Too often the Earth s surface acted as a divide between seismologists and engineers. Now it is becoming clear that the building behaviour largely depends on the seismic input and the buildings on their turn act as seismic sources, in an intricate interplay that non-linear phenomena make even more complex. These phenomena are often the cause of observed damage enhancement during past earthquakes. While research may pursue complex models to fully understand soil dynamics under seismic loading, we need also simple models valid on average, whose results can be easily transferred to end users.

Under the title Increasing Seismic Safety by Combining Engineering Technologies and Seismological Data , we grouped several topics to be discussed together by engineers and seismologists: (1) Can we use ambient noise building and soil characterisation to extract useful information for engineers? (2) How we can tell apart a frequency decrease due to distributed damage, concentrated damage, time- varying building and soil behaviour? (3) Which is the role of transients in ambient noise analysis? (4) Can we quantify the influence of existing buildings on ground-motion recordings? (5) To which extent soil-building resonance is a cause of damage enhancement? (6) How to couple soil and building non-linear behaviour?

On most questions there is an unanimous answer, but in some cases different views are present and the disagreement is faithfully reported.