Tectonic inheritance during plate boundary evolution in southern California constrained from seismic anisotropy

Abstract

Southern California hosts one of the world's best-instrumented and most thoroughly studied transform plate boundaries, yet questions as to how surface deformation transitions to convective flow and deformation at depth remain. Present-day transform motion is accommodated on the San Andreas Fault (SAF) (Figure 1

Complex Patterns of Past and Ongoing Crustal Deformations in Southern California Revealed by Seismic Azimuthal Anisotropy

“…Our model successfully fills in the resolution gap and shows distinct fast axes in the highly rotated WTR compared to the adjacent blocks (Figure 4c), strongly indicating the preservation of paleofabrics in the middle crust. Those inherited fabrics were formed during the long‐lived Farallon subduction (accretion and intrusion) and subsequent extension and have not been reset by the present transform tectonic regime (Schulte‐Pelkum et al., 2021). Assuming that paleofabric foliations formed during Farallon subduction stay perpendicular to the former NE convergent direction (thus nearly parallel to the strike of the present SAF) with intermediate to high dipping angles (Porter et al., 2011; Schulte‐Pelkum et al., 2021), our model west of the SAF clearly delineates a pronounced anisotropic pattern in the WTR that is likely associated with the clockwise rotation.…”

Tectonic Fabric in the Banda Arc‐Australian Continent Collisional Zone Imaged by Teleseismic Receiver Functions

“…The complicated and azimuthally varying RF waveforms shown in their paper, however, indicate the breakdown of this assumption. Similar RF signals have been used elsewhere to infer lithospheric anisotropy and its tectonic implications (e.g., Audet, 2015; Bar et al., 2019; Birkey et al., 2021; Bourke et al., 2020; Chen et al., 2021; Frothingham et al., 2022; Gosselin et al., 2021; Levin et al., 2021; Nikulin et al., 2019; Olugboji et al., 2016; Salimbeni et al., 2021; Schulte‐Pelkum et al., 2021; Sherrington et al., 2004; Vergne et al., 2003). In addition, the small number of RF measurements (<20–60 for more than half of stations) considered in Syuhada et al.…”

Analytical and numerical modeling of viscous anisotropy: A toolset to constrain the role of mechanical anisotropy for regional tectonics and fault loading

“…Observations of the non-coaxiality could give us constraints on the role of mechanical anisotropy in nature. Such analysis may be possible, e.g., by comparing stress inversions from focal mechanisms, surface strain rates from geodetic measurements, and integrated strain from seismic anisotropy (Schulte-Pelkum et al, 2021).…”

“…Ghosh et al (2013) implemented an anisotropic San Andreas Fault (SAF) in a 3-D global model but failed to identify robust indicators of mechanical anisotropy on regional scales. However, if mechanical anisotropy is considered in a regional scale model, it may be easier to assess the documented non-coaxiality between stress and strain (Schulte-Pelkum et al, 2021), and to eventually incorporate time dependence in a field observation validated way. This suggests an opportunity to develop new methods for inferring mechanical anisotropy from field observations and further constrain fault loading.…”