Machine stiffness appropriate for experimental simulation of earthquake processes

Loading machine stiffness is considered in an attempt to simulate strain accumulation processes prior to failure in earthquakes. We impose the similarity condition that the inelastic deformation in a test specimen relative to the loading machine corresponds with that in a spherical seismic region relative to the surrounding earth. From this constraint the appropriate ratio between the stiffnesses of machine and specimen is determined to be 1.5 ∼ 2.3. Preliminary experiments were carried out for sandstone samples. A qualitative difference between acoustic emission sequences was observed depending on whether the conditions were similar or dissimilar to the earth based on the scaling assumption. In the former case, a subsidence in acoustic emission activity prior to the main fractures was clearly and systematically observed.