断層面の主破壊と余震発生過程

抄録

Numerical simulations of aftershock occurrence are made on a three-dimensional frictional fault model with nonuniform fracture strength and viscoelastic relaxation times, After the main shock, the dropped stress on the fault plane will recover due to creep process or pore fluid flow, but the stress concentration around the edge of aftershocks will be reduced since the medium near the fault plane may have been crushed by the rupture.
We introduce a parameter Ct to represent this effect. From this model, we obtain the fracture pattern of aftershocks, the decrease of aftershock number with time, and the magnitude of largest aftershock for several values of Ct. It was found that aftershock numbers seem to decrease according to the modified Omori's formula (n(t)=A(t+c)^-p) and that the p-value becomes small and the largest aftershock has a lower magnitude for smaller value of Ct. Smaller Ct values corresponding to more crushed faults by the main shock might be more realistic, with observations.