Faults in nature are observed to slip in various modes: some faults slip continuously in a slow process called aseismic creep, while others slip at seismic speeds in earthquakes and stay highly coupled for long periods of time in between those earthquakes. However, many questions remain about this process in nature, such as the rates at which individual faults accumulate strain, and the dynamics at play when a single fault system displays multiple modes of slip over time and space. These questions are directly relevant to seismic hazard at plate boundaries and even in continental interiors. In this presentation, I investigate three examples of faults that are accumulating tectonic strain in three different settings. First, I investigate the extent of deep aseismic creep and megathrust coupling in a subduction zone setting, estimating coupling ratios and the size of the maximum-magnitude earthquake. I also analyze the kinematics of fault slip in a geothermal setting that deforms by both aseismic slip and regular earthquakes. Lastly, I systematically explore strain rates in Southern California, a region that accumulates strain due to high coupling on its major faults. Each example reveals insights into regional fault coupling from new compilations and analysis of geodetic data. Together, these examples underscore the value and utility of geodetic data in better understanding fault-related hazards and fault zone processes.

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