Stress- and structure-controlled anisotropy in a region of complex faulting—Yuha Desert, California

Elizabeth S. Cochran; Kayla A. Kroll

doi:10.1093/gji/ggv191

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Stress- and structure-controlled anisotropy in a region of complex faulting—Yuha Desert, California

Elizabeth S. Cochran·Kayla A. Kroll

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Abstract

We examine shear velocity anisotropy in the Yuha Desert, California using aftershocks of the 2010 M7.2 El Mayor-Cucapah earthquake. The Yuha Desert is underlain by a complex network of right- and left-lateral conjugate faults, some of which experienced triggered slip during the El Mayor-Cucapah earthquake. An automated method that implements multiple measurement windows and a range of bandpass filters is used to estimate the fast direction ( ϕ ) and delay time ( δt ) of the split shear waves. We find an average ϕ oriented approximately north–south suggesting it is primarily controlled by the regional maximum compressive stress direction. However, the spatial variability in ϕ reveals that the fault structures that underlie the Yuha Desert also influence the measured splitting parameters. We infer that the northeast- and northwest-oriented ϕ reflect shear fabric subparallel to the conjugate fault structures. We do not observe a simple correlation between δt and hypocentral distance. Instead, the observed spatial variation in δt suggests that near-source variation in anisotropic strength may be equal to or more important than effects local to the station. No temporal variation in splitting parameters is observed during the 70-day period following the main shock. In this region of complex faulting, we observe a spatially variable pattern of anisotropy that is both stress- and structure-controlled. This study suggests that shear fabric can form even along short, discontinuous fault strands with minimal offset.

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Geophysical Journal International Article

Source-reported bounding extent: 32.616243412727385° to 32.794201303793194° latitude; -115.94970703125° to -115.65582275390624° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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BibTeX RIS

Elizabeth S. Cochran, Kayla A. Kroll. 2015-06-26. Stress- and structure-controlled anisotropy in a region of complex faulting—Yuha Desert, California. https://doi.org/10.1093/gji%2Fggv191

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