Geodetic slip rates in the southern San Andreas Fault system: Effects of elastic heterogeneity and fault geometry

TitleGeodetic slip rates in the southern San Andreas Fault system: Effects of elastic heterogeneity and fault geometry
Publication TypeJournal Article
Year of Publication2013
AuthorsLindsey EO, Fialko Y
JournalJournal of Geophysical Research-Solid Earth
Date Published2013/02
Type of ArticleArticle
ISBN Number0148-0227
Accession NumberWOS:000317852900016
Keywordscalifornia shear zone; constraints; Crustal deformation; cycle; earthquake; half-space; histories; jacinto fault; salton; strain accumulation; triggered surface slips; trough

We use high resolution interferometric synthetic aperture radar and GPS measurements of crustal motion across the southern San Andreas Fault system to investigate the effects of elastic heterogeneity and fault geometry on inferred slip rates and locking depths. Geodetically measured strain rates are asymmetric with respect to the mapped traces of both the southern San Andreas and San Jacinto faults. Two possibilities have been proposed to explain this observation: large contrasts in crustal rigidity across the faults, or an alternate fault geometry such as a dipping San Andreas fault or a blind segment of the San Jacinto Fault. We evaluate these possibilities using a two-dimensional elastic model accounting for heterogeneous structure computed from the Southern California Earthquake Center crustal velocity model CVM-H 6.3. The results demonstrate that moderate variations in elastic properties of the crust do not produce a significant strain rate asymmetry and have only a minor effect on the inferred slip rates. However, we find that small changes in the location of faults at depth can strongly impact the results. Our preferred model includes a San Andreas Fault dipping northeast at 60 degrees, and two active branches of the San Jacinto fault zone. In this case, we infer nearly equal slip rates of 18 +/- 1 and 19 +/- 2 mm/yr for the San Andreas and San Jacinto fault zones, respectively. These values are in good agreement with geologic measurements representing average slip rates over the last 10(4)-10(6) years, implying steady long-term motion on these faults.

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