Abstract

Numerical calculations assuming linear elasticity by Böse et al. (2014) indicate that an Mw 7.75 earthquake on the Newport–Inglewood fault would cause 5  m/s of horizontal peak ground velocity (PGV) within the Los Angeles basin. However, the dynamic strain from this event would take much of the uppermost few hundred meters of basin rock beyond its frictional elastic limit. Stiff quartz‐rich beds within the basin are fragile geological features that would fail and crack before the rest of the clay‐rich rock mass. Repeated cracking would reduce the shear modulus of the quartz‐rich beds to the level that cracking barely occurred during strong events. When interpreted in this way, data from such stiff beds near the Los Angeles International Airport indicate past PGV of ∼1.6  m/s, comparable with near‐field records from the strike‐slip 2002 Denali and 1992 Landers earthquakes. Numerical calculations capable of representing nonlinear failure within shallow bedded rocks are warranted.

Online Material: Digital ROSRINE S‐wave borehole logs.

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