Interlocking of heterogeneous plate coupling and aftershock area expansion pattern for the 2011 Tohoku-Oki Mw9 earthquake

The 2011 Tohoku‐Oki earthquake (Mw9.0) ruptured a large portion of the plate boundary where the coupling was considered weak and represented by sparsely distributed small asperities. A typical asperity break produced an event of around Mw7.5 accompanied by a subsequent expansion of aftershock activi...

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Bibliographic Details
Published in:Geophysical research letters 2012-03, Vol.39 (5), p.n/a
Main Authors: Tajima, Fumiko, Kennett, Brian L. N.
Format: Article
Language:English
Subjects:
aftershocks
anomalous zone
Asperity
Boundaries
Earth sciences
Earth, ocean, space
Earthquakes
Exact sciences and technology
interlocking
Joining
megathrust event
Physical properties
plate coupling
Plate tectonics
Rupture
Seismic activity
Seismic phenomena
Seismology
Tomography
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Summary:The 2011 Tohoku‐Oki earthquake (Mw9.0) ruptured a large portion of the plate boundary where the coupling was considered weak and represented by sparsely distributed small asperities. A typical asperity break produced an event of around Mw7.5 accompanied by a subsequent expansion of aftershock activity beyond the main rupture zone. Unlike previous large earthquakes, the Mw9.0 earthquake sequence does not show much spatial expansion of aftershock activity, but the areas of slip deficit in the main rupture zone are progressively filled in by aftershocks. We show a clear image of segmentation of physical properties in the subducted slab that has been revealed by joint tomography of P and S wave arrivals. The mapped variations separate the zones of dominant high‐frequency radiation down‐dip and dominant low‐frequency radiation up‐dip on the mainshock fault. These changes indicate significant variations in the effective plate coupling that interlocked the source areas of the past distinct earthquakes. Key Points We revised the concept of asperity model in terms of effective plate coupling We showed an anomalous zone in plate coupling by a joint tomography model Our approach may detect clues for future interlocked megathrust events
ISSN:0094-8276
1944-8007
DOI:10.1029/2011GL050703