Spatial variations of shear wave anisotropy near the San Jacinto Fault Zone in Southern California

TitleSpatial variations of shear wave anisotropy near the San Jacinto Fault Zone in Southern California
Publication TypeJournal Article
Year of Publication2015
AuthorsLi Z.F, Peng Z.G, Ben-Zion Y., Vernon FL
JournalJournal of Geophysical Research-Solid Earth
Date Published2015/12
Type of ArticleArticle
ISBN Number2169-9313
Accession NumberWOS:000372204600020
Keywords1999 chi-chi; aftershock zone; andreas fault; Anza; double-difference tomography; karadere-duzce branch; los-angeles basin; north anatolian fault; seismic gap; shallow crustal anisotropy; systematic analysis

We examine crustal anisotropy at several scales along and across the San Jacinto Fault Zone (SJFZ) by systematically measuring shear wave splitting (SWS) parameters. The analyzed data are recorded by 86 stations during 2012-2014, including five linear dense arrays crossing the SJFZ at different locations and other autonomous stations within 15 km from the main fault trace. Shear phase arrivals and SWS parameters (fast directions and delay times) are obtained with automated methods. The measurement quality is then assessed using multiple criteria, resulting in 23,000 high-quality measurements. We find clear contrast of fast directions between the SW and NE sides of the SJFZ. Stations on the SW side have fast directions consistent overall with the maximum horizontal compression direction (SHmax), while stations on the NE side show mixed patterns likely reflecting lithological/topographic variations combined with fault zone damage. The fast directions in the Anza gap section with relatively simple fault geometry agree with the inferred SHmax, and the delay times at an array within that section are smaller than those observed at other across-fault arrays. These indications of less pronounced damage zone in the Anza section compared to other segments of the SJFZ are correlated generally with geometrical properties of the surface traces. Significant variations of fast directions on several across-fault arrays, with station spacing on the orders of a few tens of meters, suggest that shallow fault structures and near-surface layers play an important role in controlling the SWS parameters.

Student Publication: