Understanding Extreme Geohazards: The Science of the Disaster Risk Management Cycle European Science Foundation Conference November 28 to December 1, 2011, Sant Feliu de Guixols, Spain

Application of Coulomb, statistical, and hybrid Coulomb/statistical models to the Canterbury, New Zealand, earthquake sequence

Sandy Steacy (1), Matt Gerstenberger (2), Charles Williams (2), David Rhoades (2), and Annemarie Christophersen (2)
(1) University of Ulster, Coleraine, United Kingdom, s.steacy@ulster.ac.uk
(2)GNS Science, Coleraine, United Kingdom

The Canterbury sequence began with the M = 7.1 Darfield earthquake in September 2010 in an area of moderate known seismic hazard. It was followed in February 2011 by the M = 6.3 Christchurch earthquake which caused significant damage to the city. As of this writing, the sequence is continuing and the probability of future damaging events is still being evaluated. Here we present test results for 3 classes of models – Coulomb, statistical, and combined Coulomb/statistical – which we used to estimate likely aftershock rates following both the Darfield and Christchurch events. The models are constrained by the first 10 days of the aftershock sequences following each main earthquake. In particular, each set of early aftershocks is used to determine the receiver fault orientation for the Coulomb stress calculations, to constrain the rate-state parameters, and to determine the b and p values and the earthquake productivity rate. Rates are forecast for 30 days, and 3, 6, and 9 months into the future and compared to observation.