San Andreas tremor cascades define deep fault zone complexity

Nature Geoscience
By:

Links

Abstract

Weak seismic vibrations - tectonic tremor - can be used to delineate some plate boundary faults. Tremor on the deep San Andreas Fault, located at the boundary between the Pacific and North American plates, is thought to be a passive indicator of slow fault slip. San Andreas Fault tremor migrates at up to 30 m s-1, but the processes regulating tremor migration are unclear. Here I use a 12-year catalogue of more than 850,000 low-frequency earthquakes to systematically analyse the high-speed migration of tremor along the San Andreas Fault. I find that tremor migrates most effectively through regions of greatest tremor production and does not propagate through regions with gaps in tremor production. I interpret the rapid tremor migration as a self-regulating cascade of seismic ruptures along the fault, which implies that tremor may be an active, rather than passive participant in the slip propagation. I also identify an isolated group of tremor sources that are offset eastwards beneath the San Andreas Fault, possibly indicative of the interface between the Monterey Microplate, a hypothesized remnant of the subducted Farallon Plate, and the North American Plate. These observations illustrate a possible link between the central San Andreas Fault and tremor-producing subduction zones.

Study Area

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title San Andreas tremor cascades define deep fault zone complexity
Series title Nature Geoscience
DOI 10.1038/ngeo2335
Volume 8
Issue 2
Year Published 2015
Language English
Publisher Nature Publishing Group
Contributing office(s) Volcano Science Center
Description 8 p.
First page 145
Last page 252
Country United States
State California
Other Geospatial San Andreas Fault