Along-dip variation of teleseismic short-period radiation from the
11 March 2011 Tohoku earthquake (Mw 9.0)
Geophysical Research Letters, 38 (21):
L21309+ (Nov 12, 2011)DOI: 10.1029/2011GL049689
Abstract
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.