  Metre size inertial resonators located in the ground have been theoretically
shown to interact with a seismic wave (attenuation, band gaps) to enable
protection of surface structures such as buildings. The challenge for Civil
Engineering is to both reduce the size of these resonators and to increase
their efficiency. Here we explore steel spheres, connected to a concrete bulk
medium, either by a coating of rubber, or rubber and steel ligaments, or air
and steel ligaments. We show that for a cubic lattice periodicity of 1 metre,
we achieve stop bands in the frequency range 14 to 20 Hz; by splitting spheres
in 2 and 8 pieces, we tune down the stop bands frequencies and further increase
their bandwidth. We thus demonstrate we are able to provide a variety of
inertial resonators with stop bands below 10 Hz i.e., in the frequency range of
interest for earthquake engineering.
