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Reconciling seismicity and geodetic locking depths on the Anza section of the San Jacinto fault

TitleReconciling seismicity and geodetic locking depths on the Anza section of the San Jacinto fault
Publication TypeJournal Article
Year of Publication2016
AuthorsJiang J.L, Fialko Y
JournalGeophysical Research Letters
Date Published2016/10
Type of ArticleArticle
ISBN Number0094-8276
Accession NumberWOS:000388293800023
Keywordsandreas fault; aseismic transients; california plate-boundary; earthquake rupture; earthquakes; fault mechanics; friction; geodetic; locking; rate-and-state friction; repeating; seismicity; simulations; slip rates; southern-california; strain accumulation; stress; velocity

Observations from the Anza section of the San Jacinto Fault in Southern California reveal that microseismicity extends to depths of 15-18km, while the geodetically determined locking depth is less than similar to 10km. This contrasts with observations from other major faults in the region and also with predictions of fault models assuming a simple layered distribution of frictional properties with depth. We suggest that an anomalously shallow geodetic fault locking may result from a transition zone at the bottom of seismogenic layer with spatially heterogeneous frictional properties. Numerical models of faults that incorporate stochastic heterogeneity at transitional depths successfully reproduce the observed depth relation between seismicity and geodetic locking, as well as complex spatiotemporal patterns of microseismicity with relatively scarce repeating earthquakes. Our models predict propagation of large earthquakes to the bottom of the transition zone, and ubiquitous aseismic transients below the locked zone, potentially observable using high-precision geodetic techniques.

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