Abstract
Subduction zone plate boundary megathrust faults accommodate relative
plate motions with spatially varying sliding behavior. The 2004 Sumatra-Andaman
(Mw 9.2), 2010 Chile (Mw 8.8), and 2011 Tohoku (Mw 9.0) great earthquakes
had similar depth variations in seismic wave radiation across their
wide rupture zones - coherent teleseismic short-period radiation
preferentially emanated from the deeper portion of the megathrusts
whereas the largest fault displacements occurred at shallower depths
but produced relatively little coherent short-period radiation. We
represent these and other depth-varying seismic characteristics with
four distinct failure domains extending along the megathrust from
the trench to the down-dip edge of the seismogenic zone. We designate
the portion of the megathrust less than 15 km deep as Domain A, the
region of tsunami earthquakes. From 15 to \~35 km deep, large earthquake
displacements occur over large-scale regions with only modest coherent
short-period radiation, in what we designate as Domain B. Rupture
of smaller isolated megathrust patches dominate in Domain C, which
extends from \~35 to 55 km deep. These isolated patches produce
bursts of coherent short-period energy both in great ruptures and
in smaller, sometimes repeating, moderate-size events. For the 2011
Tohoku earthquake, the sites of coherent teleseismic short-period
radiation are close to areas where local strong ground motions originated.
Domain D, found in subduction zones where relatively young oceanic
lithosphere is being underthrust, is represented by the occurrence
of low-frequency earthquakes, seismic tremor, and slow slip events
in a transition zone to stable sliding or ductile flow below the
seismogenic zone.
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