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

Geophysical Journal International
By:  and 

Links

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

Additional publication details

Publication type Article
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