversal has been developed independently in the field of acoustics and in geophysics exploration, without the two communities being aware of the fact, as testifies the lack of the cross‐references in early papers. The elegance of time‐reversal is that it thrives with complexity. Seismologists have to deal with complex signal transmitted through the earth. Moreover, earthquakes are complex sources, involving different episodes of slip along the fault. Early in the development of time‐reversal in seismology, emphasis has been put on the need of accurate numerical schemes to back‐propagate the wavefield and the need of relatively dense data. In addition to presenting several of the landmark applications of time‐reversal in seismology, several of our results will be outlined. In the last decade, our group has studied the potential of TR with the unique approach of combining laboratory experiments with application to seismology problems. Several applications will be presented: location and characterization of the rupture of the 2004 Parkfield earthquake, location, and retrieval of the sliding motion of glaciers in Greenland, finally imaging of the source location of a seismic signal of particularly emergent nature, the tremor.