Extended Data Fig. 5: Simple kinematic model for slip propagation.

a, Model illustration. We assume 200 km × 63 km slipping patch (light yellow) embedded in a half space with its lower edge at a depth of 26 km. For displacement of each patch, we impose the time evolution of slip derived from the spring-slider model adjusted to the Guerrero example (Fig. 4d). We considered three cases for slip propagation along the strike direction at: (i) 1 km/day, (ii) 5 km/day, and (iii) a case with simultaneous slip in the entire patch. Panel b, shows an example of slip propagation for the 1 km/day case. The fault slip is converted to surface deformation using an elastic dislocation (Okada) model⁴⁸ and the normalized displacements are plotted in panels c&d, for comparison with the observed Guerrero gap GPS timeseries. The result shows that the case with a propagation rate of 5 km/day (red) is nearly indistinguishable from the case of simultaneous slip (equivalent to an infinitely fast propagation). The case with 1 km/day (blue) which is at the lower end of the typical rate of propagation of SSEs, is also only slightly altered by the effect of the propagation.