SCEC Award Number 15207 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Global Earthquake Activity Rate Model
Investigator(s)
Name Organization
Yan Kagan University of California, Los Angeles David Jackson University of California, Los Angeles
Other Participants
SCEC Priorities 2b, 4e, 1e SCEC Groups EFP, CSEP
Report Due Date 03/15/2016 Date Report Submitted 03/14/2016
Project Abstract
 We have obtained new results in the statistical analysis of global earthquake catalogs with special attention to the largest earthquakes, and examined the statistical behavior of earthquake rate variations. These results can serve as an input for updating our recent earthquake forecast, known as the ”Global Earthquake Activity Rate 1” model (GEAR1), which is based on past earthquakes and geodetic strain rates. The seismic component of the present model is based on a smoothed version of the Global Centroid Moment Tensor catalog. The tectonic component is based on the Global Strain Rate Map, a ”General Earthquake Model” product. We revised our estimates of upper magnitude limits, described as corner magnitudes, based on the massive earthquakes since 2004 and the seismic moment conservation principle. The new corner magnitude estimates are somewhat larger than but consistent with our previous estimates. For major subduction zones we find the best estimates of corner magnitude to be in the range 8.9 to 9.6 and consistent with a uniform average of 9.35. Statistical estimates tend to grow with time as larger earthquakes occur. However, by using the moment conservation principle that equates the seismic moment rate with the tectonic moment rate inferred from geodesy and geology, we obtain a consistent estimate of the corner moment largely independent of seismic history. We examine rate variations as expressed by annual earthquake numbers. Earthquakes larger than magnitude 6.5 obey the Poisson distribution; for smaller events the negative-binomial distribution provides a much better fit.
Intellectual Merit Our ultimate objective is to construct a model for computing and testing the probability that an earthquake of any size will occur within a specified region. These aims correspond specifically to SCEC research objectives.
Broader Impacts Evaluating the future rate of earthquake occurrence in in any given region is important for designing critical facilities, for comparing earthquake and tectonic moment rates, and for understanding the relationship of earthquakes to stress, material properties, fault and plate geometry, and many other features which might affect earthquake rupture. The GEAR1 method can be used by engineers and de-cision makers to estimate earthquake hazards. This project provided technical experience and training to UCLA graduate student Debbie Weiser.
Exemplary Figure Figure 3. Cumulative distribution of yearly earthquake numbers for the global PDE catalog, 1969-2014, m ≥ 5.0. The step-function shows the observed distribution, the dashed curve is the theoretical Poisson distribution for λ = 1280.7 and Eq. 6), and the solid curve is the fitted negative-binomial curve for θ = 0.0145 and τ = 18.87 and Eq. 8). The negative-binomial curve has a better fit than the Poisson curve.
In Fig. 3 we display the fit of a cumulative distribution for annual earthquake numbers in the PDE catalog. The difference between the Poisson and NBD distributions is very large in this plot, because of a lower magnitude threshold in the PDE catalog.