Oral Presentation

Surface ruptures are the foundation of the Quaternary record, illuminating coseismic processes in exceptional detail and ultimately encoding the recurrence of large earthquakes across a fault system. This talk journeys through observations from individual ruptures, earthquake pairs, and the long-term geologic record across fault networks, complemented by numerical models and laboratory experiments, to reveal the mechanics of faulting at depth encoded in these surface datasets over the earthquake cycle.

Integrating surface rupture maps, geodetic strain maps, and seismicity, I show that coseismic deformation is distributed consistently from the surface to seismogenic depth for earthquakes in the Eastern California Shear Zone. Leveraging a global dataset of >30 surface rupture maps, I show that the distribution of coseismic surface fracturing localizes systematically with fault cumulative displacement, highlighting how the fault zone architecture evolves over the lifespan of a fault. Drawing from a record of repeat surface ruptures, I place bounds on the fraction of the fractures in the fault damage zone active during an earthquake. Diffusion models paired with post-earthquake field work show that distributed deformation and rupture complexity are erased quickly following earthquakes, even in desert landscapes, helping constrain how surface ruptures evolve into the traces that comprise the Quaternary record of faulting. Combining Quaternary fault maps with surface rupture maps shows how fault geometry governs the mechanics of rupture propagation and arrest. A growing record of observations reveals that fault networks can behave coherently, producing ordered earthquake recurrence. Comparing these observations to numerical models and a new set of laboratory experiments, I show that synchronization, alternation, and supercycles emerge from elastic interactions between neighboring faults.

These insights rest on a foundation built by the community: surface rupture maps, paleoseismic chronologies, and slip rate records are the product of years of careful geologic mapping, field work, and laboratory analysis, and, increasingly, analysis of high-resolution topography and imagery. As this record grows with new earthquakes and retrospective digitization of existing datasets, so will our understanding of the mechanics of fault systems from seconds to millennia.