The 1868 Hayward fault, California, earthquake: Implications for earthquake scaling relations on partially creeping faults

Bulletin of the Seismological Society of America
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Abstract

The 21 October 1868 Hayward, California, earthquake is among the best-characterized historical earthquakes in California. In contrast to many other moderate-to-large historical events, the causative fault is clearly established. Published magnitude estimates have been fairly consistent, ranging from 6.8 to 7.2, with 95% confidence limits including values as low as 6.5. The magnitude is of particular importance for assessment of seismic hazard associated with the Hayward fault and, more generally, to develop appropriate magnitude–rupture length scaling relations for partially creeping faults. The recent reevaluation of archival accounts by Boatwright and Bundock (2008), together with the growing volume of well-calibrated intensity data from the U.S. Geological Survey “Did You Feel It?” (DYFI) system, provide an opportunity to revisit and refine the magnitude estimate. In this study, we estimate the magnitude using two different methods that use DYFI data as calibration. Both approaches yield preferred magnitude estimates of 6.3–6.6, assuming an average stress drop. A consideration of data limitations associated with settlement patterns increases the range to 6.3–6.7, with a preferred estimate of 6.5. Although magnitude estimates for historical earthquakes are inevitably uncertain, we conclude that, at a minimum, a lower-magnitude estimate represents a credible alternative interpretation of available data. We further discuss implications of our results for probabilistic seismic-hazard assessment from partially creeping faults.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title The 1868 Hayward fault, California, earthquake: Implications for earthquake scaling relations on partially creeping faults
Series title Bulletin of the Seismological Society of America
DOI 10.1785/0120140372
Volume 105
Issue 6
Year Published 2015
Language English
Publisher Seismological Society of America
Publisher location El Cerrito, CA
Contributing office(s) Earthquake Science Center
Description 16 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Bulletin of the Seismological Society of America
First page 2894
Last page 2909
Country United States
State California
City Hayward
Online Only (Y/N) N
Additional Online Files (Y/N) N