Proceedings of the 12th International INQUA meeting on paleoseismology, active tectonic and archaeoseismology

202 PATA Days 2024 An alternative interpretation of the basin data is presented on Fig. 5. This interpretation forces a linear relationship between area and age for the older (larger) basins, but reflects a sharply steeper relationship for the younger (smaller) basins beginning at ~200-250 ka. About 250 ka, the surface tip of the Santa Ana Mountains indenter have been <1.5 km south of the current Santa Ana River-Whittier fault crossing, but, as this interpretation suggests and modern microseismicity supports (Gath, 2022), the subsurface portion of the indenter was already under the Puente Hills. Fig. 4: Plot of the drainage basin areas against their calculated age showing an R2 of 0.92 and confirming the validity of using basin area as a potential temporal tool in landscape evolution. Fig. 5: An alternative to Fig. 4 showing a change in basin development at ~250 ka, interpreted to illustrate the impact of the Santa Ana indenter collision with the Puente Hills. Fig. 6: Illustration of the impact of the Santa Ana indenter distance on the progressive increase in uplift rate of the Puente Hills.