Publication Date:
2017-04-04
Description:
We investigate numerically the passage of spontaneous, dynamic in-plane shear ruptures from
initiation to their final rupture speed, using very fine grids. By carrying out more than 120 simulations, we
identify two different mechanisms controlling supershear transition. For relatively weaker faults, the rupture
speed always passes smoothly and continuously through the range of speeds between the Rayleigh and shear
wave speeds (the formerly considered forbidden zone of rupture speeds). This, however, occurs in a very short
time, before the ruptures reach the compressional wave speed. The very short time spent in this range of
speeds may explain why a jump over these speeds was seen in some earlier numerical and experimental
studies and confirms that this speed range is an unstable range, as predicted analytically for steady state,
singular cracks. On the other hand, for relatively stronger faults, we find that a daughter rupture is initiated by
the main (mother) rupture, ahead of it. The mother rupture continues to propagate at sub-Rayleigh speed and
eventually merges with the daughter rupture, whose speed jumps over the Rayleigh to shear wave speed
range. We find that this daughter rupture is essentially a “pseudorupture,” in that the two sides of the fault are
already separated, but the rupture has negligible slip and slip velocity. After the mother rupture merges with
it, the slip, the slip velocity, and the rupture speed become dominated by those of the mother rupture. The
results are independent of grid sizes and of methods used to nucleate the initial rupture.
Description:
Published
Description:
8331–8345
Description:
4T. Fisica dei terremoti e scenari cosismici
Description:
JCR Journal
Description:
open
Keywords:
Seismic source
;
Supershear ruptures
;
04. Solid Earth::04.04. Geology::04.04.06. Rheology, friction, and structure of fault zones
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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