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Propagation of an earthquake triggering front from the 2011 Tohoku‐Oki earthquake
Author(s) -
Miyazawa Masatoshi
Publication year - 2011
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2011gl049795
Subject(s) - seismology , geology , aftershock , induced seismicity , dynamic stress , front (military) , amplitude , stress (linguistics) , remotely triggered earthquakes , magnitude (astronomy) , seismic wave , focal mechanism , seismic gap , geophysics , geodesy , acceleration , physics , oceanography , linguistics , philosophy , classical mechanics , quantum mechanics , astronomy
Increases in seismicity have been widely observed at varying distances from the source area following large earthquakes. The increased number of earthquakes are usually called aftershocks if the area is within a rupture length of the mainshock, and called remotely triggered events if they are well beyond that distance. These earthquakes can be explained as being induced by static and/or dynamic stress changes due to the mainshock. However, clear observations of dynamic triggering have been inadequate to differentiate between the two mechanisms. This study shows that early post‐seismic events triggered by the 2011 M w 9.0 Tohoku‐Oki earthquake systematically propagated over Japan in a southwestern direction, associated with the strong seismic waves from the source. The propagation front was consistent with the arrivals of large amplitude surface waves traveling at 3.1 to 3.3 km/s and extending to a distance of 1,350 km. There were no observations of triggered earthquakes in the northern direction. Dynamic stress changes toward the north were comparable to or smaller than those necessary for triggering in the southwestern direction. Static stress changes were one to two orders smaller than dynamic stress changes at remote distance, indicating that static stress was not the main mechanism of the triggering. Furthermore, the dynamic stress/strain changes play an important role for remote triggering if the value is more than ∼500 kPa in stress or ∼10 −6 in strain.