Parameters for Earthquake Rupture Dynamics

Abstract

Recent progress on our understanding of earthquake rupture dynamics based on seismological observations is reviewed. One of the most important advances is the physical understanding of breakdown process that occurs at the propagating rupture front of earthquakes. The parameters such as breakdown stress drop, slip-weakening distance and fracture energy, which control the progress of dynamic rupture propagation, have now been able to be estimated. Fracture energy and hence slip-weakening distance are found to be scale dependent. To achieve such scale dependence, several different physical processes might microscopically develop, one of which dominates depending on the environmental situation at the source. Then its macroscopic behavior becomes quite simple and seems to be modeled with a single law.

A Super Asperity Model for the 2011 Off the Pacific Coast of Tohoku Earthquake

“…Strictly speaking, what this study revealed was the rupture duration of the super asperities, rather than the size of them; different assumptions on the rupture velocity may lead to different estimates of the size of the subevents. Even if we assume a super asperity 1.5 times longer and, at the same time, a rupture velocity 1.5 times greater (4.5 km/s) (in this case we are assuming a super shear rupture 23) ), the synthetic velocity waveforms in the frequency range from 0.2 to 1 Hz do not differ significantly. This type of uncertainty, however, does not affect the conclusion that "subevents much smaller than conventionally assumed asperities or SMGAs are required to accurately represent the S-wave pulses" even if we assume a terminal rupture velocity 23) .…”

“…Even if we assume a super asperity 1.5 times longer and, at the same time, a rupture velocity 1.5 times greater (4.5 km/s) (in this case we are assuming a super shear rupture 23) ), the synthetic velocity waveforms in the frequency range from 0.2 to 1 Hz do not differ significantly. This type of uncertainty, however, does not affect the conclusion that "subevents much smaller than conventionally assumed asperities or SMGAs are required to accurately represent the S-wave pulses" even if we assume a terminal rupture velocity 23) . The estimated slip on the super asperity ranges from 5.3 m (SA3_1 and SA3_2) to 42.4 m (SA2).…”