The southernmost San Andreas fault has a high probability of rupturing in a large (greater than magnitude 7.5) earthquake sometime during the next few decades. New simulations show that the chain of sedimentary basins between San Bernardino and downtown Los Angeles form an effective waveguide that channels Love waves along the southern edge of the San Bernardino and San Gabriel Mountains. Earthquake scenarios with northward rupture, in which the guided wave is efficiently excited, produce unusually high long‐period ground motions over much of the greater Los Angeles region, including intense, localized amplitude modulations arising from variations in waveguide cross‐section.

Wnt proteins control diverse biological processes through β-catenin-dependent canonical signaling and β-catenin-independent non-canonical signaling. The mechanisms by which these signaling pathways are differentially triggered and controlled are not fully understood. Dishevelled (Dvl) is a scaffold protein that serves as the branch point of these pathways. Here, we show that cholesterol selectively activates canonical Wnt signaling over non-canonical signaling under physiological conditions by specifically facilitating the membrane recruitment of the PDZ domain of Dvl and its interaction with other proteins. Single molecule imaging analysis shows that cholesterol is enriched around the Wnt-activated Frizzled and low-density lipoprotein receptor-related protein 5/6 receptors and plays an essential role for Dvl-mediated formation and maintenance of the canonical Wnt signaling complex. Collectively, our results suggest a new regulatory role of cholesterol in Wnt signaling and a potential link between cellular cholesterol levels and the balance between canonical and non-canonical Wnt signaling activities.

Computer simulations of large (M≥7.8) earthquakes rupturing the southern San Andreas Fault from SE to NW (e.g., ShakeOut, widely used for earthquake drills) have predicted strong long‐period ground motions in the densely populated Los Angeles Basin due to channeling of waves through a series of interconnected sedimentary basins. Recently, the importance of this waveguide amplification effect for seismic shaking in the Los Angeles Basin has also been confirmed from observations of the ambient seismic field. By simulating the ShakeOut earthquake scenario (based on a kinematic source description) for a medium governed by Drucker‐Prager plasticity, we show that nonlinear material behavior could reduce the earlier predictions of large long‐period ground motions in the Los Angeles Basin by up to 70% as compared to viscoelastic solutions. These reductions are primarily due to yielding near the fault, although yielding may also occur in the shallow low‐velocity deposits of the Los Angeles Basin if cohesions are close to zero. Fault zone plasticity remains important even for conservative values of cohesions, suggesting that current simulations assuming a linear response of rocks are overpredicting ground motions during future large earthquakes on the southern San Andreas Fault.

We simulate ground motion in southern California from an ensemble of 7 spontaneous rupture models of large (Mw7.8) northwest‐propagating earthquakes on the southern San Andreas fault (ShakeOut‐D). Compared to long‐period spectral accelerations from the Next Generation Attenuation (NGA) empirical relations, ShakeOut‐D predicts similar average rock‐site values (i.e., within roughly their epistemic uncertainty), but significantly larger values in Los Angeles and Ventura basins due to wave‐guide focusing effects. The ShakeOut‐D ground motion predictions differ from those of a kinematically parameterized, geometrically similar, scenario rupture: (1) the kinematic rock‐site predictions depart significantly from the common distance‐attenuation trend of the NGA and ShakeOut‐D results and (2) ShakeOut‐D predictions of long‐period spectral acceleration within the basins of the greater Los Angeles area are lower by factors of 2–3 than the corresponding kinematic predictions. We attribute these differences to a less coherent wavefield excited by the complex rupture paths of the ShakeOut‐D sources.