3-D P- and S-wave velocity structure and low-frequency earthquake locations in the Parkfield, California region

Geophysical Journal International
By: , and 

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Abstract

To refine the 3-D seismic velocity model in the greater Parkfield, California region, a new data set including regular earthquakes, shots, quarry blasts and low-frequency earthquakes (LFEs) was assembled. Hundreds of traces of each LFE family at two temporary arrays were stacked with time–frequency domain phase weighted stacking method to improve signal-to-noise ratio. We extend our model resolution to lower crustal depth with LFE data. Our result images not only previously identified features but also low velocity zones (LVZs) in the area around the LFEs and the lower crust beneath the southern Rinconada Fault. The former LVZ is consistent with high fluid pressure that can account for several aspects of LFE behaviour. The latter LVZ is consistent with a high conductivity zone in magnetotelluric studies. A new Vs model was developed with S picks that were obtained with a new autopicker. At shallow depth, the low Vs areas underlie the strongest shaking areas in the 2004 Parkfield earthquake. We relocate LFE families and analyse the location uncertainties with the NonLinLoc and tomoDD codes. The two methods yield similar results.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title 3-D P- and S-wave velocity structure and low-frequency earthquake locations in the Parkfield, California region
Series title Geophysical Journal International
DOI 10.1093/gji/ggw217
Volume 206
Issue 3
Year Published 2016
Language English
Publisher Oxford University Press
Contributing office(s) Volcano Science Center
Description 12 p.
First page 1574
Last page 1585
Country United States
State California
City Parkfield