Stress- and structure-controlled anisotropy in a region of complex faulting—Yuha Desert, California
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.
Citation Information
Publication Year | 2015 |
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Title | Stress- and structure-controlled anisotropy in a region of complex faulting—Yuha Desert, California |
DOI | 10.1093/gji/ggv191 |
Authors | Elizabeth S. Cochran, Kayla A. Kroll |
Publication Type | Article |
Publication Subtype | Journal Article |
Series Title | Geophysical Journal International |
Index ID | 70155973 |
Record Source | USGS Publications Warehouse |
USGS Organization | Earthquake Science Center |