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

December 1, 2015

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.

Citation Information

Publication Year 2015
Title The 1868 Hayward fault, California, earthquake: Implications for earthquake scaling relations on partially creeping faults
DOI 10.1785/0120140372
Authors Susan E. Hough, Stacey Martin
Publication Type Article
Publication Subtype Journal Article
Series Title Bulletin of the Seismological Society of America
Series Number
Index ID 70168440
Record Source USGS Publications Warehouse
USGS Organization Earthquake Science Center

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