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Probabilistic seismic hazard assessment is requiring an increasingly broad compilation of earthquake sources. Fault systems are often divided into characteristic ruptures based on geometric features such as bends or steps, though events such as the 2002 M 7.9 Denali, and 2011 M 9.0 Tohoku-Oki earthquakes raise the possibility that earthquakes can involve subsidiary faults and/or rupture through identified geometric barriers. Here we introduce a method to discriminate among a wide range of possible earthquakes within a large fault system and to quantify the probability of a rupture passing through a bend or step. We note that many of the conditions favoring earthquake rupture propagation can be simulated using a static Coulomb stress change approximation. Such an approach lacks inertial effects inherent in a full dynamic simulation but does capture many of the empirical observations drawn from examining past ruptures, such as continuity of rake and strike, as well as distance across gaps or stepovers. We make calculations for a test region in northern California and find that the method provides a quantitative basis for ranking possible ruptures within localized fault systems. [ABSTRACT FROM AUTHOR]

Previous approaches used to determine the rates of different earthquakes on a fault have made assumptions regarding segmentation, have been difficult to document and reproduce, and have lacked the ability to satisfy all available data constraints. We present a relatively objective and reproducible inverse methodology for determining the rate of different ruptures on a fault or fault system. The data used in the inversion include slip rate, event rate, and other constraints such as an optional a priori magnitude-frequency distribution. We demonstrate our methodology by solving for the long-term rate of ruptures on the southern San Andreas fault. Our results imply that a Gutenberg-Richter distribution is consistent with the data available for this fault; however, more work is needed to test the robustness of this assertion. More importantly, the methodology is extensible to an entire fault system (thereby including multifault ruptures) and can be used to quantify the relative benefits of collecting additional paleoseismic data at different sites. [ABSTRACT FROM AUTHOR]

This article summarizes the 1988, 1990, 1995, and 2002 Working Groups on California Earthquake Probabilities (WGCEPs). Each of these studies used the best available science to make a time-dependent earthquake forecast. All involved applying elastic-rebound-theory-motivated recurrence models to estimate the probability of rupture on discrete fault segments. The focus was necessarily limited to those faults that had sufficient information to make a time-dependent analysis, although the later studies included probabilities for other events as well. This manuscript does not give a point-by-point critique or review of the previous WGCEPs, both because it would take considerably more text and because such discussions will necessarily be documented by future working groups as they justify changes. One opinion that is emphasized, however, is that future WGCEPs should resist overcomplexity in certain aspects of the model given basic assumptions that have been made and/or limitations in our understanding of the earthquake system. For example, one might argue that the level of sophistication applied by previous WGCEPs with respect to recurrence-interval variability and uncertainty was overkill given their basic assumptions that large earthquakes obey segment boundaries, ruptures never jump from one fault to another, and earthquake-clustering effects can be ignored. [ABSTRACT FROM AUTHOR]