Continuum of earthquake rupture speeds enabled by oblique slip

Supershear Rupture, Daughter Cracks, and the Definition of Rupture Velocity

“…Tang et al. (2020) also noticed this feature on dipping strike‐slip faults with largely subshear rupture, and argued that the rupture which was not directed purely in the mode II direction suppressed supershear rupture (analogous to the mixed‐models of Andrews, 1994 and Weng & Ampuero, 2020). Our interpretation, in contrast, is that the diagonal rupture fronts are a consequence of the supershear rupture right at the surface leading the subshear rupture at depth; the diagonal rupture fronts in our interpretation are a symptom, rather than a cause, of the subshear rupture at depth.…”

Integrated rupture mechanics for slow slip events and earthquakes

“…Previous simulations show that SSE ruptures can propagate steadily at a very slow speed if facilitated by a frictional transition from rate-weakening at low slip rates to rate-strengthening at high slip rates [23][24][25] or by fault gouge dilatancy with an associated change in fluid pressure [26][27][28][29] , both of which are observed experimentally [29][30][31][32][33][34][35][36][37][38][39][40] . In addition, earthquake ruptures on long faults can steadily propagate at supershear speeds (faster than the S-wave speed), depending on the balance between fracture energy and energy release rate 41 . Though laboratory experiments 22,33 and the one-dimensional (1D) continuous Burridge-Knopoff model 42 have suggested a continuum of rupture speeds, the general rupture mechanics that controls the rupture propagation of both SSEs and earthquakes on long faults is not completely understood.…”

Slow slip events are regular earthquakes

“…Earthquake ruptures on elongated faults can steadily propagate at speeds from slower than S-wave up to P-wave speed, depending on the balance between dissipated and potential energies 14 . SSE ruptures can also steadily propagate on elongated faults [15][16][17] , facilitated by a frictional transition from rate-weakening at slow slip rates to rate-strengthening at high slip rates that has been observed experimentally [18][19][20][21][22][23][24][25][26][27][28] .…”

“…the critical stress drop by D run = 2W ∆τ run /πµ, where W is the SSE fault width and µ is the shear modulus14 . SSE fault segments need to accumulate sufficient slip deficit (that is > 0.02W σ/πµ) to be capable of accommodating runaway SSE ruptures, otherwise they act as barriers to stop rupture propagation.…”