A case study of stress proxies on the Hayward fault

Stressing rate distribution surrounging the Hayward fault (slip distribution for forward model from G. Funning)

Project Summary Currently, there are a number of seismicity analysis techniques that have been used to infer the state of stress within the lithosphere. While many of these "stress proxies" are based on theoretically plausible foundations and could potentially be incorporated in earthquake forecasting, rigorous comparisons between stress inversion results and other data that also reflect stress conditions at depth (e.g., fault creep rates) have not been performed. The Hayward fault presents an ideal locale in which to test the accuracy of these stress proxies in that we can qualitatively infer the stress along the fault by assuming that fault creep rates are inversely related to stress and thus that stress is high along asperities locked since the 1868 earthquake and low along sections that are accommodating a substantial amount of their slip budget through creep. In this study, we performed three stress analyses of Hayward fault seismicity by evaluating spatial variations of the b-value, accelerating moment release (AMR), and Load/Unload Response Ratio (LURR) methodologies. We then qualitatively compare the results of these analyses with best-fit Hayward fault slip inversions derived using GPS, InSAR, and seismicity patterns to determine if stress levels inferred from the inversions and independent data agree.

Tools Poly3D

Geographic Location Hayward Fault, East Bay, CA

Group Members Involved Amanda Thomas <Email> <Web Site>
Roland Burgmann

Project Duration Jan 2008 - current