Restraining bend tectonics in the Santa Cruz Mountains, California, imaged using Be-10 concentrations in river sands

Reverse faults frequently generate large and destructive earthquakes, yet their seismic hazard remains difficult to assess with traditional paleoseismic tools because their surface expressions are often complex and subtle. This contribution assesses the utility of millennial-scale denudation rates derived from in-situ cosmogenic Be-10 for revealing the spatial patterns and magnitudes of rock uplift produced by slip along reverse faults. We present seventeen basin-averaged denudation rates from rivers draining the Santa Cruz Mountains along the San Andreas fault (California, USA) which closely reproduce known uplift rate patterns associated with a restraining bend along the fault. An additional component of vertical deformation appears to be superposed on the uplift due to the restraining bend; this may result from regional transpression, further irregularities in the fault trace, or interactions with neighboring faults. Our results indicate that Be-10-derived denudation rates can reveal patterns of rock uplift adjacent to reverse faults over length-scales relevant for characterizing their seismic hazard potential.