An earthquake likelihood model based on proximity to mapped faults and catalogued earthquakes

David A. Rhoades, & Mark W. Stirling

Published 2012, SCEC Contribution #1521

Known earthquake sources include mapped active faults and areas where historical earthquakes have occurred. We propose a long-term earthquake likelihood model which makes use of both types of sources, but does not invoke the concepts of fault segmentation or characteristic earthquakes. The model has two components, one based on proximity to the locations of past earthquakes, taking into account their magnitudes, and another based on proximity to mapped faults, taking into account their slip-rates. The Gutenberg-Richter law is invoked for earthquake magnitudes and an inverse power law for the diminution of earthquake rate density with distance from past earthquakes and mapped faults. The model is applied to the New Zealand region using the National Seismic Hazard Model fault source model and the earthquake catalogue since 1951. The parameters of each component are optimised for the period 1987-2006, and the rate density of the combined model is estimated as an optimal linear combination of the two components. In a retrospective analysis, the combined model has an information gain (log likelihood increase) per earthquake of about 0.15 over the separate models based the earthquake and fault data. The model is suitable for comparison with other long-term models in the testing centers of the Collaboratory for the Study of Earthquake Predictability.

Citation
Rhoades, D. A., & Stirling, M. W. (2012). An earthquake likelihood model based on proximity to mapped faults and catalogued earthquakes. Bulletin of the Seismological Society of America, 102, 1593-1599.