Comparison of ETAS parameter estimates across different global tectonic zones

Annie Chu, Frederic P. Schoenberg, Peter Bird, David D. Jackson, & Yan Y. Kagan

Published 2011, SCEC Contribution #1476

Branching point process models such as the ETAS (Epidemic-Type Aftershock Sequence) models introduced by Ogata (1988, 1998) are often used in the description, characterization, simulation, and declustering of modern earthquake catalogs. The present work investigates how the parameters in these models vary across dirent tectonic zones. After considering divisions of the surface of the Earth into several zones based on the plate boundary model of Bird (2003), ETAS models are fit to the occurrence times and locations of shallow earthquakes within each zone. Computationally, the EM-type algorithm of Veen and Schoenberg (2008) is employed for the purpose of model fitting. The fits and variations in parameter estimates for distinct zones are compared, and seismological implications are discussed. In particular, we find that estimated background seismicity rates range by a factor of nearly 500 for interplate and trench events, respectively, and the estimated productivity parameter, governing the relationship between the magnitude of an earthquake and its expected number of direct aftershocks, ranges by a factor of more than 5 from events in the slow-moving zone to events in active continental areas, suggesting a much higher rate of swarming in the ridges than in the trenches and active continental zones. Despite the pronounced dirences between the seismicity patterns and parameter estimates in the dirent zones, the ETAS model with few parameters and with the same functional form seems to fit reasonably well to the seismicity in each zone.

Citation
Chu, A., Schoenberg, F. P., Bird, P., Jackson, D. D., & Kagan, Y. Y. (2011). Comparison of ETAS parameter estimates across different global tectonic zones. Bulletin of the Seismological Society of America, 101(5), 2323-2339. doi: 10.1785/0120100115.