The style of convective force transmission to plates and strain-localization within and underneath plate boundaries remain debated. To address some of the related issues, we analyze a range of deformation indicators in southern California from the surface to the asthenosphere. Present-day surface strain rates can be inferred from geodesy. At seismogenic crustal depths, stress can be inferred from focal mechanisms and splitting of shear waves from local earthquakes via crack-dependent seismic velocities. At larger depths, constraints on rock fabrics are obtained from receiver function anisotropy, Pn and P tomography, surface wave tomography, and splitting of SKS and other teleseismic core phases. We construct a synthesis of deformation-related observations focusing on quantitative comparisons of deformation style. We find consistency with roughly N-S compression and E-W extension near the surface and in the asthenospheric mantle. However, all lithospheric anisotropy indicators show deviations from this pattern. Pn fast axes and dipping foliations from receiver functions are fault-parallel with no localization to fault traces and match post-Farallon block rotations in the Western Transverse Ranges. Local shear wave splitting inferences deviate from the stress orientations inferred from focal mechanisms in significant portions of the area. We interpret these observations as an indication that lithospheric fabric, developed during Farallon subduction and subsequent extension, has not been completely reset by present-day transform motion and may influence the current deformation behavior. This provides a new perspective on the timescales of deformation memory and lithosphere-asthenosphere interactions.

Plate motions in Southern California have undergone a transition from compressional and extensional regimes to a dominantly strike-slip regime in the Miocene. Strike-slip motion is most easily accommodated on vertical faults, and major transform fault strands in the region are typically mapped as near-vertical on the surface. However, some previous work suggests these faults have a dipping or listric geometry at depth. We analyze receiver function arrivals that vary harmonically with backazimuth at all available broadband stations in the region. The results show a dominant signal from contrasts in dipping foliation as well as dipping isotropic contrasts from all crustal depths, including from the ductile middle to lower crust. We interpret these receiver function observations as a dipping fault-parallel structural fabric that is pervasive throughout the region. The strike of these structures and fabrics is parallel to that of nearby fault surface traces. We also plot microseismicity on depth profiles perpendicular to major strike-slip faults and find consistently NE-dipping lineations in seismicity shallowing in dip from near vertical (80-85) on the Elsinore Fault near the coastal ranges to 60-65 slightly further inland on the San Jacinto Fault to 50-55 on the San Andreas Fault. Taken together, the dipping features in seismicity and in rock fabric suggest that preexisting fabrics and faults likely act as strain guides in the modern slip regime, with reactivation-like mechanisms operating both above and below the brittle-ductile transition.