The Moment Duration Scaling Relation for Slow Rupture Arises From Transient Rupture Speeds

International audienceThe relation between seismic moment and earthquake duration for slow rupture follows a different power law exponent than subshear rupture. The origin of this difference in exponents remains unclear. Here, we introduce a minimal one‐dimensional Burridge‐Knopoff model which contains slow, subshear, and supershear rupture and demonstrate that different power law exponents occur because the rupture speed of slow events contains long‐lived transients. Our findings suggest that there exists a continuum of slip modes between the slow and fast slip end‐members but that the natural selection of stress on faults can cause less frequent events in the intermediate range. We find that slow events on one‐dimensional faults follow $\bar{M}_{0, slow, 1D} \propto \bar{T}^{0.63}$ with transition to $\bar{M}_{0, slow, 1D} \propto \bar{T}^{3/2}$ for longer systems or larger prestress, while the subshear events follow $\bar{M}_{0, sub-shear, 1D} \propto \bar{T}^{2}$. The model also predicts a supershear scaling relation $\bar{M}_{0, super-shear, 1D} \propto \bar{T}^{3}$. Under the assumption of radial symmetry, the generalization to two‐dimensional fault planes compares well with observations