UCERF3

It provides authoritative estimates of the likelihood and severity of potentially damaging earthquake ruptures in the long- and near-term.

[5] This allows seismicity to be distributed in a more realistic manner, which has corrected a problem with prior studies that overpredicted earthquakes of moderate size (between magnitude 6.5 and 7.0).

This requires accommodation of 34 to 48 millimeters (about one and a half inches) of slippage per year,[19] with some of that taken up in portions of the Basin and Range Province to the east of California.

In theory, this should produce some regularity in the earthquakes on a given fault, and knowing the date of the last rupture is a clue to how soon the next one can be expected.

[29] This uses a supercomputer to solve a system of linear equations that simultaneously satisfies multiple constraints such as known slip rates, etc.

[31] While UCERF3 represents a considerable improvement over UCERF2,[32] and the best available science to-date for estimating California's earthquake hazard,[33] the authors caution that it remains an approximation of the natural system.

[37] There are a number of sources of uncertainty, such as insufficient knowledge of fault geometry (especially at depth) and slip rates,[38] and there is considerable challenge in how to balance the various elements of the model to achieve the best fit with the available observations.

The data does fit if a certain constraint (the regional Magnitude-Frequency Distribution) is relaxed, but this brings back the problem over-predicting moderate events.

The model implies that achieving GR consistency would require certain changes in seismological understanding that "fall outside the current bounds of consensus-level acceptability".

[40] Whether the Gutenberg-Richter relation is inapplicable at the scale of individual faults, or some basis of the model is incorrect, "will be equally profound scientifically, and quite consequential with respect to hazard.

California (outlined in white) and buffer zone showing the 2,606 fault subsections of UCERF 3.1. Colors indicate probability (as a percentage) of experiencing an M ≥ 6.7 earthquake in the next 30 years, accounting for the stress accumulated since the last earthquake. Does not include effects from the Cascadia subduction zone (not shown) in the northwest corner.
Location of main faults in following table, with segments color-coded to show slip-rate (up to 40 mm per year). [ 12 ]
UCERF3's four levels of modeling, and some of the alternatives that form the logic-tree. [ 21 ]
Fig. C21 from Appendix C. [ 28 ] Plots of slip rates on two parallel faults (the San Andreas and the San Jacinto) as determined by three deformation models, and a "geologic" model based entirely on observed slip rates, showing variations along each segment. The grand inversion solves for these and many other variables to find values that provide an overall best fit.