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Published November 10, 2010 | Published
Journal Article Open

Probabilistic prediction of rupture length, slip and seismic ground motions for an ongoing rupture: implications for early warning for large earthquakes

Abstract

Earthquake EarlyWarning (EEW) predicts future ground shaking based on presently available data. Long ruptures present the best opportunities for EEW since many heavily shaken areas are distant from the earthquake epicentre and may receive long warning times. Predicting the shaking from large earthquakes, however, requires some estimate of the likelihood of the future evolution of an ongoing rupture. An EEW system that anticipates future rupture using the present magnitude (or rupture length) together with the Gutenberg-Richter frequencysize statistics will likely never predict a large earthquake, because of the rare occurrence of 'extreme events'. However, it seems reasonable to assume that large slip amplitudes increase the probability for evolving into a large earthquake. To investigate the relationship between the slip and the eventual size of an ongoing rupture, we simulate suites of 1-D rupture series from stochastic models of spatially heterogeneous slip. We find that while large slip amplitudes increase the probability for the continuation of a rupture and the possible evolution into a 'Big One', the recognition that rupture is occurring on a spatially smooth fault has an even stronger effect.We conclude that anEEWsystem for large earthquakes needs some mechanism for the rapid recognition of the causative fault (e.g., from real-time GPS measurements) and consideration of its 'smoothness'. An EEW system for large earthquakes on smooth faults, such as the San Andreas Fault, could be implemented in two ways: the system could issue a warning, whenever slip on the fault exceeds a few metres, because the probability for a large earthquake is high and strong shaking is expected to occur in large areas around the fault. A more sophisticated EEW system could use the present slip on the fault to estimate the future slip evolution and final rupture dimensions, and (using this information) could provide probabilistic predictions of seismic ground motions along the evolving rupture. The decision on whether an EEW system should be realized in the first or in the second way (or in a combination of both) is user-specific.

Additional Information

© 2010 The Authors. © 2010 RAS. Accepted 2010 August 12. Received 2010 August 11; in original form 2010 February 12. Article first published online: 29 Sep. 2010. This work is funded through contract G09AC00258 from USGS/ANSS to the California Institute of Technology (Caltech). This is contribution #10039 of the Seismological Laboratory, Geological and Planetary Sciences at Caltech. Calculations and most figures in this paper were generated from Matlab 7.8. The map in Fig. 11a (left-hand side)was made using the GenericMapping Tools version 4.2.1 (www.soest.hawaii.edu/gmt; Wessel & Smith 1998). We would like to thank Egill Hauksson for proofreading. We are grateful for the helpful comments of P.Martin Mai, two anonymous reviewers and the editor Yehuda Ben-Zion that helped us to improve an earlier version of this manuscript.

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