Seismic Source Imaging by Time Reversal Method

Abstract

Time-reversal methods were successfully applied in the past to acoustic waves in many fields such as medical imaging, underwater acoustics, non destructive testing and recently to seismic waves in seismology for earthquake imaging. The increasing power of computers and numerical methods (such as spectral element methods) enables one to simulate more and more accurately the propagation of seismic waves in heterogeneous media and to develop new applications, in particular time reversal in the three-dimensional Earth. Generalizing the scalar approach of Draeger and Fink (1999), the theoretical understanding of time-reversal method can be addressed for the elastic Earth by using normal mode theory. It is shown how to relate time-reversal methods on one hand, with auto-correlation of seismograms for source imaging and on the other hand, with cross-correlation between receivers for structural imaging and retrieving Green function. In the case of source imaging, automatic location in time and space of earthquakes and unknown sources is obtained by time reversal technique. In the case of big earthquakes such as the Sumatra-Andaman earthquake of December 2004, we were able to reconstruct the spatio-temporal history of the rupture. Some new applications of these techniques on synthetic tests and on real data (glacial earthquakes, seismic hum) will be displayed.

Further information

• Montagner-poster.pdf