Along-dip variation of teleseismic short-period radiation from the 11 March 2011 Tohoku earthquake (Mw 9.0)

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Abstract

[1] Locations of coherent short-period seismic wave radiation from the 11 March 2011 Tohoku earthquake (Mw 9.0) are imaged by back-projecting teleseismic P waves recorded across North America for a series of narrow, overlapping passbands centered at 8s, 4s, 2s, 1s, and 0.5s. Initially the energy release for all five passbands migrates slowly down-dip, however over time the two longer-period passbands show coherent energy release systematically shifted up-dip of the shorter-period source regions. Back-projection images of P waves from ten (point-source-like) aftershocks do not show a frequency-dependent trend, implying that the frequency dependence observed for the main shock is not an artifact created by 3D earth structure, depth phase interference, or some other deficiency. We conclude that the unstable sliding properties along the megathrust are segmented, with faster moment rate variations in the down-dip region and relatively smooth sliding further up-dip.

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