Publication Date:
2017-04-04
Description:
The introduction of the linear slip–weakening friction law permits the solution of the
elasto–dynamic equation for a rupture which develops on a fault, by removing the singularity
in the components of stress tensor, thereby ensuring a finite energy flux at the crack tip. With
this governing model, largely used by seismologists, it is possible to simulate a single
earthquake event but, in absence of remote tectonic loading, it requires the introduction of an
artificial procedure to initiate the rupture, i.e, to reach the failure stress point. In this paper, by
studying the dynamic rupture propagation and the solutions on the fault and on the free surface,
we systematically compare three conceptually and algorithmically different nucleation
strategies widely adopted in the literature: the imposition of an initially constant rupture speed,
the introduction of a shear stress asperity, and the perturbation to the initial particle velocity
field. Our results show that, contrarily to supershear ruptures which tend to “forget” their
origins, subshear ruptures are quite sensitive to the adopted nucleation procedure, which can
bias the runaway rupture. We confirm that that the most gradual transition from imposed
nucleation and spontaneous propagation is obtained by initially forcing the rupture to expand at
a properly chosen, constant speed (0.75 times the Rayleigh speed). We also numerically
demonstrate that a valid alternative to this strategy is an appropriately smoothed, elliptical
shear stress asperity. Moreover, we evaluate the optimal size of the nucleation patch where the
procedure is applied; our simulations indicate that its size has to equal the critical distance of
Day (1982) in case of supershear ruptures and to exceed it in case of subshear ruptures.
Description:
In press
Description:
3.1. Fisica dei terremoti
Description:
JCR Journal
Description:
open
Keywords:
Nucleation strategies
;
04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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