Introduction
The continuous expansion of population and the growth of lifeline systems complexity make our world increasingly exposed to seismic risk. The world’s urban areas are becoming hot spots of global risk change, because of the continuous increase of population and of complexity of lifeline systems. The explosion of urban population takes place predominantly in the developing world, where the population of large cities doubles every 15 years and that of informal settlements doubles every 7 years. Many cities are in high earthquake hazard areas so that an increasing number of people are being exposed to earthquakes (see f.i. Bilham, 2009).

Most of the European cities will not be affected by a dramatic increase of population. Nonetheless they face increasing levels of risk because of the growing industrialisation and networking of infrastructures, lifelines and economies. The networking involves other continents as a result of the economic and social globalization; this means that a huge earthquake in Europe may have global effects. Moreover a significant part of the population lives in highly vulnerable historic centres. As a consequence, a primary target for Europe must be the decrease of both human and financial/infrastructural potential losses caused by earthquakes.

During the past 35 years (1976- October 2010) Europe (including Middle East) has been hit by 162 damaging earthquakes, which represents 20% of the damaging earthquakes worldwide. The earthquakes resulted in about 62,000 casualties (6.7% of the casualties of the whole planet) and an economic loss of 110,900 Millions of Euro. (EM-DAT, the OFDA/CRED International Disaster Database, www.em-dat.net). Although parts of Europe, the US and Japan have populations exposed to similar levels of high earthquake hazard, the relative vulnerability of the European population is some 10 times greater than in Japan, and 100 times that of the US. The protection of critical infrastructure and life-lines is one of the priorities of the EU. In order to counteract this potential vulnerability, the European Council requested in 2004 the development of a European Programme for Critical Infrastructure Protection (EPCIP). Since then, comprehensive preparatory work has been undertaken, which has been included in a Green Paper.

Preventive actions, such as retrofitting of structures and the diffusion of construction codes, are of course essential elements of a comprehensive earthquake disaster mitigation strategy. However, they are not sufficient and cannot be applied easily everywhere. In European cities a substantial proportion of the population living in areas of higher earthquake hazard still resides in older (historical) buildings that do not meet modern earthquake resistant standards, and cannot currently be strengthened in an economically viable manner. In many areas of high earthquake risk there are also cultural centres of great importance.

A feasible long term objective for Europe is reducing the individual vulnerability of its population to a level comparable to that of Japan and the US. The application of real time mitigation of earthquake risk, through actions focused to decrease physical vulnerability and exposure, has the potential of significantly contributing to this goal. These actions require the development and the use of probabilistic forecasting, (characterized by high probability gain and low absolute probability values), of early warning and rapid loss and damage evaluation, taking into consideration also the evolution in time of vulnerability and risk.

The Challenge
All the components of a real time earthquake risk reduction system are treated jointly and coherently using a system level approach for the first time in REAKT. The decision system developed in WP6 will include information from operational forecasting models (WP3), early warning systems (WP4 and 7), rapid alert systems (WP4) and real time identification of physical vulnerability changes (WP5). The reliability of operational forecasting and early warning will be improved by information on the dynamics of earthquake processes and transient phenomena provided by WPs 2 and 4. Using a system level approach all uncertainties along the real time risk mitigation chain can be carried through to the various end-users, where decisions need to be taken in light of the uncertain knowledge. Critical to the success of REAKT is also the need to view the performance of the entire system from an end user perspective, which is why targeted applications (WP7) and close integration of end-users through the end-user group (EUG) are integral elements of the REAKT work plan.