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Hierarchical asperity model for multiscale characteristic earthquakes: A numerical study for the off‐Kamaishi earthquake sequence in the NE Japan subduction zone
Author(s) -
Hori Takane,
Miyazaki Shin'ichi
Publication year - 2010
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 - 10.1029/2010gl042669
Subject(s) - asperity (geotechnical engineering) , geology , seismology , subduction , induced seismicity , nucleation , tectonics , geotechnical engineering , chemistry , organic chemistry
We develop a numerical model to simulate the occurrence of multiscale characteristic earthquakes in the off‐Kamaishi area of the northeast Japan subduction zone. A notable feature of these earthquake sequences is that microearthquakes occur during the later half of interseismic period between two successive M ∼ 4.9 characteristic earthquakes, which we call moderate earthquakes. We introduce a microasperity, the rupture area of the microearthquakes, with a significantly smaller nucleation size than the size of a hyper‐asperity, the rupture area for moderate earthquakes. In contrast, the nucleation size in the rest of the hyper‐asperity, which we call a conditional asperity, is set to be comparable to the spatial size of the hyper‐asperity. Such a hierarchical asperity model successfully reproduces the observed earthquake sequences. The simulation results show that both microearthquakes and moderate earthquakes nucleate at the microasperity. The stress level in the conditional asperity determines whether a rupture terminates just outside the microasperity or propagates out into the conditional asperity.