Spatial variations in fault friction related to lithology from rupture and afterslip of the 2014 South Napa, California, earthquake

Geophysical Research Letters
By: , and 

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Abstract

Following earthquakes, faults are often observed to continue slipping aseismically. It has been proposed that this afterslip occurs on parts of the fault with rate-strengthening friction that are stressed by the mainshock, but our understanding has been limited by a lack of immediate, high-resolution observations. Here we show that the behavior of afterslip following the 2014 South Napa earthquake varied over distances of only a few kilometers. This variability cannot be explained by coseismic stress changes alone. We present daily positions from continuous and survey GPS sites that we re-measured within 12 hours of the mainshock, and surface displacements from the new Sentinel-1 radar mission. This unique geodetic data set constrains the distribution and evolution of coseismic and postseismic fault slip with exceptional resolution in space and time. We suggest that the observed heterogeneity in behavior is caused by lithological controls on the frictional properties of the fault plane.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Spatial variations in fault friction related to lithology from rupture and afterslip of the 2014 South Napa, California, earthquake
Series title Geophysical Research Letters
DOI 10.1002/2016GL069428
Volume 43
Issue 13
Year Published 2016
Language English
Publisher American Geophysical Union
Contributing office(s) Earthquake Science Center
Description 9 p.
First page 6808
Last page 6816
Country United States
State California
City San Francisco
Other Geospatial South Napa
Online Only (Y/N) N
Additional Online Files (Y/N) N