Innovative approach to seismic hazard assessment
Extensive surface rupturing triggered by two severe earthquakes in western Turkey in 1999 caused significant damage and cost thousands of lives. A multinational team, supported by the Energy, Environment and Sustainable Development Programme, visited the site to collect data with the aim of improving seismic hazard assessment in the region. Geophysicists with the Swiss Federal Institute of Technology Zurich participated in the project, entitled RELIEF. They applied their expertise to better address the impact of complex geometry on surface rupturing in seismic modelling. Another important contribution entailed the use of realistic heterogeneity in the treatment of rate and state friction. A fresh evaluation of the threat of further significant earthquakes affecting this region, namely the nearby capital Istanbul, was performed with the updated models. It marked the first time ever that earthquake cycle models were combined with those designed to predict ground-motion. The results of the simulations were remarkably consistent with the type of earthquakes that have been observed to date in the region. This held true not only for the slip characteristics of the events, but also for their distribution in time and space. Finally, with respect to surface rupturing, the revised models were able to successfully reproduce important differences between young faults and their more mature counterparts.
