A search for seismic radiation from late slip for the December 26, 2004 Sumatra-Andaman (M_w = 9.15) earthquake

The great 2004 Sumatra-Andaman (M_w = 9.15) earthquake ruptured a 1300-km-long segment of the Sumatra-Andaman Islands subduction zone in about nine minutes. The possibility of continued fault slip after the primary rupture has been raised by tsunami excitation models and by discrepancies between seismic slip models and geodetic observations. We examine the global seismic wavefield to identify any late seismic radiation that occurred during the first hour after the main rupture using stacking of deconvolutions and cross correlations of complete ground motion observations and point-source responses (Green's functions). We find no evidence for delayed seismic radiation larger than M_w = 7.5. Any major slip within an hour after the main sliding with mechanism similar to the main shock involved deformation so slow that it radiated no detectable seismic waves in the body wave or surface wave passband for periods less than ∼500 s.