Preferred frequencies for coupling of seismic waves and vibrating tall buildings

• We study coupling of seismic waves underground to vibrating tall buildings.
• We use a periodic formulation to model city effects.
• Our fast computations allow using different buildings within each cell.
• We find that resonant modes affect some buildings drastically more than others.

We study a model for the so-called “city effect” in which an earthquake can be locally enhanced by the collective response of tall buildings in a large city. We use a set of equations coupling vibrations in buildings to motion under the ground. These equations were previously studied exclusively in the case of a finite set of identical, equally spaced, buildings. These two restrictions are lifted in this paper. We may now simulate geometries involving infinitely many buildings as long as an initial pattern of buildings is repeated. Our new method using periodic domains and periodic Green׳s functions yields much faster computations. This is the main reason why we are now able to study systems of buildings of variable height, mass, and rigidity. We show how solving for the wavenumber in a non-linear equation involving the integral of a function solution to an adequate integral equation, we are able to find resonant frequencies coupling seismic waves and vibrating tall buildings. Interestingly, in the case of non-identical buildings, our simulations indicate that the response to this coupling phenomenon may differ drastically from one building to another.