--From Phys. Rev. Lett. 86, 3447 For minutes after the violent shaking of an earthquake, the ground continues to rock imperceptibly. Seismologists are unclear about the cause of this so-called seismic coda, but the 9 April PRL presents new evidence that may resolve the question. While some seismologists assume that the coda comes from waves that scatter only once before reaching the surface, the authors found evidence that the vibrations reflect many times within the Earth before being detected. They used an array of seismometers that could distinguish several types of shaking and showed that energy is divided equally among them, as theory predicts for multiply scattered waves. (R. Hennino et al., Phys. Rev. Lett. 86, 3447. Link to the paper: http://publish.aps.org/abstract/PRL/v86/p3447/ COMPLETE Focus story at http://focus.aps.org/v7/st17.html) __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>