Large earthquake faulting and implications for the seismic hazard assessment in europe: the izmit-duzce earthquake sequence of august-november 1999(turkey, mw 7.4, 7.1)

This result concerns an additional approach in that we now consider the forward modelling of dynamic rupture in the presence of geometrical complexities, and we model the faults segments in the Marmara Sea in order to assess the likelihood of very large, through-going ruptures that may threaten the city of Istanbul. In addition, we have modified and extended our innovative approach to model earthquake-cycle behaviour using realistic heterogeneity in rate-and-state friction. These simulations show how rupture complexity can be generated, and how the difference between young, immature faults (structurally complex) and smooth, mature faults can be parameterised. The resulting scenario earthquakes exhibit the same features as seen in observed seismicity in terms of their spatio-temporal evolution, the final slip distribution and the position of the hypocenter. We use these scenario events for ground-motion calculations. This approach is the first attempt ever, considering the literature in earthquake seismology and seismic hazard that directly links earthquake-cycle simulation to near-source ground-motion prediction.

The result shows the modelling of the tsunami wave in Lake Sapanca and the Gulf of Izmit that can be used to set up preparedness plans at the level of the local communities. From the scientific point of view, looking for seismites in a non-laminated lake was quite a challenge. The best proxies to highlight events have been found (thin sections for sediment structures, palynological concentration and assemblages, detrital elements in geochemistry. It is planned to extend this type of studies to longer records in lake Sapanca and also to other lakes situated in earthquake prone regions.

The results of this task consist on the presentation of field investigations along active fault branches of the North Anatolian fault in Paleoseismology. The main methods applied in the field are: geophysical prospecting, geomorphic analysis (quantitative morphology), 2D-3D trenching and dating of paleo-earthquakes.

The Integration of multidisciplinary data sets for seismic hazard assessment is performed using probabilistic and deterministic approaches. The final aim for these hazard studies is to implement the results in seismic risk assessment. To estimate the seismic risk in Istanbul, the ground motion simulation results are combined with the existing vulnerability functions for different building categories and damage maps are produced showing the distribution of collapsed buildings based on a scenario earthquake in the Marmara Sea (see RELIEF UiB Deliverable 27). Probabilistic seismic hazard assessments conducted for the region are not sufficient to account for the expected earthquake threat in this mega-city with more than 12 million inhabitants. Deterministic ground motion simulations based on complex multi-asperity fault rupture scenarios, give a more realistic estimate of the ground motions from a future large earthquake in the Marmara Sea.

The results of this task consist on the preparation of a database of maps of the 1999 earthquake faults and other fault branches of the North Anatolian Fault, the tectonic and seismicity background, the GPS data, the SPOT and SAR space-borne images, high resolution DEM, detailed geomorphological maps, historical and instrumental seismicity catalogue, strong motion records & geotechnical parameters.

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