Calculation of the local rupture speed of dynamically propagating earthquakes

Andrea Bizzarri

Abstract


The velocity at which a propagating earthquake advances on the fault surface is of pivotal importance in the contest of the source dynamics and in the modeling of the ground motions generation. In this paper the problem of the determination of the rupture speed (v_r) is considered. The comparison of different numerical schemes to compute vr from the rupture time (t_r) shows that, in general, central finite differences schemes are more accurate than forward or backward schemes, regardless the order of accuracy. Overall, the most efficient and accurate algorithm is the five–points stencil method at the second–order of accuracy. It is also shown how the determination of t_r can affect v_r ; numerical results indicate that if the fault slip velocity threshold (v_l) used to define t_r is too high (v_l ≥ 0.1 m/s) the details of the rupture are missed, for instance the rupture tip bifurcation occurring for 2–D supershear rupture. On the other hand, for v_l ≤ 0.01 m/s the results appear to be stable and independent on the choice of v_l . Finally, it is demonstrated that in the special case of the linear slip–weakening friction law the definitions of t_r from the threshold criterion on the fault slip velocity and from the achievement of the maximum yield stress are practically equivalent.

Keywords


Earthquake dynamics; Rupture speed; Supershear earthquakes; Rheology and friction of fault zones; Computational seismology

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References


DOI: https://doi.org/10.4401/ag-6279
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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X