Bridging earthquakes and earth structure along the northern San Andreas Fault

The objective of this proposal is to characterize and understand the processes by which the crust within and adjacent to the Northern San Andreas Fault Zone (NSAFZ) deforms over 10s of kyr to several Myr to link coand inter-seismic deformation to that observed geologically. I will use for this task high resolution GeoEarthScope Airborne Laser Swath Mapping (ALSM) and more broadly available lower resolution topography, the abundance of cosmogenic isotopes in river sands, low-temperature thermochronology, and numerical models of crustal deformation. Historical seismicity and space geodesy provide detailed constraints on plate-boundary kinematics in the vicinity of the northern San Andreas Fault over seconds to decades [e.g., d’Alessio et al., 2005; Bürgmann et al., 2006, 1997; Savage and Burford , 1973; Savage et al., 2004, 1998], and to a lesser degree, detailed earthquake chronologies at specific points along the fault constrain the sequence and magnitude of past earthquakes [e.g., Fumal et al., 1999; Niemi and Hall , 1992]. At the other extreme, geologic piercing points along the fault and geologic structures present in its vicinity record the accrued effects of earthquakes and continuous slip, as well as vertical motions associated with onand off-fault deformation [e.g., Bürgmann et al., 1994; Page et al., 1998; McLaughlin et al., 1999; Wakabayashi , 1999]. However, few methods exist that resolve the temporal evolution of individual fault strands within the NSAFZ that together comprise the complex fault zone that is observed both at the surface [e.g., Lawson and Reid , 1908; Prentice and Schwartz , 1991] and at depth within boreholes [e.g., Hickman et al., 2007]. Also, while geologically-observed folds and exhumed basement rocks demonstrate that vertical motions are extensively associated with the modern plate boundary [e.g., Page et al., 1979; Page, 1982, 1981; Aydin and Page, 1984; Titus et al., 2007], measuring the ratesof these motions, how they change over time, and how these changes are associated with the evolution of the larger strike-slip fault system is challenging because we generally lack chronologic methods that can be used to date deformation that accrues within this intermediate time window. Using a suite of newly acquired data and methodologies developed or exploited by my group, I will provide these constraints along the NSAFZ within the Santa Cruz Mountains (SCM; Figure 1) and use them to develop a geodynamic model that will help bridge our knowledge of deformation processes operating over seconds to decades with the long-term finite deformation recorded geologically. The primary methods I will use to image the NSAFZ evolution and the vertical rates of deformation adjacent to the fault zone in the SCM are topographic analysis of the fault zone using a wavelet-based method that extracts the location and relative morphologic ages of scarps within the zone using GeoEarthScope ALSM data [Hilley et al., 2010], analysis of coarser-resolution topographic data to identify landscape variations that may be associated with changes in vertical deformation rates [e.g., Snyder et al., 2003, 2000; Wobus et al., 2006], analysis of the abundance of cosmogenic Be in river sands to estimate landscape denudation rates (which, when used in combination with topographic inspection and analysis may be used to identify changes in vertical deformation rates over 10s of kyr time-scales) [e.g., Cyr and Granger , 2008; Wobus et al., 2005], and analysis of the abundance of Fission Track (AFT) and (U/Th)/He (A-He) in apatites adjacent to the fault zone to infer the Myr time-scale unroofing history of ranges flanking the NSAFZ [e.g., Ketcham et al., 1999; Laslett et al., 1987; Farley , 2000; Farley et al., 2002]. Together, these observational data will be used to construct a three-dimensional geodynamic model of this portion of the plate boundary using the Gale numerical model [Moresi et al., 2003]. By using this model with