Although aseismic deformation may contribute to this shortfall, I argue that the existing seismic catalogs fail to reflect the long term situation. Impelled by the systematic variation of seismic to geodetic moment rates and by the uniform strain drop observed in all earthquakes regardless of magnitude, I propose that the completeness of any seismic catalog hinges on the product of observation duration and regional strain rate. Slowly straining regions require a proportionally longer period of observation. Characterized by this product, gamma distributions model statistical properties of catalog completeness as proxied by the ratio of observed seismic moment to geodetic moment. The combination of historical seismicity, fault geology and space geodesy offers a powerful tripartite attack on earthquake hazard.
Few obstacles block similar analyses in any region of the world.
Figure 1 . With a physical model now arguing in support, the likelihood of a hard segment boundary at the southern terminus of the 1979 rupture seems very high, even based on a single rupture sample. The height and dimension of the rainbow termination fix the strength of the northern section of the fault at 40 bars or more. The hard segment boundary must be a least twice as strong to stop the rupture so quickly. Figure 2 .