Oral Presentation

The major strike-slip faults of the San Francisco Bay Area are associated with a wide variety of secondary structures that produce vertical motions. In this presentation, I will review how these structures relate to the broader strike-slip motions along faults facilitating plate boundary motions between the Pacific Plate and the Sierra Nevada/Great Valley Block, with a focus on regions where these structures produce localized vertical motions.

I will discuss methods to constrain vertical motions produced by these secondary structures over various timescales—from millions of years to decades—using geologic and thermochronologic data, watershed-scale erosion rates from cosmogenic isotopes, topographic analyses, and satellite geodesy. I will then explore how these data have been used to understand the development of specific topographies in the Bay Area, which provide constraints on the effective constitutive properties of the crust across these timescales when viewed in the context of mechanical models. Additionally, I will consider how the topography, uplift, and geometry of secondary structures along this and other strike-slip plate boundaries might be leveraged to constrain key geophysical properties, such as the friction of plate-bounding faults.

In conclusion, I will outline future opportunities for addressing fundamental and applied science questions that may interest the new Statewide California Earthquake Center. First, I will demonstrate how the distribution of long-term slip rates along secondary structures, which may act as independent seismic sources, might be inferred by integrating topographic, geochemical, and geophysical data with boundary element models. These inferences can also provide constraints on the long-term slip rates of primary strike-slip faults driving these secondary structures. Second, I will show how river profiles and watershed-scale erosion rates can elucidate the rate and tempo of vertical motions in landscapes that record secular changes in these processes. Finally, I will highlight regions in Northern California where these methods could be applied to better understand slip transfer between strike-slip faults facilitated by secondary structures that produce vertical motions, which may mechanically link strike-slip faults that comprise the plate boundary to one another.