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Bounding the Moment Deficit Rate on Crustal Faults Using Geodetic Data: Application to Southern California

Jeremy L. Maurer, Kaj M. Johnson, & Paul Segall

Published December 15, 2018, SCEC Contribution #9000

The interseismic moment deficit rate (MDR) constrains the potential for future moment release in earthquakes. Published estimates of the geodetic MDR in Southern California vary by a factor of 3 depending on the type of forward model, method of estimation, and data quality. It is our aim to determine to what degree these discrepancies may be explained by quantifying the uncertainty for a given class of forward models, accounting for data errors and limited model resolution. We apply a new method, the Constrained Optimization Bounding Estimator, to bound the MDR in Southern California using geodetic data and an elastic plate-block model. Total MDR ranges from 1.3 to 2.0×1019 N-m/yr, equivalent to one MW 8.17–8.31 over 160 years, higher than the observed seismic moment since 1850. This observation, together with published estimates of off-fault moment rate, could imply that significant permanent (inelastic) deformation is taking place in Southern California or that future earthquakes will make up the difference. Uncertainty in MDR from Constrained Optimization Bounding Estimator using a single model is comparable to the range of published MDR estimates using elastic block models but about a factor of 8 smaller than the range of all published models. Thus, the choice of forward model dominates the uncertainty in MDR for Southern California. While additional data would be helpful for constraining the MDR, as much or more effort is needed to quantify the prediction errors associated with a given model and to develop observations that narrow the possible range of forward models under consideration.

Maurer, J. L., Johnson, K. M., & Segall, P. (2018). Bounding the Moment Deficit Rate on Crustal Faults Using Geodetic Data: Application to Southern California. Journal of Geophysical Research: Solid Earth,. doi: 10.1029/2018JB016097.