Abstract: In order to determine the seismic vulnerability of a structure, a vibration sensor is placed on each of the top surface of a layer of the structure and the ground surface near the structure so as to record vibrations. A seismic vulnerability data processor assumes a transfer function of vibration of the top surface of the layer of the structure based on a spectral ratio between the vibration recorded on the top surface of the layer of the structure and the vibration recorded on the ground surface, thereby obtaining a predominant frequency and amplification factor of vibration of the top surface of the layer of the structure. A seismic vulnerability index of the layer of the structure resulting from a deformation of the layer is obtained based on the obtained predominant frequency and amplification factor of vibration of the top surface of the layer of the structure and on the height of the layer of the structure.

Abstract: The soundness of a block-shaped structure is evaluated by disposing one set of at least two three-way sensors on a structure, measuring microtremors, determining the contribution factor of rocking vibration, which occupies part of overall vibration, based upon the results of microtremor measurement, and determining extent of rocking vibration at an arbitrary position of the block-shaped structure based upon the contribution factor. Rocking vibration becomes more prevalent as the state of support afforded by the block-shaped structure becomes more unstable. Accordingly, if rocking vibration becomes dominant and exceeds unity, this fact can be used to evaluate the soundness of the block-shaped structure to collapse.