Depth-varying rupture properties of subduction zone megathrust faults

• Published in: Journal of Geophysical Research: Solid Earth Vol. 117; no. B4
• Main Authors: Lay, Thorne, Kanamori, Hiroo, Ammon, Charles J., Koper, Keith D., Hutko, Alexander R., Ye, Lingling, Yue, Han, Rushing, Teresa M.
• Format: Journal Article
• Language: English
• Published: Washington, DC Blackwell Publishing Ltd 01-04-2012; American Geophysical Union
• Subjects: 2004 Sumatra-Andaman; 2010 Chile earthquake; 2011 Tohoku earthquake; asperities; Continental dynamics; Earth sciences; Earth, ocean, space; earthquake rupture; Earthquakes; Exact sciences and technology; Geophysics; Ground motion; Lithosphere; megathrusts; Plate tectonics; Seismic activity; Seismic waves; Seismology; Transition zone; South America; Asia; Honshu; Japan; Sumatra; Tohoku; Far East; Chile; Indonesia; Sea surface; plates; lithosphere; dip; ground motion; Transition zone; earthquakes; faults; low frequency; rupture; transition zones; depth; slip; radiation; fault displacements; tsunamis; subduction zones; plate boundaries; Natural hazards; flow; trenches; energy; seismic waves
• ISSN: 0148-0227; 2169-9313; 2156-2202; 2169-9356
• DOI: 10.1029/2011JB009133

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 (Mw9.0) 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 downdip edge of the seismogenic zone. We designate the portion of the megathrust less than 15 km below the ocean surface 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 at depths of 30–45 km in subduction zones where relatively young oceanic lithosphere is being underthrust with shallow plate dip, 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.
Key Points
Seismic radiation from megathrust earthquake rupture varies with depth
A 4‐domain model of radiation segmentation is introduced for megathrusts
Strong‐ground motions originate from the down‐dip region