Models that attempt to incorporate earthquake physics play an increasingly important role in seismology and are prevalent in seismic hazard assessment. Most often, the physical ideas that inform these models are heuristically motivated and based on expert opinion. The Uniform California Earthquake Rupture Forecast (UCERF2) employs several such models. To increase the testability of the upcoming UCERF3, we propose to investigate the characteristic earthquake hypothesis, the relation of maximum magnitude to fault length, and the Coulomb Stress hypothesis. For many faults, seismologists identified so-called characteristic earthquakes and include them as expected target earthquakes in hazard assessment. The most prominent and best studied example is the sequence of magnitude 6 events at Parkfield, CA. Studies have shown that this phenomenon possibly could be explained by low sample size from the upper magnitude ranges of the frequency-magnitude distribution. The relation of maximum magnitude to fault length plays a major role in hazard assessment as it is used to estimate the size of future large events at particular faults. This relation is based purely on a posteriori observations and has not been tested using a priori predictions. The most complicated of the selected models is the Coulomb Stress model. It shows great descriptive capabilities but is also relies on a posteriori observations through fitting of the free parameters. Its uncertainty range remains relatively unexplored. Common to all of these conceptual models is the fact that they were never rigorously tested for their predictive power, owing in some part to the difficulty in formulating them as testable hypotheses. We propose to explore the uncertainty ranges of these hypotheses and to translate them into testable hypotheses to be tested rigorously in the framework of the Collaboratory for the Study of Earthquake Predictability. This study will add more testability to the UCERF3 effort and help to understand and to quantify the impact of these models on seismic hazard assessment.
