Stress- and structure-controlled anisotropy in a region of complex faulting—Yuha Desert, California
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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.
Study Area
Publication type | Article |
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Publication Subtype | Journal Article |
Title | Stress- and structure-controlled anisotropy in a region of complex faulting—Yuha Desert, California |
Series title | Geophysical Journal International |
DOI | 10.1093/gji/ggv191 |
Volume | 202 |
Issue | 2 |
Year Published | 2015 |
Language | English |
Publisher | Oxford University Press |
Contributing office(s) | Earthquake Science Center |
Description | 13 p. |
First page | 1109 |
Last page | 1121 |
Country | United States |
State | California |
Other Geospatial | Yuha Desert |
Online Only (Y/N) | N |
Additional Online Files (Y/N) | N |
Google Analytic Metrics | Metrics page |