The main article of this study discusses a series of dynamic rupture models on the northern San Jacinto fault. Each set of models in the series adds an additional level of complexity, mostly in terms of the initial stresses imposed on the fault. This electronic supplement contains plots of ground motions from models used to calibrate the stress conditions.
For all figures, the fault is shown in white, and the letters mark nearby cities (SB, San Bernardino; Fon, Fontana; Red, Redlands; Riv, Riverside; Yuc, Yucaipa; Per, Perris; Ban, Banning; SJ, San Jacinto; and Hem, Hemet).
Figure S1. Peak horizontal particle velocity for ruptures on the northern San Jacinto fault, incorporating a regional stress orientation of N7°E, an input stress drop of 5.5 MPa, variable input S, and a complex material setting taken from the Southern California Earthquake Center (SCEC) Community Velocity Model. The nucleation point is marked with a star. Note that rupture does not jump the stepover in any of these models and that the input S must be greater than 5.5 in order to prevent a spontaneous nucleation on the northern Claremont strand.
Figure S2. Peak horizontal particle velocity for ruptures on the northern San Jacinto fault, incorporating a regional stress orientation of N7°E, an input stress drop of 9.5 MPa, variable input S, and a complex material setting taken from the SCEC Community Velocity Model. The initial nucleation point is marked with a star. The primary difference between these models and the ones with a 5.5 MPa stress drop (Fig. S1) is in the intensity and distribution of the strongest ground motion. The rupture extent on the Claremont strand is no longer than in the lower stress drop cases, and the rupture extent on the Casa Loma strand is only slightly longer. Note that the Casa Loma nucleation model, with an S of 0.7, results in the rupture jumping onto the Claremont strand, but the resulting rupture does not propagate very far along strike.
Figure S3. Peak horizontal particle velocity for ruptures on the northern San Jacinto fault, with input stress drop of 9.5 MPa and input S of 0.7. Nucleation points, corresponding to Figure 4 in the main article, are marked with black stars. The primary difference between these models and the 5.5 MPa and S = 0.6 stress drop cases (Fig. 9 in the main article) is in the intensity and distribution of strong motion, not in the along-strike extent of rupture.
Figure S4. Peak horizontal particle velocity for ruptures on the northern San Jacinto fault, with the regional stress field rotated to N17°E and N3°W. The nucleation point is marked by a star. A N17°E orientation produces shorter ruptures with weaker ground motion compared to the inferred real orientation N7°E. An orientation of N3°W produces stronger ground motion and longer ruptures when compared to N7°E and produces jumping rupture in higher-input stress drop models.
Figure S5. Ruptures initiated at nucleation point A, indicated by a black star, in all four stochastic/regional stress realizations (Fig. 6a–d in the main article), with an input stress drop of 9.5 MPa and an input S of 0.25. Despite the high stress drop and low S, the rupture does not propagate far past the forced nucleation zone in any of these models. However, the resulting ground-motion pattern even from these failed nucleations still highlights the differences between the four stress realizations.
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